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Linux/fs/proc/root.c

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  1 /*
  2  *  linux/fs/proc/root.c
  3  *
  4  *  Copyright (C) 1991, 1992 Linus Torvalds
  5  *
  6  *  proc root directory handling functions
  7  */
  8 
  9 #include <asm/uaccess.h>
 10 
 11 #include <linux/errno.h>
 12 #include <linux/time.h>
 13 #include <linux/proc_fs.h>
 14 #include <linux/stat.h>
 15 #include <linux/init.h>
 16 #include <linux/sched.h>
 17 #include <linux/module.h>
 18 #include <linux/bitops.h>
 19 #include <linux/user_namespace.h>
 20 #include <linux/mount.h>
 21 #include <linux/pid_namespace.h>
 22 #include <linux/parser.h>
 23 
 24 #include "internal.h"
 25 
 26 static int proc_test_super(struct super_block *sb, void *data)
 27 {
 28         return sb->s_fs_info == data;
 29 }
 30 
 31 static int proc_set_super(struct super_block *sb, void *data)
 32 {
 33         int err = set_anon_super(sb, NULL);
 34         if (!err) {
 35                 struct pid_namespace *ns = (struct pid_namespace *)data;
 36                 sb->s_fs_info = get_pid_ns(ns);
 37         }
 38         return err;
 39 }
 40 
 41 enum {
 42         Opt_gid, Opt_hidepid, Opt_err,
 43 };
 44 
 45 static const match_table_t tokens = {
 46         {Opt_hidepid, "hidepid=%u"},
 47         {Opt_gid, "gid=%u"},
 48         {Opt_err, NULL},
 49 };
 50 
 51 static int proc_parse_options(char *options, struct pid_namespace *pid)
 52 {
 53         char *p;
 54         substring_t args[MAX_OPT_ARGS];
 55         int option;
 56 
 57         if (!options)
 58                 return 1;
 59 
 60         while ((p = strsep(&options, ",")) != NULL) {
 61                 int token;
 62                 if (!*p)
 63                         continue;
 64 
 65                 args[0].to = args[0].from = NULL;
 66                 token = match_token(p, tokens, args);
 67                 switch (token) {
 68                 case Opt_gid:
 69                         if (match_int(&args[0], &option))
 70                                 return 0;
 71                         pid->pid_gid = make_kgid(current_user_ns(), option);
 72                         break;
 73                 case Opt_hidepid:
 74                         if (match_int(&args[0], &option))
 75                                 return 0;
 76                         if (option < 0 || option > 2) {
 77                                 pr_err("proc: hidepid value must be between 0 and 2.\n");
 78                                 return 0;
 79                         }
 80                         pid->hide_pid = option;
 81                         break;
 82                 default:
 83                         pr_err("proc: unrecognized mount option \"%s\" "
 84                                "or missing value\n", p);
 85                         return 0;
 86                 }
 87         }
 88 
 89         return 1;
 90 }
 91 
 92 int proc_remount(struct super_block *sb, int *flags, char *data)
 93 {
 94         struct pid_namespace *pid = sb->s_fs_info;
 95 
 96         sync_filesystem(sb);
 97         return !proc_parse_options(data, pid);
 98 }
 99 
100 static struct dentry *proc_mount(struct file_system_type *fs_type,
101         int flags, const char *dev_name, void *data)
102 {
103         int err;
104         struct super_block *sb;
105         struct pid_namespace *ns;
106         char *options;
107 
108         if (flags & MS_KERNMOUNT) {
109                 ns = (struct pid_namespace *)data;
110                 options = NULL;
111         } else {
112                 ns = task_active_pid_ns(current);
113                 options = data;
114 
115                 /* Does the mounter have privilege over the pid namespace? */
116                 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
117                         return ERR_PTR(-EPERM);
118         }
119 
120         sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
121         if (IS_ERR(sb))
122                 return ERR_CAST(sb);
123 
124         /*
125          * procfs isn't actually a stacking filesystem; however, there is
126          * too much magic going on inside it to permit stacking things on
127          * top of it
128          */
129         sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
130 
131         if (!proc_parse_options(options, ns)) {
132                 deactivate_locked_super(sb);
133                 return ERR_PTR(-EINVAL);
134         }
135 
136         if (!sb->s_root) {
