1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (c) 2018 Facebook
4 */
5 #include <linux/bpf.h>
6 #include <linux/err.h>
7 #include <linux/sock_diag.h>
8 #include <net/sock_reuseport.h>
9 #include <linux/btf_ids.h>
10
11 struct reuseport_array {
12 struct bpf_map map;
13 struct sock __rcu *ptrs[];
14 };
15
16 static struct reuseport_array *reuseport_array(struct bpf_map *map)
17 {
18 return (struct reuseport_array *)map;
19 }
20
21 /* The caller must hold the reuseport_lock */
22 void bpf_sk_reuseport_detach(struct sock *sk)
23 {
24 struct sock __rcu **socks;
25
26 write_lock_bh(&sk->sk_callback_lock);
27 socks = __locked_read_sk_user_data_with_flags(sk, SK_USER_DATA_BPF);
28 if (socks) {
29 WRITE_ONCE(sk->sk_user_data, NULL);
30 /*
31 * Do not move this NULL assignment outside of
32 * sk->sk_callback_lock because there is
33 * a race with reuseport_array_free()
34 * which does not hold the reuseport_lock.
35 */
36 RCU_INIT_POINTER(*socks, NULL);
37 }
38 write_unlock_bh(&sk->sk_callback_lock);
39 }
40
41 static int reuseport_array_alloc_check(union bpf_attr *attr)
42 {
43 if (attr->value_size != sizeof(u32) &&
44 attr->value_size != sizeof(u64))
45 return -EINVAL;
46
47 return array_map_alloc_check(attr);
48 }
49
50 static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
51 {
52 struct reuseport_array *array = reuseport_array(map);
53 u32 index = *(u32 *)key;
54
55 if (unlikely(index >= array->map.max_entries))
56 return NULL;
57
58 return rcu_dereference(array->ptrs[index]);
59 }
60
61 /* Called from syscall only */
62 static long reuseport_array_delete_elem(struct bpf_map *map, void *key)
63 {
64 struct reuseport_array *array = reuseport_array(map);
65 u32 index = *(u32 *)key;
66 struct sock *sk;
67 int err;
68
69 if (index >= map->max_entries)
70 return -E2BIG;
71
72 if (!rcu_access_pointer(array->ptrs[index]))
73 return -ENOENT;
74
75 spin_lock_bh(&reuseport_lock);
76
77 sk = rcu_dereference_protected(array->ptrs[index],
78 lockdep_is_held(&reuseport_lock));
79 if (sk) {
80 write_lock_bh(&sk->sk_callback_lock);
81 WRITE_ONCE(sk->sk_user_data, NULL);
82 RCU_INIT_POINTER(array->ptrs[index], NULL);
83 write_unlock_bh(&sk->sk_callback_lock);
84 err = 0;
85 } else {
86 err = -ENOENT;
87 }
88
89 spin_unlock_bh(&reuseport_lock);
90
91 return err;
92 }
93
94 static void reuseport_array_free(struct bpf_map *map)
95 {
96 struct reuseport_array *array = reuseport_array(map);
97 struct sock *sk;
98 u32 i;
99
100 /*
101 * ops->map_*_elem() will not be able to access this
102 * array now. Hence, this function only races with
103 * bpf_sk_reuseport_detach() which was triggered by
104 * close() or disconnect().
105 *
106 * This function and bpf_sk_reuseport_detach() are
107 * both removing sk from "array". Who removes it
108 * first does not matter.
109 *
110 * The only concern here is bpf_sk_reuseport_detach()
111 * may access "array" which is being freed here.
112 * bpf_sk_reuseport_detach() access this "array"
113 * through sk->sk_user_data _and_ with sk->sk_callback_lock
114 * held which is enough because this "array" is not freed
115 * until all sk->sk_user_data has stopped referencing this "array".
116 *
117 * Hence, due to the above, taking "reuseport_lock" is not
118 * needed here.
119 */
120
121 /*
122 * Since reuseport_lock is not taken, sk is accessed under
123 * rcu_read_lock()
124 */
125 rcu_read_lock();
126 for (i = 0; i < map->max_entries; i++) {
127 sk = rcu_dereference(array->ptrs[i]);
128 if (sk) {
129 write_lock_bh(&sk->sk_callback_lock);
130 /*
131 * No need for WRITE_ONCE(). At this point,
132 * no one is reading it without taking the
133 * sk->sk_callback_lock.
134 */
135 sk->sk_user_data = NULL;
136 write_unlock_bh(&sk->sk_callback_lock);
137 RCU_INIT_POINTER(array->ptrs[i], NULL);
138 }
139 }
140 rcu_read_unlock();
141
142 /*
143 * Once reaching here, all sk->sk_user_data is not
144 * referencing this "array". "array" can be freed now.
