xref: /openbmc/linux/kernel/nsproxy.c (revision f5ad1c74) 
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 (likely(old_ns->time_ns_for_children == old_ns->time_ns)) {
161 			get_nsproxy(old_ns);
162 			return 0;
163 		}
164 	} else if (!ns_capable(user_ns, CAP_SYS_ADMIN))
165 		return -EPERM;
166 
167 	/*
168 	 * CLONE_NEWIPC must detach from the undolist: after switching
169 	 * to a new ipc namespace, the semaphore arrays from the old
170 	 * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
171 	 * means share undolist with parent, so we must forbid using
172 	 * it along with CLONE_NEWIPC.
173 	 */
174 	if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
175 		(CLONE_NEWIPC | CLONE_SYSVSEM))
176 		return -EINVAL;
177 
178 	new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);
179 	if (IS_ERR(new_ns))
180 		return  PTR_ERR(new_ns);
181 
182 	timens_on_fork(new_ns, tsk);
183 
184 	tsk->nsproxy = new_ns;
185 	return 0;
186 }
187 
188 void free_nsproxy(struct nsproxy *ns)
189 {
190 	if (ns->mnt_ns)
191 		put_mnt_ns(ns->mnt_ns);
192 	if (ns->uts_ns)
193 		put_uts_ns(ns->uts_ns);
194 	if (ns->ipc_ns)
195 		put_ipc_ns(ns->ipc_ns);
196 	if (ns->pid_ns_for_children)
197 		put_pid_ns(ns->pid_ns_for_children);
198 	if (ns->time_ns)
199 		put_time_ns(ns->time_ns);
200 	if (ns->time_ns_for_children)
201 		put_time_ns(ns->time_ns_for_children);
202 	put_cgroup_ns(ns->cgroup_ns);
203 	put_net(ns->net_ns);
204 	kmem_cache_free(nsproxy_cachep, ns);
205 }
206 
207 /*
208  * Called from unshare. Unshare all the namespaces part of nsproxy.
209  * On success, returns the new nsproxy.
210  */
211 int unshare_nsproxy_namespaces(unsigned long unshare_flags,
212 	struct nsproxy **new_nsp, struct cred *new_cred, struct fs_struct *new_fs)
213 {
214 	struct user_namespace *user_ns;
215 	int err = 0;
216 
217 	if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
218 			       CLONE_NEWNET | CLONE_NEWPID | CLONE_NEWCGROUP |
219 			       CLONE_NEWTIME)))
220 		return 0;
221 
222 	user_ns = new_cred ? new_cred->user_ns : current_user_ns();
223 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
224 		return -EPERM;
225 
226 	*new_nsp = create_new_namespaces(unshare_flags, current, user_ns,
227 					 new_fs ? new_fs : current->fs);
228 	if (IS_ERR(*new_nsp)) {
229 		err = PTR_ERR(*new_nsp);
230 		goto out;
231 	}
232 
233 out:
234 	return err;
235 }
236 
237 void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
238 {
239 	struct nsproxy *ns;
240 
241 	might_sleep();
242 
243 	task_lock(p);
244 	ns = p->nsproxy;
245 	p->nsproxy = new;
246 	task_unlock(p);
247 
248 	if (ns)
249 		put_nsproxy(ns);
250 }
251 
252 void exit_task_namespaces(struct task_struct *p)
253 {
254 	switch_task_namespaces(p, NULL);
255 }
256 
257 static int check_setns_flags(unsigned long flags)
258 {
259 	if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
260 				 CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER |
261 				 CLONE_NEWPID | CLONE_NEWCGROUP)))
262 		return -EINVAL;
263 
264 #ifndef CONFIG_USER_NS
265 	if (flags & CLONE_NEWUSER)
266 		return -EINVAL;
267 #endif
268 #ifndef CONFIG_PID_NS
269 	if (flags & CLONE_NEWPID)
270 		return -EINVAL;
271 #endif
272 #ifndef CONFIG_UTS_NS
273 	if (flags & CLONE_NEWUTS)
274 		return -EINVAL;
275 #endif
276 #ifndef CONFIG_IPC_NS
277 	if (flags & CLONE_NEWIPC)
278 		return -EINVAL;
279 #endif
280 #ifndef CONFIG_CGROUPS
281 	if (flags & CLONE_NEWCGROUP)
282 		return -EINVAL;
283 #endif
284 #ifndef CONFIG_NET_NS
285 	if (flags & CLONE_NEWNET)
286 		return -EINVAL;
287 #endif
288 #ifndef CONFIG_TIME_NS
289 	if (flags & CLONE_NEWTIME)
290 		return -EINVAL;
291 #endif
292 
293 	return 0;
294 }
295 
296 static void put_nsset(struct nsset *nsset)
297 {
298 	unsigned flags = nsset->flags;
299 
300 	if (flags & CLONE_NEWUSER)
301 		put_cred(nsset_cred(nsset));
302 	/*
303 	 * We only created a temporary copy if we attached to more than just
304 	 * the mount namespace.
