1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/proc/root.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * proc root directory handling functions
8 */
9 #include <linux/errno.h>
10 #include <linux/time.h>
11 #include <linux/proc_fs.h>
12 #include <linux/stat.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/sched/stat.h>
16 #include <linux/module.h>
17 #include <linux/bitops.h>
18 #include <linux/user_namespace.h>
19 #include <linux/fs_context.h>
20 #include <linux/mount.h>
21 #include <linux/pid_namespace.h>
22 #include <linux/fs_parser.h>
23 #include <linux/cred.h>
24 #include <linux/magic.h>
25 #include <linux/slab.h>
26
27 #include "internal.h"
28
29 struct proc_fs_context {
30 struct pid_namespace *pid_ns;
31 unsigned int mask;
32 enum proc_hidepid hidepid;
33 int gid;
34 enum proc_pidonly pidonly;
35 };
36
37 enum proc_param {
38 Opt_gid,
39 Opt_hidepid,
40 Opt_subset,
41 };
42
43 static const struct fs_parameter_spec proc_fs_parameters[] = {
44 fsparam_u32("gid", Opt_gid),
45 fsparam_string("hidepid", Opt_hidepid),
46 fsparam_string("subset", Opt_subset),
47 {}
48 };
49
50 static inline int valid_hidepid(unsigned int value)
51 {
52 return (value == HIDEPID_OFF ||
53 value == HIDEPID_NO_ACCESS ||
54 value == HIDEPID_INVISIBLE ||
55 value == HIDEPID_NOT_PTRACEABLE);
56 }
57
58 static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param)
59 {
60 struct proc_fs_context *ctx = fc->fs_private;
61 struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);
62 struct fs_parse_result result;
63 int base = (unsigned long)hidepid_u32_spec.data;
64
65 if (param->type != fs_value_is_string)
66 return invalf(fc, "proc: unexpected type of hidepid value\n");
67
68 if (!kstrtouint(param->string, base, &result.uint_32)) {
69 if (!valid_hidepid(result.uint_32))
70 return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
71 ctx->hidepid = result.uint_32;
72 return 0;
73 }
74
75 if (!strcmp(param->string, "off"))
76 ctx->hidepid = HIDEPID_OFF;
77 else if (!strcmp(param->string, "noaccess"))
78 ctx->hidepid = HIDEPID_NO_ACCESS;
79 else if (!strcmp(param->string, "invisible"))
80 ctx->hidepid = HIDEPID_INVISIBLE;
81 else if (!strcmp(param->string, "ptraceable"))
82 ctx->hidepid = HIDEPID_NOT_PTRACEABLE;
83 else
84 return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
85
86 return 0;
87 }
88
89 static int proc_parse_subset_param(struct fs_context *fc, char *value)
90 {
91 struct proc_fs_context *ctx = fc->fs_private;
92
93 while (value) {
94 char *ptr = strchr(value, ',');
95
96 if (ptr != NULL)
97 *ptr++ = '\0';
98
99 if (*value != '\0') {
100 if (!strcmp(value, "pid")) {
101 ctx->pidonly = PROC_PIDONLY_ON;
102 } else {
103 return invalf(fc, "proc: unsupported subset option - %s\n", value);
104 }
105 }
106 value = ptr;
107 }
108
109 return 0;
110 }
111
112 static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
113 {
114 struct proc_fs_context *ctx = fc->fs_private;
115 struct fs_parse_result result;
116 int opt;
117
118 opt = fs_parse(fc, proc_fs_parameters, param, &result);
119 if (opt < 0)
120 return opt;
121
122 switch (opt) {
123 case Opt_gid:
124 ctx->gid = result.uint_32;
125 break;
126
127 case Opt_hidepid:
128 if (proc_parse_hidepid_param(fc, param))
129 return -EINVAL;
130 break;
131
132 case Opt_subset:
133 if (proc_parse_subset_param(fc, param->string) < 0)
134 return -EINVAL;
135 break;
136
137 default:
138 return -EINVAL;
139 }
140
141 ctx->mask |= 1 << opt;
142 return 0;
143 }
144
145 static void proc_apply_options(struct proc_fs_info *fs_info,
146 struct fs_context *fc,
147 struct user_namespace *user_ns)
148 {
149 struct proc_fs_context *ctx = fc->fs_private;
150
151 if (ctx->mask & (1 << Opt_gid))
152 fs_info->pid_gid = make_kgid(user_ns, ctx->gid);
153 if (ctx->mask & (1 << Opt_hidepid))
154 fs_info->hide_pid = ctx->hidepid;
155 if (ctx->mask & (1 << Opt_subset))
156 fs_info->pidonly = ctx->pidonly;
157 }
158
159 static int proc_fill_super(struct super_block *s, struct fs_context *fc)
160 {
161 struct proc_fs_context *ctx = fc->fs_private;
162 struct inode *root_inode;
163 struct proc_fs_info *fs_info;
164 int ret;
165
166 fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL);
167 if (!fs_info)
168 return -ENOMEM;
169
170 fs_info->pid_ns = get_pid_ns(ctx->pid_ns);
171 proc_apply_options(fs_info, fc, current_user_ns());
172
173 /* User space would break if executables or devices appear on proc */
174 s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
175 s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
176 s->s_blocksize = 1024;
177 s->s_blocksize_bits = 10;
178 s->s_magic = PROC_SUPER_MAGIC;
179 s->s_op = &proc_sops;
180 s->s_time_gran = 1;
181 s->s_fs_info = fs_info;
182
183 /*
184 * procfs isn't actually a stacking filesystem; however, there is
185 * too much magic going on inside it to permit stacking things on
186 * top of it
187 */
188 s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
189
