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
26static int proc_test_super(struct super_block *sb, void *data)
27{
28	return sb->s_fs_info == data;
29}
30
31static 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
41enum {
42	Opt_gid, Opt_hidepid, Opt_err,
43};
44
45static const match_table_t tokens = {
46	{Opt_hidepid, "hidepid=%u"},
47	{Opt_gid, "gid=%u"},
48	{Opt_err, NULL},
49};
50
51static 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
92int 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
100static 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	}
145
146	return dget(sb->s_root);
147}
148
149static void proc_kill_sb(struct super_block *sb)
150{
151	struct pid_namespace *ns;
152
153	ns = (struct pid_namespace *)sb->s_fs_info;
154	if (ns->proc_self)
155		dput(ns->proc_self);
156	if (ns->proc_thread_self)
157		dput(ns->proc_thread_self);
158	kill_anon_super(sb);
159	put_pid_ns(ns);
160}
161
162static struct file_system_type proc_fs_type = {
163	.name		= "proc",
164	.mount		= proc_mount,
165	.kill_sb	= proc_kill_sb,
166	.fs_flags	= FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
167};
168
169void __init proc_root_init(void)
170{
171	int err;
172
173	proc_init_inodecache();
174	err = register_filesystem(&proc_fs_type);
175	if (err)
176		return;
177
178	proc_self_init();
179	proc_thread_self_init();
180	proc_symlink("mounts", NULL, "self/mounts");
181
182	proc_net_init();
183
184#ifdef CONFIG_SYSVIPC
185	proc_mkdir("sysvipc", NULL);
186#endif
187	proc_mkdir("fs", NULL);
188	proc_mkdir("driver", NULL);
189	proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
190#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
191	/* just give it a mountpoint */
192	proc_create_mount_point("openprom");
193#endif
194	proc_tty_init();
195	proc_mkdir("bus", NULL);
196	proc_sys_init();
197}
198
199static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
200)
201{
202	generic_fillattr(d_inode(dentry), stat);
203	stat->nlink = proc_root.nlink + nr_processes();
204	return 0;
205}
206
207static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
208{
209	if (!proc_pid_lookup(dir, dentry, flags))
210		return NULL;
211
212	return proc_lookup(dir, dentry, flags);
213}
214
215static int proc_root_readdir(struct file *file, struct dir_context *ctx)
216{
217	if (ctx->pos < FIRST_PROCESS_ENTRY) {
218		int error = proc_readdir(file, ctx);
219		if (unlikely(error <= 0))
220			return error;
221		ctx->pos = FIRST_PROCESS_ENTRY;
222	}
223
224	return proc_pid_readdir(file, ctx);
225}
226
227/*
228 * The root /proc directory is special, as it has the
229 * <pid> directories. Thus we don't use the generic
230 * directory handling functions for that..
231 */
232static const struct file_operations proc_root_operations = {
233	.read		 = generic_read_dir,
234	.iterate	 = proc_root_readdir,
235	.llseek		= default_llseek,
236};
237
238/*
239 * proc root can do almost nothing..
240 */
241static const struct inode_operations proc_root_inode_operations = {
242	.lookup		= proc_root_lookup,
243	.getattr	= proc_root_getattr,
244};
245
246/*
247 * This is the root "inode" in the /proc tree..
248 */
249struct proc_dir_entry proc_root = {
250	.low_ino	= PROC_ROOT_INO,
251	.namelen	= 5,
252	.mode		= S_IFDIR | S_IRUGO | S_IXUGO,
253	.nlink		= 2,
254	.count		= ATOMIC_INIT(1),
255	.proc_iops	= &proc_root_inode_operations,
256	.proc_fops	= &proc_root_operations,
257	.parent		= &proc_root,
258	.subdir		= RB_ROOT,
259	.name		= "/proc",
260};
261
262int pid_ns_prepare_proc(struct pid_namespace *ns)
263{
264	struct vfsmount *mnt;
265
266	mnt = kern_mount_data(&proc_fs_type, ns);
267	if (IS_ERR(mnt))
268		return PTR_ERR(mnt);
269
270	ns->proc_mnt = mnt;
271	return 0;
272}
273
274void pid_ns_release_proc(struct pid_namespace *ns)
275{
276	kern_unmount(ns->proc_mnt);
277}
278