1 // SPDX-License-Identifier: GPL-2.0-only 1 // SPDX-License-Identifier: GPL-2.0-only
2 /* 2 /*
3 * fs/userfaultfd.c 3 * fs/userfaultfd.c
4 * 4 *
5 * Copyright (C) 2007 Davide Libenzi <davide 5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 * Copyright (C) 2008-2009 Red Hat, Inc. 6 * Copyright (C) 2008-2009 Red Hat, Inc.
7 * Copyright (C) 2015 Red Hat, Inc. 7 * Copyright (C) 2015 Red Hat, Inc.
8 * 8 *
9 * Some part derived from fs/eventfd.c (anon 9 * Some part derived from fs/eventfd.c (anon inode setup) and
10 * mm/ksm.c (mm hashing). 10 * mm/ksm.c (mm hashing).
11 */ 11 */
12 12
13 #include <linux/list.h> 13 #include <linux/list.h>
14 #include <linux/hashtable.h> 14 #include <linux/hashtable.h>
15 #include <linux/sched/signal.h> 15 #include <linux/sched/signal.h>
16 #include <linux/sched/mm.h> 16 #include <linux/sched/mm.h>
17 #include <linux/mm.h> 17 #include <linux/mm.h>
18 #include <linux/mm_inline.h> <<
19 #include <linux/mmu_notifier.h> <<
20 #include <linux/poll.h> 18 #include <linux/poll.h>
21 #include <linux/slab.h> 19 #include <linux/slab.h>
22 #include <linux/seq_file.h> 20 #include <linux/seq_file.h>
23 #include <linux/file.h> 21 #include <linux/file.h>
24 #include <linux/bug.h> 22 #include <linux/bug.h>
25 #include <linux/anon_inodes.h> 23 #include <linux/anon_inodes.h>
26 #include <linux/syscalls.h> 24 #include <linux/syscalls.h>
27 #include <linux/userfaultfd_k.h> 25 #include <linux/userfaultfd_k.h>
28 #include <linux/mempolicy.h> 26 #include <linux/mempolicy.h>
29 #include <linux/ioctl.h> 27 #include <linux/ioctl.h>
30 #include <linux/security.h> 28 #include <linux/security.h>
31 #include <linux/hugetlb.h> 29 #include <linux/hugetlb.h>
32 #include <linux/swapops.h> !! 30
33 #include <linux/miscdevice.h> !! 31 int sysctl_unprivileged_userfaultfd __read_mostly = 1;
34 #include <linux/uio.h> !! 32
35 !! 33 static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
36 static int sysctl_unprivileged_userfaultfd __r !! 34
37 !! 35 enum userfaultfd_state {
38 #ifdef CONFIG_SYSCTL !! 36 UFFD_STATE_WAIT_API,
39 static struct ctl_table vm_userfaultfd_table[] !! 37 UFFD_STATE_RUNNING,
40 { <<
41 .procname = "unprivilege <<
42 .data = &sysctl_unpr <<
43 .maxlen = sizeof(sysct <<
44 .mode = 0644, <<
45 .proc_handler = proc_dointve <<
46 .extra1 = SYSCTL_ZERO, <<
47 .extra2 = SYSCTL_ONE, <<
48 }, <<
49 }; 38 };
50 #endif <<
51 39
52 static struct kmem_cache *userfaultfd_ctx_cach !! 40 /*
>> 41 * Start with fault_pending_wqh and fault_wqh so they're more likely
>> 42 * to be in the same cacheline.
>> 43 *
>> 44 * Locking order:
>> 45 * fd_wqh.lock
>> 46 * fault_pending_wqh.lock
>> 47 * fault_wqh.lock
>> 48 * event_wqh.lock
>> 49 *
>> 50 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks,
>> 51 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's
>> 52 * also taken in IRQ context.
>> 53 */
>> 54 struct userfaultfd_ctx {
>> 55 /* waitqueue head for the pending (i.e. not read) userfaults */
>> 56 wait_queue_head_t fault_pending_wqh;
>> 57 /* waitqueue head for the userfaults */
>> 58 wait_queue_head_t fault_wqh;
>> 59 /* waitqueue head for the pseudo fd to wakeup poll/read */
>> 60 wait_queue_head_t fd_wqh;
>> 61 /* waitqueue head for events */
>> 62 wait_queue_head_t event_wqh;
>> 63 /* a refile sequence protected by fault_pending_wqh lock */
>> 64 struct seqcount refile_seq;
>> 65 /* pseudo fd refcounting */
>> 66 refcount_t refcount;
>> 67 /* userfaultfd syscall flags */
>> 68 unsigned int flags;
>> 69 /* features requested from the userspace */
>> 70 unsigned int features;
>> 71 /* state machine */
>> 72 enum userfaultfd_state state;
>> 73 /* released */
>> 74 bool released;
>> 75 /* memory mappings are changing because of non-cooperative event */
>> 76 bool mmap_changing;
>> 77 /* mm with one ore more vmas attached to this userfaultfd_ctx */
>> 78 struct mm_struct *mm;
>> 79 };
53 80
54 struct userfaultfd_fork_ctx { 81 struct userfaultfd_fork_ctx {
55 struct userfaultfd_ctx *orig; 82 struct userfaultfd_ctx *orig;
56 struct userfaultfd_ctx *new; 83 struct userfaultfd_ctx *new;
57 struct list_head list; 84 struct list_head list;
58 }; 85 };
59 86
60 struct userfaultfd_unmap_ctx { 87 struct userfaultfd_unmap_ctx {
61 struct userfaultfd_ctx *ctx; 88 struct userfaultfd_ctx *ctx;
62 unsigned long start; 89 unsigned long start;
63 unsigned long end; 90 unsigned long end;
64 struct list_head list; 91 struct list_head list;
65 }; 92 };
66 93
67 struct userfaultfd_wait_queue { 94 struct userfaultfd_wait_queue {
68 struct uffd_msg msg; 95 struct uffd_msg msg;
69 wait_queue_entry_t wq; 96 wait_queue_entry_t wq;
70 struct userfaultfd_ctx *ctx; 97 struct userfaultfd_ctx *ctx;
71 bool waken; 98 bool waken;
72 }; 99 };
73 100
74 struct userfaultfd_wake_range { 101 struct userfaultfd_wake_range {
75 unsigned long start; 102 unsigned long start;
76 unsigned long len; 103 unsigned long len;
77 }; 104 };
78 105
79 /* internal indication that UFFD_API ioctl was <<
80 #define UFFD_FEATURE_INITIALIZED <<
81 <<
82 static bool userfaultfd_is_initialized(struct <<
83 { <<
84 return ctx->features & UFFD_FEATURE_IN <<
85 } <<
86 <<
87 static bool userfaultfd_wp_async_ctx(struct us <<
88 { <<
89 return ctx && (ctx->features & UFFD_FE <<
90 } <<
91 <<
92 /* <<
93 * Whether WP_UNPOPULATED is enabled on the uf <<
94 * meaningful when userfaultfd_wp()==true on t <<
95 * anonymous. <<
96 */ <<
97 bool userfaultfd_wp_unpopulated(struct vm_area <<
98 { <<
99 struct userfaultfd_ctx *ctx = vma->vm_ <<
100 <<
101 if (!ctx) <<
102 return false; <<
103 <<
104 return ctx->features & UFFD_FEATURE_WP <<
105 } <<
106 <<
107 static void userfaultfd_set_vm_flags(struct vm <<
108 vm_flags_ <<
109 { <<
110 const bool uffd_wp_changed = (vma->vm_ <<
111 <<
112 vm_flags_reset(vma, flags); <<
113 /* <<
114 * For shared mappings, we want to ena <<
115 * userfaultfd-wp is enabled (see vma_ <<
116 * recalculate vma->vm_page_prot whene <<
117 */ <<
118 if ((vma->vm_flags & VM_SHARED) && uff <<
119 vma_set_page_prot(vma); <<
120 } <<
121 <<
122 static int userfaultfd_wake_function(wait_queu 106 static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode,
123 int wake_ 107 int wake_flags, void *key)
124 { 108 {
125 struct userfaultfd_wake_range *range = 109 struct userfaultfd_wake_range *range = key;
126 int ret; 110 int ret;
127 struct userfaultfd_wait_queue *uwq; 111 struct userfaultfd_wait_queue *uwq;
128 unsigned long start, len; 112 unsigned long start, len;
129 113
130 uwq = container_of(wq, struct userfaul 114 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
131 ret = 0; 115 ret = 0;
132 /* len == 0 means wake all */ 116 /* len == 0 means wake all */
133 start = range->start; 117 start = range->start;
134 len = range->len; 118 len = range->len;
135 if (len && (start > uwq->msg.arg.pagef 119 if (len && (start > uwq->msg.arg.pagefault.address ||
136 start + len <= uwq->msg.ar 120 start + len <= uwq->msg.arg.pagefault.address))
137 goto out; 121 goto out;
138 WRITE_ONCE(uwq->waken, true); 122 WRITE_ONCE(uwq->waken, true);
139 /* 123 /*
140 * The Program-Order guarantees provid 124 * The Program-Order guarantees provided by the scheduler
141 * ensure uwq->waken is visible before 125 * ensure uwq->waken is visible before the task is woken.
142 */ 126 */
143 ret = wake_up_state(wq->private, mode) 127 ret = wake_up_state(wq->private, mode);
144 if (ret) { 128 if (ret) {
145 /* 129 /*
146 * Wake only once, autoremove 130 * Wake only once, autoremove behavior.
147 * 131 *
148 * After the effect of list_de 132 * After the effect of list_del_init is visible to the other
149 * CPUs, the waitqueue may dis 133 * CPUs, the waitqueue may disappear from under us, see the
150 * !list_empty_careful() in ha 134 * !list_empty_careful() in handle_userfault().
151 * 135 *
152 * try_to_wake_up() has an imp 136 * try_to_wake_up() has an implicit smp_mb(), and the
153 * wq->private is read before 137 * wq->private is read before calling the extern function
154 * "wake_up_state" (which in t 138 * "wake_up_state" (which in turns calls try_to_wake_up).
155 */ 139 */
156 list_del_init(&wq->entry); 140 list_del_init(&wq->entry);
157 } 141 }
158 out: 142 out:
159 return ret; 143 return ret;
160 } 144 }
161 145
162 /** 146 /**
163 * userfaultfd_ctx_get - Acquires a reference 147 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd
164 * context. 148 * context.
165 * @ctx: [in] Pointer to the userfaultfd conte 149 * @ctx: [in] Pointer to the userfaultfd context.
166 */ 150 */
167 static void userfaultfd_ctx_get(struct userfau 151 static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
168 { 152 {
169 refcount_inc(&ctx->refcount); 153 refcount_inc(&ctx->refcount);
170 } 154 }
171 155
172 /** 156 /**
173 * userfaultfd_ctx_put - Releases a reference 157 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd
174 * context. 158 * context.
175 * @ctx: [in] Pointer to userfaultfd context. 159 * @ctx: [in] Pointer to userfaultfd context.
176 * 160 *
177 * The userfaultfd context reference must have 161 * The userfaultfd context reference must have been previously acquired either
178 * with userfaultfd_ctx_get() or userfaultfd_c 162 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget().
179 */ 163 */
180 static void userfaultfd_ctx_put(struct userfau 164 static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
181 { 165 {
182 if (refcount_dec_and_test(&ctx->refcou 166 if (refcount_dec_and_test(&ctx->refcount)) {
183 VM_BUG_ON(spin_is_locked(&ctx- 167 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
184 VM_BUG_ON(waitqueue_active(&ct 168 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
185 VM_BUG_ON(spin_is_locked(&ctx- 169 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
186 VM_BUG_ON(waitqueue_active(&ct 170 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh));
187 VM_BUG_ON(spin_is_locked(&ctx- 171 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock));
188 VM_BUG_ON(waitqueue_active(&ct 172 VM_BUG_ON(waitqueue_active(&ctx->event_wqh));
189 VM_BUG_ON(spin_is_locked(&ctx- 173 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock));
190 VM_BUG_ON(waitqueue_active(&ct 174 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh));
191 mmdrop(ctx->mm); 175 mmdrop(ctx->mm);
192 kmem_cache_free(userfaultfd_ct 176 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
193 } 177 }
194 } 178 }
195 179
196 static inline void msg_init(struct uffd_msg *m 180 static inline void msg_init(struct uffd_msg *msg)
197 { 181 {
198 BUILD_BUG_ON(sizeof(struct uffd_msg) ! 182 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);
199 /* 183 /*
200 * Must use memset to zero out the pad 184 * Must use memset to zero out the paddings or kernel data is
201 * leaked to userland. 185 * leaked to userland.
202 */ 186 */
203 memset(msg, 0, sizeof(struct uffd_msg) 187 memset(msg, 0, sizeof(struct uffd_msg));
204 } 188 }
205 189
206 static inline struct uffd_msg userfault_msg(un 190 static inline struct uffd_msg userfault_msg(unsigned long address,
207 un <<
208 un 191 unsigned int flags,
209 un 192 unsigned long reason,
210 un 193 unsigned int features)
211 { 194 {
212 struct uffd_msg msg; 195 struct uffd_msg msg;
213 <<
214 msg_init(&msg); 196 msg_init(&msg);
215 msg.event = UFFD_EVENT_PAGEFAULT; 197 msg.event = UFFD_EVENT_PAGEFAULT;
216 !! 198 msg.arg.pagefault.address = address;
217 msg.arg.pagefault.address = (features <<
218 real_addre <<
219 <<
220 /* <<
221 * These flags indicate why the userfa <<
222 * - UFFD_PAGEFAULT_FLAG_WP indicates <<
223 * - UFFD_PAGEFAULT_FLAG_MINOR indicat <<
224 * - Neither of these flags being set <<
225 * <<
226 * Separately, UFFD_PAGEFAULT_FLAG_WRI <<
227 * fault. Otherwise, it was a read fau <<
228 */ <<
229 if (flags & FAULT_FLAG_WRITE) 199 if (flags & FAULT_FLAG_WRITE)
>> 200 /*
>> 201 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
>> 202 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE
>> 203 * was not set in a UFFD_EVENT_PAGEFAULT, it means it
>> 204 * was a read fault, otherwise if set it means it's
>> 205 * a write fault.
>> 206 */
230 msg.arg.pagefault.flags |= UFF 207 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
231 if (reason & VM_UFFD_WP) 208 if (reason & VM_UFFD_WP)
>> 209 /*
>> 210 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
>> 211 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was
>> 212 * not set in a UFFD_EVENT_PAGEFAULT, it means it was
>> 213 * a missing fault, otherwise if set it means it's a
>> 214 * write protect fault.
>> 215 */
232 msg.arg.pagefault.flags |= UFF 216 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
233 if (reason & VM_UFFD_MINOR) <<
234 msg.arg.pagefault.flags |= UFF <<
235 if (features & UFFD_FEATURE_THREAD_ID) 217 if (features & UFFD_FEATURE_THREAD_ID)
236 msg.arg.pagefault.feat.ptid = 218 msg.arg.pagefault.feat.ptid = task_pid_vnr(current);
237 return msg; 219 return msg;
238 } 220 }
239 221
240 #ifdef CONFIG_HUGETLB_PAGE 222 #ifdef CONFIG_HUGETLB_PAGE
241 /* 223 /*
242 * Same functionality as userfaultfd_must_wait 224 * Same functionality as userfaultfd_must_wait below with modifications for
243 * hugepmd ranges. 225 * hugepmd ranges.
244 */ 226 */
245 static inline bool userfaultfd_huge_must_wait( 227 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
246 !! 228 struct vm_area_struct *vma,
247 !! 229 unsigned long address,
>> 230 unsigned long flags,
>> 231 unsigned long reason)
248 { 232 {
249 struct vm_area_struct *vma = vmf->vma; !! 233 struct mm_struct *mm = ctx->mm;
250 pte_t *ptep, pte; 234 pte_t *ptep, pte;
251 bool ret = true; 235 bool ret = true;
252 236
253 assert_fault_locked(vmf); !! 237 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
>> 238
>> 239 ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
254 240
255 ptep = hugetlb_walk(vma, vmf->address, <<
256 if (!ptep) 241 if (!ptep)
257 goto out; 242 goto out;
258 243
259 ret = false; 244 ret = false;
260 pte = huge_ptep_get(vma->vm_mm, vmf->a !! 245 pte = huge_ptep_get(ptep);
261 246
262 /* 247 /*
263 * Lockless access: we're in a wait_ev 248 * Lockless access: we're in a wait_event so it's ok if it
264 * changes under us. PTE markers shou !! 249 * changes under us.
265 * ptes here. <<
266 */ 250 */
267 if (huge_pte_none_mostly(pte)) !! 251 if (huge_pte_none(pte))
268 ret = true; 252 ret = true;
269 if (!huge_pte_write(pte) && (reason & 253 if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
270 ret = true; 254 ret = true;
271 out: 255 out:
272 return ret; 256 return ret;
273 } 257 }
274 #else 258 #else
275 static inline bool userfaultfd_huge_must_wait( 259 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
276 !! 260 struct vm_area_struct *vma,
277 !! 261 unsigned long address,
>> 262 unsigned long flags,
>> 263 unsigned long reason)
278 { 264 {
279 return false; /* should never get he 265 return false; /* should never get here */
280 } 266 }
281 #endif /* CONFIG_HUGETLB_PAGE */ 267 #endif /* CONFIG_HUGETLB_PAGE */
282 268
283 /* 269 /*
284 * Verify the pagetables are still not ok afte 270 * Verify the pagetables are still not ok after having reigstered into
285 * the fault_pending_wqh to avoid userland hav 271 * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
286 * userfault that has already been resolved, i !! 272 * userfault that has already been resolved, if userfaultfd_read and
287 * UFFDIO_COPY|ZEROPAGE are being run simultan 273 * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
288 * threads. 274 * threads.
