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 
mounts_poll(struct file * file,poll_table * wait)21 static __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 
40 struct proc_fs_opts {
41 	int flag;
42 	const char *str;
43 };
44 
show_sb_opts(struct seq_file * m,struct super_block * sb)45 static 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 
show_mnt_opts(struct seq_file * m,struct vfsmount * mnt)64 static void show_mnt_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 
mangle(struct seq_file * m,const char * s)87 static inline void mangle(struct seq_file *m, const char *s)
88 {
89 	seq_escape(m, s, " \t\n\\#");
90 }
91 
show_type(struct seq_file * m,struct super_block * sb)92 static 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 
show_vfsmnt(struct seq_file * m,struct vfsmount * mnt)101 static 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 ? r->mnt_devname : "none");
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_mnt_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");
131 out:
132 	return err;
133 }
134 
show_mountinfo(struct seq_file * m,struct vfsmount * mnt)135 static 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 	if (sb->s_op->show_path) {
146 		err = sb->s_op->show_path(m, mnt->mnt_root);
147 		if (err)
148 			goto out;
149 	} else {
150 		seq_dentry(m, mnt->mnt_root, " \t\n\\");
151 	}
152 	seq_putc(m, ' ');
153 
154 	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
155 	err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
156 	if (err)
157 		goto out;
158 
159 	seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
160 	show_mnt_opts(m, mnt);
161 
162 	/* Tagged fields ("foo:X" or "bar") */
163 	if (IS_MNT_SHARED(r))
164 		seq_printf(m, " shared:%i", r->mnt_group_id);
165 	if (IS_MNT_SLAVE(r)) {
166 		int master = r->mnt_master->mnt_group_id;
167 		int dom = get_dominating_id(r, &p->root);
168 		seq_printf(m, " master:%i", master);
169 		if (dom && dom != master)
170 			seq_printf(m, " propagate_from:%i", dom);
171 	}
172 	if (IS_MNT_UNBINDABLE(r))
173 		seq_puts(m, " unbindable");
174 
175 	/* Filesystem specific data */
176 	seq_puts(m, " - ");
177 	show_type(m, sb);
178 	seq_putc(m, ' ');
179 	if (sb->s_op->show_devname) {
180 		err = sb->s_op->show_devname(m, mnt->mnt_root);
181 		if (err)
182 			goto out;
183 	} else {
184 		mangle(m, r->mnt_devname ? r->mnt_devname : "none");
185 	}
186 	seq_puts(m, sb_rdonly(sb) ? " ro" : " rw");
187 	err = show_sb_opts(m, sb);
188 	if (err)
189 		goto out;
190 	if (sb->s_op->show_options)
191 		err = sb->s_op->show_options(m, mnt->mnt_root);
192 	seq_putc(m, '\n');
193 out:
194 	return err;
195 }
196 
show_vfsstat(struct seq_file * m,struct vfsmount * mnt)197 static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
198 {
199 	struct proc_mounts *p = m->private;
200 	struct mount *r = real_mount(mnt);
201 	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
202 	struct super_block *sb = mnt_path.dentry->d_sb;
203 	int err;
204 
205 	/* device */
206 	if (sb->s_op->show_devname) {
207 		seq_puts(m, "device ");
208 		err = sb->s_op->show_devname(m, mnt_path.dentry);
209 		if (err)
210 			goto out;
211 	} else {
212 		if (r->mnt_devname) {
213 			seq_puts(m, "device ");
214 			mangle(m, r->mnt_devname);
215 		} else
216 			seq_puts(m, "no device");
217 	}
218 
219 	/* mount point */
220 	seq_puts(m, " mounted on ");
221 	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
222 	err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
