xref: /linux/fs/proc/root.c (revision 0d456bad36d42d16022be045c8a53ddbb59ee478)
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/mount.h>
20 #include <linux/pid_namespace.h>
21 #include <linux/parser.h>
22 
23 #include "internal.h"
24 
25 static int proc_test_super(struct super_block *sb, void *data)
26 {
27 	return sb->s_fs_info == data;
28 }
29 
30 static int proc_set_super(struct super_block *sb, void *data)
31 {
32 	int err = set_anon_super(sb, NULL);
33 	if (!err) {
34 		struct pid_namespace *ns = (struct pid_namespace *)data;
35 		sb->s_fs_info = get_pid_ns(ns);
36 	}
37 	return err;
38 }
39 
40 enum {
41 	Opt_gid, Opt_hidepid, Opt_err,
42 };
43 
44 static const match_table_t tokens = {
45 	{Opt_hidepid, "hidepid=%u"},
46 	{Opt_gid, "gid=%u"},
47 	{Opt_err, NULL},
48 };
49 
50 static int proc_parse_options(char *options, struct pid_namespace *pid)
51 {
52 	char *p;
53 	substring_t args[MAX_OPT_ARGS];
54 	int option;
55 
56 	if (!options)
57 		return 1;
58 
59 	while ((p = strsep(&options, ",")) != NULL) {
60 		int token;
61 		if (!*p)
62 			continue;
63 
64 		args[0].to = args[0].from = NULL;
65 		token = match_token(p, tokens, args);
66 		switch (token) {
67 		case Opt_gid:
68 			if (match_int(&args[0], &option))
69 				return 0;
70 			pid->pid_gid = make_kgid(current_user_ns(), option);
71 			break;
72 		case Opt_hidepid:
73 			if (match_int(&args[0], &option))
74 				return 0;
75 			if (option < 0 || option > 2) {
76 				pr_err("proc: hidepid value must be between 0 and 2.\n");
77 				return 0;
78 			}
79 			pid->hide_pid = option;
80 			break;
81 		default:
82 			pr_err("proc: unrecognized mount option \"%s\" "
83 			       "or missing value\n", p);
84 			return 0;
85 		}
86 	}
87 
88 	return 1;
89 }
90 
91 int proc_remount(struct super_block *sb, int *flags, char *data)
92 {
93 	struct pid_namespace *pid = sb->s_fs_info;
94 	return !proc_parse_options(data, pid);
95 }
96 
97 static struct dentry *proc_mount(struct file_system_type *fs_type,
98 	int flags, const char *dev_name, void *data)
99 {
100 	int err;
101 	struct super_block *sb;
102 	struct pid_namespace *ns;
103 	char *options;
104 
105 	if (flags & MS_KERNMOUNT) {
106 		ns = (struct pid_namespace *)data;
107 		options = NULL;
108 	} else {
109 		ns = task_active_pid_ns(current);
110 		options = data;
111 	}
112 
113 	sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
114 	if (IS_ERR(sb))
115 		return ERR_CAST(sb);
116 
117 	if (!proc_parse_options(options, ns)) {
118 		deactivate_locked_super(sb);
119 		return ERR_PTR(-EINVAL);
120 	}
121 
122 	if (!sb->s_root) {
123 		err = proc_fill_super(sb);
124 		if (err) {
125 			deactivate_locked_super(sb);
126 			return ERR_PTR(err);
127 		}
128 
129 		sb->s_flags |= MS_ACTIVE;
130 	}
131 
132 	return dget(sb->s_root);
133 }
134 
135 static void proc_kill_sb(struct super_block *sb)
136 {
137 	struct pid_namespace *ns;
138 
139 	ns = (struct pid_namespace *)sb->s_fs_info;
140 	kill_anon_super(sb);
141 	put_pid_ns(ns);
142 }
143 
144 static struct file_system_type proc_fs_type = {
145 	.name		= "proc",
146 	.mount		= proc_mount,
147 	.kill_sb	= proc_kill_sb,
148 	.fs_flags	= FS_USERNS_MOUNT,
149 };
150 
151 void __init proc_root_init(void)
152 {
153 	int err;
154 
155 	proc_init_inodecache();
156 	err = register_filesystem(&proc_fs_type);
157 	if (err)
158 		return;
159 
160 	proc_self_init();
161 	proc_symlink("mounts", NULL, "self/mounts");
162 
163 	proc_net_init();
164 
165 #ifdef CONFIG_SYSVIPC
166 	proc_mkdir("sysvipc", NULL);
167 #endif
168 	proc_mkdir("fs", NULL);
169 	proc_mkdir("driver", NULL);
170 	proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
171 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
172 	/* just give it a mountpoint */
173 	proc_mkdir("openprom", NULL);
174 #endif
175 	proc_tty_init();
176 #ifdef CONFIG_PROC_DEVICETREE
177 	proc_device_tree_init();
178 #endif
179 	proc_mkdir("bus", NULL);
180 	proc_sys_init();
181 }
182 
183 static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
184 )
185 {
186 	generic_fillattr(dentry->d_inode, stat);
187 	stat->nlink = proc_root.nlink + nr_processes();
188 	return 0;
189 }
190 
191 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
192 {
193 	if (!proc_lookup(dir, dentry, flags))
194 		return NULL;
195 
196 	return proc_pid_lookup(dir, dentry, flags);
197 }
198 
199 static int proc_root_readdir(struct file * filp,
200 	void * dirent, filldir_t filldir)
201 {
202 	unsigned int nr = filp->f_pos;
203 	int ret;
204 
205 	if (nr < FIRST_PROCESS_ENTRY) {
206 		int error = proc_readdir(filp, dirent, filldir);
207 		if (error <= 0)
208 			return error;
209 		filp->f_pos = FIRST_PROCESS_ENTRY;
210 	}
211 
212 	ret = proc_pid_readdir(filp, dirent, filldir);
213 	return ret;
214 }
215 
216 /*
217  * The root /proc directory is special, as it has the
218  * <pid> directories. Thus we don't use the generic
219  * directory handling functions for that..
220  */
221 static const struct file_operations proc_root_operations = {
222 	.read		 = generic_read_dir,
223 	.readdir	 = proc_root_readdir,
224 	.llseek		= default_llseek,
225 };
226 
227 /*
228  * proc root can do almost nothing..
229  */
230 static const struct inode_operations proc_root_inode_operations = {
231 	.lookup		= proc_root_lookup,
232 	.getattr	= proc_root_getattr,
233 };
234 
235 /*
236  * This is the root "inode" in the /proc tree..
237  */
238 struct proc_dir_entry proc_root = {
239 	.low_ino	= PROC_ROOT_INO,
240 	.namelen	= 5,
241 	.mode		= S_IFDIR | S_IRUGO | S_IXUGO,
242 	.nlink		= 2,
243 	.count		= ATOMIC_INIT(1),
244 	.proc_iops	= &proc_root_inode_operations,
245 	.proc_fops	= &proc_root_operations,
246 	.parent		= &proc_root,
247 	.name		= "/proc",
248 };
249 
250 int pid_ns_prepare_proc(struct pid_namespace *ns)
251 {
252 	struct vfsmount *mnt;
253 
254 	mnt = kern_mount_data(&proc_fs_type, ns);
255 	if (IS_ERR(mnt))
256 		return PTR_ERR(mnt);
257 
258 	ns->proc_mnt = mnt;
259 	return 0;
260 }
261 
262 void pid_ns_release_proc(struct pid_namespace *ns)
263 {
264 	kern_unmount(ns->proc_mnt);
265 }
266