1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/mount.h>
3 #include <linux/pseudo_fs.h>
4 #include <linux/file.h>
5 #include <linux/fs.h>
6 #include <linux/proc_fs.h>
7 #include <linux/proc_ns.h>
8 #include <linux/magic.h>
9 #include <linux/ktime.h>
10 #include <linux/seq_file.h>
11 #include <linux/pid_namespace.h>
12 #include <linux/user_namespace.h>
13 #include <linux/nsfs.h>
14 #include <linux/uaccess.h>
15 #include <linux/mnt_namespace.h>
16 
17 #include "mount.h"
18 #include "internal.h"
19 
20 static struct vfsmount *nsfs_mnt;
21 
22 static long ns_ioctl(struct file *filp, unsigned int ioctl,
23 			unsigned long arg);
24 static const struct file_operations ns_file_operations = {
25 	.unlocked_ioctl = ns_ioctl,
26 	.compat_ioctl   = compat_ptr_ioctl,
27 };
28 
29 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
30 {
31 	struct inode *inode = d_inode(dentry);
32 	struct ns_common *ns = inode->i_private;
33 	const struct proc_ns_operations *ns_ops = ns->ops;
34 
35 	return dynamic_dname(buffer, buflen, "%s:[%lu]",
36 		ns_ops->name, inode->i_ino);
37 }
38 
39 const struct dentry_operations ns_dentry_operations = {
40 	.d_dname	= ns_dname,
41 	.d_prune	= stashed_dentry_prune,
42 };
43 
44 static void nsfs_evict(struct inode *inode)
45 {
46 	struct ns_common *ns = inode->i_private;
47 	clear_inode(inode);
48 	ns->ops->put(ns);
49 }
50 
51 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
52 		     void *private_data)
53 {
54 	struct ns_common *ns;
55 
56 	ns = ns_get_cb(private_data);
57 	if (!ns)
58 		return -ENOENT;
59 
60 	return path_from_stashed(&ns->stashed, nsfs_mnt, ns, path);
61 }
62 
63 struct ns_get_path_task_args {
64 	const struct proc_ns_operations *ns_ops;
65 	struct task_struct *task;
66 };
67 
68 static struct ns_common *ns_get_path_task(void *private_data)
69 {
70 	struct ns_get_path_task_args *args = private_data;
71 
72 	return args->ns_ops->get(args->task);
73 }
74 
75 int ns_get_path(struct path *path, struct task_struct *task,
76 		  const struct proc_ns_operations *ns_ops)
77 {
78 	struct ns_get_path_task_args args = {
79 		.ns_ops	= ns_ops,
80 		.task	= task,
81 	};
82 
83 	return ns_get_path_cb(path, ns_get_path_task, &args);
84 }
85 
86 /**
87  * open_namespace - open a namespace
88  * @ns: the namespace to open
89  *
90  * This will consume a reference to @ns indendent of success or failure.
91  *
92  * Return: A file descriptor on success or a negative error code on failure.
93  */
94 int open_namespace(struct ns_common *ns)
95 {
96 	struct path path __free(path_put) = {};
97 	struct file *f;
98 	int err;
99 
100 	/* call first to consume reference */
101 	err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
102 	if (err < 0)
103 		return err;
104 
105 	CLASS(get_unused_fd, fd)(O_CLOEXEC);
106 	if (fd < 0)
107 		return fd;
108 
109 	f = dentry_open(&path, O_RDONLY, current_cred());
110 	if (IS_ERR(f))
111 		return PTR_ERR(f);
112 
113 	fd_install(fd, f);
114 	return take_fd(fd);
115 }
116 
117 int open_related_ns(struct ns_common *ns,
118 		   struct ns_common *(*get_ns)(struct ns_common *ns))
119 {
120 	struct ns_common *relative;
121 
122 	relative = get_ns(ns);
123 	if (IS_ERR(relative))
124 		return PTR_ERR(relative);
125 
126 	return open_namespace(relative);
127 }
128 EXPORT_SYMBOL_GPL(open_related_ns);
129 
130 static int copy_ns_info_to_user(const struct mnt_namespace *mnt_ns,
131 				struct mnt_ns_info __user *uinfo, size_t usize,
132 				struct mnt_ns_info *kinfo)
133 {
134 	/*
135 	 * If userspace and the kernel have the same struct size it can just
136 	 * be copied. If userspace provides an older struct, only the bits that
137 	 * userspace knows about will be copied. If userspace provides a new
138 	 * struct, only the bits that the kernel knows aobut will be copied and
139 	 * the size value will be set to the size the kernel knows about.