289 */ 275 */
290 static inline bool userfaultfd_must_wait(struc 276 static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
291 struc !! 277 unsigned long address,
>> 278 unsigned long flags,
292 unsig 279 unsigned long reason)
293 { 280 {
294 struct mm_struct *mm = ctx->mm; 281 struct mm_struct *mm = ctx->mm;
295 unsigned long address = vmf->address; <<
296 pgd_t *pgd; 282 pgd_t *pgd;
297 p4d_t *p4d; 283 p4d_t *p4d;
298 pud_t *pud; 284 pud_t *pud;
299 pmd_t *pmd, _pmd; 285 pmd_t *pmd, _pmd;
300 pte_t *pte; 286 pte_t *pte;
301 pte_t ptent; <<
302 bool ret = true; 287 bool ret = true;
303 288
304 assert_fault_locked(vmf); !! 289 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
305 290
306 pgd = pgd_offset(mm, address); 291 pgd = pgd_offset(mm, address);
307 if (!pgd_present(*pgd)) 292 if (!pgd_present(*pgd))
308 goto out; 293 goto out;
309 p4d = p4d_offset(pgd, address); 294 p4d = p4d_offset(pgd, address);
310 if (!p4d_present(*p4d)) 295 if (!p4d_present(*p4d))
311 goto out; 296 goto out;
312 pud = pud_offset(p4d, address); 297 pud = pud_offset(p4d, address);
313 if (!pud_present(*pud)) 298 if (!pud_present(*pud))
314 goto out; 299 goto out;
315 pmd = pmd_offset(pud, address); 300 pmd = pmd_offset(pud, address);
316 again: !! 301 /*
317 _pmd = pmdp_get_lockless(pmd); !! 302 * READ_ONCE must function as a barrier with narrower scope
>> 303 * and it must be equivalent to:
>> 304 * _pmd = *pmd; barrier();
>> 305 *
>> 306 * This is to deal with the instability (as in
>> 307 * pmd_trans_unstable) of the pmd.
>> 308 */
>> 309 _pmd = READ_ONCE(*pmd);
318 if (pmd_none(_pmd)) 310 if (pmd_none(_pmd))
319 goto out; 311 goto out;
320 312
321 ret = false; 313 ret = false;
322 if (!pmd_present(_pmd) || pmd_devmap(_ !! 314 if (!pmd_present(_pmd))
323 goto out; 315 goto out;
324 316
325 if (pmd_trans_huge(_pmd)) { !! 317 if (pmd_trans_huge(_pmd))
326 if (!pmd_write(_pmd) && (reaso <<
327 ret = true; <<
328 goto out; 318 goto out;
329 } <<
330 319
>> 320 /*
>> 321 * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it
>> 322 * and use the standard pte_offset_map() instead of parsing _pmd.
>> 323 */
331 pte = pte_offset_map(pmd, address); 324 pte = pte_offset_map(pmd, address);
332 if (!pte) { <<
333 ret = true; <<
334 goto again; <<
335 } <<
336 /* 325 /*
337 * Lockless access: we're in a wait_ev 326 * Lockless access: we're in a wait_event so it's ok if it
338 * changes under us. PTE markers shou !! 327 * changes under us.
339 * ptes here. <<
340 */ 328 */
341 ptent = ptep_get(pte); !! 329 if (pte_none(*pte))
342 if (pte_none_mostly(ptent)) <<
343 ret = true; <<
344 if (!pte_write(ptent) && (reason & VM_ <<
345 ret = true; 330 ret = true;
346 pte_unmap(pte); 331 pte_unmap(pte);
347 332
348 out: 333 out:
349 return ret; 334 return ret;
350 } 335 }
351 336
352 static inline unsigned int userfaultfd_get_blo <<
353 { <<
354 if (flags & FAULT_FLAG_INTERRUPTIBLE) <<
355 return TASK_INTERRUPTIBLE; <<
356 <<
357 if (flags & FAULT_FLAG_KILLABLE) <<
358 return TASK_KILLABLE; <<
359 <<
360 return TASK_UNINTERRUPTIBLE; <<
361 } <<
362 <<
363 /* 337 /*
364 * The locking rules involved in returning VM_ 338 * The locking rules involved in returning VM_FAULT_RETRY depending on
365 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NO 339 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
366 * FAULT_FLAG_KILLABLE are not straightforward 340 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution"
367 * recommendation in __lock_page_or_retry is n 341 * recommendation in __lock_page_or_retry is not an understatement.
368 * 342 *
369 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_ !! 343 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released
370 * before returning VM_FAULT_RETRY only if FAU 344 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is
371 * not set. 345 * not set.
372 * 346 *
373 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_ 347 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not
374 * set, VM_FAULT_RETRY can still be returned i 348 * set, VM_FAULT_RETRY can still be returned if and only if there are
375 * fatal_signal_pending()s, and the mmap_lock !! 349 * fatal_signal_pending()s, and the mmap_sem must be released before
376 * returning it. 350 * returning it.
377 */ 351 */
378 vm_fault_t handle_userfault(struct vm_fault *v 352 vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
379 { 353 {
380 struct vm_area_struct *vma = vmf->vma; !! 354 struct mm_struct *mm = vmf->vma->vm_mm;
381 struct mm_struct *mm = vma->vm_mm; <<
382 struct userfaultfd_ctx *ctx; 355 struct userfaultfd_ctx *ctx;
383 struct userfaultfd_wait_queue uwq; 356 struct userfaultfd_wait_queue uwq;
384 vm_fault_t ret = VM_FAULT_SIGBUS; 357 vm_fault_t ret = VM_FAULT_SIGBUS;
385 bool must_wait; !! 358 bool must_wait, return_to_userland;
386 unsigned int blocking_state; !! 359 long blocking_state;
387 360
388 /* 361 /*
389 * We don't do userfault handling for 362 * We don't do userfault handling for the final child pid update.
390 * 363 *
391 * We also don't do userfault handling 364 * We also don't do userfault handling during
392 * coredumping. hugetlbfs has the spec 365 * coredumping. hugetlbfs has the special
393 * hugetlb_follow_page_mask() to skip !! 366 * follow_hugetlb_page() to skip missing pages in the
394 * FOLL_DUMP case, anon memory also ch 367 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
395 * the no_page_table() helper in follo 368 * the no_page_table() helper in follow_page_mask(), but the
396 * shmem_vm_ops->fault method is invok 369 * shmem_vm_ops->fault method is invoked even during
397 * coredumping and it ends up here. !! 370 * coredumping without mmap_sem and it ends up here.
398 */ 371 */
399 if (current->flags & (PF_EXITING|PF_DU 372 if (current->flags & (PF_EXITING|PF_DUMPCORE))
400 goto out; 373 goto out;
401 374
402 assert_fault_locked(vmf); !! 375 /*
>> 376 * Coredumping runs without mmap_sem so we can only check that
>> 377 * the mmap_sem is held, if PF_DUMPCORE was not set.
>> 378 */
>> 379 WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
403 380
404 ctx = vma->vm_userfaultfd_ctx.ctx; !! 381 ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
405 if (!ctx) 382 if (!ctx)
406 goto out; 383 goto out;
407 384
408 BUG_ON(ctx->mm != mm); 385 BUG_ON(ctx->mm != mm);
409 386
410 /* Any unrecognized flag is a bug. */ !! 387 VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));
411 VM_BUG_ON(reason & ~__VM_UFFD_FLAGS); !! 388 VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));
412 /* 0 or > 1 flags set is a bug; we exp <<
413 VM_BUG_ON(!reason || (reason & (reason <<
414 389
415 if (ctx->features & UFFD_FEATURE_SIGBU 390 if (ctx->features & UFFD_FEATURE_SIGBUS)
416 goto out; 391 goto out;
417 if (!(vmf->flags & FAULT_FLAG_USER) && <<
418 goto out; <<
419 392
420 /* 393 /*
421 * If it's already released don't get 394 * If it's already released don't get it. This avoids to loop
422 * in __get_user_pages if userfaultfd_ 395 * in __get_user_pages if userfaultfd_release waits on the
423 * caller of handle_userfault to relea !! 396 * caller of handle_userfault to release the mmap_sem.
424 */ 397 */
425 if (unlikely(READ_ONCE(ctx->released)) 398 if (unlikely(READ_ONCE(ctx->released))) {
426 /* 399 /*
427 * Don't return VM_FAULT_SIGBU 400 * Don't return VM_FAULT_SIGBUS in this case, so a non
428 * cooperative manager can clo 401 * cooperative manager can close the uffd after the
429 * last UFFDIO_COPY, without r 402 * last UFFDIO_COPY, without risking to trigger an
430 * involuntary SIGBUS if the p 403 * involuntary SIGBUS if the process was starting the
431 * userfaultfd while the userf 404 * userfaultfd while the userfaultfd was still armed
432 * (but after the last UFFDIO_ 405 * (but after the last UFFDIO_COPY). If the uffd
433 * wasn't already closed when 406 * wasn't already closed when the userfault reached
434 * this point, that would norm 407 * this point, that would normally be solved by
435 * userfaultfd_must_wait retur 408 * userfaultfd_must_wait returning 'false'.
436 * 409 *
437 * If we were to return VM_FAU 410 * If we were to return VM_FAULT_SIGBUS here, the non
438 * cooperative manager would b 411 * cooperative manager would be instead forced to
439 * always call UFFDIO_UNREGIST 412 * always call UFFDIO_UNREGISTER before it can safely
440 * close the uffd. 413 * close the uffd.
441 */ 414 */
442 ret = VM_FAULT_NOPAGE; 415 ret = VM_FAULT_NOPAGE;
443 goto out; 416 goto out;
444 } 417 }
445 418
446 /* 419 /*
447 * Check that we can return VM_FAULT_R 420 * Check that we can return VM_FAULT_RETRY.
448 * 421 *
449 * NOTE: it should become possible to 422 * NOTE: it should become possible to return VM_FAULT_RETRY
450 * even if FAULT_FLAG_TRIED is set wit 423 * even if FAULT_FLAG_TRIED is set without leading to gup()
451 * -EBUSY failures, if the userfaultfd 424 * -EBUSY failures, if the userfaultfd is to be extended for
452 * VM_UFFD_WP tracking and we intend t 425 * VM_UFFD_WP tracking and we intend to arm the userfault
453 * without first stopping userland acc 426 * without first stopping userland access to the memory. For
454 * VM_UFFD_MISSING userfaults this is 427 * VM_UFFD_MISSING userfaults this is enough for now.
455 */ 428 */
456 if (unlikely(!(vmf->flags & FAULT_FLAG 429 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) {
457 /* 430 /*
458 * Validate the invariant that 431 * Validate the invariant that nowait must allow retry
459 * to be sure not to return SI 432 * to be sure not to return SIGBUS erroneously on
460 * nowait invocations. 433 * nowait invocations.
461 */ 434 */
462 BUG_ON(vmf->flags & FAULT_FLAG 435 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
463 #ifdef CONFIG_DEBUG_VM 436 #ifdef CONFIG_DEBUG_VM
464 if (printk_ratelimit()) { 437 if (printk_ratelimit()) {
465 printk(KERN_WARNING 438 printk(KERN_WARNING
466 "FAULT_FLAG_ALL 439 "FAULT_FLAG_ALLOW_RETRY missing %x\n",
467 vmf->flags); 440 vmf->flags);
468 dump_stack(); 441 dump_stack();
469 } 442 }
470 #endif 443 #endif
471 goto out; 444 goto out;
472 } 445 }
473 446
474 /* 447 /*
475 * Handle nowait, not much to do other 448 * Handle nowait, not much to do other than tell it to retry
476 * and wait. 449 * and wait.
477 */ 450 */
478 ret = VM_FAULT_RETRY; 451 ret = VM_FAULT_RETRY;
479 if (vmf->flags & FAULT_FLAG_RETRY_NOWA 452 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
480 goto out; 453 goto out;
481 454
482 /* take the reference before dropping !! 455 /* take the reference before dropping the mmap_sem */
483 userfaultfd_ctx_get(ctx); 456 userfaultfd_ctx_get(ctx);
484 457
485 init_waitqueue_func_entry(&uwq.wq, use 458 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
486 uwq.wq.private = current; 459 uwq.wq.private = current;
487 uwq.msg = userfault_msg(vmf->address, !! 460 uwq.msg = userfault_msg(vmf->address, vmf->flags, reason,
488 reason, ctx->f !! 461 ctx->features);
489 uwq.ctx = ctx; 462 uwq.ctx = ctx;
490 uwq.waken = false; 463 uwq.waken = false;
491 464
492 blocking_state = userfaultfd_get_block !! 465 return_to_userland =
493 !! 466 (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) ==
494 /* !! 467 (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE);
495 * Take the vma lock now, in order to !! 468 blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
496 * userfaultfd_huge_must_wait() later. !! 469 TASK_KILLABLE;
497 * (sleepable) vma lock can modify the <<
498 * must be before explicitly calling s <<
499 */ <<
500 if (is_vm_hugetlb_page(vma)) <<
501 hugetlb_vma_lock_read(vma); <<
502 470
503 spin_lock_irq(&ctx->fault_pending_wqh. 471 spin_lock_irq(&ctx->fault_pending_wqh.lock);
504 /* 472 /*
505 * After the __add_wait_queue the uwq 473 * After the __add_wait_queue the uwq is visible to userland
506 * through poll/read(). 474 * through poll/read().
507 */ 475 */
508 __add_wait_queue(&ctx->fault_pending_w 476 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq);
509 /* 477 /*
510 * The smp_mb() after __set_current_st 478 * The smp_mb() after __set_current_state prevents the reads
511 * following the spin_unlock to happen 479 * following the spin_unlock to happen before the list_add in
512 * __add_wait_queue. 480 * __add_wait_queue.
513 */ 481 */
514 set_current_state(blocking_state); 482 set_current_state(blocking_state);
515 spin_unlock_irq(&ctx->fault_pending_wq 483 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
516 484
517 if (!is_vm_hugetlb_page(vma)) !! 485 if (!is_vm_hugetlb_page(vmf->vma))
518 must_wait = userfaultfd_must_w !! 486 must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
>> 487 reason);
519 else 488 else
520 must_wait = userfaultfd_huge_m !! 489 must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma,
521 if (is_vm_hugetlb_page(vma)) !! 490 vmf->address,
522 hugetlb_vma_unlock_read(vma); !! 491 vmf->flags, reason);
523 release_fault_lock(vmf); !! 492 up_read(&mm->mmap_sem);
524 !! 493
525 if (likely(must_wait && !READ_ONCE(ctx !! 494 if (likely(must_wait && !READ_ONCE(ctx->released) &&
>> 495 (return_to_userland ? !signal_pending(current) :
>> 496 !fatal_signal_pending(current)))) {
526 wake_up_poll(&ctx->fd_wqh, EPO 497 wake_up_poll(&ctx->fd_wqh, EPOLLIN);
527 schedule(); 498 schedule();
>> 499 ret |= VM_FAULT_MAJOR;
>> 500
>> 501 /*
>> 502 * False wakeups can orginate even from rwsem before
>> 503 * up_read() however userfaults will wait either for a
>> 504 * targeted wakeup on the specific uwq waitqueue from
>> 505 * wake_userfault() or for signals or for uffd
>> 506 * release.
>> 507 */
>> 508 while (!READ_ONCE(uwq.waken)) {
>> 509 /*
>> 510 * This needs the full smp_store_mb()
>> 511 * guarantee as the state write must be
>> 512 * visible to other CPUs before reading
>> 513 * uwq.waken from other CPUs.
>> 514 */
>> 515 set_current_state(blocking_state);
>> 516 if (READ_ONCE(uwq.waken) ||
>> 517 READ_ONCE(ctx->released) ||
>> 518 (return_to_userland ? signal_pending(current) :
>> 519 fatal_signal_pending(current)))
>> 520 break;
>> 521 schedule();
>> 522 }
528 } 523 }
529 524
530 __set_current_state(TASK_RUNNING); 525 __set_current_state(TASK_RUNNING);
531 526
>> 527 if (return_to_userland) {
>> 528 if (signal_pending(current) &&
>> 529 !fatal_signal_pending(current)) {
>> 530 /*
>> 531 * If we got a SIGSTOP or SIGCONT and this is
>> 532 * a normal userland page fault, just let
>> 533 * userland return so the signal will be
>> 534 * handled and gdb debugging works. The page
>> 535 * fault code immediately after we return from
>> 536 * this function is going to release the
>> 537 * mmap_sem and it's not depending on it
>> 538 * (unlike gup would if we were not to return
>> 539 * VM_FAULT_RETRY).
>> 540 *
>> 541 * If a fatal signal is pending we still take
>> 542 * the streamlined VM_FAULT_RETRY failure path
>> 543 * and there's no need to retake the mmap_sem
>> 544 * in such case.
