xref: /linux/kernel/nsproxy.c (revision 46ff24efe04ac96a129dd01138640c3447a525e1) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  Copyright (C) 2006 IBM Corporation
4  *
5  *  Author: Serge Hallyn <serue@us.ibm.com>
6  *
7  *  Jun 2006 - namespaces support
8  *             OpenVZ, SWsoft Inc.
9  *             Pavel Emelianov <xemul@openvz.org>
10  */
11 
12 #include <linux/slab.h>
13 #include <linux/export.h>
14 #include <linux/nsproxy.h>
15 #include <linux/init_task.h>
16 #include <linux/mnt_namespace.h>
17 #include <linux/utsname.h>
18 #include <linux/pid_namespace.h>
19 #include <net/net_namespace.h>
20 #include <linux/ipc_namespace.h>
21 #include <linux/time_namespace.h>
22 #include <linux/fs_struct.h>
23 #include <linux/proc_fs.h>
24 #include <linux/proc_ns.h>
25 #include <linux/file.h>
26 #include <linux/syscalls.h>
27 #include <linux/cgroup.h>
28 #include <linux/perf_event.h>
29 
30 static struct kmem_cache *nsproxy_cachep;
31 
32 struct nsproxy init_nsproxy = {
33 	.count			= ATOMIC_INIT(1),
34 	.uts_ns			= &init_uts_ns,
35 #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)
36 	.ipc_ns			= &init_ipc_ns,
37 #endif
38 	.mnt_ns			= NULL,
39 	.pid_ns_for_children	= &init_pid_ns,
40 #ifdef CONFIG_NET
41 	.net_ns			= &init_net,
42 #endif
43 #ifdef CONFIG_CGROUPS
44 	.cgroup_ns		= &init_cgroup_ns,
45 #endif
46 #ifdef CONFIG_TIME_NS
47 	.time_ns		= &init_time_ns,
48 	.time_ns_for_children	= &init_time_ns,
49 #endif
50 };
51 
52 static inline struct nsproxy *create_nsproxy(void)
53 {
54 	struct nsproxy *nsproxy;
55 
56 	nsproxy = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL);
57 	if (nsproxy)
58 		atomic_set(&nsproxy->count, 1);
59 	return nsproxy;
60 }
61 
62 /*
63  * Create new nsproxy and all of its the associated namespaces.
64  * Return the newly created nsproxy.  Do not attach this to the task,
65  * leave it to the caller to do proper locking and attach it to task.
66  */
67 static struct nsproxy *create_new_namespaces(unsigned long flags,
68 	struct task_struct *tsk, struct user_namespace *user_ns,
69 	struct fs_struct *new_fs)
70 {
71 	struct nsproxy *new_nsp;
72 	int err;
73 
74 	new_nsp = create_nsproxy();
75 	if (!new_nsp)
76 		return ERR_PTR(-ENOMEM);
77 
78 	new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, user_ns, new_fs);
79 	if (IS_ERR(new_nsp->mnt_ns)) {
80 		err = PTR_ERR(new_nsp->mnt_ns);
81 		goto out_ns;
82 	}
83 
84 	new_nsp->uts_ns = copy_utsname(flags, user_ns, tsk->nsproxy->uts_ns);
85 	if (IS_ERR(new_nsp->uts_ns)) {
86 		err = PTR_ERR(new_nsp->uts_ns);
87 		goto out_uts;
88 	}
89 
90 	new_nsp->ipc_ns = copy_ipcs(flags, user_ns, tsk->nsproxy->ipc_ns);
91 	if (IS_ERR(new_nsp->ipc_ns)) {
92 		err = PTR_ERR(new_nsp->ipc_ns);
93 		goto out_ipc;
94 	}
95 
96 	new_nsp->pid_ns_for_children =
97 		copy_pid_ns(flags, user_ns, tsk->nsproxy->pid_ns_for_children);
98 	if (IS_ERR(new_nsp->pid_ns_for_children)) {
99 		err = PTR_ERR(new_nsp->pid_ns_for_children);
100 		goto out_pid;
101 	}
102 
103 	new_nsp->cgroup_ns = copy_cgroup_ns(flags, user_ns,
104 					    tsk->nsproxy->cgroup_ns);
105 	if (IS_ERR(new_nsp->cgroup_ns)) {