305 	 */
306 	if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS))
307 		free_fs_struct(nsset->fs);
308 	if (nsset->nsproxy)
309 		free_nsproxy(nsset->nsproxy);
310 }
311 
312 static int prepare_nsset(unsigned flags, struct nsset *nsset)
313 {
314 	struct task_struct *me = current;
315 
316 	nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
317 	if (IS_ERR(nsset->nsproxy))
318 		return PTR_ERR(nsset->nsproxy);
319 
320 	if (flags & CLONE_NEWUSER)
321 		nsset->cred = prepare_creds();
322 	else
323 		nsset->cred = current_cred();
324 	if (!nsset->cred)
325 		goto out;
326 
327 	/* Only create a temporary copy of fs_struct if we really need to. */
328 	if (flags == CLONE_NEWNS) {
329 		nsset->fs = me->fs;
330 	} else if (flags & CLONE_NEWNS) {
331 		nsset->fs = copy_fs_struct(me->fs);
332 		if (!nsset->fs)
333 			goto out;
334 	}
335 
336 	nsset->flags = flags;
337 	return 0;
338 
339 out:
340 	put_nsset(nsset);
341 	return -ENOMEM;
342 }
343 
344 static inline int validate_ns(struct nsset *nsset, struct ns_common *ns)
345 {
346 	return ns->ops->install(nsset, ns);
347 }
348 
349 /*
350  * This is the inverse operation to unshare().
351  * Ordering is equivalent to the standard ordering used everywhere else
352  * during unshare and process creation. The switch to the new set of
353  * namespaces occurs at the point of no return after installation of
354  * all requested namespaces was successful in commit_nsset().
355  */
356 static int validate_nsset(struct nsset *nsset, struct pid *pid)
357 {
358 	int ret = 0;
359 	unsigned flags = nsset->flags;
360 	struct user_namespace *user_ns = NULL;
361 	struct pid_namespace *pid_ns = NULL;
362 	struct nsproxy *nsp;
363 	struct task_struct *tsk;
364 
365 	/* Take a "snapshot" of the target task's namespaces. */
366 	rcu_read_lock();
367 	tsk = pid_task(pid, PIDTYPE_PID);
368 	if (!tsk) {
369 		rcu_read_unlock();
370 		return -ESRCH;
371 	}
372 
373 	if (!ptrace_may_access(tsk, PTRACE_MODE_READ_REALCREDS)) {
374 		rcu_read_unlock();
375 		return -EPERM;
376 	}
377 
378 	task_lock(tsk);
379 	nsp = tsk->nsproxy;
380 	if (nsp)
381 		get_nsproxy(nsp);
382 	task_unlock(tsk);
383 	if (!nsp) {
384 		rcu_read_unlock();
385 		return -ESRCH;
386 	}
387 
388 #ifdef CONFIG_PID_NS
389 	if (flags & CLONE_NEWPID) {
390 		pid_ns = task_active_pid_ns(tsk);
391 		if (unlikely(!pid_ns)) {
392 			rcu_read_unlock();
393 			ret = -ESRCH;
394 			goto out;
395 		}
396 		get_pid_ns(pid_ns);
397 	}
398 #endif
399 
400 #ifdef CONFIG_USER_NS
401 	if (flags & CLONE_NEWUSER)
402 		user_ns = get_user_ns(__task_cred(tsk)->user_ns);
403 #endif
404 	rcu_read_unlock();
405 
406 	/*
407 	 * Install requested namespaces. The caller will have
408 	 * verified earlier that the requested namespaces are
409 	 * supported on this kernel. We don't report errors here
410 	 * if a namespace is requested that isn't supported.