>> 545 */
>> 546 down_read(&mm->mmap_sem);
>> 547 ret = VM_FAULT_NOPAGE;
>> 548 }
>> 549 }
>> 550
532 /* 551 /*
533 * Here we race with the list_del; lis 552 * Here we race with the list_del; list_add in
534 * userfaultfd_ctx_read(), however bec 553 * userfaultfd_ctx_read(), however because we don't ever run
535 * list_del_init() to refile across th 554 * list_del_init() to refile across the two lists, the prev
536 * and next pointers will never point 555 * and next pointers will never point to self. list_add also
537 * would never let any of the two poin 556 * would never let any of the two pointers to point to
538 * self. So list_empty_careful won't r 557 * self. So list_empty_careful won't risk to see both pointers
539 * pointing to self at any time during 558 * pointing to self at any time during the list refile. The
540 * only case where list_del_init() is 559 * only case where list_del_init() is called is the full
541 * removal in the wake function and th 560 * removal in the wake function and there we don't re-list_add
542 * and it's fine not to block on the s 561 * and it's fine not to block on the spinlock. The uwq on this
543 * kernel stack can be released after 562 * kernel stack can be released after the list_del_init.
544 */ 563 */
545 if (!list_empty_careful(&uwq.wq.entry) 564 if (!list_empty_careful(&uwq.wq.entry)) {
546 spin_lock_irq(&ctx->fault_pend 565 spin_lock_irq(&ctx->fault_pending_wqh.lock);
547 /* 566 /*
548 * No need of list_del_init(), 567 * No need of list_del_init(), the uwq on the stack
549 * will be freed shortly anywa 568 * will be freed shortly anyway.
550 */ 569 */
551 list_del(&uwq.wq.entry); 570 list_del(&uwq.wq.entry);
552 spin_unlock_irq(&ctx->fault_pe 571 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
553 } 572 }
554 573
555 /* 574 /*
556 * ctx may go away after this if the u 575 * ctx may go away after this if the userfault pseudo fd is
557 * already released. 576 * already released.
558 */ 577 */
559 userfaultfd_ctx_put(ctx); 578 userfaultfd_ctx_put(ctx);
560 579
561 out: 580 out:
562 return ret; 581 return ret;
563 } 582 }
564 583
565 static void userfaultfd_event_wait_completion( 584 static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
566 585 struct userfaultfd_wait_queue *ewq)
567 { 586 {
568 struct userfaultfd_ctx *release_new_ct 587 struct userfaultfd_ctx *release_new_ctx;
569 588
570 if (WARN_ON_ONCE(current->flags & PF_E 589 if (WARN_ON_ONCE(current->flags & PF_EXITING))
571 goto out; 590 goto out;
572 591
573 ewq->ctx = ctx; 592 ewq->ctx = ctx;
574 init_waitqueue_entry(&ewq->wq, current 593 init_waitqueue_entry(&ewq->wq, current);
575 release_new_ctx = NULL; 594 release_new_ctx = NULL;
576 595
577 spin_lock_irq(&ctx->event_wqh.lock); 596 spin_lock_irq(&ctx->event_wqh.lock);
578 /* 597 /*
579 * After the __add_wait_queue the uwq 598 * After the __add_wait_queue the uwq is visible to userland
580 * through poll/read(). 599 * through poll/read().
581 */ 600 */
582 __add_wait_queue(&ctx->event_wqh, &ewq 601 __add_wait_queue(&ctx->event_wqh, &ewq->wq);
583 for (;;) { 602 for (;;) {
584 set_current_state(TASK_KILLABL 603 set_current_state(TASK_KILLABLE);
585 if (ewq->msg.event == 0) 604 if (ewq->msg.event == 0)
586 break; 605 break;
587 if (READ_ONCE(ctx->released) | 606 if (READ_ONCE(ctx->released) ||
588 fatal_signal_pending(curre 607 fatal_signal_pending(current)) {
589 /* 608 /*
590 * &ewq->wq may be que 609 * &ewq->wq may be queued in fork_event, but
591 * __remove_wait_queue 610 * __remove_wait_queue ignores the head
592 * parameter. It would 611 * parameter. It would be a problem if it
593 * didn't. 612 * didn't.
594 */ 613 */
595 __remove_wait_queue(&c 614 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
596 if (ewq->msg.event == 615 if (ewq->msg.event == UFFD_EVENT_FORK) {
597 struct userfau 616 struct userfaultfd_ctx *new;
598 617
599 new = (struct 618 new = (struct userfaultfd_ctx *)
600 (unsig 619 (unsigned long)
601 ewq->m 620 ewq->msg.arg.reserved.reserved1;
602 release_new_ct 621 release_new_ctx = new;
603 } 622 }
604 break; 623 break;
605 } 624 }
606 625
607 spin_unlock_irq(&ctx->event_wq 626 spin_unlock_irq(&ctx->event_wqh.lock);
608 627
609 wake_up_poll(&ctx->fd_wqh, EPO 628 wake_up_poll(&ctx->fd_wqh, EPOLLIN);
610 schedule(); 629 schedule();
611 630
612 spin_lock_irq(&ctx->event_wqh. 631 spin_lock_irq(&ctx->event_wqh.lock);
613 } 632 }
614 __set_current_state(TASK_RUNNING); 633 __set_current_state(TASK_RUNNING);
615 spin_unlock_irq(&ctx->event_wqh.lock); 634 spin_unlock_irq(&ctx->event_wqh.lock);
616 635
617 if (release_new_ctx) { 636 if (release_new_ctx) {
618 struct vm_area_struct *vma; 637 struct vm_area_struct *vma;
619 struct mm_struct *mm = release 638 struct mm_struct *mm = release_new_ctx->mm;
620 VMA_ITERATOR(vmi, mm, 0); <<
621 639
622 /* the various vma->vm_userfau 640 /* the various vma->vm_userfaultfd_ctx still points to it */
623 mmap_write_lock(mm); !! 641 down_write(&mm->mmap_sem);
624 for_each_vma(vmi, vma) { !! 642 /* no task can run (and in turn coredump) yet */
>> 643 VM_WARN_ON(!mmget_still_valid(mm));
>> 644 for (vma = mm->mmap; vma; vma = vma->vm_next)
625 if (vma->vm_userfaultf 645 if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
626 vma_start_writ <<
627 vma->vm_userfa 646 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
628 userfaultfd_se !! 647 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
629 <<
630 } 648 }
631 } !! 649 up_write(&mm->mmap_sem);
632 mmap_write_unlock(mm); <<
633 650
634 userfaultfd_ctx_put(release_ne 651 userfaultfd_ctx_put(release_new_ctx);
635 } 652 }
636 653
637 /* 654 /*
638 * ctx may go away after this if the u 655 * ctx may go away after this if the userfault pseudo fd is
639 * already released. 656 * already released.
640 */ 657 */
641 out: 658 out:
642 atomic_dec(&ctx->mmap_changing); !! 659 WRITE_ONCE(ctx->mmap_changing, false);
643 VM_BUG_ON(atomic_read(&ctx->mmap_chang <<
644 userfaultfd_ctx_put(ctx); 660 userfaultfd_ctx_put(ctx);
645 } 661 }
646 662
647 static void userfaultfd_event_complete(struct 663 static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx,
648 struct 664 struct userfaultfd_wait_queue *ewq)
649 { 665 {
650 ewq->msg.event = 0; 666 ewq->msg.event = 0;
651 wake_up_locked(&ctx->event_wqh); 667 wake_up_locked(&ctx->event_wqh);
652 __remove_wait_queue(&ctx->event_wqh, & 668 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
653 } 669 }
654 670
655 int dup_userfaultfd(struct vm_area_struct *vma 671 int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
656 { 672 {
657 struct userfaultfd_ctx *ctx = NULL, *o 673 struct userfaultfd_ctx *ctx = NULL, *octx;
658 struct userfaultfd_fork_ctx *fctx; 674 struct userfaultfd_fork_ctx *fctx;
659 675
660 octx = vma->vm_userfaultfd_ctx.ctx; 676 octx = vma->vm_userfaultfd_ctx.ctx;
661 if (!octx) !! 677 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
662 return 0; <<
663 <<
664 if (!(octx->features & UFFD_FEATURE_EV <<
665 vma_start_write(vma); <<
666 vma->vm_userfaultfd_ctx = NULL 678 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
667 userfaultfd_set_vm_flags(vma, !! 679 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
668 return 0; 680 return 0;
669 } 681 }
670 682
671 list_for_each_entry(fctx, fcs, list) 683 list_for_each_entry(fctx, fcs, list)
672 if (fctx->orig == octx) { 684 if (fctx->orig == octx) {
673 ctx = fctx->new; 685 ctx = fctx->new;
674 break; 686 break;
675 } 687 }
676 688
677 if (!ctx) { 689 if (!ctx) {
678 fctx = kmalloc(sizeof(*fctx), 690 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL);
679 if (!fctx) 691 if (!fctx)
680 return -ENOMEM; 692 return -ENOMEM;
681 693
682 ctx = kmem_cache_alloc(userfau 694 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
683 if (!ctx) { 695 if (!ctx) {
684 kfree(fctx); 696 kfree(fctx);
685 return -ENOMEM; 697 return -ENOMEM;
686 } 698 }
687 699
688 refcount_set(&ctx->refcount, 1 700 refcount_set(&ctx->refcount, 1);
689 ctx->flags = octx->flags; 701 ctx->flags = octx->flags;
>> 702 ctx->state = UFFD_STATE_RUNNING;
690 ctx->features = octx->features 703 ctx->features = octx->features;
691 ctx->released = false; 704 ctx->released = false;
692 init_rwsem(&ctx->map_changing_ !! 705 ctx->mmap_changing = false;
693 atomic_set(&ctx->mmap_changing <<
694 ctx->mm = vma->vm_mm; 706 ctx->mm = vma->vm_mm;
695 mmgrab(ctx->mm); 707 mmgrab(ctx->mm);
696 708
697 userfaultfd_ctx_get(octx); 709 userfaultfd_ctx_get(octx);
698 down_write(&octx->map_changing !! 710 WRITE_ONCE(octx->mmap_changing, true);
699 atomic_inc(&octx->mmap_changin <<
700 up_write(&octx->map_changing_l <<
701 fctx->orig = octx; 711 fctx->orig = octx;
702 fctx->new = ctx; 712 fctx->new = ctx;
703 list_add_tail(&fctx->list, fcs 713 list_add_tail(&fctx->list, fcs);
704 } 714 }
705 715
706 vma->vm_userfaultfd_ctx.ctx = ctx; 716 vma->vm_userfaultfd_ctx.ctx = ctx;
707 return 0; 717 return 0;
708 } 718 }
709 719
710 static void dup_fctx(struct userfaultfd_fork_c 720 static void dup_fctx(struct userfaultfd_fork_ctx *fctx)
711 { 721 {
712 struct userfaultfd_ctx *ctx = fctx->or 722 struct userfaultfd_ctx *ctx = fctx->orig;
713 struct userfaultfd_wait_queue ewq; 723 struct userfaultfd_wait_queue ewq;
714 724
715 msg_init(&ewq.msg); 725 msg_init(&ewq.msg);
716 726
717 ewq.msg.event = UFFD_EVENT_FORK; 727 ewq.msg.event = UFFD_EVENT_FORK;
718 ewq.msg.arg.reserved.reserved1 = (unsi 728 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new;
719 729
720 userfaultfd_event_wait_completion(ctx, 730 userfaultfd_event_wait_completion(ctx, &ewq);
721 } 731 }
722 732
723 void dup_userfaultfd_complete(struct list_head 733 void dup_userfaultfd_complete(struct list_head *fcs)
724 { 734 {
725 struct userfaultfd_fork_ctx *fctx, *n; 735 struct userfaultfd_fork_ctx *fctx, *n;
726 736
727 list_for_each_entry_safe(fctx, n, fcs, 737 list_for_each_entry_safe(fctx, n, fcs, list) {
728 dup_fctx(fctx); 738 dup_fctx(fctx);
729 list_del(&fctx->list); 739 list_del(&fctx->list);
730 kfree(fctx); 740 kfree(fctx);
731 } 741 }
732 } 742 }
733 743
734 void mremap_userfaultfd_prep(struct vm_area_st 744 void mremap_userfaultfd_prep(struct vm_area_struct *vma,
735 struct vm_userfau 745 struct vm_userfaultfd_ctx *vm_ctx)
736 { 746 {
737 struct userfaultfd_ctx *ctx; 747 struct userfaultfd_ctx *ctx;
738 748
739 ctx = vma->vm_userfaultfd_ctx.ctx; 749 ctx = vma->vm_userfaultfd_ctx.ctx;
740 750
741 if (!ctx) 751 if (!ctx)
742 return; 752 return;
743 753
744 if (ctx->features & UFFD_FEATURE_EVENT 754 if (ctx->features & UFFD_FEATURE_EVENT_REMAP) {
745 vm_ctx->ctx = ctx; 755 vm_ctx->ctx = ctx;
746 userfaultfd_ctx_get(ctx); 756 userfaultfd_ctx_get(ctx);
747 down_write(&ctx->map_changing_ !! 757 WRITE_ONCE(ctx->mmap_changing, true);
748 atomic_inc(&ctx->mmap_changing <<
749 up_write(&ctx->map_changing_lo <<
750 } else { 758 } else {
751 /* Drop uffd context if remap 759 /* Drop uffd context if remap feature not enabled */
752 vma_start_write(vma); <<
753 vma->vm_userfaultfd_ctx = NULL 760 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
754 userfaultfd_set_vm_flags(vma, !! 761 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
755 } 762 }
756 } 763 }
757 764
758 void mremap_userfaultfd_complete(struct vm_use 765 void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx,
759 unsigned long 766 unsigned long from, unsigned long to,
760 unsigned long 767 unsigned long len)
761 { 768 {
762 struct userfaultfd_ctx *ctx = vm_ctx-> 769 struct userfaultfd_ctx *ctx = vm_ctx->ctx;
763 struct userfaultfd_wait_queue ewq; 770 struct userfaultfd_wait_queue ewq;
764 771
765 if (!ctx) 772 if (!ctx)
766 return; 773 return;
767 774
768 if (to & ~PAGE_MASK) { 775 if (to & ~PAGE_MASK) {
769 userfaultfd_ctx_put(ctx); 776 userfaultfd_ctx_put(ctx);
770 return; 777 return;
771 } 778 }
772 779
773 msg_init(&ewq.msg); 780 msg_init(&ewq.msg);
774 781
775 ewq.msg.event = UFFD_EVENT_REMAP; 782 ewq.msg.event = UFFD_EVENT_REMAP;
776 ewq.msg.arg.remap.from = from; 783 ewq.msg.arg.remap.from = from;
777 ewq.msg.arg.remap.to = to; 784 ewq.msg.arg.remap.to = to;
778 ewq.msg.arg.remap.len = len; 785 ewq.msg.arg.remap.len = len;
779 786
780 userfaultfd_event_wait_completion(ctx, 787 userfaultfd_event_wait_completion(ctx, &ewq);
781 } 788 }
782 789
783 bool userfaultfd_remove(struct vm_area_struct 790 bool userfaultfd_remove(struct vm_area_struct *vma,
784 unsigned long start, u 791 unsigned long start, unsigned long end)
785 { 792 {
786 struct mm_struct *mm = vma->vm_mm; 793 struct mm_struct *mm = vma->vm_mm;
787 struct userfaultfd_ctx *ctx; 794 struct userfaultfd_ctx *ctx;
788 struct userfaultfd_wait_queue ewq; 795 struct userfaultfd_wait_queue ewq;
789 796
790 ctx = vma->vm_userfaultfd_ctx.ctx; 797 ctx = vma->vm_userfaultfd_ctx.ctx;
791 if (!ctx || !(ctx->features & UFFD_FEA 798 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE))
792 return true; 799 return true;
793 800
794 userfaultfd_ctx_get(ctx); 801 userfaultfd_ctx_get(ctx);
795 down_write(&ctx->map_changing_lock); !! 802 WRITE_ONCE(ctx->mmap_changing, true);
796 atomic_inc(&ctx->mmap_changing); !! 803 up_read(&mm->mmap_sem);
797 up_write(&ctx->map_changing_lock); <<
798 mmap_read_unlock(mm); <<
799 804
800 msg_init(&ewq.msg); 805 msg_init(&ewq.msg);
801 806
802 ewq.msg.event = UFFD_EVENT_REMOVE; 807 ewq.msg.event = UFFD_EVENT_REMOVE;
803 ewq.msg.arg.remove.start = start; 808 ewq.msg.arg.remove.start = start;
804 ewq.msg.arg.remove.end = end; 809 ewq.msg.arg.remove.end = end;
805 810
806 userfaultfd_event_wait_completion(ctx, 811 userfaultfd_event_wait_completion(ctx, &ewq);
807 812
808 return false; 813 return false;
809 } 814 }
810 815
811 static bool has_unmap_ctx(struct userfaultfd_c 816 static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
812 unsigned long start, 817 unsigned long start, unsigned long end)
813 { 818 {
814 struct userfaultfd_unmap_ctx *unmap_ct 819 struct userfaultfd_unmap_ctx *unmap_ctx;
815 820
816 list_for_each_entry(unmap_ctx, unmaps, 821 list_for_each_entry(unmap_ctx, unmaps, list)
817 if (unmap_ctx->ctx == ctx && u 822 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start &&
818 unmap_ctx->end == end) 823 unmap_ctx->end == end)
819 return true; 824 return true;
820 825
821 return false; 826 return false;
822 } 827 }
823 828
824 int userfaultfd_unmap_prep(struct vm_area_stru !! 829 int userfaultfd_unmap_prep(struct vm_area_struct *vma,
825 unsigned long end, !! 830 unsigned long start, unsigned long end,
826 { !! 831 struct list_head *unmaps)
827 struct userfaultfd_unmap_ctx *unmap_ct !! 832 {
828 struct userfaultfd_ctx *ctx = vma->vm_ !! 833 for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
>> 834 struct userfaultfd_unmap_ctx *unmap_ctx;
>> 835 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
829 836
830 if (!ctx || !(ctx->features & UFFD_FEA !! 837 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) ||
831 has_unmap_ctx(ctx, unmaps, start, !! 838 has_unmap_ctx(ctx, unmaps, start, end))
832 return 0; !! 839 continue;
833 840
834 unmap_ctx = kzalloc(sizeof(*unmap_ctx) !! 841 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL);
835 if (!unmap_ctx) !! 842 if (!unmap_ctx)
836 return -ENOMEM; !! 843 return -ENOMEM;
837 844
838 userfaultfd_ctx_get(ctx); !! 845 userfaultfd_ctx_get(ctx);
839 down_write(&ctx->map_changing_lock); !! 846 WRITE_ONCE(ctx->mmap_changing, true);
840 atomic_inc(&ctx->mmap_changing); !! 847 unmap_ctx->ctx = ctx;
841 up_write(&ctx->map_changing_lock); !! 848 unmap_ctx->start = start;
842 unmap_ctx->ctx = ctx; !! 849 unmap_ctx->end = end;
843 unmap_ctx->start = start; !! 850 list_add_tail(&unmap_ctx->list, unmaps);
844 unmap_ctx->end = end; !! 851 }
845 list_add_tail(&unmap_ctx->list, unmaps <<
846 852
847 return 0; 853 return 0;
848 } 854 }
849 855
850 void userfaultfd_unmap_complete(struct mm_stru 856 void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
851 { 857 {
852 struct userfaultfd_unmap_ctx *ctx, *n; 858 struct userfaultfd_unmap_ctx *ctx, *n;
853 struct userfaultfd_wait_queue ewq; 859 struct userfaultfd_wait_queue ewq;
854 860
855 list_for_each_entry_safe(ctx, n, uf, l 861 list_for_each_entry_safe(ctx, n, uf, list) {
856 msg_init(&ewq.msg); 862 msg_init(&ewq.msg);
857 863
858 ewq.msg.event = UFFD_EVENT_UNM 864 ewq.msg.event = UFFD_EVENT_UNMAP;
859 ewq.msg.arg.remove.start = ctx 865 ewq.msg.arg.remove.start = ctx->start;
860 ewq.msg.arg.remove.end = ctx-> 866 ewq.msg.arg.remove.end = ctx->end;
861 867
862 userfaultfd_event_wait_complet 868 userfaultfd_event_wait_completion(ctx->ctx, &ewq);
863 869
864 list_del(&ctx->list); 870 list_del(&ctx->list);
865 kfree(ctx); 871 kfree(ctx);
866 } 872 }
867 } 873 }
868 874
869 static int userfaultfd_release(struct inode *i 875 static int userfaultfd_release(struct inode *inode, struct file *file)
870 { 876 {
871 struct userfaultfd_ctx *ctx = file->pr 877 struct userfaultfd_ctx *ctx = file->private_data;
872 struct mm_struct *mm = ctx->mm; 878 struct mm_struct *mm = ctx->mm;
873 struct vm_area_struct *vma, *prev; 879 struct vm_area_struct *vma, *prev;
874 /* len == 0 means wake all */ 880 /* len == 0 means wake all */
875 struct userfaultfd_wake_range range = 881 struct userfaultfd_wake_range range = { .len = 0, };
876 unsigned long new_flags; 882 unsigned long new_flags;
877 VMA_ITERATOR(vmi, mm, 0); !! 883 bool still_valid;
878 884
879 WRITE_ONCE(ctx->released, true); 885 WRITE_ONCE(ctx->released, true);
880 886
881 if (!mmget_not_zero(mm)) 887 if (!mmget_not_zero(mm))
882 goto wakeup; 888 goto wakeup;
883 889
884 /* 890 /*
885 * Flush page faults out of all CPUs. 891 * Flush page faults out of all CPUs. NOTE: all page faults
886 * must be retried without returning V 892 * must be retried without returning VM_FAULT_SIGBUS if
887 * userfaultfd_ctx_get() succeeds but 893 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
888 * changes while handle_userfault rele !! 894 * changes while handle_userfault released the mmap_sem. So
889 * it's critical that released is set 895 * it's critical that released is set to true (above), before
890 * taking the mmap_lock for writing. !! 896 * taking the mmap_sem for writing.