145 */
146 bpf_map_area_free(array);
147 }
148
149 static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
150 {
151 int numa_node = bpf_map_attr_numa_node(attr);
152 struct reuseport_array *array;
153
154 /* allocate all map elements and zero-initialize them */
155 array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node);
156 if (!array)
157 return ERR_PTR(-ENOMEM);
158
159 /* copy mandatory map attributes */
160 bpf_map_init_from_attr(&array->map, attr);
161
162 return &array->map;
163 }
164
165 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
166 void *value)
167 {
168 struct sock *sk;
169 int err;
170
171 if (map->value_size != sizeof(u64))
172 return -ENOSPC;
173
174 rcu_read_lock();
175 sk = reuseport_array_lookup_elem(map, key);
176 if (sk) {
177 *(u64 *)value = __sock_gen_cookie(sk);
178 err = 0;
179 } else {
180 err = -ENOENT;
181 }
182 rcu_read_unlock();
183
184 return err;
185 }
186
187 static int
188 reuseport_array_update_check(const struct reuseport_array *array,
189 const struct sock *nsk,
190 const struct sock *osk,
191 const struct sock_reuseport *nsk_reuse,
192 u32 map_flags)
193 {
194 if (osk && map_flags == BPF_NOEXIST)
195 return -EEXIST;
196
197 if (!osk && map_flags == BPF_EXIST)
198 return -ENOENT;
199
200 if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
201 return -ENOTSUPP;
202
203 if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
204 return -ENOTSUPP;
205
206 if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
207 return -ENOTSUPP;
208
209 /*
210 * sk must be hashed (i.e. listening in the TCP case or binded
211 * in the UDP case) and
212 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
213 *
214 * Also, sk will be used in bpf helper that is protected by
215 * rcu_read_lock().
216 */
217 if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
218 return -EINVAL;
219
220 /* READ_ONCE because the sk->sk_callback_lock may not be held here */
221 if (READ_ONCE(nsk->sk_user_data))
222 return -EBUSY;
223
224 return 0;
225 }
226
227 /*
228 * Called from syscall only.
229 * The "nsk" in the fd refcnt.
230 * The "osk" and "reuse" are protected by reuseport_lock.
231 */
232 int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
233 void *value, u64 map_flags)
234 {
235 struct reuseport_array *array = reuseport_array(map);
236 struct sock *free_osk = NULL, *osk, *nsk;
237 struct sock_reuseport *reuse;
238 u32 index = *(u32 *)key;
239 uintptr_t sk_user_data;
240 struct socket *socket;
241 int err, fd;
242
243 if (map_flags > BPF_EXIST)
244 return -EINVAL;
245
246 if (index >= map->max_entries)
247 return -E2BIG;
248
249 if (map->value_size == sizeof(u64)) {
250 u64 fd64 = *(u64 *)value;
251
252 if (fd64 > S32_MAX)
253 return -EINVAL;
254 fd = fd64;
255 } else {
256 fd = *(int *)value;
257 }
258
259 socket = sockfd_lookup(fd, &err);
260 if (!socket)
261 return err;
262
263 nsk = socket->sk;
264 if (!nsk) {
265 err = -EINVAL;
266 goto put_file;
267 }
268
269 /* Quick checks before taking reuseport_lock */
270 err = reuseport_array_update_check(array, nsk,
271 rcu_access_pointer(array->ptrs[index]),
272 rcu_access_pointer(nsk->sk_reuseport_cb),
273 map_flags);
274 if (err)
275 goto put_file;
276
277 spin_lock_bh(&reuseport_lock);
278 /*
279 * Some of the checks only need reuseport_lock
280 * but it is done under sk_callback_lock also
281 * for simplicity reason.
282 */
283 write_lock_bh(&nsk->sk_callback_lock);
284
285 osk = rcu_dereference_protected(array->ptrs[index],
286 lockdep_is_held(&reuseport_lock));
287 reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
288 lockdep_is_held(&reuseport_lock));
289 err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
290 if (err)
291 goto put_file_unlock;
292
293 sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
294 SK_USER_DATA_BPF;
295 WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
296 rcu_assign_pointer(array->ptrs[index], nsk);
297 free_osk = osk;
298 err = 0;
299
300 put_file_unlock:
301 write_unlock_bh(&nsk->sk_callback_lock);
302
303 if (free_osk) {
304 write_lock_bh(&free_osk->sk_callback_lock);
305 WRITE_ONCE(free_osk->sk_user_data, NULL);
306 write_unlock_bh(&free_osk->sk_callback_lock);
307 }
308
309 spin_unlock_bh(&reuseport_lock);
310 put_file:
311 fput(socket->file);
312 return err;
313 }
314
315 /* Called from syscall */
316 static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
317 void *next_key)
318 {
319 struct reuseport_array *array = reuseport_array(map);
320 u32 index = key ? *(u32 *)key : U32_MAX;
321 u32 *next = (u32 *)next_key;
322
323 if (index >= array->map.max_entries) {
324 *next = 0;
325 return 0;
326 }
327
328 if (index == array->map.max_entries - 1)
329 return -ENOENT;
330
331 *next = index + 1;
332 return 0;
333 }
334
335 static u64 reuseport_array_mem_usage(const struct bpf_map *map)
336 {
337 struct reuseport_array *array;
338
339 return struct_size(array, ptrs, map->max_entries);
340 }
341
342 BTF_ID_LIST_SINGLE(reuseport_array_map_btf_ids, struct, reuseport_array)
343 const struct bpf_map_ops reuseport_array_ops = {
344 .map_meta_equal = bpf_map_meta_equal,
345 .map_alloc_check = reuseport_array_alloc_check,
346 .map_alloc = reuseport_array_alloc,
347 .map_free = reuseport_array_free,
348 .map_lookup_elem = reuseport_array_lookup_elem,
349 .map_get_next_key = reuseport_array_get_next_key,
350 .map_delete_elem = reuseport_array_delete_elem,
351 .map_mem_usage = reuseport_array_mem_usage,
352 .map_btf_id = &reuseport_array_map_btf_ids[0],
353 };
354
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