1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  linux/fs/proc/root.c
4 *
5 *  Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 *  proc root directory handling functions
8 */
9#include <linux/errno.h>
10#include <linux/time.h>
11#include <linux/proc_fs.h>
12#include <linux/stat.h>
13#include <linux/init.h>
14#include <linux/sched.h>
15#include <linux/sched/stat.h>
16#include <linux/module.h>
17#include <linux/bitops.h>
18#include <linux/user_namespace.h>
19#include <linux/fs_context.h>
20#include <linux/mount.h>
21#include <linux/pid_namespace.h>
22#include <linux/fs_parser.h>
23#include <linux/cred.h>
24#include <linux/magic.h>
25#include <linux/slab.h>
26
27#include "internal.h"
28
29struct proc_fs_context {
30	struct pid_namespace	*pid_ns;
31	unsigned int		mask;
32	enum proc_hidepid	hidepid;
33	int			gid;
34	enum proc_pidonly	pidonly;
35};
36
37enum proc_param {
38	Opt_gid,
39	Opt_hidepid,
40	Opt_subset,
41};
42
43static const struct fs_parameter_spec proc_fs_parameters[] = {
44	fsparam_u32("gid",	Opt_gid),
45	fsparam_string("hidepid",	Opt_hidepid),
46	fsparam_string("subset",	Opt_subset),
47	{}
48};
49
50static inline int valid_hidepid(unsigned int value)
51{
52	return (value == HIDEPID_OFF ||
53		value == HIDEPID_NO_ACCESS ||
54		value == HIDEPID_INVISIBLE ||
55		value == HIDEPID_NOT_PTRACEABLE);
56}
57
58static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param)
59{
60	struct proc_fs_context *ctx = fc->fs_private;
61	struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);
62	struct fs_parse_result result;
63	int base = (unsigned long)hidepid_u32_spec.data;
64
65	if (param->type != fs_value_is_string)
66		return invalf(fc, "proc: unexpected type of hidepid value\n");
67
68	if (!kstrtouint(param->string, base, &result.uint_32)) {
69		if (!valid_hidepid(result.uint_32))
70			return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
71		ctx->hidepid = result.uint_32;
72		return 0;
73	}
74
75	if (!strcmp(param->string, "off"))
76		ctx->hidepid = HIDEPID_OFF;
77	else if (!strcmp(param->string, "noaccess"))
78		ctx->hidepid = HIDEPID_NO_ACCESS;
79	else if (!strcmp(param->string, "invisible"))
80		ctx->hidepid = HIDEPID_INVISIBLE;
81	else if (!strcmp(param->string, "ptraceable"))
82		ctx->hidepid = HIDEPID_NOT_PTRACEABLE;
83	else
84		return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
85
86	return 0;
87}
88
89static int proc_parse_subset_param(struct fs_context *fc, char *value)
90{
91	struct proc_fs_context *ctx = fc->fs_private;
92
93	while (value) {
94		char *ptr = strchr(value, ',');
95
96		if (ptr != NULL)
97			*ptr++ = '\0';
98
99		if (*value != '\0') {
100			if (!strcmp(value, "pid")) {
101				ctx->pidonly = PROC_PIDONLY_ON;
102			} else {
103				return invalf(fc, "proc: unsupported subset option - %s\n", value);
104			}
105		}
106		value = ptr;
107	}
108
109	return 0;
110}
111
112static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
113{
114	struct proc_fs_context *ctx = fc->fs_private;
115	struct fs_parse_result result;
116	int opt;
117
118	opt = fs_parse(fc, proc_fs_parameters, param, &result);
119	if (opt < 0)
120		return opt;
121
122	switch (opt) {
123	case Opt_gid:
124		ctx->gid = result.uint_32;
125		break;
126
127	case Opt_hidepid:
128		if (proc_parse_hidepid_param(fc, param))
129			return -EINVAL;
130		break;
131
132	case Opt_subset:
133		if (proc_parse_subset_param(fc, param->string) < 0)
134			return -EINVAL;
135		break;
136
137	default:
138		return -EINVAL;
139	}
140
141	ctx->mask |= 1 << opt;
142	return 0;
143}
144
145static void proc_apply_options(struct proc_fs_info *fs_info,
146			       struct fs_context *fc,
147			       struct user_namespace *user_ns)
148{
149	struct proc_fs_context *ctx = fc->fs_private;
150
151	if (ctx->mask & (1 << Opt_gid))
152		fs_info->pid_gid = make_kgid(user_ns, ctx->gid);
153	if (ctx->mask & (1 << Opt_hidepid))
154		fs_info->hide_pid = ctx->hidepid;
155	if (ctx->mask & (1 << Opt_subset))
156		fs_info->pidonly = ctx->pidonly;
157}
158
159static int proc_fill_super(struct super_block *s, struct fs_context *fc)
160{
161	struct proc_fs_context *ctx = fc->fs_private;
162	struct inode *root_inode;
163	struct proc_fs_info *fs_info;
164	int ret;
165
166	fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL);
167	if (!fs_info)
168		return -ENOMEM;
169
170	fs_info->pid_ns = get_pid_ns(ctx->pid_ns);
171	proc_apply_options(fs_info, fc, current_user_ns());
172
173	/* User space would break if executables or devices appear on proc */
174	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
175	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
176	s->s_blocksize = 1024;
177	s->s_blocksize_bits = 10;
178	s->s_magic = PROC_SUPER_MAGIC;
179	s->s_op = &proc_sops;
180	s->s_time_gran = 1;
181	s->s_fs_info = fs_info;
182
183	/*
184	 * procfs isn't actually a stacking filesystem; however, there is
185	 * too much magic going on inside it to permit stacking things on
186	 * top of it
187	 */
