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Linux/fs/proc/root.c

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

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