891 */ 897 */
892 mmap_write_lock(mm); !! 898 down_write(&mm->mmap_sem);
>> 899 still_valid = mmget_still_valid(mm);
893 prev = NULL; 900 prev = NULL;
894 for_each_vma(vmi, vma) { !! 901 for (vma = mm->mmap; vma; vma = vma->vm_next) {
895 cond_resched(); 902 cond_resched();
896 BUG_ON(!!vma->vm_userfaultfd_c 903 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
897 !!(vma->vm_flags & __VM !! 904 !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
898 if (vma->vm_userfaultfd_ctx.ct 905 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
899 prev = vma; 906 prev = vma;
900 continue; 907 continue;
901 } 908 }
902 /* Reset ptes for the whole vm !! 909 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
903 if (userfaultfd_wp(vma)) !! 910 if (still_valid) {
904 uffd_wp_range(vma, vma !! 911 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
905 vma->vm_ !! 912 new_flags, vma->anon_vma,
906 new_flags = vma->vm_flags & ~_ !! 913 vma->vm_file, vma->vm_pgoff,
907 vma = vma_modify_flags_uffd(&v !! 914 vma_policy(vma),
908 vm !! 915 NULL_VM_UFFD_CTX);
909 NU !! 916 if (prev)
910 !! 917 vma = prev;
911 vma_start_write(vma); !! 918 else
912 userfaultfd_set_vm_flags(vma, !! 919 prev = vma;
>> 920 }
>> 921 vma->vm_flags = new_flags;
913 vma->vm_userfaultfd_ctx = NULL 922 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
914 <<
915 prev = vma; <<
916 } 923 }
917 mmap_write_unlock(mm); !! 924 up_write(&mm->mmap_sem);
918 mmput(mm); 925 mmput(mm);
919 wakeup: 926 wakeup:
920 /* 927 /*
921 * After no new page faults can wait o 928 * After no new page faults can wait on this fault_*wqh, flush
922 * the last page faults that may have 929 * the last page faults that may have been already waiting on
923 * the fault_*wqh. 930 * the fault_*wqh.
924 */ 931 */
925 spin_lock_irq(&ctx->fault_pending_wqh. 932 spin_lock_irq(&ctx->fault_pending_wqh.lock);
926 __wake_up_locked_key(&ctx->fault_pendi 933 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
927 __wake_up(&ctx->fault_wqh, TASK_NORMAL 934 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range);
928 spin_unlock_irq(&ctx->fault_pending_wq 935 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
929 936
930 /* Flush pending events that may still 937 /* Flush pending events that may still wait on event_wqh */
931 wake_up_all(&ctx->event_wqh); 938 wake_up_all(&ctx->event_wqh);
932 939
933 wake_up_poll(&ctx->fd_wqh, EPOLLHUP); 940 wake_up_poll(&ctx->fd_wqh, EPOLLHUP);
934 userfaultfd_ctx_put(ctx); 941 userfaultfd_ctx_put(ctx);
935 return 0; 942 return 0;
936 } 943 }
937 944
938 /* fault_pending_wqh.lock must be hold by the 945 /* fault_pending_wqh.lock must be hold by the caller */
939 static inline struct userfaultfd_wait_queue *f 946 static inline struct userfaultfd_wait_queue *find_userfault_in(
940 wait_queue_head_t *wqh) 947 wait_queue_head_t *wqh)
941 { 948 {
942 wait_queue_entry_t *wq; 949 wait_queue_entry_t *wq;
943 struct userfaultfd_wait_queue *uwq; 950 struct userfaultfd_wait_queue *uwq;
944 951
945 lockdep_assert_held(&wqh->lock); 952 lockdep_assert_held(&wqh->lock);
946 953
947 uwq = NULL; 954 uwq = NULL;
948 if (!waitqueue_active(wqh)) 955 if (!waitqueue_active(wqh))
949 goto out; 956 goto out;
950 /* walk in reverse to provide FIFO beh 957 /* walk in reverse to provide FIFO behavior to read userfaults */
951 wq = list_last_entry(&wqh->head, typeo 958 wq = list_last_entry(&wqh->head, typeof(*wq), entry);
952 uwq = container_of(wq, struct userfaul 959 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
953 out: 960 out:
954 return uwq; 961 return uwq;
955 } 962 }
956 963
957 static inline struct userfaultfd_wait_queue *f 964 static inline struct userfaultfd_wait_queue *find_userfault(
958 struct userfaultfd_ctx *ctx) 965 struct userfaultfd_ctx *ctx)
959 { 966 {
960 return find_userfault_in(&ctx->fault_p 967 return find_userfault_in(&ctx->fault_pending_wqh);
961 } 968 }
962 969
963 static inline struct userfaultfd_wait_queue *f 970 static inline struct userfaultfd_wait_queue *find_userfault_evt(
964 struct userfaultfd_ctx *ctx) 971 struct userfaultfd_ctx *ctx)
965 { 972 {
966 return find_userfault_in(&ctx->event_w 973 return find_userfault_in(&ctx->event_wqh);
967 } 974 }
968 975
969 static __poll_t userfaultfd_poll(struct file * 976 static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
970 { 977 {
971 struct userfaultfd_ctx *ctx = file->pr 978 struct userfaultfd_ctx *ctx = file->private_data;
972 __poll_t ret; 979 __poll_t ret;
973 980
974 poll_wait(file, &ctx->fd_wqh, wait); 981 poll_wait(file, &ctx->fd_wqh, wait);
975 982
976 if (!userfaultfd_is_initialized(ctx)) !! 983 switch (ctx->state) {
>> 984 case UFFD_STATE_WAIT_API:
977 return EPOLLERR; 985 return EPOLLERR;
>> 986 case UFFD_STATE_RUNNING:
>> 987 /*
>> 988 * poll() never guarantees that read won't block.
>> 989 * userfaults can be waken before they're read().
>> 990 */
>> 991 if (unlikely(!(file->f_flags & O_NONBLOCK)))
>> 992 return EPOLLERR;
>> 993 /*
>> 994 * lockless access to see if there are pending faults
>> 995 * __pollwait last action is the add_wait_queue but
>> 996 * the spin_unlock would allow the waitqueue_active to
>> 997 * pass above the actual list_add inside
>> 998 * add_wait_queue critical section. So use a full
>> 999 * memory barrier to serialize the list_add write of
>> 1000 * add_wait_queue() with the waitqueue_active read
>> 1001 * below.
>> 1002 */
>> 1003 ret = 0;
>> 1004 smp_mb();
>> 1005 if (waitqueue_active(&ctx->fault_pending_wqh))
>> 1006 ret = EPOLLIN;
>> 1007 else if (waitqueue_active(&ctx->event_wqh))
>> 1008 ret = EPOLLIN;
978 1009
979 /* !! 1010 return ret;
980 * poll() never guarantees that read w !! 1011 default:
981 * userfaults can be waken before they !! 1012 WARN_ON_ONCE(1);
982 */ <<
983 if (unlikely(!(file->f_flags & O_NONBL <<
984 return EPOLLERR; 1013 return EPOLLERR;
985 /* !! 1014 }
986 * lockless access to see if there are <<
987 * __pollwait last action is the add_w <<
988 * the spin_unlock would allow the wai <<
989 * pass above the actual list_add insi <<
990 * add_wait_queue critical section. So <<
991 * memory barrier to serialize the lis <<
992 * add_wait_queue() with the waitqueue <<
993 * below. <<
994 */ <<
995 ret = 0; <<
996 smp_mb(); <<
997 if (waitqueue_active(&ctx->fault_pendi <<
998 ret = EPOLLIN; <<
999 else if (waitqueue_active(&ctx->event_ <<
1000 ret = EPOLLIN; <<
1001 <<
1002 return ret; <<
1003 } 1015 }
1004 1016
1005 static const struct file_operations userfault 1017 static const struct file_operations userfaultfd_fops;
1006 1018
1007 static int resolve_userfault_fork(struct user !! 1019 static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
1008 struct inod !! 1020 struct userfaultfd_ctx *new,
1009 struct uffd 1021 struct uffd_msg *msg)
1010 { 1022 {
1011 int fd; 1023 int fd;
1012 1024
1013 fd = anon_inode_create_getfd("[userfa !! 1025 fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new,
1014 O_RDONLY | (new->flag !! 1026 O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS));
1015 if (fd < 0) 1027 if (fd < 0)
1016 return fd; 1028 return fd;
1017 1029
1018 msg->arg.reserved.reserved1 = 0; 1030 msg->arg.reserved.reserved1 = 0;
1019 msg->arg.fork.ufd = fd; 1031 msg->arg.fork.ufd = fd;
1020 return 0; 1032 return 0;
1021 } 1033 }
1022 1034
1023 static ssize_t userfaultfd_ctx_read(struct us 1035 static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
1024 struct uf !! 1036 struct uffd_msg *msg)
1025 { 1037 {
1026 ssize_t ret; 1038 ssize_t ret;
1027 DECLARE_WAITQUEUE(wait, current); 1039 DECLARE_WAITQUEUE(wait, current);
1028 struct userfaultfd_wait_queue *uwq; 1040 struct userfaultfd_wait_queue *uwq;
1029 /* 1041 /*
1030 * Handling fork event requires sleep 1042 * Handling fork event requires sleeping operations, so
1031 * we drop the event_wqh lock, then d 1043 * we drop the event_wqh lock, then do these ops, then
1032 * lock it back and wake up the waite 1044 * lock it back and wake up the waiter. While the lock is
1033 * dropped the ewq may go away so we 1045 * dropped the ewq may go away so we keep track of it
1034 * carefully. 1046 * carefully.
1035 */ 1047 */
1036 LIST_HEAD(fork_event); 1048 LIST_HEAD(fork_event);
1037 struct userfaultfd_ctx *fork_nctx = N 1049 struct userfaultfd_ctx *fork_nctx = NULL;
1038 1050
1039 /* always take the fd_wqh lock before 1051 /* always take the fd_wqh lock before the fault_pending_wqh lock */
1040 spin_lock_irq(&ctx->fd_wqh.lock); 1052 spin_lock_irq(&ctx->fd_wqh.lock);
1041 __add_wait_queue(&ctx->fd_wqh, &wait) 1053 __add_wait_queue(&ctx->fd_wqh, &wait);
1042 for (;;) { 1054 for (;;) {
1043 set_current_state(TASK_INTERR 1055 set_current_state(TASK_INTERRUPTIBLE);
1044 spin_lock(&ctx->fault_pending 1056 spin_lock(&ctx->fault_pending_wqh.lock);
1045 uwq = find_userfault(ctx); 1057 uwq = find_userfault(ctx);
1046 if (uwq) { 1058 if (uwq) {
1047 /* 1059 /*
1048 * Use a seqcount to 1060 * Use a seqcount to repeat the lockless check
1049 * in wake_userfault( 1061 * in wake_userfault() to avoid missing
1050 * wakeups because du 1062 * wakeups because during the refile both
1051 * waitqueue could be 1063 * waitqueue could become empty if this is the
1052 * only userfault. 1064 * only userfault.
1053 */ 1065 */
1054 write_seqcount_begin( 1066 write_seqcount_begin(&ctx->refile_seq);
1055 1067
1056 /* 1068 /*
1057 * The fault_pending_ 1069 * The fault_pending_wqh.lock prevents the uwq
1058 * to disappear from 1070 * to disappear from under us.
1059 * 1071 *
1060 * Refile this userfa 1072 * Refile this userfault from
1061 * fault_pending_wqh 1073 * fault_pending_wqh to fault_wqh, it's not
1062 * pending anymore af 1074 * pending anymore after we read it.
1063 * 1075 *
1064 * Use list_del() by 1076 * Use list_del() by hand (as
1065 * userfaultfd_wake_f 1077 * userfaultfd_wake_function also uses
1066 * list_del_init() by 1078 * list_del_init() by hand) to be sure nobody
1067 * changes __remove_w 1079 * changes __remove_wait_queue() to use
1068 * list_del_init() in 1080 * list_del_init() in turn breaking the
1069 * !list_empty_carefu 1081 * !list_empty_careful() check in
1070 * handle_userfault() 1082 * handle_userfault(). The uwq->wq.head list
1071 * must never be empt 1083 * must never be empty at any time during the
1072 * refile, or the wai 1084 * refile, or the waitqueue could disappear
1073 * from under us. The 1085 * from under us. The "wait_queue_head_t"
1074 * parameter of __rem 1086 * parameter of __remove_wait_queue() is unused
1075 * anyway. 1087 * anyway.