190 /* procfs dentries and inodes don't require IO to create */
191 s->s_shrink->seeks = 0;
192
193 pde_get(&proc_root);
194 root_inode = proc_get_inode(s, &proc_root);
195 if (!root_inode) {
196 pr_err("proc_fill_super: get root inode failed\n");
197 return -ENOMEM;
198 }
199
200 s->s_root = d_make_root(root_inode);
201 if (!s->s_root) {
202 pr_err("proc_fill_super: allocate dentry failed\n");
203 return -ENOMEM;
204 }
205
206 ret = proc_setup_self(s);
207 if (ret) {
208 return ret;
209 }
210 return proc_setup_thread_self(s);
211 }
212
213 static int proc_reconfigure(struct fs_context *fc)
214 {
215 struct super_block *sb = fc->root->d_sb;
216 struct proc_fs_info *fs_info = proc_sb_info(sb);
217
218 sync_filesystem(sb);
219
220 proc_apply_options(fs_info, fc, current_user_ns());
221 return 0;
222 }
223
224 static int proc_get_tree(struct fs_context *fc)
225 {
226 return get_tree_nodev(fc, proc_fill_super);
227 }
228
229 static void proc_fs_context_free(struct fs_context *fc)
230 {
231 struct proc_fs_context *ctx = fc->fs_private;
232
233 put_pid_ns(ctx->pid_ns);
234 kfree(ctx);
235 }
236
237 static const struct fs_context_operations proc_fs_context_ops = {
238 .free = proc_fs_context_free,
239 .parse_param = proc_parse_param,
240 .get_tree = proc_get_tree,
241 .reconfigure = proc_reconfigure,
242 };
243
244 static int proc_init_fs_context(struct fs_context *fc)
245 {
246 struct proc_fs_context *ctx;
247
248 ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
249 if (!ctx)
250 return -ENOMEM;
251
252 ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
253 put_user_ns(fc->user_ns);
254 fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
255 fc->fs_private = ctx;
256 fc->ops = &proc_fs_context_ops;
257 return 0;
258 }
259
260 static void proc_kill_sb(struct super_block *sb)
261 {
262 struct proc_fs_info *fs_info = proc_sb_info(sb);
263
264 if (!fs_info) {
265 kill_anon_super(sb);
266 return;
267 }
268
269 dput(fs_info->proc_self);
270 dput(fs_info->proc_thread_self);
271
272 kill_anon_super(sb);
273 put_pid_ns(fs_info->pid_ns);
274 kfree_rcu(fs_info, rcu);
275 }
276
277 static struct file_system_type proc_fs_type = {
278 .name = "proc",
279 .init_fs_context = proc_init_fs_context,
280 .parameters = proc_fs_parameters,
281 .kill_sb = proc_kill_sb,
282 .fs_flags = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,
283 };
284
285 void __init proc_root_init(void)
286 {
287 proc_init_kmemcache();
288 set_proc_pid_nlink();
289 proc_self_init();
290 proc_thread_self_init();
291 proc_symlink("mounts", NULL, "self/mounts");
292
293 proc_net_init();
294 proc_mkdir("fs", NULL);
295 proc_mkdir("driver", NULL);
296 proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
297 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
298 /* just give it a mountpoint */
299 proc_create_mount_point("openprom");
300 #endif
301 proc_tty_init();
302 proc_mkdir("bus", NULL);
303 proc_sys_init();
304
305 /*
306 * Last things last. It is not like userspace processes eager
307 * to open /proc files exist at this point but register last
308 * anyway.
309 */
310 register_filesystem(&proc_fs_type);
311 }
312
313 static int proc_root_getattr(struct mnt_idmap *idmap,
314 const struct path *path, struct kstat *stat,
315 u32 request_mask, unsigned int query_flags)
316 {
317 generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
318 stat);
319 stat->nlink = proc_root.nlink + nr_processes();
320 return 0;
321 }
322
323 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
324 {
325 if (!proc_pid_lookup(dentry, flags))
326 return NULL;
327
328 return proc_lookup(dir, dentry, flags);
329 }
330
331 static int proc_root_readdir(struct file *file, struct dir_context *ctx)
332 {
333 if (ctx->pos < FIRST_PROCESS_ENTRY) {
334 int error = proc_readdir(file, ctx);
335 if (unlikely(error <= 0))
336 return error;
337 ctx->pos = FIRST_PROCESS_ENTRY;
338 }
339
340 return proc_pid_readdir(file, ctx);
341 }
342
343 /*
344 * The root /proc directory is special, as it has the
345 * <pid> directories. Thus we don't use the generic
346 * directory handling functions for that..
347 */
348 static const struct file_operations proc_root_operations = {
349 .read = generic_read_dir,
350 .iterate_shared = proc_root_readdir,
351 .llseek = generic_file_llseek,
352 };
353
354 /*
355 * proc root can do almost nothing..
356 */
357 static const struct inode_operations proc_root_inode_operations = {
358 .lookup = proc_root_lookup,
359 .getattr = proc_root_getattr,
360 };
361
362 /*
363 * This is the root "inode" in the /proc tree..
364 */
365 struct proc_dir_entry proc_root = {
366 .low_ino = PROC_ROOT_INO,
367 .namelen = 5,
368 .mode = S_IFDIR | S_IRUGO | S_IXUGO,
369 .nlink = 2,
370 .refcnt = REFCOUNT_INIT(1),
371 .proc_iops = &proc_root_inode_operations,
372 .proc_dir_ops = &proc_root_operations,
373 .parent = &proc_root,
374 .subdir = RB_ROOT,
375 .name = "/proc",
376 };
377
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