proc_namespace.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
  4 *
  5 * In fact, that's a piece of procfs; it's *almost* isolated from
  6 * the rest of fs/proc, but has rather close relationships with
  7 * fs/namespace.c, thus here instead of fs/proc
  8 *
  9 */
 10#include <linux/mnt_namespace.h>
 11#include <linux/nsproxy.h>
 12#include <linux/security.h>
 13#include <linux/fs_struct.h>
 14#include <linux/sched/task.h>
 15
 16#include "proc/internal.h" /* only for get_proc_task() in ->open() */
 17
 18#include "pnode.h"
 19#include "internal.h"
 20
 21static __poll_t mounts_poll(struct file *file, poll_table *wait)
 22{
 23	struct seq_file *m = file->private_data;
 24	struct proc_mounts *p = m->private;
 25	struct mnt_namespace *ns = p->ns;
 26	__poll_t res = EPOLLIN | EPOLLRDNORM;
 27	int event;
 28
 29	poll_wait(file, &p->ns->poll, wait);
 30
 31	event = READ_ONCE(ns->event);
 32	if (m->poll_event != event) {
 33		m->poll_event = event;
 34		res |= EPOLLERR | EPOLLPRI;
 35	}
 36
 37	return res;
 38}
 39
 40struct proc_fs_opts {
 41	int flag;
 42	const char *str;
 43};
 44
 45static int show_sb_opts(struct seq_file *m, struct super_block *sb)
 46{
 47	static const struct proc_fs_opts fs_opts[] = {
 48		{ SB_SYNCHRONOUS, ",sync" },
 49		{ SB_DIRSYNC, ",dirsync" },
 50		{ SB_MANDLOCK, ",mand" },
 51		{ SB_LAZYTIME, ",lazytime" },
 52		{ 0, NULL }
 53	};
 54	const struct proc_fs_opts *fs_infop;
 55
 56	for (fs_infop = fs_opts; fs_infop->flag; fs_infop++) {
 57		if (sb->s_flags & fs_infop->flag)
 58			seq_puts(m, fs_infop->str);
 59	}
 60
 61	return security_sb_show_options(m, sb);
 62}
 63
 64static void show_vfsmnt_opts(struct seq_file *m, struct vfsmount *mnt)
 65{
 66	static const struct proc_fs_opts mnt_opts[] = {
 67		{ MNT_NOSUID, ",nosuid" },
 68		{ MNT_NODEV, ",nodev" },
 69		{ MNT_NOEXEC, ",noexec" },
 70		{ MNT_NOATIME, ",noatime" },
 71		{ MNT_NODIRATIME, ",nodiratime" },
 72		{ MNT_RELATIME, ",relatime" },
 73		{ MNT_NOSYMFOLLOW, ",nosymfollow" },
 74		{ 0, NULL }
 75	};
 76	const struct proc_fs_opts *fs_infop;
 77
 78	for (fs_infop = mnt_opts; fs_infop->flag; fs_infop++) {
 79		if (mnt->mnt_flags & fs_infop->flag)
 80			seq_puts(m, fs_infop->str);
 81	}
 82
 83	if (is_idmapped_mnt(mnt))
 84		seq_puts(m, ",idmapped");
 85}
 86
 87static inline void mangle(struct seq_file *m, const char *s)
 88{
 89	seq_escape(m, s, " \t\n\\#");
 90}
 91
 92static void show_type(struct seq_file *m, struct super_block *sb)
 93{
 94	mangle(m, sb->s_type->name);
 95	if (sb->s_subtype) {
 96		seq_putc(m, '.');
 97		mangle(m, sb->s_subtype);
 98	}
 99}
100
101static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
102{
103	struct proc_mounts *p = m->private;
104	struct mount *r = real_mount(mnt);
105	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
106	struct super_block *sb = mnt_path.dentry->d_sb;
107	int err;
108
109	if (sb->s_op->show_devname) {
110		err = sb->s_op->show_devname(m, mnt_path.dentry);
111		if (err)
112			goto out;
113	} else {
114		mangle(m, r->mnt_devname);
115	}
116	seq_putc(m, ' ');
117	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
118	err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
119	if (err)
120		goto out;
121	seq_putc(m, ' ');
122	show_type(m, sb);
123	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
124	err = show_sb_opts(m, sb);
125	if (err)
126		goto out;
127	show_vfsmnt_opts(m, mnt);
128	if (sb->s_op->show_options)
129		err = sb->s_op->show_options(m, mnt_path.dentry);
130	seq_puts(m, " 0 0\n");
131out:
132	return err;
133}
134
135static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
136{
137	struct proc_mounts *p = m->private;
138	struct mount *r = real_mount(mnt);
139	struct super_block *sb = mnt->mnt_sb;
140	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
141	int err;
142
143	seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
144		   MAJOR(sb->s_dev), MINOR(sb->s_dev));
145	err = show_path(m, mnt->mnt_root);
146	if (err)
147		goto out;
148	seq_putc(m, ' ');
149
150	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
151	err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
152	if (err)
153		goto out;
154
155	seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
156	show_vfsmnt_opts(m, mnt);
157
158	/* Tagged fields ("foo:X" or "bar") */
159	if (IS_MNT_SHARED(r))
160		seq_printf(m, " shared:%i", r->mnt_group_id);
161	if (IS_MNT_SLAVE(r)) {
