xref: /openbmc/linux/kernel/nsproxy.c (revision e7bae9bb) 
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 	int ret;
157 
158 	if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
159 			      CLONE_NEWPID | CLONE_NEWNET |
160 			      CLONE_NEWCGROUP | CLONE_NEWTIME)))) {
161 		if (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 	ret = timens_on_fork(new_ns, tsk);
184 	if (ret) {
185 		free_nsproxy(new_ns);
186 		return ret;
187 	}
188 
189 	tsk->nsproxy = new_ns;
190 	return 0;
191 }
192 
193 void free_nsproxy(struct nsproxy *ns)
194 {
195 	if (ns->mnt_ns)
196 		put_mnt_ns(ns->mnt_ns);
197 	if (ns->uts_ns)
198 		put_uts_ns(ns->uts_ns);
199 	if (ns->ipc_ns)
200 		put_ipc_ns(ns->ipc_ns);
201 	if (ns->pid_ns_for_children)
202 		put_pid_ns(ns->pid_ns_for_children);
203 	if (ns->time_ns)
204 		put_time_ns(ns->time_ns);
205 	if (ns->time_ns_for_children)
206 		put_time_ns(ns->time_ns_for_children);
207 	put_cgroup_ns(ns->cgroup_ns);
208 	put_net(ns->net_ns);
209 	kmem_cache_free(nsproxy_cachep, ns);
210 }
211 
212 /*
213  * Called from unshare. Unshare all the namespaces part of nsproxy.
214  * On success, returns the new nsproxy.
215  */
216 int unshare_nsproxy_namespaces(unsigned long unshare_flags,
217 	struct nsproxy **new_nsp, struct cred *new_cred, struct fs_struct *new_fs)
218 {
219 	struct user_namespace *user_ns;
220 	int err = 0;
221 
222 	if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
223 			       CLONE_NEWNET | CLONE_NEWPID | CLONE_NEWCGROUP |
224 			       CLONE_NEWTIME)))
225 		return 0;
226 
227 	user_ns = new_cred ? new_cred->user_ns : current_user_ns();
228 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
229 		return -EPERM;
230 
231 	*new_nsp = create_new_namespaces(unshare_flags, current, user_ns,
232 					 new_fs ? new_fs : current->fs);
233 	if (IS_ERR(*new_nsp)) {
234 		err = PTR_ERR(*new_nsp);
235 		goto out;
236 	}
237 
238 out:
239 	return err;
240 }
241 
242 void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
243 {
244 	struct nsproxy *ns;
245 
246 	might_sleep();
247 
248 	task_lock(p);
249 	ns = p->nsproxy;
250 	p->nsproxy = new;
251 	task_unlock(p);
252 
253 	if (ns && atomic_dec_and_test(&ns->count))
254 		free_nsproxy(ns);
255 }
256 
257 void exit_task_namespaces(struct task_struct *p)
258 {
259 	switch_task_namespaces(p, NULL);
260 }
261 
262 static int check_setns_flags(unsigned long flags)
263 {
264 	if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
265 				 CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER |
266 				 CLONE_NEWPID | CLONE_NEWCGROUP)))
267 		return -EINVAL;
268 
269 #ifndef CONFIG_USER_NS
270 	if (flags & CLONE_NEWUSER)
271 		return -EINVAL;
272 #endif
273 #ifndef CONFIG_PID_NS
274 	if (flags & CLONE_NEWPID)
275 		return -EINVAL;
276 #endif
277 #ifndef CONFIG_UTS_NS
278 	if (flags & CLONE_NEWUTS)
279 		return -EINVAL;
280 #endif
281 #ifndef CONFIG_IPC_NS
282 	if (flags & CLONE_NEWIPC)
283 		return -EINVAL;
284 #endif
285 #ifndef CONFIG_CGROUPS
286 	if (flags & CLONE_NEWCGROUP)
287 		return -EINVAL;
288 #endif
289 #ifndef CONFIG_NET_NS
290 	if (flags & CLONE_NEWNET)
291 		return -EINVAL;
292 #endif
293 #ifndef CONFIG_TIME_NS
294 	if (flags & CLONE_NEWTIME)
295 		return -EINVAL;
296 #endif
297 
298 	return 0;
299 }
300 
301 static void put_nsset(struct nsset *nsset)
302 {
303 	unsigned flags = nsset->flags;
304 
305 	if (flags & CLONE_NEWUSER)
306 		put_cred(nsset_cred(nsset));
307 	/*
308 	 * We only created a temporary copy if we attached to more than just
309 	 * the mount namespace.