1076 */ 1088 */
1077 list_del(&uwq->wq.ent 1089 list_del(&uwq->wq.entry);
1078 add_wait_queue(&ctx-> 1090 add_wait_queue(&ctx->fault_wqh, &uwq->wq);
1079 1091
1080 write_seqcount_end(&c 1092 write_seqcount_end(&ctx->refile_seq);
1081 1093
1082 /* careful to always 1094 /* careful to always initialize msg if ret == 0 */
1083 *msg = uwq->msg; 1095 *msg = uwq->msg;
1084 spin_unlock(&ctx->fau 1096 spin_unlock(&ctx->fault_pending_wqh.lock);
1085 ret = 0; 1097 ret = 0;
1086 break; 1098 break;
1087 } 1099 }
1088 spin_unlock(&ctx->fault_pendi 1100 spin_unlock(&ctx->fault_pending_wqh.lock);
1089 1101
1090 spin_lock(&ctx->event_wqh.loc 1102 spin_lock(&ctx->event_wqh.lock);
1091 uwq = find_userfault_evt(ctx) 1103 uwq = find_userfault_evt(ctx);
1092 if (uwq) { 1104 if (uwq) {
1093 *msg = uwq->msg; 1105 *msg = uwq->msg;
1094 1106
1095 if (uwq->msg.event == 1107 if (uwq->msg.event == UFFD_EVENT_FORK) {
1096 fork_nctx = ( 1108 fork_nctx = (struct userfaultfd_ctx *)
1097 (unsi 1109 (unsigned long)
1098 uwq-> 1110 uwq->msg.arg.reserved.reserved1;
1099 list_move(&uw 1111 list_move(&uwq->wq.entry, &fork_event);
1100 /* 1112 /*
1101 * fork_nctx 1113 * fork_nctx can be freed as soon as
1102 * we drop th 1114 * we drop the lock, unless we take a
1103 * reference 1115 * reference on it.
1104 */ 1116 */
1105 userfaultfd_c 1117 userfaultfd_ctx_get(fork_nctx);
1106 spin_unlock(& 1118 spin_unlock(&ctx->event_wqh.lock);
1107 ret = 0; 1119 ret = 0;
1108 break; 1120 break;
1109 } 1121 }
1110 1122
1111 userfaultfd_event_com 1123 userfaultfd_event_complete(ctx, uwq);
1112 spin_unlock(&ctx->eve 1124 spin_unlock(&ctx->event_wqh.lock);
1113 ret = 0; 1125 ret = 0;
1114 break; 1126 break;
1115 } 1127 }
1116 spin_unlock(&ctx->event_wqh.l 1128 spin_unlock(&ctx->event_wqh.lock);
1117 1129
1118 if (signal_pending(current)) 1130 if (signal_pending(current)) {
1119 ret = -ERESTARTSYS; 1131 ret = -ERESTARTSYS;
1120 break; 1132 break;
1121 } 1133 }
1122 if (no_wait) { 1134 if (no_wait) {
1123 ret = -EAGAIN; 1135 ret = -EAGAIN;
1124 break; 1136 break;
1125 } 1137 }
1126 spin_unlock_irq(&ctx->fd_wqh. 1138 spin_unlock_irq(&ctx->fd_wqh.lock);
1127 schedule(); 1139 schedule();
1128 spin_lock_irq(&ctx->fd_wqh.lo 1140 spin_lock_irq(&ctx->fd_wqh.lock);
1129 } 1141 }
1130 __remove_wait_queue(&ctx->fd_wqh, &wa 1142 __remove_wait_queue(&ctx->fd_wqh, &wait);
1131 __set_current_state(TASK_RUNNING); 1143 __set_current_state(TASK_RUNNING);
1132 spin_unlock_irq(&ctx->fd_wqh.lock); 1144 spin_unlock_irq(&ctx->fd_wqh.lock);
1133 1145
1134 if (!ret && msg->event == UFFD_EVENT_ 1146 if (!ret && msg->event == UFFD_EVENT_FORK) {
1135 ret = resolve_userfault_fork( !! 1147 ret = resolve_userfault_fork(ctx, fork_nctx, msg);
1136 spin_lock_irq(&ctx->event_wqh 1148 spin_lock_irq(&ctx->event_wqh.lock);
1137 if (!list_empty(&fork_event)) 1149 if (!list_empty(&fork_event)) {
1138 /* 1150 /*
1139 * The fork thread di 1151 * The fork thread didn't abort, so we can
1140 * drop the temporary 1152 * drop the temporary refcount.
1141 */ 1153 */
1142 userfaultfd_ctx_put(f 1154 userfaultfd_ctx_put(fork_nctx);
1143 1155
1144 uwq = list_first_entr 1156 uwq = list_first_entry(&fork_event,
1145 1157 typeof(*uwq),
1146 1158 wq.entry);
1147 /* 1159 /*
1148 * If fork_event list 1160 * If fork_event list wasn't empty and in turn
1149 * the event wasn't a 1161 * the event wasn't already released by fork
1150 * (the event is allo 1162 * (the event is allocated on fork kernel
1151 * stack), put the ev 1163 * stack), put the event back to its place in
1152 * the event_wq. fork 1164 * the event_wq. fork_event head will be freed
1153 * as soon as we retu 1165 * as soon as we return so the event cannot
1154 * stay queued there 1166 * stay queued there no matter the current
1155 * "ret" value. 1167 * "ret" value.
1156 */ 1168 */
1157 list_del(&uwq->wq.ent 1169 list_del(&uwq->wq.entry);
1158 __add_wait_queue(&ctx 1170 __add_wait_queue(&ctx->event_wqh, &uwq->wq);
1159 1171
1160 /* 1172 /*
1161 * Leave the event in 1173 * Leave the event in the waitqueue and report
1162 * error to userland 1174 * error to userland if we failed to resolve
1163 * the userfault fork 1175 * the userfault fork.
1164 */ 1176 */
1165 if (likely(!ret)) 1177 if (likely(!ret))
1166 userfaultfd_e 1178 userfaultfd_event_complete(ctx, uwq);
1167 } else { 1179 } else {
1168 /* 1180 /*
1169 * Here the fork thre 1181 * Here the fork thread aborted and the
1170 * refcount from the 1182 * refcount from the fork thread on fork_nctx
1171 * has already been r 1183 * has already been released. We still hold
1172 * the reference we t 1184 * the reference we took before releasing the
1173 * lock above. If res 1185 * lock above. If resolve_userfault_fork
1174 * failed we've to dr 1186 * failed we've to drop it because the
1175 * fork_nctx has to b 1187 * fork_nctx has to be freed in such case. If
1176 * it succeeded we'll 1188 * it succeeded we'll hold it because the new
1177 * uffd references it 1189 * uffd references it.
1178 */ 1190 */
1179 if (ret) 1191 if (ret)
1180 userfaultfd_c 1192 userfaultfd_ctx_put(fork_nctx);
1181 } 1193 }
1182 spin_unlock_irq(&ctx->event_w 1194 spin_unlock_irq(&ctx->event_wqh.lock);
1183 } 1195 }
1184 1196
1185 return ret; 1197 return ret;
1186 } 1198 }
1187 1199
1188 static ssize_t userfaultfd_read_iter(struct k !! 1200 static ssize_t userfaultfd_read(struct file *file, char __user *buf,
>> 1201 size_t count, loff_t *ppos)
1189 { 1202 {
1190 struct file *file = iocb->ki_filp; <<
1191 struct userfaultfd_ctx *ctx = file->p 1203 struct userfaultfd_ctx *ctx = file->private_data;
1192 ssize_t _ret, ret = 0; 1204 ssize_t _ret, ret = 0;
1193 struct uffd_msg msg; 1205 struct uffd_msg msg;
1194 struct inode *inode = file_inode(file !! 1206 int no_wait = file->f_flags & O_NONBLOCK;
1195 bool no_wait; <<
1196 1207
1197 if (!userfaultfd_is_initialized(ctx)) !! 1208 if (ctx->state == UFFD_STATE_WAIT_API)
1198 return -EINVAL; 1209 return -EINVAL;
1199 1210
1200 no_wait = file->f_flags & O_NONBLOCK <<
1201 for (;;) { 1211 for (;;) {
1202 if (iov_iter_count(to) < size !! 1212 if (count < sizeof(msg))
1203 return ret ? ret : -E 1213 return ret ? ret : -EINVAL;
1204 _ret = userfaultfd_ctx_read(c !! 1214 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
1205 if (_ret < 0) 1215 if (_ret < 0)
1206 return ret ? ret : _r 1216 return ret ? ret : _ret;
1207 _ret = !copy_to_iter_full(&ms !! 1217 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
1208 if (_ret) <<
1209 return ret ? ret : -E 1218 return ret ? ret : -EFAULT;
1210 ret += sizeof(msg); 1219 ret += sizeof(msg);
>> 1220 buf += sizeof(msg);
>> 1221 count -= sizeof(msg);
1211 /* 1222 /*
1212 * Allow to read more than on 1223 * Allow to read more than one fault at time but only
1213 * block if waiting for the v 1224 * block if waiting for the very first one.
1214 */ 1225 */
1215 no_wait = true; !! 1226 no_wait = O_NONBLOCK;
1216 } 1227 }
1217 } 1228 }
1218 1229
1219 static void __wake_userfault(struct userfault 1230 static void __wake_userfault(struct userfaultfd_ctx *ctx,
1220 struct userfault 1231 struct userfaultfd_wake_range *range)
1221 { 1232 {
1222 spin_lock_irq(&ctx->fault_pending_wqh 1233 spin_lock_irq(&ctx->fault_pending_wqh.lock);
1223 /* wake all in the range and autoremo 1234 /* wake all in the range and autoremove */
1224 if (waitqueue_active(&ctx->fault_pend 1235 if (waitqueue_active(&ctx->fault_pending_wqh))
1225 __wake_up_locked_key(&ctx->fa 1236 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
1226 range); 1237 range);
1227 if (waitqueue_active(&ctx->fault_wqh) 1238 if (waitqueue_active(&ctx->fault_wqh))
1228 __wake_up(&ctx->fault_wqh, TA 1239 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range);
1229 spin_unlock_irq(&ctx->fault_pending_w 1240 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
1230 } 1241 }
1231 1242
1232 static __always_inline void wake_userfault(st 1243 static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
1233 st 1244 struct userfaultfd_wake_range *range)
1234 { 1245 {
1235 unsigned seq; 1246 unsigned seq;
1236 bool need_wakeup; 1247 bool need_wakeup;
1237 1248
1238 /* 1249 /*
1239 * To be sure waitqueue_active() is n 1250 * To be sure waitqueue_active() is not reordered by the CPU
1240 * before the pagetable update, use a 1251 * before the pagetable update, use an explicit SMP memory
1241 * barrier here. PT lock release or m !! 1252 * barrier here. PT lock release or up_read(mmap_sem) still
1242 * have release semantics that can al 1253 * have release semantics that can allow the
1243 * waitqueue_active() to be reordered 1254 * waitqueue_active() to be reordered before the pte update.
1244 */ 1255 */
1245 smp_mb(); 1256 smp_mb();
1246 1257
1247 /* 1258 /*
1248 * Use waitqueue_active because it's 1259 * Use waitqueue_active because it's very frequent to
1249 * change the address space atomicall 1260 * change the address space atomically even if there are no
1250 * userfaults yet. So we take the spi 1261 * userfaults yet. So we take the spinlock only when we're
1251 * sure we've userfaults to wake. 1262 * sure we've userfaults to wake.
1252 */ 1263 */
1253 do { 1264 do {
1254 seq = read_seqcount_begin(&ct 1265 seq = read_seqcount_begin(&ctx->refile_seq);
1255 need_wakeup = waitqueue_activ 1266 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
1256 waitqueue_active(&ctx 1267 waitqueue_active(&ctx->fault_wqh);
1257 cond_resched(); 1268 cond_resched();
1258 } while (read_seqcount_retry(&ctx->re 1269 } while (read_seqcount_retry(&ctx->refile_seq, seq));
1259 if (need_wakeup) 1270 if (need_wakeup)
1260 __wake_userfault(ctx, range); 1271 __wake_userfault(ctx, range);
1261 } 1272 }
1262 1273
1263 static __always_inline int validate_unaligned !! 1274 static __always_inline int validate_range(struct mm_struct *mm,
1264 struct mm_struct *mm, __u64 start, __ !! 1275 __u64 *start, __u64 len)
1265 { 1276 {
1266 __u64 task_size = mm->task_size; 1277 __u64 task_size = mm->task_size;
1267 1278
>> 1279 *start = untagged_addr(*start);
>> 1280
>> 1281 if (*start & ~PAGE_MASK)
>> 1282 return -EINVAL;
1268 if (len & ~PAGE_MASK) 1283 if (len & ~PAGE_MASK)
1269 return -EINVAL; 1284 return -EINVAL;
1270 if (!len) 1285 if (!len)
1271 return -EINVAL; 1286 return -EINVAL;
1272 if (start < mmap_min_addr) !! 1287 if (*start < mmap_min_addr)
1273 return -EINVAL; <<
1274 if (start >= task_size) <<
1275 return -EINVAL; 1288 return -EINVAL;
1276 if (len > task_size - start) !! 1289 if (*start >= task_size)
1277 return -EINVAL; 1290 return -EINVAL;
1278 if (start + len <= start) !! 1291 if (len > task_size - *start)
1279 return -EINVAL; 1292 return -EINVAL;
1280 return 0; 1293 return 0;
1281 } 1294 }
1282 1295
1283 static __always_inline int validate_range(str !! 1296 static inline bool vma_can_userfault(struct vm_area_struct *vma)
1284 __u <<
1285 { 1297 {
1286 if (start & ~PAGE_MASK) !! 1298 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
1287 return -EINVAL; !! 1299 vma_is_shmem(vma);
1288 <<
1289 return validate_unaligned_range(mm, s <<
1290 } 1300 }
1291 1301
1292 static int userfaultfd_register(struct userfa 1302 static int userfaultfd_register(struct userfaultfd_ctx *ctx,
1293 unsigned long 1303 unsigned long arg)
1294 { 1304 {
1295 struct mm_struct *mm = ctx->mm; 1305 struct mm_struct *mm = ctx->mm;
1296 struct vm_area_struct *vma, *prev, *c 1306 struct vm_area_struct *vma, *prev, *cur;
1297 int ret; 1307 int ret;
1298 struct uffdio_register uffdio_registe 1308 struct uffdio_register uffdio_register;
1299 struct uffdio_register __user *user_u 1309 struct uffdio_register __user *user_uffdio_register;
1300 unsigned long vm_flags, new_flags; 1310 unsigned long vm_flags, new_flags;
1301 bool found; 1311 bool found;
1302 bool basic_ioctls; 1312 bool basic_ioctls;
1303 unsigned long start, end, vma_end; 1313 unsigned long start, end, vma_end;
1304 struct vma_iterator vmi; <<
1305 bool wp_async = userfaultfd_wp_async_ <<
1306 1314
1307 user_uffdio_register = (struct uffdio 1315 user_uffdio_register = (struct uffdio_register __user *) arg;
1308 1316
1309 ret = -EFAULT; 1317 ret = -EFAULT;
1310 if (copy_from_user(&uffdio_register, 1318 if (copy_from_user(&uffdio_register, user_uffdio_register,
1311 sizeof(uffdio_regi 1319 sizeof(uffdio_register)-sizeof(__u64)))
1312 goto out; 1320 goto out;
1313 1321
1314 ret = -EINVAL; 1322 ret = -EINVAL;
1315 if (!uffdio_register.mode) 1323 if (!uffdio_register.mode)
1316 goto out; 1324 goto out;
1317 if (uffdio_register.mode & ~UFFD_API_ !! 1325 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
>> 1326 UFFDIO_REGISTER_MODE_WP))
1318 goto out; 1327 goto out;
1319 vm_flags = 0; 1328 vm_flags = 0;
1320 if (uffdio_register.mode & UFFDIO_REG 1329 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
1321 vm_flags |= VM_UFFD_MISSING; 1330 vm_flags |= VM_UFFD_MISSING;
1322 if (uffdio_register.mode & UFFDIO_REG 1331 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
1323 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP <<
1324 goto out; <<
1325 #endif <<
1326 vm_flags |= VM_UFFD_WP; 1332 vm_flags |= VM_UFFD_WP;
1327 } !! 1333 /*
1328 if (uffdio_register.mode & UFFDIO_REG !! 1334 * FIXME: remove the below error constraint by
1329 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR !! 1335 * implementing the wprotect tracking mode.
>> 1336 */
>> 1337 ret = -EINVAL;
1330 goto out; 1338 goto out;
1331 #endif <<
1332 vm_flags |= VM_UFFD_MINOR; <<
1333 } 1339 }
1334 1340
1335 ret = validate_range(mm, uffdio_regis !! 1341 ret = validate_range(mm, &uffdio_register.range.start,
1336 uffdio_register. 1342 uffdio_register.range.len);
1337 if (ret) 1343 if (ret)
1338 goto out; 1344 goto out;
1339 1345
1340 start = uffdio_register.range.start; 1346 start = uffdio_register.range.start;
1341 end = start + uffdio_register.range.l 1347 end = start + uffdio_register.range.len;
1342 1348
1343 ret = -ENOMEM; 1349 ret = -ENOMEM;
1344 if (!mmget_not_zero(mm)) 1350 if (!mmget_not_zero(mm))
1345 goto out; 1351 goto out;
1346 1352
1347 ret = -EINVAL; !! 1353 down_write(&mm->mmap_sem);
1348 mmap_write_lock(mm); !! 1354 if (!mmget_still_valid(mm))
1349 vma_iter_init(&vmi, mm, start); !! 1355 goto out_unlock;
1350 vma = vma_find(&vmi, end); !! 1356 vma = find_vma_prev(mm, start, &prev);
1351 if (!vma) 1357 if (!vma)
1352 goto out_unlock; 1358 goto out_unlock;
1353 1359
>> 1360 /* check that there's at least one vma in the range */
>> 1361 ret = -EINVAL;
>> 1362 if (vma->vm_start >= end)
>> 1363 goto out_unlock;
>> 1364
1354 /* 1365 /*
1355 * If the first vma contains huge pag 1366 * If the first vma contains huge pages, make sure start address
1356 * is aligned to huge page size. 1367 * is aligned to huge page size.