137                 err = proc_fill_super(sb);
138                 if (err) {
139                         deactivate_locked_super(sb);
140                         return ERR_PTR(err);
141                 }
142 
143                 sb->s_flags |= MS_ACTIVE;
144                 /* User space would break if executables appear on proc */
145                 sb->s_iflags |= SB_I_NOEXEC;
146         }
147 
148         return dget(sb->s_root);
149 }
150 
151 static void proc_kill_sb(struct super_block *sb)
152 {
153         struct pid_namespace *ns;
154 
155         ns = (struct pid_namespace *)sb->s_fs_info;
156         if (ns->proc_self)
157                 dput(ns->proc_self);
158         if (ns->proc_thread_self)
159                 dput(ns->proc_thread_self);
160         kill_anon_super(sb);
161         put_pid_ns(ns);
162 }
163 
164 static struct file_system_type proc_fs_type = {
165         .name           = "proc",
166         .mount          = proc_mount,
167         .kill_sb        = proc_kill_sb,
168         .fs_flags       = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
169 };
170 
171 void __init proc_root_init(void)
172 {
173         int err;
174 
175         proc_init_inodecache();
176         err = register_filesystem(&proc_fs_type);
177         if (err)
178                 return;
179 
180         proc_self_init();
181         proc_thread_self_init();
182         proc_symlink("mounts", NULL, "self/mounts");
183 
184         proc_net_init();
185 
186 #ifdef CONFIG_SYSVIPC
187         proc_mkdir("sysvipc", NULL);
188 #endif
189         proc_mkdir("fs", NULL);
190         proc_mkdir("driver", NULL);
191         proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
192 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
193         /* just give it a mountpoint */
194         proc_create_mount_point("openprom");
195 #endif
196         proc_tty_init();
197         proc_mkdir("bus", NULL);
198         proc_sys_init();
199 }
200 
201 static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
202 )
203 {
204         generic_fillattr(d_inode(dentry), stat);
205         stat->nlink = proc_root.nlink + nr_processes();
206         return 0;
207 }
208 
209 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
210 {
211         if (!proc_pid_lookup(dir, dentry, flags))
212                 return NULL;
213         
214         return proc_lookup(dir, dentry, flags);
215 }
216 
217 static int proc_root_readdir(struct file *file, struct dir_context *ctx)
218 {
219         if (ctx->pos < FIRST_PROCESS_ENTRY) {
220                 int error = proc_readdir(file, ctx);
221                 if (unlikely(error <= 0))
222                         return error;
223                 ctx->pos = FIRST_PROCESS_ENTRY;
224         }
225 
226         return proc_pid_readdir(file, ctx);
227 }
228 
229 /*
230  * The root /proc directory is special, as it has the
231  * <pid> directories. Thus we don't use the generic
232  * directory handling functions for that..
233  */
234 static const struct file_operations proc_root_operations = {
235         .read            = generic_read_dir,
236         .iterate_shared  = proc_root_readdir,
237         .llseek         = generic_file_llseek,
238 };
239 
240 /*
241  * proc root can do almost nothing..
242  */
243 static const struct inode_operations proc_root_inode_operations = {
244         .lookup         = proc_root_lookup,
245         .getattr        = proc_root_getattr,
246 };
247 
248 /*
249  * This is the root "inode" in the /proc tree..
250  */
251 struct proc_dir_entry proc_root = {
252         .low_ino        = PROC_ROOT_INO, 
253         .namelen        = 5, 
254         .mode           = S_IFDIR | S_IRUGO | S_IXUGO, 
255         .nlink          = 2, 
256         .count          = ATOMIC_INIT(1),
257         .proc_iops      = &proc_root_inode_operations, 
258         .proc_fops      = &proc_root_operations,
259         .parent         = &proc_root,
260         .subdir         = RB_ROOT,
261         .name           = "/proc",
262 };
263 
264 int pid_ns_prepare_proc(struct pid_namespace *ns)
265 {
266         struct vfsmount *mnt;
267 
268         mnt = kern_mount_data(&proc_fs_type, ns);
269         if (IS_ERR(mnt))
270                 return PTR_ERR(mnt);
271 
272         ns->proc_mnt = mnt;
273         return 0;
274 }
275 
276 void pid_ns_release_proc(struct pid_namespace *ns)
277 {
278         kern_unmount(ns->proc_mnt);
279 }
280 

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