310 	 */
311 	if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS))
312 		free_fs_struct(nsset->fs);
313 	if (nsset->nsproxy)
314 		free_nsproxy(nsset->nsproxy);
315 }
316 
317 static int prepare_nsset(unsigned flags, struct nsset *nsset)
318 {
319 	struct task_struct *me = current;
320 
321 	nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
322 	if (IS_ERR(nsset->nsproxy))
323 		return PTR_ERR(nsset->nsproxy);
324 
325 	if (flags & CLONE_NEWUSER)
326 		nsset->cred = prepare_creds();
327 	else
328 		nsset->cred = current_cred();
329 	if (!nsset->cred)
330 		goto out;
331 
332 	/* Only create a temporary copy of fs_struct if we really need to. */
333 	if (flags == CLONE_NEWNS) {
334 		nsset->fs = me->fs;
335 	} else if (flags & CLONE_NEWNS) {
336 		nsset->fs = copy_fs_struct(me->fs);
337 		if (!nsset->fs)
338 			goto out;
339 	}
340 
341 	nsset->flags = flags;
342 	return 0;
343 
344 out:
345 	put_nsset(nsset);
346 	return -ENOMEM;
347 }
348 
349 static inline int validate_ns(struct nsset *nsset, struct ns_common *ns)
350 {
351 	return ns->ops->install(nsset, ns);
352 }
353 
354 /*
355  * This is the inverse operation to unshare().
356  * Ordering is equivalent to the standard ordering used everywhere else
357  * during unshare and process creation. The switch to the new set of
358  * namespaces occurs at the point of no return after installation of
359  * all requested namespaces was successful in commit_nsset().
360  */
361 static int validate_nsset(struct nsset *nsset, struct pid *pid)
362 {
363 	int ret = 0;
364 	unsigned flags = nsset->flags;
365 	struct user_namespace *user_ns = NULL;
366 	struct pid_namespace *pid_ns = NULL;
367 	struct nsproxy *nsp;
368 	struct task_struct *tsk;
369 
370 	/* Take a "snapshot" of the target task's namespaces. */
371 	rcu_read_lock();
372 	tsk = pid_task(pid, PIDTYPE_PID);
373 	if (!tsk) {
374 		rcu_read_unlock();
375 		return -ESRCH;
376 	}
377 
378 	if (!ptrace_may_access(tsk, PTRACE_MODE_READ_REALCREDS)) {
379 		rcu_read_unlock();
380 		return -EPERM;
381 	}
382 
383 	task_lock(tsk);
384 	nsp = tsk->nsproxy;
385 	if (nsp)
386 		get_nsproxy(nsp);
387 	task_unlock(tsk);
388 	if (!nsp) {
389 		rcu_read_unlock();
390 		return -ESRCH;
391 	}
392 
393 #ifdef CONFIG_PID_NS
394 	if (flags & CLONE_NEWPID) {
395 		pid_ns = task_active_pid_ns(tsk);
396 		if (unlikely(!pid_ns)) {
397 			rcu_read_unlock();
398 			ret = -ESRCH;
399 			goto out;
400 		}
401 		get_pid_ns(pid_ns);
402 	}
403 #endif
404 
405 #ifdef CONFIG_USER_NS
406 	if (flags & CLONE_NEWUSER)
407 		user_ns = get_user_ns(__task_cred(tsk)->user_ns);
408 #endif
409 	rcu_read_unlock();
410 
411 	/*
412 	 * Install requested namespaces. The caller will have
413 	 * verified earlier that the requested namespaces are
414 	 * supported on this kernel. We don't report errors here
415 	 * if a namespace is requested that isn't supported.