106 		err = PTR_ERR(new_nsp->cgroup_ns);
107 		goto out_cgroup;
108 	}
109 
110 	new_nsp->net_ns = copy_net_ns(flags, user_ns, tsk->nsproxy->net_ns);
111 	if (IS_ERR(new_nsp->net_ns)) {
112 		err = PTR_ERR(new_nsp->net_ns);
113 		goto out_net;
114 	}
115 
116 	new_nsp->time_ns_for_children = copy_time_ns(flags, user_ns,
117 					tsk->nsproxy->time_ns_for_children);
118 	if (IS_ERR(new_nsp->time_ns_for_children)) {
119 		err = PTR_ERR(new_nsp->time_ns_for_children);
120 		goto out_time;
121 	}
122 	new_nsp->time_ns = get_time_ns(tsk->nsproxy->time_ns);
123 
124 	return new_nsp;
125 
126 out_time:
127 	put_net(new_nsp->net_ns);
128 out_net:
129 	put_cgroup_ns(new_nsp->cgroup_ns);
130 out_cgroup:
131 	if (new_nsp->pid_ns_for_children)
132 		put_pid_ns(new_nsp->pid_ns_for_children);
133 out_pid:
134 	if (new_nsp->ipc_ns)
135 		put_ipc_ns(new_nsp->ipc_ns);
136 out_ipc:
137 	if (new_nsp->uts_ns)
138 		put_uts_ns(new_nsp->uts_ns);
139 out_uts:
140 	if (new_nsp->mnt_ns)
141 		put_mnt_ns(new_nsp->mnt_ns);
142 out_ns:
143 	kmem_cache_free(nsproxy_cachep, new_nsp);
144 	return ERR_PTR(err);
145 }
146 
147 /*
148  * called from clone.  This now handles copy for nsproxy and all
149  * namespaces therein.
150  */
151 int copy_namespaces(unsigned long flags, struct task_struct *tsk)
152 {
153 	struct nsproxy *old_ns = tsk->nsproxy;
154 	struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);
155 	struct nsproxy *new_ns;
156 
157 	if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
158 			      CLONE_NEWPID | CLONE_NEWNET |
159 			      CLONE_NEWCGROUP | CLONE_NEWTIME)))) {
160 		if ((flags & CLONE_VM) ||
161 		    likely(old_ns->time_ns_for_children == old_ns->time_ns)) {
162 			get_nsproxy(old_ns);
163 			return 0;
164 		}
165 	} else if (!ns_capable(user_ns, CAP_SYS_ADMIN))
166 		return -EPERM;
167 
168 	/*
169 	 * CLONE_NEWIPC must detach from the undolist: after switching
170 	 * to a new ipc namespace, the semaphore arrays from the old
171 	 * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
172 	 * means share undolist with parent, so we must forbid using
173 	 * it along with CLONE_NEWIPC.
174 	 */
175 	if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
176 		(CLONE_NEWIPC | CLONE_SYSVSEM))
177 		return -EINVAL;
178 
179 	new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);
180 	if (IS_ERR(new_ns))
181 		return  PTR_ERR(new_ns);
182 
183 	if ((flags & CLONE_VM) == 0)
184 		timens_on_fork(new_ns, tsk);
185 
186 	tsk->nsproxy = new_ns;
187 	return 0;
188 }
189 
190 void free_nsproxy(struct nsproxy *ns)
191 {
192 	if (ns->mnt_ns)
193 		put_mnt_ns(ns->mnt_ns);
194 	if (ns->uts_ns)
195 		put_uts_ns(ns->uts_ns);
196 	if (ns->ipc_ns)
197 		put_ipc_ns(ns->ipc_ns);
198 	if (ns->pid_ns_for_children)
199 		put_pid_ns(ns->pid_ns_for_children);
200 	if (ns->time_ns)
201 		put_time_ns(ns->time_ns);
202 	if (ns->time_ns_for_children)
203 		put_time_ns(ns->time_ns_for_children);
204 	put_cgroup_ns(ns->cgroup_ns);
205 	put_net(ns->net_ns);
206 	kmem_cache_free(nsproxy_cachep, ns);
207 }
208 
209 /*
210  * Called from unshare. Unshare all the namespaces part of nsproxy.