1357 */ 1368 */
1358 if (is_vm_hugetlb_page(vma)) { 1369 if (is_vm_hugetlb_page(vma)) {
1359 unsigned long vma_hpagesize = 1370 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1360 1371
1361 if (start & (vma_hpagesize - 1372 if (start & (vma_hpagesize - 1))
1362 goto out_unlock; 1373 goto out_unlock;
1363 } 1374 }
1364 1375
1365 /* 1376 /*
1366 * Search for not compatible vmas. 1377 * Search for not compatible vmas.
1367 */ 1378 */
1368 found = false; 1379 found = false;
1369 basic_ioctls = false; 1380 basic_ioctls = false;
1370 cur = vma; !! 1381 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1371 do { <<
1372 cond_resched(); 1382 cond_resched();
1373 1383
1374 BUG_ON(!!cur->vm_userfaultfd_ 1384 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1375 !!(cur->vm_flags & __V !! 1385 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1376 1386
1377 /* check not compatible vmas 1387 /* check not compatible vmas */
1378 ret = -EINVAL; 1388 ret = -EINVAL;
1379 if (!vma_can_userfault(cur, v !! 1389 if (!vma_can_userfault(cur))
1380 goto out_unlock; 1390 goto out_unlock;
1381 1391
1382 /* 1392 /*
1383 * UFFDIO_COPY will fill file 1393 * UFFDIO_COPY will fill file holes even without
1384 * PROT_WRITE. This check enf 1394 * PROT_WRITE. This check enforces that if this is a
1385 * MAP_SHARED, the process ha 1395 * MAP_SHARED, the process has write permission to the backing
1386 * file. If VM_MAYWRITE is se 1396 * file. If VM_MAYWRITE is set it also enforces that on a
1387 * MAP_SHARED vma: there is n 1397 * MAP_SHARED vma: there is no F_WRITE_SEAL and no further
1388 * F_WRITE_SEAL can be taken 1398 * F_WRITE_SEAL can be taken until the vma is destroyed.
1389 */ 1399 */
1390 ret = -EPERM; 1400 ret = -EPERM;
1391 if (unlikely(!(cur->vm_flags 1401 if (unlikely(!(cur->vm_flags & VM_MAYWRITE)))
1392 goto out_unlock; 1402 goto out_unlock;
1393 1403
1394 /* 1404 /*
1395 * If this vma contains endin 1405 * If this vma contains ending address, and huge pages
1396 * check alignment. 1406 * check alignment.
1397 */ 1407 */
1398 if (is_vm_hugetlb_page(cur) & 1408 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
1399 end > cur->vm_start) { 1409 end > cur->vm_start) {
1400 unsigned long vma_hpa 1410 unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
1401 1411
1402 ret = -EINVAL; 1412 ret = -EINVAL;
1403 1413
1404 if (end & (vma_hpages 1414 if (end & (vma_hpagesize - 1))
1405 goto out_unlo 1415 goto out_unlock;
1406 } 1416 }
1407 if ((vm_flags & VM_UFFD_WP) & <<
1408 goto out_unlock; <<
1409 1417
1410 /* 1418 /*
1411 * Check that this vma isn't 1419 * Check that this vma isn't already owned by a
1412 * different userfaultfd. We 1420 * different userfaultfd. We can't allow more than one
1413 * userfaultfd to own a singl 1421 * userfaultfd to own a single vma simultaneously or we
1414 * wouldn't know which one to 1422 * wouldn't know which one to deliver the userfaults to.
1415 */ 1423 */
1416 ret = -EBUSY; 1424 ret = -EBUSY;
1417 if (cur->vm_userfaultfd_ctx.c 1425 if (cur->vm_userfaultfd_ctx.ctx &&
1418 cur->vm_userfaultfd_ctx.c 1426 cur->vm_userfaultfd_ctx.ctx != ctx)
1419 goto out_unlock; 1427 goto out_unlock;
1420 1428
1421 /* 1429 /*
1422 * Note vmas containing huge 1430 * Note vmas containing huge pages
1423 */ 1431 */
1424 if (is_vm_hugetlb_page(cur)) 1432 if (is_vm_hugetlb_page(cur))
1425 basic_ioctls = true; 1433 basic_ioctls = true;
1426 1434
1427 found = true; 1435 found = true;
1428 } for_each_vma_range(vmi, cur, end); !! 1436 }
1429 BUG_ON(!found); 1437 BUG_ON(!found);
1430 1438
1431 vma_iter_set(&vmi, start); <<
1432 prev = vma_prev(&vmi); <<
1433 if (vma->vm_start < start) 1439 if (vma->vm_start < start)
1434 prev = vma; 1440 prev = vma;
1435 1441
1436 ret = 0; 1442 ret = 0;
1437 for_each_vma_range(vmi, vma, end) { !! 1443 do {
1438 cond_resched(); 1444 cond_resched();
1439 1445
1440 BUG_ON(!vma_can_userfault(vma !! 1446 BUG_ON(!vma_can_userfault(vma));
1441 BUG_ON(vma->vm_userfaultfd_ct 1447 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1442 vma->vm_userfaultfd_ct 1448 vma->vm_userfaultfd_ctx.ctx != ctx);
1443 WARN_ON(!(vma->vm_flags & VM_ 1449 WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
1444 1450
1445 /* 1451 /*
1446 * Nothing to do: this vma is 1452 * Nothing to do: this vma is already registered into this
1447 * userfaultfd and with the r 1453 * userfaultfd and with the right tracking mode too.
1448 */ 1454 */
1449 if (vma->vm_userfaultfd_ctx.c 1455 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1450 (vma->vm_flags & vm_flags 1456 (vma->vm_flags & vm_flags) == vm_flags)
1451 goto skip; 1457 goto skip;
1452 1458
1453 if (vma->vm_start > start) 1459 if (vma->vm_start > start)
1454 start = vma->vm_start 1460 start = vma->vm_start;
1455 vma_end = min(end, vma->vm_en 1461 vma_end = min(end, vma->vm_end);
1456 1462
1457 new_flags = (vma->vm_flags & !! 1463 new_flags = (vma->vm_flags &
1458 vma = vma_modify_flags_uffd(& !! 1464 ~(VM_UFFD_MISSING|VM_UFFD_WP)) | vm_flags;
1459 n !! 1465 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1460 ( !! 1466 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1461 if (IS_ERR(vma)) { !! 1467 vma_policy(vma),
1462 ret = PTR_ERR(vma); !! 1468 ((struct vm_userfaultfd_ctx){ ctx }));
1463 break; !! 1469 if (prev) {
>> 1470 vma = prev;
>> 1471 goto next;
1464 } 1472 }
1465 !! 1473 if (vma->vm_start < start) {
>> 1474 ret = split_vma(mm, vma, start, 1);
>> 1475 if (ret)
>> 1476 break;
>> 1477 }
>> 1478 if (vma->vm_end > end) {
>> 1479 ret = split_vma(mm, vma, end, 0);
>> 1480 if (ret)
>> 1481 break;
>> 1482 }
>> 1483 next:
1466 /* 1484 /*
1467 * In the vma_merge() success 1485 * In the vma_merge() successful mprotect-like case 8:
1468 * the next vma was merged in 1486 * the next vma was merged into the current one and
1469 * the current one has not be 1487 * the current one has not been updated yet.
1470 */ 1488 */
1471 vma_start_write(vma); !! 1489 vma->vm_flags = new_flags;
1472 userfaultfd_set_vm_flags(vma, <<
1473 vma->vm_userfaultfd_ctx.ctx = 1490 vma->vm_userfaultfd_ctx.ctx = ctx;
1474 1491
1475 if (is_vm_hugetlb_page(vma) & <<
1476 hugetlb_unshare_all_p <<
1477 <<
1478 skip: 1492 skip:
1479 prev = vma; 1493 prev = vma;
1480 start = vma->vm_end; 1494 start = vma->vm_end;
1481 } !! 1495 vma = vma->vm_next;
1482 !! 1496 } while (vma && vma->vm_start < end);
1483 out_unlock: 1497 out_unlock:
1484 mmap_write_unlock(mm); !! 1498 up_write(&mm->mmap_sem);
1485 mmput(mm); 1499 mmput(mm);
1486 if (!ret) { 1500 if (!ret) {
1487 __u64 ioctls_out; <<
1488 <<
1489 ioctls_out = basic_ioctls ? U <<
1490 UFFD_API_RANGE_IOCTLS; <<
1491 <<
1492 /* <<
1493 * Declare the WP ioctl only <<
1494 * specified and all checks p <<
1495 */ <<
1496 if (!(uffdio_register.mode & <<
1497 ioctls_out &= ~((__u6 <<
1498 <<
1499 /* CONTINUE ioctl is only sup <<
1500 if (!(uffdio_register.mode & <<
1501 ioctls_out &= ~((__u6 <<
1502 <<
1503 /* 1501 /*
1504 * Now that we scanned all vm 1502 * Now that we scanned all vmas we can already tell
1505 * userland which ioctls meth 1503 * userland which ioctls methods are guaranteed to
1506 * succeed on this range. 1504 * succeed on this range.
1507 */ 1505 */
1508 if (put_user(ioctls_out, &use !! 1506 if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
>> 1507 UFFD_API_RANGE_IOCTLS,
>> 1508 &user_uffdio_register->ioctls))
1509 ret = -EFAULT; 1509 ret = -EFAULT;
1510 } 1510 }
1511 out: 1511 out:
1512 return ret; 1512 return ret;
1513 } 1513 }
1514 1514
1515 static int userfaultfd_unregister(struct user 1515 static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
1516 unsigned lo 1516 unsigned long arg)
1517 { 1517 {
1518 struct mm_struct *mm = ctx->mm; 1518 struct mm_struct *mm = ctx->mm;
1519 struct vm_area_struct *vma, *prev, *c 1519 struct vm_area_struct *vma, *prev, *cur;
1520 int ret; 1520 int ret;
1521 struct uffdio_range uffdio_unregister 1521 struct uffdio_range uffdio_unregister;
1522 unsigned long new_flags; 1522 unsigned long new_flags;
1523 bool found; 1523 bool found;
1524 unsigned long start, end, vma_end; 1524 unsigned long start, end, vma_end;
1525 const void __user *buf = (void __user 1525 const void __user *buf = (void __user *)arg;
1526 struct vma_iterator vmi; <<
1527 bool wp_async = userfaultfd_wp_async_ <<
1528 1526
1529 ret = -EFAULT; 1527 ret = -EFAULT;
1530 if (copy_from_user(&uffdio_unregister 1528 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
1531 goto out; 1529 goto out;
1532 1530
1533 ret = validate_range(mm, uffdio_unreg !! 1531 ret = validate_range(mm, &uffdio_unregister.start,
1534 uffdio_unregiste 1532 uffdio_unregister.len);
1535 if (ret) 1533 if (ret)
1536 goto out; 1534 goto out;
1537 1535
1538 start = uffdio_unregister.start; 1536 start = uffdio_unregister.start;
1539 end = start + uffdio_unregister.len; 1537 end = start + uffdio_unregister.len;
1540 1538
1541 ret = -ENOMEM; 1539 ret = -ENOMEM;
1542 if (!mmget_not_zero(mm)) 1540 if (!mmget_not_zero(mm))
1543 goto out; 1541 goto out;
1544 1542
1545 mmap_write_lock(mm); !! 1543 down_write(&mm->mmap_sem);
1546 ret = -EINVAL; !! 1544 if (!mmget_still_valid(mm))
1547 vma_iter_init(&vmi, mm, start); !! 1545 goto out_unlock;
1548 vma = vma_find(&vmi, end); !! 1546 vma = find_vma_prev(mm, start, &prev);
1549 if (!vma) 1547 if (!vma)
1550 goto out_unlock; 1548 goto out_unlock;
1551 1549
>> 1550 /* check that there's at least one vma in the range */
>> 1551 ret = -EINVAL;
>> 1552 if (vma->vm_start >= end)
>> 1553 goto out_unlock;
>> 1554
1552 /* 1555 /*
1553 * If the first vma contains huge pag 1556 * If the first vma contains huge pages, make sure start address
1554 * is aligned to huge page size. 1557 * is aligned to huge page size.
1555 */ 1558 */
1556 if (is_vm_hugetlb_page(vma)) { 1559 if (is_vm_hugetlb_page(vma)) {
1557 unsigned long vma_hpagesize = 1560 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1558 1561
1559 if (start & (vma_hpagesize - 1562 if (start & (vma_hpagesize - 1))
1560 goto out_unlock; 1563 goto out_unlock;
1561 } 1564 }
1562 1565
1563 /* 1566 /*
1564 * Search for not compatible vmas. 1567 * Search for not compatible vmas.
1565 */ 1568 */
1566 found = false; 1569 found = false;
1567 cur = vma; !! 1570 ret = -EINVAL;
1568 do { !! 1571 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1569 cond_resched(); 1572 cond_resched();
1570 1573
1571 BUG_ON(!!cur->vm_userfaultfd_ 1574 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1572 !!(cur->vm_flags & __V !! 1575 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1573 1576
1574 /* 1577 /*
1575 * Check not compatible vmas, 1578 * Check not compatible vmas, not strictly required
1576 * here as not compatible vma 1579 * here as not compatible vmas cannot have an
1577 * userfaultfd_ctx registered 1580 * userfaultfd_ctx registered on them, but this
1578 * provides for more strict b 1581 * provides for more strict behavior to notice
1579 * unregistration errors. 1582 * unregistration errors.
1580 */ 1583 */
1581 if (!vma_can_userfault(cur, c !! 1584 if (!vma_can_userfault(cur))
1582 goto out_unlock; 1585 goto out_unlock;
1583 1586
1584 found = true; 1587 found = true;
1585 } for_each_vma_range(vmi, cur, end); !! 1588 }
1586 BUG_ON(!found); 1589 BUG_ON(!found);
1587 1590
1588 vma_iter_set(&vmi, start); <<
1589 prev = vma_prev(&vmi); <<
1590 if (vma->vm_start < start) 1591 if (vma->vm_start < start)
1591 prev = vma; 1592 prev = vma;
1592 1593
1593 ret = 0; 1594 ret = 0;
1594 for_each_vma_range(vmi, vma, end) { !! 1595 do {
1595 cond_resched(); 1596 cond_resched();
1596 1597
1597 BUG_ON(!vma_can_userfault(vma !! 1598 BUG_ON(!vma_can_userfault(vma));
1598 1599
1599 /* 1600 /*
1600 * Nothing to do: this vma is 1601 * Nothing to do: this vma is already registered into this
1601 * userfaultfd and with the r 1602 * userfaultfd and with the right tracking mode too.
1602 */ 1603 */
1603 if (!vma->vm_userfaultfd_ctx. 1604 if (!vma->vm_userfaultfd_ctx.ctx)
1604 goto skip; 1605 goto skip;
1605 1606
1606 WARN_ON(!(vma->vm_flags & VM_ 1607 WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
1607 1608
1608 if (vma->vm_start > start) 1609 if (vma->vm_start > start)
1609 start = vma->vm_start 1610 start = vma->vm_start;
1610 vma_end = min(end, vma->vm_en 1611 vma_end = min(end, vma->vm_end);
1611 1612
1612 if (userfaultfd_missing(vma)) 1613 if (userfaultfd_missing(vma)) {
1613 /* 1614 /*
1614 * Wake any concurren 1615 * Wake any concurrent pending userfault while
1615 * we unregister, so 1616 * we unregister, so they will not hang
1616 * permanently and it 1617 * permanently and it avoids userland to call
1617 * UFFDIO_WAKE explic 1618 * UFFDIO_WAKE explicitly.
1618 */ 1619 */
1619 struct userfaultfd_wa 1620 struct userfaultfd_wake_range range;
1620 range.start = start; 1621 range.start = start;
1621 range.len = vma_end - 1622 range.len = vma_end - start;
1622 wake_userfault(vma->v 1623 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
1623 } 1624 }
1624 1625
1625 /* Reset ptes for the whole v !! 1626 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
1626 if (userfaultfd_wp(vma)) !! 1627 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1627 uffd_wp_range(vma, st !! 1628 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1628 !! 1629 vma_policy(vma),
1629 new_flags = vma->vm_flags & ~ !! 1630 NULL_VM_UFFD_CTX);
1630 vma = vma_modify_flags_uffd(& !! 1631 if (prev) {
1631 n !! 1632 vma = prev;
1632 if (IS_ERR(vma)) { !! 1633 goto next;
1633 ret = PTR_ERR(vma); <<
1634 break; <<
1635 } 1634 }
1636 !! 1635 if (vma->vm_start < start) {
>> 1636 ret = split_vma(mm, vma, start, 1);
>> 1637 if (ret)
>> 1638 break;
>> 1639 }
>> 1640 if (vma->vm_end > end) {
>> 1641 ret = split_vma(mm, vma, end, 0);
>> 1642 if (ret)
>> 1643 break;
>> 1644 }
>> 1645 next:
1637 /* 1646 /*
1638 * In the vma_merge() success 1647 * In the vma_merge() successful mprotect-like case 8:
1639 * the next vma was merged in 1648 * the next vma was merged into the current one and
1640 * the current one has not be 1649 * the current one has not been updated yet.