416 	 */
417 #ifdef CONFIG_USER_NS
418 	if (flags & CLONE_NEWUSER) {
419 		ret = validate_ns(nsset, &user_ns->ns);
420 		if (ret)
421 			goto out;
422 	}
423 #endif
424 
425 	if (flags & CLONE_NEWNS) {
426 		ret = validate_ns(nsset, from_mnt_ns(nsp->mnt_ns));
427 		if (ret)
428 			goto out;
429 	}
430 
431 #ifdef CONFIG_UTS_NS
432 	if (flags & CLONE_NEWUTS) {
433 		ret = validate_ns(nsset, &nsp->uts_ns->ns);
434 		if (ret)
435 			goto out;
436 	}
437 #endif
438 
439 #ifdef CONFIG_IPC_NS
440 	if (flags & CLONE_NEWIPC) {
441 		ret = validate_ns(nsset, &nsp->ipc_ns->ns);
442 		if (ret)
443 			goto out;
444 	}
445 #endif
446 
447 #ifdef CONFIG_PID_NS
448 	if (flags & CLONE_NEWPID) {
449 		ret = validate_ns(nsset, &pid_ns->ns);
450 		if (ret)
451 			goto out;
452 	}
453 #endif
454 
455 #ifdef CONFIG_CGROUPS
456 	if (flags & CLONE_NEWCGROUP) {
457 		ret = validate_ns(nsset, &nsp->cgroup_ns->ns);
458 		if (ret)
459 			goto out;
460 	}
461 #endif
462 
463 #ifdef CONFIG_NET_NS
464 	if (flags & CLONE_NEWNET) {
465 		ret = validate_ns(nsset, &nsp->net_ns->ns);
466 		if (ret)
467 			goto out;
468 	}
469 #endif
470 
471 #ifdef CONFIG_TIME_NS
472 	if (flags & CLONE_NEWTIME) {
473 		ret = validate_ns(nsset, &nsp->time_ns->ns);
474 		if (ret)
475 			goto out;
476 	}
477 #endif
478 
479 out:
480 	if (pid_ns)
481 		put_pid_ns(pid_ns);
482 	if (nsp)
483 		put_nsproxy(nsp);
484 	put_user_ns(user_ns);
485 
486 	return ret;
487 }
488 
489 /*
490  * This is the point of no return. There are just a few namespaces
491  * that do some actual work here and it's sufficiently minimal that
492  * a separate ns_common operation seems unnecessary for now.
493  * Unshare is doing the same thing. If we'll end up needing to do
494  * more in a given namespace or a helper here is ultimately not
495  * exported anymore a simple commit handler for each namespace
496  * should be added to ns_common.
497  */
498 static void commit_nsset(struct nsset *nsset)
499 {
500 	unsigned flags = nsset->flags;
501 	struct task_struct *me = current;
502 
503 #ifdef CONFIG_USER_NS
504 	if (flags & CLONE_NEWUSER) {
505 		/* transfer ownership */
506 		commit_creds(nsset_cred(nsset));
507 		nsset->cred = NULL;
508 	}
509 #endif
510 
511 	/* We only need to commit if we have used a temporary fs_struct. */
512 	if ((flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) {
513 		set_fs_root(me->fs, &nsset->fs->root);
514 		set_fs_pwd(me->fs, &nsset->fs->pwd);
515 	}
516 
517 #ifdef CONFIG_IPC_NS
518 	if (flags & CLONE_NEWIPC)
519 		exit_sem(me);
520 #endif
521 
522 #ifdef CONFIG_TIME_NS
523 	if (flags & CLONE_NEWTIME)
524 		timens_commit(me, nsset->nsproxy->time_ns);
525 #endif
526 
527 	/* transfer ownership */
528 	switch_task_namespaces(me, nsset->nsproxy);
529 	nsset->nsproxy = NULL;
530 }
531 
532 SYSCALL_DEFINE2(setns, int, fd, int, flags)
533 {
534 	struct file *file;
535 	struct ns_common *ns = NULL;
536 	struct nsset nsset = {};
537 	int err = 0;
538 
539 	file = fget(fd);
540 	if (!file)
541 		return -EBADF;
542 
543 	if (proc_ns_file(file)) {
544 		ns = get_proc_ns(file_inode(file));
545 		if (flags && (ns->ops->type != flags))
546 			err = -EINVAL;
547 		flags = ns->ops->type;
548 	} else if (!IS_ERR(pidfd_pid(file))) {
549 		err = check_setns_flags(flags);
550 	} else {
551 		err = -EINVAL;
552 	}
553 	if (err)
554 		goto out;
555 
556 	err = prepare_nsset(flags, &nsset);
557 	if (err)
558 		goto out;
559 
560 	if (proc_ns_file(file))
561 		err = validate_ns(&nsset, ns);
562 	else
563 		err = validate_nsset(&nsset, file->private_data);
564 	if (!err) {
565 		commit_nsset(&nsset);
566 		perf_event_namespaces(current);
567 	}
568 	put_nsset(&nsset);
569 out:
570 	fput(file);
571 	return err;
572 }
573 
574 int __init nsproxy_cache_init(void)
575 {
576 	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
577 	return 0;
578 }
579