223 	if (err)
224 		goto out;
225 	seq_putc(m, ' ');
226 
227 	/* file system type */
228 	seq_puts(m, "with fstype ");
229 	show_type(m, sb);
230 
231 	/* optional statistics */
232 	if (sb->s_op->show_stats) {
233 		seq_putc(m, ' ');
234 		err = sb->s_op->show_stats(m, mnt_path.dentry);
235 	}
236 
237 	seq_putc(m, '\n');
238 out:
239 	return err;
240 }
241 
mounts_open_common(struct inode * inode,struct file * file,int (* show)(struct seq_file *,struct vfsmount *))242 static int mounts_open_common(struct inode *inode, struct file *file,
243 			      int (*show)(struct seq_file *, struct vfsmount *))
244 {
245 	struct task_struct *task = get_proc_task(inode);
246 	struct nsproxy *nsp;
247 	struct mnt_namespace *ns = NULL;
248 	struct path root;
249 	struct proc_mounts *p;
250 	struct seq_file *m;
251 	int ret = -EINVAL;
252 
253 	if (!task)
254 		goto err;
255 
256 	task_lock(task);
257 	nsp = task->nsproxy;
258 	if (!nsp || !nsp->mnt_ns) {
259 		task_unlock(task);
260 		put_task_struct(task);
261 		goto err;
262 	}
263 	ns = nsp->mnt_ns;
264 	get_mnt_ns(ns);
265 	if (!task->fs) {
266 		task_unlock(task);
267 		put_task_struct(task);
268 		ret = -ENOENT;
269 		goto err_put_ns;
270 	}
271 	get_fs_root(task->fs, &root);
272 	task_unlock(task);
273 	put_task_struct(task);
274 
275 	ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
276 	if (ret)
277 		goto err_put_path;
278 
279 	m = file->private_data;
280 	m->poll_event = ns->event;
281 
282 	p = m->private;
283 	p->ns = ns;
284 	p->root = root;
285 	p->show = show;
286 	INIT_LIST_HEAD(&p->cursor.mnt_list);
287 	p->cursor.mnt.mnt_flags = MNT_CURSOR;
288 
289 	return 0;
290 
291  err_put_path:
292 	path_put(&root);
293  err_put_ns:
294 	put_mnt_ns(ns);
295  err:
296 	return ret;
297 }
298 
mounts_release(struct inode * inode,struct file * file)299 static int mounts_release(struct inode *inode, struct file *file)
300 {
301 	struct seq_file *m = file->private_data;
302 	struct proc_mounts *p = m->private;
303 	path_put(&p->root);
304 	mnt_cursor_del(p->ns, &p->cursor);
305 	put_mnt_ns(p->ns);
306 	return seq_release_private(inode, file);
307 }
308 
mounts_open(struct inode * inode,struct file * file)309 static int mounts_open(struct inode *inode, struct file *file)
310 {
311 	return mounts_open_common(inode, file, show_vfsmnt);
312 }
313 
mountinfo_open(struct inode * inode,struct file * file)314 static int mountinfo_open(struct inode *inode, struct file *file)
315 {
316 	return mounts_open_common(inode, file, show_mountinfo);
317 }
318 
mountstats_open(struct inode * inode,struct file * file)319 static int mountstats_open(struct inode *inode, struct file *file)
320 {
321 	return mounts_open_common(inode, file, show_vfsstat);
322 }
323 
324 const struct file_operations proc_mounts_operations = {
325 	.open		= mounts_open,
326 	.read_iter	= seq_read_iter,
327 	.splice_read	= generic_file_splice_read,
328 	.llseek		= seq_lseek,
329 	.release	= mounts_release,
330 	.poll		= mounts_poll,
331 };
332 
333 const struct file_operations proc_mountinfo_operations = {
334 	.open		= mountinfo_open,
335 	.read_iter	= seq_read_iter,
336 	.splice_read	= generic_file_splice_read,
337 	.llseek		= seq_lseek,
338 	.release	= mounts_release,
339 	.poll		= mounts_poll,
340 };
341 
342 const struct file_operations proc_mountstats_operations = {
343 	.open		= mountstats_open,
344 	.read_iter	= seq_read_iter,
345 	.splice_read	= generic_file_splice_read,
346 	.llseek		= seq_lseek,
347 	.release	= mounts_release,
348 };
349