1641 */ 1650 */
1642 vma_start_write(vma); !! 1651 vma->vm_flags = new_flags;
1643 userfaultfd_set_vm_flags(vma, <<
1644 vma->vm_userfaultfd_ctx = NUL 1652 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
1645 1653
1646 skip: 1654 skip:
1647 prev = vma; 1655 prev = vma;
1648 start = vma->vm_end; 1656 start = vma->vm_end;
1649 } !! 1657 vma = vma->vm_next;
1650 !! 1658 } while (vma && vma->vm_start < end);
1651 out_unlock: 1659 out_unlock:
1652 mmap_write_unlock(mm); !! 1660 up_write(&mm->mmap_sem);
1653 mmput(mm); 1661 mmput(mm);
1654 out: 1662 out:
1655 return ret; 1663 return ret;
1656 } 1664 }
1657 1665
1658 /* 1666 /*
1659 * userfaultfd_wake may be used in combinatio 1667 * userfaultfd_wake may be used in combination with the
1660 * UFFDIO_*_MODE_DONTWAKE to wakeup userfault 1668 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
1661 */ 1669 */
1662 static int userfaultfd_wake(struct userfaultf 1670 static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
1663 unsigned long arg 1671 unsigned long arg)
1664 { 1672 {
1665 int ret; 1673 int ret;
1666 struct uffdio_range uffdio_wake; 1674 struct uffdio_range uffdio_wake;
1667 struct userfaultfd_wake_range range; 1675 struct userfaultfd_wake_range range;
1668 const void __user *buf = (void __user 1676 const void __user *buf = (void __user *)arg;
1669 1677
1670 ret = -EFAULT; 1678 ret = -EFAULT;
1671 if (copy_from_user(&uffdio_wake, buf, 1679 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
1672 goto out; 1680 goto out;
1673 1681
1674 ret = validate_range(ctx->mm, uffdio_ !! 1682 ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len);
1675 if (ret) 1683 if (ret)
1676 goto out; 1684 goto out;
1677 1685
1678 range.start = uffdio_wake.start; 1686 range.start = uffdio_wake.start;
1679 range.len = uffdio_wake.len; 1687 range.len = uffdio_wake.len;
1680 1688
1681 /* 1689 /*
1682 * len == 0 means wake all and we don 1690 * len == 0 means wake all and we don't want to wake all here,
1683 * so check it again to be sure. 1691 * so check it again to be sure.
1684 */ 1692 */
1685 VM_BUG_ON(!range.len); 1693 VM_BUG_ON(!range.len);
1686 1694
1687 wake_userfault(ctx, &range); 1695 wake_userfault(ctx, &range);
1688 ret = 0; 1696 ret = 0;
1689 1697
1690 out: 1698 out:
1691 return ret; 1699 return ret;
1692 } 1700 }
1693 1701
1694 static int userfaultfd_copy(struct userfaultf 1702 static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
1695 unsigned long arg 1703 unsigned long arg)
1696 { 1704 {
1697 __s64 ret; 1705 __s64 ret;
1698 struct uffdio_copy uffdio_copy; 1706 struct uffdio_copy uffdio_copy;
1699 struct uffdio_copy __user *user_uffdi 1707 struct uffdio_copy __user *user_uffdio_copy;
1700 struct userfaultfd_wake_range range; 1708 struct userfaultfd_wake_range range;
1701 uffd_flags_t flags = 0; <<
1702 1709
1703 user_uffdio_copy = (struct uffdio_cop 1710 user_uffdio_copy = (struct uffdio_copy __user *) arg;
1704 1711
1705 ret = -EAGAIN; 1712 ret = -EAGAIN;
1706 if (atomic_read(&ctx->mmap_changing)) !! 1713 if (READ_ONCE(ctx->mmap_changing))
1707 goto out; 1714 goto out;
1708 1715
1709 ret = -EFAULT; 1716 ret = -EFAULT;
1710 if (copy_from_user(&uffdio_copy, user 1717 if (copy_from_user(&uffdio_copy, user_uffdio_copy,
1711 /* don't copy "cop 1718 /* don't copy "copy" last field */
1712 sizeof(uffdio_copy 1719 sizeof(uffdio_copy)-sizeof(__s64)))
1713 goto out; 1720 goto out;
1714 1721
1715 ret = validate_unaligned_range(ctx->m !! 1722 ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len);
1716 uffdio <<
1717 if (ret) 1723 if (ret)
1718 goto out; 1724 goto out;
1719 ret = validate_range(ctx->mm, uffdio_ !! 1725 /*
1720 if (ret) !! 1726 * double check for wraparound just in case. copy_from_user()
1721 goto out; !! 1727 * will later check uffdio_copy.src + uffdio_copy.len to fit
1722 !! 1728 * in the userland range.
>> 1729 */
1723 ret = -EINVAL; 1730 ret = -EINVAL;
1724 if (uffdio_copy.mode & ~(UFFDIO_COPY_ !! 1731 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
>> 1732 goto out;
>> 1733 if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE)
1725 goto out; 1734 goto out;
1726 if (uffdio_copy.mode & UFFDIO_COPY_MO <<
1727 flags |= MFILL_ATOMIC_WP; <<
1728 if (mmget_not_zero(ctx->mm)) { 1735 if (mmget_not_zero(ctx->mm)) {
1729 ret = mfill_atomic_copy(ctx, !! 1736 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
1730 uffdi !! 1737 uffdio_copy.len, &ctx->mmap_changing);
1731 mmput(ctx->mm); 1738 mmput(ctx->mm);
1732 } else { 1739 } else {
1733 return -ESRCH; 1740 return -ESRCH;
1734 } 1741 }
1735 if (unlikely(put_user(ret, &user_uffd 1742 if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
1736 return -EFAULT; 1743 return -EFAULT;
1737 if (ret < 0) 1744 if (ret < 0)
1738 goto out; 1745 goto out;
1739 BUG_ON(!ret); 1746 BUG_ON(!ret);
1740 /* len == 0 would wake all */ 1747 /* len == 0 would wake all */
1741 range.len = ret; 1748 range.len = ret;
1742 if (!(uffdio_copy.mode & UFFDIO_COPY_ 1749 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) {
1743 range.start = uffdio_copy.dst 1750 range.start = uffdio_copy.dst;
1744 wake_userfault(ctx, &range); 1751 wake_userfault(ctx, &range);
1745 } 1752 }
1746 ret = range.len == uffdio_copy.len ? 1753 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN;
1747 out: 1754 out:
1748 return ret; 1755 return ret;
1749 } 1756 }
1750 1757
1751 static int userfaultfd_zeropage(struct userfa 1758 static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
1752 unsigned long 1759 unsigned long arg)
1753 { 1760 {
1754 __s64 ret; 1761 __s64 ret;
1755 struct uffdio_zeropage uffdio_zeropag 1762 struct uffdio_zeropage uffdio_zeropage;
1756 struct uffdio_zeropage __user *user_u 1763 struct uffdio_zeropage __user *user_uffdio_zeropage;
1757 struct userfaultfd_wake_range range; 1764 struct userfaultfd_wake_range range;
1758 1765
1759 user_uffdio_zeropage = (struct uffdio 1766 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg;
1760 1767
1761 ret = -EAGAIN; 1768 ret = -EAGAIN;
1762 if (atomic_read(&ctx->mmap_changing)) !! 1769 if (READ_ONCE(ctx->mmap_changing))
1763 goto out; 1770 goto out;
1764 1771
1765 ret = -EFAULT; 1772 ret = -EFAULT;
1766 if (copy_from_user(&uffdio_zeropage, 1773 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage,
1767 /* don't copy "zer 1774 /* don't copy "zeropage" last field */
1768 sizeof(uffdio_zero 1775 sizeof(uffdio_zeropage)-sizeof(__s64)))
1769 goto out; 1776 goto out;
1770 1777
1771 ret = validate_range(ctx->mm, uffdio_ !! 1778 ret = validate_range(ctx->mm, &uffdio_zeropage.range.start,
1772 uffdio_zeropage. 1779 uffdio_zeropage.range.len);
1773 if (ret) 1780 if (ret)
1774 goto out; 1781 goto out;
1775 ret = -EINVAL; 1782 ret = -EINVAL;
1776 if (uffdio_zeropage.mode & ~UFFDIO_ZE 1783 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE)
1777 goto out; 1784 goto out;
1778 1785
1779 if (mmget_not_zero(ctx->mm)) { 1786 if (mmget_not_zero(ctx->mm)) {
1780 ret = mfill_atomic_zeropage(c !! 1787 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
1781 uf !! 1788 uffdio_zeropage.range.len,
>> 1789 &ctx->mmap_changing);
1782 mmput(ctx->mm); 1790 mmput(ctx->mm);
1783 } else { 1791 } else {
1784 return -ESRCH; 1792 return -ESRCH;
1785 } 1793 }
1786 if (unlikely(put_user(ret, &user_uffd 1794 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
1787 return -EFAULT; 1795 return -EFAULT;
1788 if (ret < 0) 1796 if (ret < 0)
1789 goto out; 1797 goto out;
1790 /* len == 0 would wake all */ 1798 /* len == 0 would wake all */
1791 BUG_ON(!ret); 1799 BUG_ON(!ret);
1792 range.len = ret; 1800 range.len = ret;
1793 if (!(uffdio_zeropage.mode & UFFDIO_Z 1801 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) {
1794 range.start = uffdio_zeropage 1802 range.start = uffdio_zeropage.range.start;
1795 wake_userfault(ctx, &range); 1803 wake_userfault(ctx, &range);
1796 } 1804 }
1797 ret = range.len == uffdio_zeropage.ra 1805 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN;
1798 out: 1806 out:
1799 return ret; 1807 return ret;
1800 } 1808 }
1801 1809
1802 static int userfaultfd_writeprotect(struct us <<
1803 unsigned <<
1804 { <<
1805 int ret; <<
1806 struct uffdio_writeprotect uffdio_wp; <<
1807 struct uffdio_writeprotect __user *us <<
1808 struct userfaultfd_wake_range range; <<
1809 bool mode_wp, mode_dontwake; <<
1810 <<
1811 if (atomic_read(&ctx->mmap_changing)) <<
1812 return -EAGAIN; <<
1813 <<
1814 user_uffdio_wp = (struct uffdio_write <<
1815 <<
1816 if (copy_from_user(&uffdio_wp, user_u <<
1817 sizeof(struct uffd <<
1818 return -EFAULT; <<
1819 <<
1820 ret = validate_range(ctx->mm, uffdio_ <<
1821 uffdio_wp.range. <<
1822 if (ret) <<
1823 return ret; <<
1824 <<
1825 if (uffdio_wp.mode & ~(UFFDIO_WRITEPR <<
1826 UFFDIO_WRITEPR <<
1827 return -EINVAL; <<
1828 <<
1829 mode_wp = uffdio_wp.mode & UFFDIO_WRI <<
1830 mode_dontwake = uffdio_wp.mode & UFFD <<
1831 <<
1832 if (mode_wp && mode_dontwake) <<
1833 return -EINVAL; <<
1834 <<
1835 if (mmget_not_zero(ctx->mm)) { <<
1836 ret = mwriteprotect_range(ctx <<
1837 uff <<
1838 mmput(ctx->mm); <<
1839 } else { <<
1840 return -ESRCH; <<
1841 } <<
1842 <<
1843 if (ret) <<
1844 return ret; <<
1845 <<
1846 if (!mode_wp && !mode_dontwake) { <<
1847 range.start = uffdio_wp.range <<
1848 range.len = uffdio_wp.range.l <<
1849 wake_userfault(ctx, &range); <<
1850 } <<
1851 return ret; <<
1852 } <<
1853 <<
1854 static int userfaultfd_continue(struct userfa <<
1855 { <<
1856 __s64 ret; <<
1857 struct uffdio_continue uffdio_continu <<
1858 struct uffdio_continue __user *user_u <<
1859 struct userfaultfd_wake_range range; <<
1860 uffd_flags_t flags = 0; <<
1861 <<
1862 user_uffdio_continue = (struct uffdio <<
1863 <<
1864 ret = -EAGAIN; <<
1865 if (atomic_read(&ctx->mmap_changing)) <<
1866 goto out; <<
1867 <<
1868 ret = -EFAULT; <<
1869 if (copy_from_user(&uffdio_continue, <<
1870 /* don't copy the <<
1871 sizeof(uffdio_cont <<
1872 goto out; <<
1873 <<
1874 ret = validate_range(ctx->mm, uffdio_ <<
1875 uffdio_continue. <<
1876 if (ret) <<
1877 goto out; <<
1878 <<
1879 ret = -EINVAL; <<
1880 if (uffdio_continue.mode & ~(UFFDIO_C <<
1881 UFFDIO_C <<
1882 goto out; <<
1883 if (uffdio_continue.mode & UFFDIO_CON <<
1884 flags |= MFILL_ATOMIC_WP; <<
1885 <<
1886 if (mmget_not_zero(ctx->mm)) { <<
1887 ret = mfill_atomic_continue(c <<
1888 u <<
1889 mmput(ctx->mm); <<
1890 } else { <<
1891 return -ESRCH; <<
1892 } <<
1893 <<
1894 if (unlikely(put_user(ret, &user_uffd <<
1895 return -EFAULT; <<
1896 if (ret < 0) <<
1897 goto out; <<
1898 <<
1899 /* len == 0 would wake all */ <<
1900 BUG_ON(!ret); <<
1901 range.len = ret; <<
1902 if (!(uffdio_continue.mode & UFFDIO_C <<
1903 range.start = uffdio_continue <<
1904 wake_userfault(ctx, &range); <<
1905 } <<
1906 ret = range.len == uffdio_continue.ra <<
1907 <<
1908 out: <<
1909 return ret; <<
1910 } <<
1911 <<
1912 static inline int userfaultfd_poison(struct u <<
1913 { <<
1914 __s64 ret; <<
1915 struct uffdio_poison uffdio_poison; <<
1916 struct uffdio_poison __user *user_uff <<
1917 struct userfaultfd_wake_range range; <<
1918 <<
1919 user_uffdio_poison = (struct uffdio_p <<
1920 <<
1921 ret = -EAGAIN; <<
1922 if (atomic_read(&ctx->mmap_changing)) <<
1923 goto out; <<
1924 <<
1925 ret = -EFAULT; <<
1926 if (copy_from_user(&uffdio_poison, us <<
1927 /* don't copy the <<
1928 sizeof(uffdio_pois <<
1929 goto out; <<
1930 <<
1931 ret = validate_range(ctx->mm, uffdio_ <<
1932 uffdio_poison.ra <<
1933 if (ret) <<
1934 goto out; <<
1935 <<
1936 ret = -EINVAL; <<
1937 if (uffdio_poison.mode & ~UFFDIO_POIS <<
1938 goto out; <<
1939 <<
1940 if (mmget_not_zero(ctx->mm)) { <<
1941 ret = mfill_atomic_poison(ctx <<
1942 uff <<
1943 mmput(ctx->mm); <<
1944 } else { <<
1945 return -ESRCH; <<
1946 } <<
1947 <<
1948 if (unlikely(put_user(ret, &user_uffd <<
1949 return -EFAULT; <<
1950 if (ret < 0) <<
1951 goto out; <<
1952 <<
1953 /* len == 0 would wake all */ <<
1954 BUG_ON(!ret); <<
1955 range.len = ret; <<
1956 if (!(uffdio_poison.mode & UFFDIO_POI <<
1957 range.start = uffdio_poison.r <<
1958 wake_userfault(ctx, &range); <<
1959 } <<
1960 ret = range.len == uffdio_poison.rang <<
1961 <<
1962 out: <<
1963 return ret; <<
1964 } <<
1965 <<
1966 bool userfaultfd_wp_async(struct vm_area_stru <<
1967 { <<
1968 return userfaultfd_wp_async_ctx(vma-> <<
1969 } <<
1970 <<
1971 static inline unsigned int uffd_ctx_features( 1810 static inline unsigned int uffd_ctx_features(__u64 user_features)
1972 { 1811 {
1973 /* 1812 /*
1974 * For the current set of features th !! 1813 * For the current set of features the bits just coincide
1975 * UFFD_FEATURE_INITIALIZED to mark t <<
1976 */ 1814 */
1977 return (unsigned int)user_features | !! 1815 return (unsigned int)user_features;
1978 } <<
1979 <<
1980 static int userfaultfd_move(struct userfaultf <<
1981 unsigned long arg <<
1982 { <<
1983 __s64 ret; <<
1984 struct uffdio_move uffdio_move; <<
1985 struct uffdio_move __user *user_uffdi <<
1986 struct userfaultfd_wake_range range; <<
1987 struct mm_struct *mm = ctx->mm; <<
1988 <<
1989 user_uffdio_move = (struct uffdio_mov <<
1990 <<
1991 if (atomic_read(&ctx->mmap_changing)) <<
1992 return -EAGAIN; <<
1993 <<
1994 if (copy_from_user(&uffdio_move, user <<
1995 /* don't copy "mov <<
1996 sizeof(uffdio_move <<
1997 return -EFAULT; <<
1998 <<
1999 /* Do not allow cross-mm moves. */ <<
2000 if (mm != current->mm) <<
2001 return -EINVAL; <<
2002 <<
2003 ret = validate_range(mm, uffdio_move. <<
2004 if (ret) <<
2005 return ret; <<
2006 <<
2007 ret = validate_range(mm, uffdio_move. <<
2008 if (ret) <<
2009 return ret; <<
2010 <<
2011 if (uffdio_move.mode & ~(UFFDIO_MOVE_ <<
2012 UFFDIO_MOVE <<
2013 return -EINVAL; <<
2014 <<
2015 if (mmget_not_zero(mm)) { <<
2016 ret = move_pages(ctx, uffdio_ <<
2017 uffdio_move. <<
2018 mmput(mm); <<
2019 } else { <<
2020 return -ESRCH; <<
2021 } <<
2022 <<
2023 if (unlikely(put_user(ret, &user_uffd <<
2024 return -EFAULT; <<
2025 if (ret < 0) <<
2026 goto out; <<
2027 <<
2028 /* len == 0 would wake all */ <<
2029 VM_WARN_ON(!ret); <<
2030 range.len = ret; <<
2031 if (!(uffdio_move.mode & UFFDIO_MOVE_ <<
2032 range.start = uffdio_move.dst <<
2033 wake_userfault(ctx, &range); <<
2034 } <<
2035 ret = range.len == uffdio_move.len ? <<
2036 <<
2037 out: <<
2038 return ret; <<
2039 } 1816 }
2040 1817
2041 /* 1818 /*
2042 * userland asks for a certain API version an 1819 * userland asks for a certain API version and we return which bits
2043 * and ioctl commands are implemented in this 1820 * and ioctl commands are implemented in this kernel for such API
2044 * version or -EINVAL if unknown. 1821 * version or -EINVAL if unknown.