140 	 */
141 	kinfo->size		= min(usize, sizeof(*kinfo));
142 	kinfo->mnt_ns_id	= mnt_ns->seq;
143 	kinfo->nr_mounts	= READ_ONCE(mnt_ns->nr_mounts);
144 	/* Subtract the root mount of the mount namespace. */
145 	if (kinfo->nr_mounts)
146 		kinfo->nr_mounts--;
147 
148 	if (copy_to_user(uinfo, kinfo, kinfo->size))
149 		return -EFAULT;
150 
151 	return 0;
152 }
153 
154 static bool nsfs_ioctl_valid(unsigned int cmd)
155 {
156 	switch (cmd) {
157 	case NS_GET_USERNS:
158 	case NS_GET_PARENT:
159 	case NS_GET_NSTYPE:
160 	case NS_GET_OWNER_UID:
161 	case NS_GET_MNTNS_ID:
162 	case NS_GET_PID_FROM_PIDNS:
163 	case NS_GET_TGID_FROM_PIDNS:
164 	case NS_GET_PID_IN_PIDNS:
165 	case NS_GET_TGID_IN_PIDNS:
166 		return (_IOC_TYPE(cmd) == _IOC_TYPE(cmd));
167 	}
168 
169 	/* Extensible ioctls require some extra handling. */
170 	switch (_IOC_NR(cmd)) {
171 	case _IOC_NR(NS_MNT_GET_INFO):
172 	case _IOC_NR(NS_MNT_GET_NEXT):
173 	case _IOC_NR(NS_MNT_GET_PREV):
174 		return (_IOC_TYPE(cmd) == _IOC_TYPE(cmd));
175 	}
176 
177 	return false;
178 }
179 
180 static long ns_ioctl(struct file *filp, unsigned int ioctl,
181 			unsigned long arg)
182 {
183 	struct user_namespace *user_ns;
184 	struct pid_namespace *pid_ns;
185 	struct task_struct *tsk;
186 	struct ns_common *ns;
187 	struct mnt_namespace *mnt_ns;
188 	bool previous = false;
189 	uid_t __user *argp;
190 	uid_t uid;
191 	int ret;
192 
193 	if (!nsfs_ioctl_valid(ioctl))
194 		return -ENOIOCTLCMD;
195 
196 	ns = get_proc_ns(file_inode(filp));
197 	switch (ioctl) {
198 	case NS_GET_USERNS:
199 		return open_related_ns(ns, ns_get_owner);
200 	case NS_GET_PARENT:
201 		if (!ns->ops->get_parent)
202 			return -EINVAL;
203 		return open_related_ns(ns, ns->ops->get_parent);
204 	case NS_GET_NSTYPE:
205 		return ns->ops->type;
206 	case NS_GET_OWNER_UID:
207 		if (ns->ops->type != CLONE_NEWUSER)
208 			return -EINVAL;
209 		user_ns = container_of(ns, struct user_namespace, ns);
210 		argp = (uid_t __user *) arg;
211 		uid = from_kuid_munged(current_user_ns(), user_ns->owner);
212 		return put_user(uid, argp);
213 	case NS_GET_MNTNS_ID: {
214 		__u64 __user *idp;
215 		__u64 id;
216 
217 		if (ns->ops->type != CLONE_NEWNS)
218 			return -EINVAL;
219 
220 		mnt_ns = container_of(ns, struct mnt_namespace, ns);
221 		idp = (__u64 __user *)arg;
222 		id = mnt_ns->seq;
223 		return put_user(id, idp);
224 	}
225 	case NS_GET_PID_FROM_PIDNS:
226 		fallthrough;
227 	case NS_GET_TGID_FROM_PIDNS:
228 		fallthrough;
229 	case NS_GET_PID_IN_PIDNS:
230 		fallthrough;
231 	case NS_GET_TGID_IN_PIDNS: {
232 		if (ns->ops->type != CLONE_NEWPID)
233 			return -EINVAL;
234 
235 		ret = -ESRCH;
236 		pid_ns = container_of(ns, struct pid_namespace, ns);
237 
238 		guard(rcu)();
239 
240 		if (ioctl == NS_GET_PID_IN_PIDNS ||
241 		    ioctl == NS_GET_TGID_IN_PIDNS)
242 			tsk = find_task_by_vpid(arg);
243 		else
244 			tsk = find_task_by_pid_ns(arg, pid_ns);
245 		if (!tsk)
246 			break;
247 
248 		switch (ioctl) {
249 		case NS_GET_PID_FROM_PIDNS:
250 			ret = task_pid_vnr(tsk);
251 			break;
252 		case NS_GET_TGID_FROM_PIDNS:
253 			ret = task_tgid_vnr(tsk);
254 			break;
255 		case NS_GET_PID_IN_PIDNS:
256 			ret = task_pid_nr_ns(tsk, pid_ns);
257 			break;
258 		case NS_GET_TGID_IN_PIDNS:
259 			ret = task_tgid_nr_ns(tsk, pid_ns);
260 			break;
261 		default:
262 			ret = 0;
263 			break;
264 		}
265 
266 		if (!ret)
267 			ret = -ESRCH;
268 		return ret;
269 	}
270 	}
271 
272 	/* extensible ioctls */
273 	switch (_IOC_NR(ioctl)) {
274 	case _IOC_NR(NS_MNT_GET_INFO): {
275 		struct mnt_ns_info kinfo = {};
276 		struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
277 		size_t usize = _IOC_SIZE(ioctl);
278 
279 		if (ns->ops->type != CLONE_NEWNS)
280 			return -EINVAL;
281 
282 		if (!uinfo)
283 			return -EINVAL;
284 
285 		if (usize < MNT_NS_INFO_SIZE_VER0)
286 			return -EINVAL;
287 
288 		return copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
289 	}
290 	case _IOC_NR(NS_MNT_GET_PREV):
291 		previous = true;
292 		fallthrough;
293 	case _IOC_NR(NS_MNT_GET_NEXT): {