211  * On success, returns the new nsproxy.
212  */
213 int unshare_nsproxy_namespaces(unsigned long unshare_flags,
214 	struct nsproxy **new_nsp, struct cred *new_cred, struct fs_struct *new_fs)
215 {
216 	struct user_namespace *user_ns;
217 	int err = 0;
218 
219 	if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
220 			       CLONE_NEWNET | CLONE_NEWPID | CLONE_NEWCGROUP |
221 			       CLONE_NEWTIME)))
222 		return 0;
223 
224 	user_ns = new_cred ? new_cred->user_ns : current_user_ns();
225 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
226 		return -EPERM;
227 
228 	*new_nsp = create_new_namespaces(unshare_flags, current, user_ns,
229 					 new_fs ? new_fs : current->fs);
230 	if (IS_ERR(*new_nsp)) {
231 		err = PTR_ERR(*new_nsp);
232 		goto out;
233 	}
234 
235 out:
236 	return err;
237 }
238 
239 void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
240 {
241 	struct nsproxy *ns;
242 
243 	might_sleep();
244 
245 	task_lock(p);
246 	ns = p->nsproxy;
247 	p->nsproxy = new;
248 	task_unlock(p);
249 
250 	if (ns)
251 		put_nsproxy(ns);
252 }
253 
254 void exit_task_namespaces(struct task_struct *p)
255 {
256 	switch_task_namespaces(p, NULL);
257 }
258 
259 int exec_task_namespaces(void)
260 {
261 	struct task_struct *tsk = current;
262 	struct nsproxy *new;
263 
264 	if (tsk->nsproxy->time_ns_for_children == tsk->nsproxy->time_ns)
265 		return 0;
266 
267 	new = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs);
268 	if (IS_ERR(new))
269 		return PTR_ERR(new);
270 
271 	timens_on_fork(new, tsk);
272 	switch_task_namespaces(tsk, new);
273 	return 0;
274 }
275 
276 static int check_setns_flags(unsigned long flags)
277 {
278 	if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
279 				 CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER |
280 				 CLONE_NEWPID | CLONE_NEWCGROUP)))
281 		return -EINVAL;
282 
283 #ifndef CONFIG_USER_NS
284 	if (flags & CLONE_NEWUSER)
285 		return -EINVAL;
286 #endif
287 #ifndef CONFIG_PID_NS
288 	if (flags & CLONE_NEWPID)
289 		return -EINVAL;
290 #endif
291 #ifndef CONFIG_UTS_NS
292 	if (flags & CLONE_NEWUTS)
293 		return -EINVAL;
294 #endif
295 #ifndef CONFIG_IPC_NS
296 	if (flags & CLONE_NEWIPC)
297 		return -EINVAL;
298 #endif
299 #ifndef CONFIG_CGROUPS
300 	if (flags & CLONE_NEWCGROUP)
301 		return -EINVAL;
302 #endif
303 #ifndef CONFIG_NET_NS
304 	if (flags & CLONE_NEWNET)
305 		return -EINVAL;
306 #endif
307 #ifndef CONFIG_TIME_NS
308 	if (flags & CLONE_NEWTIME)
309 		return -EINVAL;
310 #endif
311 
312 	return 0;
313 }
314 
315 static void put_nsset(struct nsset *nsset)
316 {
317 	unsigned flags = nsset->flags;
318 
319 	if (flags & CLONE_NEWUSER)
320 		put_cred(nsset_cred(nsset));
321 	/*
322 	 * We only created a temporary copy if we attached to more than just
323 	 * the mount namespace.
