xref: /openbmc/linux/fs/proc/root.c (revision 5bd8e16d) 
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 (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
114 			return ERR_PTR(-EPERM);
115 
116 		/* Does the mounter have privilege over the pid namespace? */
117 		if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
118 			return ERR_PTR(-EPERM);
119 	}
120 
121 	sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
122 	if (IS_ERR(sb))
123 		return ERR_CAST(sb);
124 
125 	if (!proc_parse_options(options, ns)) {
126 		deactivate_locked_super(sb);
127 		return ERR_PTR(-EINVAL);
128 	}
129 
130 	if (!sb->s_root) {
131 		err = proc_fill_super(sb);
132 		if (err) {
133 			deactivate_locked_super(sb);
134 			return ERR_PTR(err);
135 		}
136 
137 		sb->s_flags |= MS_ACTIVE;
138 	}
139 
140 	return dget(sb->s_root);
141 }
142 
143 static void proc_kill_sb(struct super_block *sb)
144 {
145 	struct pid_namespace *ns;
146 
147 	ns = (struct pid_namespace *)sb->s_fs_info;
148 	if (ns->proc_self)
149 		dput(ns->proc_self);
150 	kill_anon_super(sb);
151 	put_pid_ns(ns);
152 }
153 
154 static struct file_system_type proc_fs_type = {
155 	.name		= "proc",
156 	.mount		= proc_mount,
157 	.kill_sb	= proc_kill_sb,
158 	.fs_flags	= FS_USERNS_MOUNT,
159 };
160 
161 void __init proc_root_init(void)
162 {
163 	int err;
164 
165 	proc_init_inodecache();
166 	err = register_filesystem(&proc_fs_type);
167 	if (err)
168 		return;
169 
170 	proc_self_init();
171 	proc_symlink("mounts", NULL, "self/mounts");
172 
173 	proc_net_init();
174 
175 #ifdef CONFIG_SYSVIPC
176 	proc_mkdir("sysvipc", NULL);
177 #endif
178 	proc_mkdir("fs", NULL);
179 	proc_mkdir("driver", NULL);
180 	proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
181 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
182 	/* just give it a mountpoint */
183 	proc_mkdir("openprom", NULL);
184 #endif
185 	proc_tty_init();
186 #ifdef CONFIG_PROC_DEVICETREE
187 	proc_device_tree_init();
188 #endif
189 	proc_mkdir("bus", NULL);
190 	proc_sys_init();
191 }
192 
193 static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
194 )
195 {
196 	generic_fillattr(dentry->d_inode, stat);
197 	stat->nlink = proc_root.nlink + nr_processes();
198 	return 0;
199 }
200 
201 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
202 {
203 	if (!proc_lookup(dir, dentry, flags))
204 		return NULL;
205 
206 	return proc_pid_lookup(dir, dentry, flags);
207 }
208 
209 static int proc_root_readdir(struct file *file, struct dir_context *ctx)
210 {
211 	if (ctx->pos < FIRST_PROCESS_ENTRY) {
212 		int error = proc_readdir(file, ctx);
213 		if (unlikely(error <= 0))
214 			return error;
215 		ctx->pos = FIRST_PROCESS_ENTRY;
216 	}
217 
218 	return proc_pid_readdir(file, ctx);
219 }
220 
221 /*
222  * The root /proc directory is special, as it has the
223  * <pid> directories. Thus we don't use the generic
224  * directory handling functions for that..
225  */
226 static const struct file_operations proc_root_operations = {
227 	.read		 = generic_read_dir,
228 	.iterate	 = proc_root_readdir,
229 	.llseek		= default_llseek,
230 };
231 
232 /*
233  * proc root can do almost nothing..
234  */
235 static const struct inode_operations proc_root_inode_operations = {
236 	.lookup		= proc_root_lookup,
237 	.getattr	= proc_root_getattr,
238 };
239 
240 /*
241  * This is the root "inode" in the /proc tree..
242  */
243 struct proc_dir_entry proc_root = {
244 	.low_ino	= PROC_ROOT_INO,
245 	.namelen	= 5,
246 	.mode		= S_IFDIR | S_IRUGO | S_IXUGO,
247 	.nlink		= 2,
248 	.count		= ATOMIC_INIT(1),
249 	.proc_iops	= &proc_root_inode_operations,
250 	.proc_fops	= &proc_root_operations,
251 	.parent		= &proc_root,
252 	.name		= "/proc",
253 };
254 
255 int pid_ns_prepare_proc(struct pid_namespace *ns)
256 {
257 	struct vfsmount *mnt;
258 
259 	mnt = kern_mount_data(&proc_fs_type, ns);
260 	if (IS_ERR(mnt))
261 		return PTR_ERR(mnt);
262 
263 	ns->proc_mnt = mnt;
264 	return 0;
265 }
266 
267 void pid_ns_release_proc(struct pid_namespace *ns)
268 {
269 	kern_unmount(ns->proc_mnt);
270 }
271