xref: /openbmc/linux/fs/proc/root.c (revision ca79522c) 
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 	return !proc_parse_options(data, pid);
96 }
97 
98 static struct dentry *proc_mount(struct file_system_type *fs_type,
99 	int flags, const char *dev_name, void *data)
100 {
101 	int err;
102 	struct super_block *sb;
103 	struct pid_namespace *ns;
104 	char *options;
105 
106 	if (flags & MS_KERNMOUNT) {
107 		ns = (struct pid_namespace *)data;
108 		options = NULL;
109 	} else {
110 		ns = task_active_pid_ns(current);
111 		options = data;
112 
113 		if (!current_user_ns()->may_mount_proc)
114 			return ERR_PTR(-EPERM);
115 	}
116 
117 	sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
118 	if (IS_ERR(sb))
119 		return ERR_CAST(sb);
120 
121 	if (!proc_parse_options(options, ns)) {
122 		deactivate_locked_super(sb);
123 		return ERR_PTR(-EINVAL);
124 	}
125 
126 	if (!sb->s_root) {
127 		err = proc_fill_super(sb);
128 		if (err) {
129 			deactivate_locked_super(sb);
130 			return ERR_PTR(err);
131 		}
132 
133 		sb->s_flags |= MS_ACTIVE;
134 	}
135 
136 	return dget(sb->s_root);
137 }
138 
139 static void proc_kill_sb(struct super_block *sb)
140 {
141 	struct pid_namespace *ns;
142 
143 	ns = (struct pid_namespace *)sb->s_fs_info;
144 	if (ns->proc_self)
145 		dput(ns->proc_self);
146 	kill_anon_super(sb);
147 	put_pid_ns(ns);
148 }
149 
150 static struct file_system_type proc_fs_type = {
151 	.name		= "proc",
152 	.mount		= proc_mount,
153 	.kill_sb	= proc_kill_sb,
154 	.fs_flags	= FS_USERNS_MOUNT,
155 };
156 
157 void __init proc_root_init(void)
158 {
159 	int err;
160 
161 	proc_init_inodecache();
162 	err = register_filesystem(&proc_fs_type);
163 	if (err)
164 		return;
165 
166 	proc_self_init();
167 	proc_symlink("mounts", NULL, "self/mounts");
168 
169 	proc_net_init();
170 
171 #ifdef CONFIG_SYSVIPC
172 	proc_mkdir("sysvipc", NULL);
173 #endif
174 	proc_mkdir("fs", NULL);
175 	proc_mkdir("driver", NULL);
176 	proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
177 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
178 	/* just give it a mountpoint */
179 	proc_mkdir("openprom", NULL);
180 #endif
181 	proc_tty_init();
182 #ifdef CONFIG_PROC_DEVICETREE
183 	proc_device_tree_init();
184 #endif
185 	proc_mkdir("bus", NULL);
186 	proc_sys_init();
187 }
188 
189 static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
190 )
191 {
192 	generic_fillattr(dentry->d_inode, stat);
193 	stat->nlink = proc_root.nlink + nr_processes();
194 	return 0;
195 }
196 
197 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
198 {
199 	if (!proc_lookup(dir, dentry, flags))
200 		return NULL;
201 
202 	return proc_pid_lookup(dir, dentry, flags);
203 }
204 
205 static int proc_root_readdir(struct file * filp,
206 	void * dirent, filldir_t filldir)
207 {
208 	unsigned int nr = filp->f_pos;
209 	int ret;
210 
211 	if (nr < FIRST_PROCESS_ENTRY) {
212 		int error = proc_readdir(filp, dirent, filldir);
213 		if (error <= 0)
214 			return error;
215 		filp->f_pos = FIRST_PROCESS_ENTRY;
216 	}
217 
218 	ret = proc_pid_readdir(filp, dirent, filldir);
219 	return ret;
220 }
221 
222 /*
223  * The root /proc directory is special, as it has the
224  * <pid> directories. Thus we don't use the generic
225  * directory handling functions for that..
226  */
227 static const struct file_operations proc_root_operations = {
228 	.read		 = generic_read_dir,
229 	.readdir	 = proc_root_readdir,
230 	.llseek		= default_llseek,
231 };
232 
233 /*
234  * proc root can do almost nothing..
235  */
236 static const struct inode_operations proc_root_inode_operations = {
237 	.lookup		= proc_root_lookup,
238 	.getattr	= proc_root_getattr,
239 };
240 
241 /*
242  * This is the root "inode" in the /proc tree..
243  */
244 struct proc_dir_entry proc_root = {
245 	.low_ino	= PROC_ROOT_INO,
246 	.namelen	= 5,
247 	.mode		= S_IFDIR | S_IRUGO | S_IXUGO,
248 	.nlink		= 2,
249 	.count		= ATOMIC_INIT(1),
250 	.proc_iops	= &proc_root_inode_operations,
251 	.proc_fops	= &proc_root_operations,
252 	.parent		= &proc_root,
253 	.name		= "/proc",
254 };
255 
256 int pid_ns_prepare_proc(struct pid_namespace *ns)
257 {
258 	struct vfsmount *mnt;
259 
260 	mnt = kern_mount_data(&proc_fs_type, ns);
261 	if (IS_ERR(mnt))
262 		return PTR_ERR(mnt);
263 
264 	ns->proc_mnt = mnt;
265 	return 0;
266 }
267 
268 void pid_ns_release_proc(struct pid_namespace *ns)
269 {
270 	kern_unmount(ns->proc_mnt);
271 }
272