2045 */ 1822 */
2046 static int userfaultfd_api(struct userfaultfd 1823 static int userfaultfd_api(struct userfaultfd_ctx *ctx,
2047 unsigned long arg) 1824 unsigned long arg)
2048 { 1825 {
2049 struct uffdio_api uffdio_api; 1826 struct uffdio_api uffdio_api;
2050 void __user *buf = (void __user *)arg 1827 void __user *buf = (void __user *)arg;
2051 unsigned int ctx_features; <<
2052 int ret; 1828 int ret;
2053 __u64 features; 1829 __u64 features;
2054 1830
>> 1831 ret = -EINVAL;
>> 1832 if (ctx->state != UFFD_STATE_WAIT_API)
>> 1833 goto out;
2055 ret = -EFAULT; 1834 ret = -EFAULT;
2056 if (copy_from_user(&uffdio_api, buf, 1835 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
2057 goto out; 1836 goto out;
2058 features = uffdio_api.features; 1837 features = uffdio_api.features;
2059 ret = -EINVAL; 1838 ret = -EINVAL;
2060 if (uffdio_api.api != UFFD_API) !! 1839 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
2061 goto err_out; 1840 goto err_out;
2062 ret = -EPERM; 1841 ret = -EPERM;
2063 if ((features & UFFD_FEATURE_EVENT_FO 1842 if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
2064 goto err_out; 1843 goto err_out;
2065 <<
2066 /* WP_ASYNC relies on WP_UNPOPULATED, <<
2067 if (features & UFFD_FEATURE_WP_ASYNC) <<
2068 features |= UFFD_FEATURE_WP_U <<
2069 <<
2070 /* report all available features and 1844 /* report all available features and ioctls to userland */
2071 uffdio_api.features = UFFD_API_FEATUR 1845 uffdio_api.features = UFFD_API_FEATURES;
2072 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR <<
2073 uffdio_api.features &= <<
2074 ~(UFFD_FEATURE_MINOR_HUGETLBF <<
2075 #endif <<
2076 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP <<
2077 uffdio_api.features &= ~UFFD_FEATURE_ <<
2078 #endif <<
2079 #ifndef CONFIG_PTE_MARKER_UFFD_WP <<
2080 uffdio_api.features &= ~UFFD_FEATURE_ <<
2081 uffdio_api.features &= ~UFFD_FEATURE_ <<
2082 uffdio_api.features &= ~UFFD_FEATURE_ <<
2083 #endif <<
2084 <<
2085 ret = -EINVAL; <<
2086 if (features & ~uffdio_api.features) <<
2087 goto err_out; <<
2088 <<
2089 uffdio_api.ioctls = UFFD_API_IOCTLS; 1846 uffdio_api.ioctls = UFFD_API_IOCTLS;
2090 ret = -EFAULT; 1847 ret = -EFAULT;
2091 if (copy_to_user(buf, &uffdio_api, si 1848 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
2092 goto out; 1849 goto out;
2093 !! 1850 ctx->state = UFFD_STATE_RUNNING;
2094 /* only enable the requested features 1851 /* only enable the requested features for this uffd context */
2095 ctx_features = uffd_ctx_features(feat !! 1852 ctx->features = uffd_ctx_features(features);
2096 ret = -EINVAL; <<
2097 if (cmpxchg(&ctx->features, 0, ctx_fe <<
2098 goto err_out; <<
2099 <<
2100 ret = 0; 1853 ret = 0;
2101 out: 1854 out:
2102 return ret; 1855 return ret;
2103 err_out: 1856 err_out:
2104 memset(&uffdio_api, 0, sizeof(uffdio_ 1857 memset(&uffdio_api, 0, sizeof(uffdio_api));
2105 if (copy_to_user(buf, &uffdio_api, si 1858 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
2106 ret = -EFAULT; 1859 ret = -EFAULT;
2107 goto out; 1860 goto out;
2108 } 1861 }
2109 1862
2110 static long userfaultfd_ioctl(struct file *fi 1863 static long userfaultfd_ioctl(struct file *file, unsigned cmd,
2111 unsigned long a 1864 unsigned long arg)
2112 { 1865 {
2113 int ret = -EINVAL; 1866 int ret = -EINVAL;
2114 struct userfaultfd_ctx *ctx = file->p 1867 struct userfaultfd_ctx *ctx = file->private_data;
2115 1868
2116 if (cmd != UFFDIO_API && !userfaultfd !! 1869 if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
2117 return -EINVAL; 1870 return -EINVAL;
2118 1871
2119 switch(cmd) { 1872 switch(cmd) {
2120 case UFFDIO_API: 1873 case UFFDIO_API:
2121 ret = userfaultfd_api(ctx, ar 1874 ret = userfaultfd_api(ctx, arg);
2122 break; 1875 break;
2123 case UFFDIO_REGISTER: 1876 case UFFDIO_REGISTER:
2124 ret = userfaultfd_register(ct 1877 ret = userfaultfd_register(ctx, arg);
2125 break; 1878 break;
2126 case UFFDIO_UNREGISTER: 1879 case UFFDIO_UNREGISTER:
2127 ret = userfaultfd_unregister( 1880 ret = userfaultfd_unregister(ctx, arg);
2128 break; 1881 break;
2129 case UFFDIO_WAKE: 1882 case UFFDIO_WAKE:
2130 ret = userfaultfd_wake(ctx, a 1883 ret = userfaultfd_wake(ctx, arg);
2131 break; 1884 break;
2132 case UFFDIO_COPY: 1885 case UFFDIO_COPY:
2133 ret = userfaultfd_copy(ctx, a 1886 ret = userfaultfd_copy(ctx, arg);
2134 break; 1887 break;
2135 case UFFDIO_ZEROPAGE: 1888 case UFFDIO_ZEROPAGE:
2136 ret = userfaultfd_zeropage(ct 1889 ret = userfaultfd_zeropage(ctx, arg);
2137 break; 1890 break;
2138 case UFFDIO_MOVE: <<
2139 ret = userfaultfd_move(ctx, a <<
2140 break; <<
2141 case UFFDIO_WRITEPROTECT: <<
2142 ret = userfaultfd_writeprotec <<
2143 break; <<
2144 case UFFDIO_CONTINUE: <<
2145 ret = userfaultfd_continue(ct <<
2146 break; <<
2147 case UFFDIO_POISON: <<
2148 ret = userfaultfd_poison(ctx, <<
2149 break; <<
2150 } 1891 }
2151 return ret; 1892 return ret;
2152 } 1893 }
2153 1894
2154 #ifdef CONFIG_PROC_FS 1895 #ifdef CONFIG_PROC_FS
2155 static void userfaultfd_show_fdinfo(struct se 1896 static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
2156 { 1897 {
2157 struct userfaultfd_ctx *ctx = f->priv 1898 struct userfaultfd_ctx *ctx = f->private_data;
2158 wait_queue_entry_t *wq; 1899 wait_queue_entry_t *wq;
2159 unsigned long pending = 0, total = 0; 1900 unsigned long pending = 0, total = 0;
2160 1901
2161 spin_lock_irq(&ctx->fault_pending_wqh 1902 spin_lock_irq(&ctx->fault_pending_wqh.lock);
2162 list_for_each_entry(wq, &ctx->fault_p 1903 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) {
2163 pending++; 1904 pending++;
2164 total++; 1905 total++;
2165 } 1906 }
2166 list_for_each_entry(wq, &ctx->fault_w 1907 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) {
2167 total++; 1908 total++;
2168 } 1909 }
2169 spin_unlock_irq(&ctx->fault_pending_w 1910 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
2170 1911
2171 /* 1912 /*
2172 * If more protocols will be added, t 1913 * If more protocols will be added, there will be all shown
2173 * separated by a space. Like this: 1914 * separated by a space. Like this:
2174 * protocols: aa:... bb:... 1915 * protocols: aa:... bb:...
2175 */ 1916 */
2176 seq_printf(m, "pending:\t%lu\ntotal:\ 1917 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
2177 pending, total, UFFD_API, 1918 pending, total, UFFD_API, ctx->features,
2178 UFFD_API_IOCTLS|UFFD_API_R 1919 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
2179 } 1920 }
2180 #endif 1921 #endif
2181 1922
2182 static const struct file_operations userfault 1923 static const struct file_operations userfaultfd_fops = {
2183 #ifdef CONFIG_PROC_FS 1924 #ifdef CONFIG_PROC_FS
2184 .show_fdinfo = userfaultfd_show_fd 1925 .show_fdinfo = userfaultfd_show_fdinfo,
2185 #endif 1926 #endif
2186 .release = userfaultfd_release 1927 .release = userfaultfd_release,
2187 .poll = userfaultfd_poll, 1928 .poll = userfaultfd_poll,
2188 .read_iter = userfaultfd_read_it !! 1929 .read = userfaultfd_read,
2189 .unlocked_ioctl = userfaultfd_ioctl, 1930 .unlocked_ioctl = userfaultfd_ioctl,
2190 .compat_ioctl = compat_ptr_ioctl, 1931 .compat_ioctl = compat_ptr_ioctl,
2191 .llseek = noop_llseek, 1932 .llseek = noop_llseek,
2192 }; 1933 };
2193 1934
2194 static void init_once_userfaultfd_ctx(void *m 1935 static void init_once_userfaultfd_ctx(void *mem)
2195 { 1936 {
2196 struct userfaultfd_ctx *ctx = (struct 1937 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem;
2197 1938
2198 init_waitqueue_head(&ctx->fault_pendi 1939 init_waitqueue_head(&ctx->fault_pending_wqh);
2199 init_waitqueue_head(&ctx->fault_wqh); 1940 init_waitqueue_head(&ctx->fault_wqh);
2200 init_waitqueue_head(&ctx->event_wqh); 1941 init_waitqueue_head(&ctx->event_wqh);
2201 init_waitqueue_head(&ctx->fd_wqh); 1942 init_waitqueue_head(&ctx->fd_wqh);
2202 seqcount_spinlock_init(&ctx->refile_s !! 1943 seqcount_init(&ctx->refile_seq);
2203 } 1944 }
2204 1945
2205 static int new_userfaultfd(int flags) !! 1946 SYSCALL_DEFINE1(userfaultfd, int, flags)
2206 { 1947 {
2207 struct userfaultfd_ctx *ctx; 1948 struct userfaultfd_ctx *ctx;
2208 struct file *file; <<
2209 int fd; 1949 int fd;
2210 1950
>> 1951 if (!sysctl_unprivileged_userfaultfd && !capable(CAP_SYS_PTRACE))
>> 1952 return -EPERM;
>> 1953
2211 BUG_ON(!current->mm); 1954 BUG_ON(!current->mm);
2212 1955
2213 /* Check the UFFD_* constants for con 1956 /* Check the UFFD_* constants for consistency. */
2214 BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UF <<
2215 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXE 1957 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
2216 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBL 1958 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
2217 1959
2218 if (flags & ~(UFFD_SHARED_FCNTL_FLAGS !! 1960 if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
2219 return -EINVAL; 1961 return -EINVAL;
2220 1962
2221 ctx = kmem_cache_alloc(userfaultfd_ct 1963 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
2222 if (!ctx) 1964 if (!ctx)
2223 return -ENOMEM; 1965 return -ENOMEM;
2224 1966
2225 refcount_set(&ctx->refcount, 1); 1967 refcount_set(&ctx->refcount, 1);
2226 ctx->flags = flags; 1968 ctx->flags = flags;
2227 ctx->features = 0; 1969 ctx->features = 0;
>> 1970 ctx->state = UFFD_STATE_WAIT_API;
2228 ctx->released = false; 1971 ctx->released = false;
2229 init_rwsem(&ctx->map_changing_lock); !! 1972 ctx->mmap_changing = false;
2230 atomic_set(&ctx->mmap_changing, 0); <<
2231 ctx->mm = current->mm; 1973 ctx->mm = current->mm;
2232 <<
2233 fd = get_unused_fd_flags(flags & UFFD <<
2234 if (fd < 0) <<
2235 goto err_out; <<
2236 <<
2237 /* Create a new inode so that the LSM <<
2238 file = anon_inode_create_getfile("[us <<
2239 O_RDONLY | (flags & U <<
2240 if (IS_ERR(file)) { <<
2241 put_unused_fd(fd); <<
2242 fd = PTR_ERR(file); <<
2243 goto err_out; <<
2244 } <<
2245 /* prevent the mm struct to be freed 1974 /* prevent the mm struct to be freed */
2246 mmgrab(ctx->mm); 1975 mmgrab(ctx->mm);
2247 file->f_mode |= FMODE_NOWAIT; <<
2248 fd_install(fd, file); <<
2249 return fd; <<
2250 err_out: <<
2251 kmem_cache_free(userfaultfd_ctx_cache <<
2252 return fd; <<
2253 } <<
2254 <<
2255 static inline bool userfaultfd_syscall_allowe <<
2256 { <<
2257 /* Userspace-only page faults are alw <<
2258 if (flags & UFFD_USER_MODE_ONLY) <<
2259 return true; <<
2260 <<
2261 /* <<
2262 * The user is requesting a userfault <<
2263 * Privileged users are always allowe <<
2264 */ <<
2265 if (capable(CAP_SYS_PTRACE)) <<
2266 return true; <<
2267 <<
2268 /* Otherwise, access to kernel fault <<
2269 return sysctl_unprivileged_userfaultf <<
2270 } <<
2271 1976
2272 SYSCALL_DEFINE1(userfaultfd, int, flags) !! 1977 fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
2273 { !! 1978 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
2274 if (!userfaultfd_syscall_allowed(flag !! 1979 if (fd < 0) {
2275 return -EPERM; !! 1980 mmdrop(ctx->mm);
2276 !! 1981 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
2277 return new_userfaultfd(flags); !! 1982 }
2278 } !! 1983 return fd;
2279 <<
2280 static long userfaultfd_dev_ioctl(struct file <<
2281 { <<
2282 if (cmd != USERFAULTFD_IOC_NEW) <<
2283 return -EINVAL; <<
2284 <<
2285 return new_userfaultfd(flags); <<
2286 } 1984 }
2287 1985
2288 static const struct file_operations userfault <<
2289 .unlocked_ioctl = userfaultfd_dev_ioc <<
2290 .compat_ioctl = userfaultfd_dev_ioctl <<
2291 .owner = THIS_MODULE, <<
2292 .llseek = noop_llseek, <<
2293 }; <<
2294 <<
2295 static struct miscdevice userfaultfd_misc = { <<
2296 .minor = MISC_DYNAMIC_MINOR, <<
2297 .name = "userfaultfd", <<
2298 .fops = &userfaultfd_dev_fops <<
2299 }; <<
2300 <<
2301 static int __init userfaultfd_init(void) 1986 static int __init userfaultfd_init(void)
2302 { 1987 {
2303 int ret; <<
2304 <<
2305 ret = misc_register(&userfaultfd_misc <<
2306 if (ret) <<
2307 return ret; <<
2308 <<
2309 userfaultfd_ctx_cachep = kmem_cache_c 1988 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
2310 1989 sizeof(struct userfaultfd_ctx),
2311 1990 0,
2312 1991 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
2313 1992 init_once_userfaultfd_ctx);
2314 #ifdef CONFIG_SYSCTL <<
2315 register_sysctl_init("vm", vm_userfau <<
2316 #endif <<
2317 return 0; 1993 return 0;
2318 } 1994 }
2319 __initcall(userfaultfd_init); 1995 __initcall(userfaultfd_init);
2320 1996
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