162		int master = r->mnt_master->mnt_group_id;
163		int dom = get_dominating_id(r, &p->root);
164		seq_printf(m, " master:%i", master);
165		if (dom && dom != master)
166			seq_printf(m, " propagate_from:%i", dom);
167	}
168	if (IS_MNT_UNBINDABLE(r))
169		seq_puts(m, " unbindable");
170
171	/* Filesystem specific data */
172	seq_puts(m, " - ");
173	show_type(m, sb);
174	seq_putc(m, ' ');
175	if (sb->s_op->show_devname) {
176		err = sb->s_op->show_devname(m, mnt->mnt_root);
177		if (err)
178			goto out;
179	} else {
180		mangle(m, r->mnt_devname);
181	}
182	seq_puts(m, sb_rdonly(sb) ? " ro" : " rw");
183	err = show_sb_opts(m, sb);
184	if (err)
185		goto out;
186	if (sb->s_op->show_options)
187		err = sb->s_op->show_options(m, mnt->mnt_root);
188	seq_putc(m, '\n');
189out:
190	return err;
191}
192
193static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
194{
195	struct proc_mounts *p = m->private;
196	struct mount *r = real_mount(mnt);
197	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
198	struct super_block *sb = mnt_path.dentry->d_sb;
199	int err;
200
201	/* device */
202	seq_puts(m, "device ");
203	if (sb->s_op->show_devname) {
204		err = sb->s_op->show_devname(m, mnt_path.dentry);
205		if (err)
206			goto out;
207	} else {
208		mangle(m, r->mnt_devname);
209	}
210
211	/* mount point */
212	seq_puts(m, " mounted on ");
213	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
214	err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
215	if (err)
216		goto out;
217	seq_putc(m, ' ');
218
219	/* file system type */
220	seq_puts(m, "with fstype ");
221	show_type(m, sb);
222
223	/* optional statistics */
224	if (sb->s_op->show_stats) {
225		seq_putc(m, ' ');
226		err = sb->s_op->show_stats(m, mnt_path.dentry);
227	}
228
229	seq_putc(m, '\n');
230out:
231	return err;
232}
233
234static int mounts_open_common(struct inode *inode, struct file *file,
235			      int (*show)(struct seq_file *, struct vfsmount *))
236{
237	struct task_struct *task = get_proc_task(inode);
238	struct nsproxy *nsp;
239	struct mnt_namespace *ns = NULL;
240	struct path root;
241	struct proc_mounts *p;
242	struct seq_file *m;
243	int ret = -EINVAL;
244
245	if (!task)
246		goto err;
247
248	task_lock(task);
249	nsp = task->nsproxy;
250	if (!nsp || !nsp->mnt_ns) {
251		task_unlock(task);
252		put_task_struct(task);
253		goto err;
254	}
255	ns = nsp->mnt_ns;
256	get_mnt_ns(ns);
257	if (!task->fs) {
258		task_unlock(task);
259		put_task_struct(task);
260		ret = -ENOENT;
261		goto err_put_ns;
262	}
263	get_fs_root(task->fs, &root);
264	task_unlock(task);
265	put_task_struct(task);
266
267	ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
268	if (ret)
269		goto err_put_path;
270
271	m = file->private_data;
272	m->poll_event = ns->event;
273
274	p = m->private;
275	p->ns = ns;
276	p->root = root;
277	p->show = show;
278
279	return 0;
280
281 err_put_path:
282	path_put(&root);
283 err_put_ns:
284	put_mnt_ns(ns);
285 err:
286	return ret;
287}
288
289static int mounts_release(struct inode *inode, struct file *file)
290{
291	struct seq_file *m = file->private_data;
292	struct proc_mounts *p = m->private;
293	path_put(&p->root);
294	put_mnt_ns(p->ns);
295	return seq_release_private(inode, file);
296}
297
298static int mounts_open(struct inode *inode, struct file *file)
299{
300	return mounts_open_common(inode, file, show_vfsmnt);
301}
302
303static int mountinfo_open(struct inode *inode, struct file *file)
304{
305	return mounts_open_common(inode, file, show_mountinfo);
306}
307
308static int mountstats_open(struct inode *inode, struct file *file)
309{
310	return mounts_open_common(inode, file, show_vfsstat);
311}
312
313const struct file_operations proc_mounts_operations = {
314	.open		= mounts_open,
315	.read_iter	= seq_read_iter,
316	.splice_read	= copy_splice_read,
317	.llseek		= seq_lseek,
318	.release	= mounts_release,
319	.poll		= mounts_poll,
320};
321
322const struct file_operations proc_mountinfo_operations = {
323	.open		= mountinfo_open,
324	.read_iter	= seq_read_iter,
325	.splice_read	= copy_splice_read,
326	.llseek		= seq_lseek,
327	.release	= mounts_release,
328	.poll		= mounts_poll,
329};
330
331const struct file_operations proc_mountstats_operations = {
332	.open		= mountstats_open,
333	.read_iter	= seq_read_iter,
334	.splice_read	= copy_splice_read,
335	.llseek		= seq_lseek,
336	.release	= mounts_release,
337};