324 	 */
325 	if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS))
326 		free_fs_struct(nsset->fs);
327 	if (nsset->nsproxy)
328 		free_nsproxy(nsset->nsproxy);
329 }
330 
331 static int prepare_nsset(unsigned flags, struct nsset *nsset)
332 {
333 	struct task_struct *me = current;
334 
335 	nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
336 	if (IS_ERR(nsset->nsproxy))
337 		return PTR_ERR(nsset->nsproxy);
338 
339 	if (flags & CLONE_NEWUSER)
340 		nsset->cred = prepare_creds();
341 	else
342 		nsset->cred = current_cred();
343 	if (!nsset->cred)
344 		goto out;
345 
346 	/* Only create a temporary copy of fs_struct if we really need to. */
347 	if (flags == CLONE_NEWNS) {
348 		nsset->fs = me->fs;
349 	} else if (flags & CLONE_NEWNS) {
350 		nsset->fs = copy_fs_struct(me->fs);
351 		if (!nsset->fs)
352 			goto out;
353 	}
354 
355 	nsset->flags = flags;
356 	return 0;
357 
358 out:
359 	put_nsset(nsset);
360 	return -ENOMEM;
361 }
362 
363 static inline int validate_ns(struct nsset *nsset, struct ns_common *ns)
364 {
365 	return ns->ops->install(nsset, ns);
366 }
367 
368 /*
369  * This is the inverse operation to unshare().
370  * Ordering is equivalent to the standard ordering used everywhere else
371  * during unshare and process creation. The switch to the new set of
372  * namespaces occurs at the point of no return after installation of
373  * all requested namespaces was successful in commit_nsset().
374  */
375 static int validate_nsset(struct nsset *nsset, struct pid *pid)
376 {
377 	int ret = 0;
378 	unsigned flags = nsset->flags;
379 	struct user_namespace *user_ns = NULL;
380 	struct pid_namespace *pid_ns = NULL;
381 	struct nsproxy *nsp;
382 	struct task_struct *tsk;
383 
384 	/* Take a "snapshot" of the target task's namespaces. */
385 	rcu_read_lock();
386 	tsk = pid_task(pid, PIDTYPE_PID);
387 	if (!tsk) {
388 		rcu_read_unlock();
389 		return -ESRCH;
390 	}
391 
392 	if (!ptrace_may_access(tsk, PTRACE_MODE_READ_REALCREDS)) {
393 		rcu_read_unlock();
394 		return -EPERM;
395 	}
396 
397 	task_lock(tsk);
398 	nsp = tsk->nsproxy;
399 	if (nsp)
400 		get_nsproxy(nsp);
401 	task_unlock(tsk);
402 	if (!nsp) {
403 		rcu_read_unlock();
404 		return -ESRCH;
405 	}
406 
407 #ifdef CONFIG_PID_NS
408 	if (flags & CLONE_NEWPID) {
409 		pid_ns = task_active_pid_ns(tsk);
410 		if (unlikely(!pid_ns)) {
411 			rcu_read_unlock();
412 			ret = -ESRCH;
413 			goto out;
414 		}
415 		get_pid_ns(pid_ns);
416 	}
417 #endif
418 
419 #ifdef CONFIG_USER_NS
420 	if (flags & CLONE_NEWUSER)
421 		user_ns = get_user_ns(__task_cred(tsk)->user_ns);
422 #endif
423 	rcu_read_unlock();
424 
425 	/*
426 	 * Install requested namespaces. The caller will have
427 	 * verified earlier that the requested namespaces are
428 	 * supported on this kernel. We don't report errors here
429 	 * if a namespace is requested that isn't supported.