294 		struct mnt_ns_info kinfo = {};
295 		struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
296 		struct path path __free(path_put) = {};
297 		struct file *f __free(fput) = NULL;
298 		size_t usize = _IOC_SIZE(ioctl);
299 
300 		if (ns->ops->type != CLONE_NEWNS)
301 			return -EINVAL;
302 
303 		if (usize < MNT_NS_INFO_SIZE_VER0)
304 			return -EINVAL;
305 
306 		mnt_ns = get_sequential_mnt_ns(to_mnt_ns(ns), previous);
307 		if (IS_ERR(mnt_ns))
308 			return PTR_ERR(mnt_ns);
309 
310 		ns = to_ns_common(mnt_ns);
311 		/* Transfer ownership of @mnt_ns reference to @path. */
312 		ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
313 		if (ret)
314 			return ret;
315 
316 		CLASS(get_unused_fd, fd)(O_CLOEXEC);
317 		if (fd < 0)
318 			return fd;
319 
320 		f = dentry_open(&path, O_RDONLY, current_cred());
321 		if (IS_ERR(f))
322 			return PTR_ERR(f);
323 
324 		if (uinfo) {
325 			/*
326 			 * If @uinfo is passed return all information about the
327 			 * mount namespace as well.
328 			 */
329 			ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
330 			if (ret)
331 				return ret;
332 		}
333 
334 		/* Transfer reference of @f to caller's fdtable. */
335 		fd_install(fd, no_free_ptr(f));
336 		/* File descriptor is live so hand it off to the caller. */
337 		return take_fd(fd);
338 	}
339 	default:
340 		ret = -ENOTTY;
341 	}
342 
343 	return ret;
344 }
345 
346 int ns_get_name(char *buf, size_t size, struct task_struct *task,
347 			const struct proc_ns_operations *ns_ops)
348 {
349 	struct ns_common *ns;
350 	int res = -ENOENT;
351 	const char *name;
352 	ns = ns_ops->get(task);
353 	if (ns) {
354 		name = ns_ops->real_ns_name ? : ns_ops->name;
355 		res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
356 		ns_ops->put(ns);
357 	}
358 	return res;
359 }
360 
361 bool proc_ns_file(const struct file *file)
362 {
363 	return file->f_op == &ns_file_operations;
364 }
365 
366 /**
367  * ns_match() - Returns true if current namespace matches dev/ino provided.
368  * @ns: current namespace
369  * @dev: dev_t from nsfs that will be matched against current nsfs
370  * @ino: ino_t from nsfs that will be matched against current nsfs
371  *
372  * Return: true if dev and ino matches the current nsfs.
373  */
374 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
375 {
376 	return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
377 }
378 
379 
380 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
381 {
382 	struct inode *inode = d_inode(dentry);
383 	const struct ns_common *ns = inode->i_private;
384 	const struct proc_ns_operations *ns_ops = ns->ops;
385 
386 	seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
387 	return 0;
388 }
389 
390 static const struct super_operations nsfs_ops = {
391 	.statfs = simple_statfs,
392 	.evict_inode = nsfs_evict,
393 	.show_path = nsfs_show_path,
394 };
395 
396 static int nsfs_init_inode(struct inode *inode, void *data)
397 {
398 	struct ns_common *ns = data;
399 
400 	inode->i_private = data;
401 	inode->i_mode |= S_IRUGO;
402 	inode->i_fop = &ns_file_operations;
403 	inode->i_ino = ns->inum;
404 	return 0;
405 }
406 
407 static void nsfs_put_data(void *data)
408 {
409 	struct ns_common *ns = data;
410 	ns->ops->put(ns);
411 }
412 
413 static const struct stashed_operations nsfs_stashed_ops = {
414 	.init_inode = nsfs_init_inode,
415 	.put_data = nsfs_put_data,
416 };
417 
418 static int nsfs_init_fs_context(struct fs_context *fc)
419 {
420 	struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
421 	if (!ctx)
422 		return -ENOMEM;
423 	ctx->ops = &nsfs_ops;
424 	ctx->dops = &ns_dentry_operations;
425 	fc->s_fs_info = (void *)&nsfs_stashed_ops;
426 	return 0;
427 }
428 
429 static struct file_system_type nsfs = {
430 	.name = "nsfs",
431 	.init_fs_context = nsfs_init_fs_context,
432 	.kill_sb = kill_anon_super,
433 };
434 
435 void __init nsfs_init(void)
436 {
437 	nsfs_mnt = kern_mount(&nsfs);
438 	if (IS_ERR(nsfs_mnt))
439 		panic("can't set nsfs up\n");
440 	nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
441 }
442