188	s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
189
190	/* procfs dentries and inodes don't require IO to create */
191	s->s_shrink->seeks = 0;
192
193	pde_get(&proc_root);
194	root_inode = proc_get_inode(s, &proc_root);
195	if (!root_inode) {
196		pr_err("proc_fill_super: get root inode failed\n");
197		return -ENOMEM;
198	}
199
200	s->s_root = d_make_root(root_inode);
201	if (!s->s_root) {
202		pr_err("proc_fill_super: allocate dentry failed\n");
203		return -ENOMEM;
204	}
205
206	ret = proc_setup_self(s);
207	if (ret) {
208		return ret;
209	}
210	return proc_setup_thread_self(s);
211}
212
213static int proc_reconfigure(struct fs_context *fc)
214{
215	struct super_block *sb = fc->root->d_sb;
216	struct proc_fs_info *fs_info = proc_sb_info(sb);
217
218	sync_filesystem(sb);
219
220	proc_apply_options(fs_info, fc, current_user_ns());
221	return 0;
222}
223
224static int proc_get_tree(struct fs_context *fc)
225{
226	return get_tree_nodev(fc, proc_fill_super);
227}
228
229static void proc_fs_context_free(struct fs_context *fc)
230{
231	struct proc_fs_context *ctx = fc->fs_private;
232
233	put_pid_ns(ctx->pid_ns);
234	kfree(ctx);
235}
236
237static const struct fs_context_operations proc_fs_context_ops = {
238	.free		= proc_fs_context_free,
239	.parse_param	= proc_parse_param,
240	.get_tree	= proc_get_tree,
241	.reconfigure	= proc_reconfigure,
242};
243
244static int proc_init_fs_context(struct fs_context *fc)
245{
246	struct proc_fs_context *ctx;
247
248	ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
249	if (!ctx)
250		return -ENOMEM;
251
252	ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
253	put_user_ns(fc->user_ns);
254	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
255	fc->fs_private = ctx;
256	fc->ops = &proc_fs_context_ops;
257	return 0;
258}
259
260static void proc_kill_sb(struct super_block *sb)
261{
262	struct proc_fs_info *fs_info = proc_sb_info(sb);
263
264	if (!fs_info) {
265		kill_anon_super(sb);
266		return;
267	}
268
269	dput(fs_info->proc_self);
270	dput(fs_info->proc_thread_self);
271
272	kill_anon_super(sb);
273	put_pid_ns(fs_info->pid_ns);
274	kfree_rcu(fs_info, rcu);
275}
276
277static struct file_system_type proc_fs_type = {
278	.name			= "proc",
279	.init_fs_context	= proc_init_fs_context,
280	.parameters		= proc_fs_parameters,
281	.kill_sb		= proc_kill_sb,
282	.fs_flags		= FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,
283};
284
285void __init proc_root_init(void)
286{
287	proc_init_kmemcache();
288	set_proc_pid_nlink();
289	proc_self_init();
290	proc_thread_self_init();
291	proc_symlink("mounts", NULL, "self/mounts");
292
293	proc_net_init();
294	proc_mkdir("fs", NULL);
295	proc_mkdir("driver", NULL);
296	proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
297#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
298	/* just give it a mountpoint */
299	proc_create_mount_point("openprom");
300#endif
301	proc_tty_init();
302	proc_mkdir("bus", NULL);
303	proc_sys_init();
304
305	/*
306	 * Last things last. It is not like userspace processes eager
307	 * to open /proc files exist at this point but register last
308	 * anyway.
309	 */
310	register_filesystem(&proc_fs_type);
311}
312
313static int proc_root_getattr(struct mnt_idmap *idmap,
314			     const struct path *path, struct kstat *stat,
315			     u32 request_mask, unsigned int query_flags)
316{
317	generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
318			 stat);
319	stat->nlink = proc_root.nlink + nr_processes();
320	return 0;
321}
322
323static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
324{
325	if (!proc_pid_lookup(dentry, flags))
326		return NULL;
327
328	return proc_lookup(dir, dentry, flags);
329}
330
331static int proc_root_readdir(struct file *file, struct dir_context *ctx)
332{
333	if (ctx->pos < FIRST_PROCESS_ENTRY) {
334		int error = proc_readdir(file, ctx);
335		if (unlikely(error <= 0))
336			return error;
337		ctx->pos = FIRST_PROCESS_ENTRY;
338	}
339
340	return proc_pid_readdir(file, ctx);
341}
342
343/*
344 * The root /proc directory is special, as it has the
345 * <pid> directories. Thus we don't use the generic
346 * directory handling functions for that..
347 */
348static const struct file_operations proc_root_operations = {
349	.read		 = generic_read_dir,
350	.iterate_shared	 = proc_root_readdir,
351	.llseek		= generic_file_llseek,
352};
353
354/*
355 * proc root can do almost nothing..
356 */
357static const struct inode_operations proc_root_inode_operations = {
358	.lookup		= proc_root_lookup,
359	.getattr	= proc_root_getattr,
360};
361
362/*
363 * This is the root "inode" in the /proc tree..
364 */
365struct proc_dir_entry proc_root = {
366	.low_ino	= PROC_ROOT_INO,
367	.namelen	= 5,
368	.mode		= S_IFDIR | S_IRUGO | S_IXUGO,
369	.nlink		= 2,
370	.refcnt		= REFCOUNT_INIT(1),
371	.proc_iops	= &proc_root_inode_operations,
372	.proc_dir_ops	= &proc_root_operations,
373	.parent		= &proc_root,
374	.subdir		= RB_ROOT,
375	.name		= "/proc",
376};
377