430 	 */
431 #ifdef CONFIG_USER_NS
432 	if (flags & CLONE_NEWUSER) {
433 		ret = validate_ns(nsset, &user_ns->ns);
434 		if (ret)
435 			goto out;
436 	}
437 #endif
438 
439 	if (flags & CLONE_NEWNS) {
440 		ret = validate_ns(nsset, from_mnt_ns(nsp->mnt_ns));
441 		if (ret)
442 			goto out;
443 	}
444 
445 #ifdef CONFIG_UTS_NS
446 	if (flags & CLONE_NEWUTS) {
447 		ret = validate_ns(nsset, &nsp->uts_ns->ns);
448 		if (ret)
449 			goto out;
450 	}
451 #endif
452 
453 #ifdef CONFIG_IPC_NS
454 	if (flags & CLONE_NEWIPC) {
455 		ret = validate_ns(nsset, &nsp->ipc_ns->ns);
456 		if (ret)
457 			goto out;
458 	}
459 #endif
460 
461 #ifdef CONFIG_PID_NS
462 	if (flags & CLONE_NEWPID) {
463 		ret = validate_ns(nsset, &pid_ns->ns);
464 		if (ret)
465 			goto out;
466 	}
467 #endif
468 
469 #ifdef CONFIG_CGROUPS
470 	if (flags & CLONE_NEWCGROUP) {
471 		ret = validate_ns(nsset, &nsp->cgroup_ns->ns);
472 		if (ret)
473 			goto out;
474 	}
475 #endif
476 
477 #ifdef CONFIG_NET_NS
478 	if (flags & CLONE_NEWNET) {
479 		ret = validate_ns(nsset, &nsp->net_ns->ns);
480 		if (ret)
481 			goto out;
482 	}
483 #endif
484 
485 #ifdef CONFIG_TIME_NS
486 	if (flags & CLONE_NEWTIME) {
487 		ret = validate_ns(nsset, &nsp->time_ns->ns);
488 		if (ret)
489 			goto out;
490 	}
491 #endif
492 
493 out:
494 	if (pid_ns)
495 		put_pid_ns(pid_ns);
496 	if (nsp)
497 		put_nsproxy(nsp);
498 	put_user_ns(user_ns);
499 
500 	return ret;
501 }
502 
503 /*
504  * This is the point of no return. There are just a few namespaces
505  * that do some actual work here and it's sufficiently minimal that
506  * a separate ns_common operation seems unnecessary for now.
507  * Unshare is doing the same thing. If we'll end up needing to do
508  * more in a given namespace or a helper here is ultimately not
509  * exported anymore a simple commit handler for each namespace
510  * should be added to ns_common.
511  */
512 static void commit_nsset(struct nsset *nsset)
513 {
514 	unsigned flags = nsset->flags;
515 	struct task_struct *me = current;
516 
517 #ifdef CONFIG_USER_NS
518 	if (flags & CLONE_NEWUSER) {
519 		/* transfer ownership */
520 		commit_creds(nsset_cred(nsset));
521 		nsset->cred = NULL;
522 	}
523 #endif
524 
525 	/* We only need to commit if we have used a temporary fs_struct. */
526 	if ((flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) {
527 		set_fs_root(me->fs, &nsset->fs->root);
528 		set_fs_pwd(me->fs, &nsset->fs->pwd);
529 	}
530 
531 #ifdef CONFIG_IPC_NS
532 	if (flags & CLONE_NEWIPC)
533 		exit_sem(me);
534 #endif
535 
536 #ifdef CONFIG_TIME_NS
537 	if (flags & CLONE_NEWTIME)
538 		timens_commit(me, nsset->nsproxy->time_ns);
539 #endif
540 
541 	/* transfer ownership */
542 	switch_task_namespaces(me, nsset->nsproxy);
543 	nsset->nsproxy = NULL;
544 }
545 
546 SYSCALL_DEFINE2(setns, int, fd, int, flags)
547 {
548 	struct file *file;
549 	struct ns_common *ns = NULL;
550 	struct nsset nsset = {};
551 	int err = 0;
552 
553 	file = fget(fd);
554 	if (!file)
555 		return -EBADF;
556 
557 	if (proc_ns_file(file)) {
558 		ns = get_proc_ns(file_inode(file));
559 		if (flags && (ns->ops->type != flags))
560 			err = -EINVAL;
561 		flags = ns->ops->type;
562 	} else if (!IS_ERR(pidfd_pid(file))) {
563 		err = check_setns_flags(flags);
564 	} else {
565 		err = -EINVAL;
566 	}
567 	if (err)
568 		goto out;
569 
570 	err = prepare_nsset(flags, &nsset);
571 	if (err)
572 		goto out;
573 
574 	if (proc_ns_file(file))
575 		err = validate_ns(&nsset, ns);
576 	else
577 		err = validate_nsset(&nsset, file->private_data);
578 	if (!err) {
579 		commit_nsset(&nsset);
580 		perf_event_namespaces(current);
581 	}
582 	put_nsset(&nsset);
583 out:
584 	fput(file);
585 	return err;
586 }
587 
588 int __init nsproxy_cache_init(void)
589 {
590 	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC|SLAB_ACCOUNT);
591 	return 0;
592 }
593