411 	 */
412 #ifdef CONFIG_USER_NS
413 	if (flags & CLONE_NEWUSER) {
414 		ret = validate_ns(nsset, &user_ns->ns);
415 		if (ret)
416 			goto out;
417 	}
418 #endif
419 
420 	if (flags & CLONE_NEWNS) {
421 		ret = validate_ns(nsset, from_mnt_ns(nsp->mnt_ns));
422 		if (ret)
423 			goto out;
424 	}
425 
426 #ifdef CONFIG_UTS_NS
427 	if (flags & CLONE_NEWUTS) {
428 		ret = validate_ns(nsset, &nsp->uts_ns->ns);
429 		if (ret)
430 			goto out;
431 	}
432 #endif
433 
434 #ifdef CONFIG_IPC_NS
435 	if (flags & CLONE_NEWIPC) {
436 		ret = validate_ns(nsset, &nsp->ipc_ns->ns);
437 		if (ret)
438 			goto out;
439 	}
440 #endif
441 
442 #ifdef CONFIG_PID_NS
443 	if (flags & CLONE_NEWPID) {
444 		ret = validate_ns(nsset, &pid_ns->ns);
445 		if (ret)
446 			goto out;
447 	}
448 #endif
449 
450 #ifdef CONFIG_CGROUPS
451 	if (flags & CLONE_NEWCGROUP) {
452 		ret = validate_ns(nsset, &nsp->cgroup_ns->ns);
453 		if (ret)
454 			goto out;
455 	}
456 #endif
457 
458 #ifdef CONFIG_NET_NS
459 	if (flags & CLONE_NEWNET) {
460 		ret = validate_ns(nsset, &nsp->net_ns->ns);
461 		if (ret)
462 			goto out;
463 	}
464 #endif
465 
466 #ifdef CONFIG_TIME_NS
467 	if (flags & CLONE_NEWTIME) {
468 		ret = validate_ns(nsset, &nsp->time_ns->ns);
469 		if (ret)
470 			goto out;
471 	}
472 #endif
473 
474 out:
475 	if (pid_ns)
476 		put_pid_ns(pid_ns);
477 	if (nsp)
478 		put_nsproxy(nsp);
479 	put_user_ns(user_ns);
480 
481 	return ret;
482 }
483 
484 /*
485  * This is the point of no return. There are just a few namespaces
486  * that do some actual work here and it's sufficiently minimal that
487  * a separate ns_common operation seems unnecessary for now.
488  * Unshare is doing the same thing. If we'll end up needing to do
489  * more in a given namespace or a helper here is ultimately not
490  * exported anymore a simple commit handler for each namespace
491  * should be added to ns_common.
492  */
493 static void commit_nsset(struct nsset *nsset)
494 {
495 	unsigned flags = nsset->flags;
496 	struct task_struct *me = current;
497 
498 #ifdef CONFIG_USER_NS
499 	if (flags & CLONE_NEWUSER) {
500 		/* transfer ownership */
501 		commit_creds(nsset_cred(nsset));
502 		nsset->cred = NULL;
503 	}
504 #endif
505 
506 	/* We only need to commit if we have used a temporary fs_struct. */
507 	if ((flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) {
508 		set_fs_root(me->fs, &nsset->fs->root);
509 		set_fs_pwd(me->fs, &nsset->fs->pwd);
510 	}
511 
512 #ifdef CONFIG_IPC_NS
513 	if (flags & CLONE_NEWIPC)
514 		exit_sem(me);
515 #endif
516 
517 #ifdef CONFIG_TIME_NS
518 	if (flags & CLONE_NEWTIME)
519 		timens_commit(me, nsset->nsproxy->time_ns);
520 #endif
521 
522 	/* transfer ownership */
523 	switch_task_namespaces(me, nsset->nsproxy);
524 	nsset->nsproxy = NULL;
525 }
526 
527 SYSCALL_DEFINE2(setns, int, fd, int, flags)
528 {
529 	struct file *file;
530 	struct ns_common *ns = NULL;
531 	struct nsset nsset = {};
532 	int err = 0;
533 
534 	file = fget(fd);
535 	if (!file)
536 		return -EBADF;
537 
538 	if (proc_ns_file(file)) {
539 		ns = get_proc_ns(file_inode(file));
540 		if (flags && (ns->ops->type != flags))
541 			err = -EINVAL;
542 		flags = ns->ops->type;
543 	} else if (!IS_ERR(pidfd_pid(file))) {
544 		err = check_setns_flags(flags);
545 	} else {
546 		err = -EINVAL;
547 	}
548 	if (err)
549 		goto out;
550 
551 	err = prepare_nsset(flags, &nsset);
552 	if (err)
553 		goto out;
554 
555 	if (proc_ns_file(file))
556 		err = validate_ns(&nsset, ns);
557 	else
558 		err = validate_nsset(&nsset, file->private_data);
559 	if (!err) {
560 		commit_nsset(&nsset);
561 		perf_event_namespaces(current);
562 	}
563 	put_nsset(&nsset);
564 out:
565 	fput(file);
566 	return err;
567 }
568 
569 int __init nsproxy_cache_init(void)
570 {
571 	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
572 	return 0;
573 }
574