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 #include <linux/ipc_namespace.h>
17 #include <linux/time_namespace.h>
18 #include <linux/utsname.h>
19 #include <linux/exportfs.h>
20 #include <linux/nstree.h>
21 #include <net/net_namespace.h>
22
23 #include "mount.h"
24 #include "internal.h"
25
26 static struct vfsmount *nsfs_mnt;
27
28 static struct path nsfs_root_path = {};
29
nsfs_get_root(struct path * path)30 void nsfs_get_root(struct path *path)
31 {
32 *path = nsfs_root_path;
33 path_get(path);
34 }
35
36 static long ns_ioctl(struct file *filp, unsigned int ioctl,
37 unsigned long arg);
38 static const struct file_operations ns_file_operations = {
39 .unlocked_ioctl = ns_ioctl,
40 .compat_ioctl = compat_ptr_ioctl,
41 };
42
ns_dname(struct dentry * dentry,char * buffer,int buflen)43 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
44 {
45 struct inode *inode = d_inode(dentry);
46 struct ns_common *ns = inode->i_private;
47 const struct proc_ns_operations *ns_ops = ns->ops;
48
49 return dynamic_dname(buffer, buflen, "%s:[%lu]",
50 ns_ops->name, inode->i_ino);
51 }
52
53 const struct dentry_operations ns_dentry_operations = {
54 .d_dname = ns_dname,
55 .d_prune = stashed_dentry_prune,
56 };
57
nsfs_evict(struct inode * inode)58 static void nsfs_evict(struct inode *inode)
59 {
60 struct ns_common *ns = inode->i_private;
61 clear_inode(inode);
62 ns->ops->put(ns);
63 }
64
ns_get_path_cb(struct path * path,ns_get_path_helper_t * ns_get_cb,void * private_data)65 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
66 void *private_data)
67 {
68 struct ns_common *ns;
69
70 ns = ns_get_cb(private_data);
71 if (!ns)
72 return -ENOENT;
73
74 return path_from_stashed(&ns->stashed, nsfs_mnt, ns, path);
75 }
76
77 struct ns_get_path_task_args {
78 const struct proc_ns_operations *ns_ops;
79 struct task_struct *task;
80 };
81
ns_get_path_task(void * private_data)82 static struct ns_common *ns_get_path_task(void *private_data)
83 {
84 struct ns_get_path_task_args *args = private_data;
85
86 return args->ns_ops->get(args->task);
87 }
88
ns_get_path(struct path * path,struct task_struct * task,const struct proc_ns_operations * ns_ops)89 int ns_get_path(struct path *path, struct task_struct *task,
90 const struct proc_ns_operations *ns_ops)
91 {
92 struct ns_get_path_task_args args = {
93 .ns_ops = ns_ops,
94 .task = task,
95 };
96
97 return ns_get_path_cb(path, ns_get_path_task, &args);
98 }
99
100 /**
101 * open_namespace - open a namespace
102 * @ns: the namespace to open
103 *
104 * This will consume a reference to @ns indendent of success or failure.
105 *
106 * Return: A file descriptor on success or a negative error code on failure.
107 */
open_namespace(struct ns_common * ns)108 int open_namespace(struct ns_common *ns)
109 {
110 struct path path __free(path_put) = {};
111 struct file *f;
112 int err;
113
114 /* call first to consume reference */
115 err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
116 if (err < 0)
117 return err;
118
119 CLASS(get_unused_fd, fd)(O_CLOEXEC);
120 if (fd < 0)
121 return fd;
122
123 f = dentry_open(&path, O_RDONLY, current_cred());
124 if (IS_ERR(f))
125 return PTR_ERR(f);
126
127 fd_install(fd, f);
128 return take_fd(fd);
129 }
130
open_related_ns(struct ns_common * ns,struct ns_common * (* get_ns)(struct ns_common * ns))131 int open_related_ns(struct ns_common *ns,
132 struct ns_common *(*get_ns)(struct ns_common *ns))
133 {
134 struct ns_common *relative;
135
136 relative = get_ns(ns);
137 if (IS_ERR(relative))
138 return PTR_ERR(relative);
139
140 return open_namespace(relative);
141 }
142 EXPORT_SYMBOL_GPL(open_related_ns);
143
copy_ns_info_to_user(const struct mnt_namespace * mnt_ns,struct mnt_ns_info __user * uinfo,size_t usize,struct mnt_ns_info * kinfo)144 static int copy_ns_info_to_user(const struct mnt_namespace *mnt_ns,
145 struct mnt_ns_info __user *uinfo, size_t usize,
146 struct mnt_ns_info *kinfo)
147 {
148 /*
149 * If userspace and the kernel have the same struct size it can just
150 * be copied. If userspace provides an older struct, only the bits that
151 * userspace knows about will be copied. If userspace provides a new
152 * struct, only the bits that the kernel knows aobut will be copied and
153 * the size value will be set to the size the kernel knows about.
154 */
155 kinfo->size = min(usize, sizeof(*kinfo));
156 kinfo->mnt_ns_id = mnt_ns->ns.ns_id;
157 kinfo->nr_mounts = READ_ONCE(mnt_ns->nr_mounts);
158 /* Subtract the root mount of the mount namespace. */
159 if (kinfo->nr_mounts)
160 kinfo->nr_mounts--;
161
162 if (copy_to_user(uinfo, kinfo, kinfo->size))
163 return -EFAULT;
164
165 return 0;
166 }
167
nsfs_ioctl_valid(unsigned int cmd)168 static bool nsfs_ioctl_valid(unsigned int cmd)
169 {
170 switch (cmd) {
171 case NS_GET_USERNS:
172 case NS_GET_PARENT:
173 case NS_GET_NSTYPE:
174 case NS_GET_OWNER_UID:
175 case NS_GET_MNTNS_ID:
176 case NS_GET_PID_FROM_PIDNS:
177 case NS_GET_TGID_FROM_PIDNS:
178 case NS_GET_PID_IN_PIDNS:
179 case NS_GET_TGID_IN_PIDNS:
180 case NS_GET_ID:
181 return true;
182 }
183
184 /* Extensible ioctls require some extra handling. */
185 switch (_IOC_NR(cmd)) {
186 case _IOC_NR(NS_MNT_GET_INFO):
187 return extensible_ioctl_valid(cmd, NS_MNT_GET_INFO, MNT_NS_INFO_SIZE_VER0);
188 case _IOC_NR(NS_MNT_GET_NEXT):
189 return extensible_ioctl_valid(cmd, NS_MNT_GET_NEXT, MNT_NS_INFO_SIZE_VER0);
190 case _IOC_NR(NS_MNT_GET_PREV):
191 return extensible_ioctl_valid(cmd, NS_MNT_GET_PREV, MNT_NS_INFO_SIZE_VER0);
192 }
193
194 return false;
195 }
196
ns_ioctl(struct file * filp,unsigned int ioctl,unsigned long arg)197 static long ns_ioctl(struct file *filp, unsigned int ioctl,
198 unsigned long arg)
199 {
200 struct user_namespace *user_ns;
201 struct pid_namespace *pid_ns;
202 struct task_struct *tsk;
203 struct ns_common *ns;
204 struct mnt_namespace *mnt_ns;
205 bool previous = false;
206 uid_t __user *argp;
207 uid_t uid;
208 int ret;
209
210 if (!nsfs_ioctl_valid(ioctl))
211 return -ENOIOCTLCMD;
212
213 ns = get_proc_ns(file_inode(filp));
214 switch (ioctl) {
215 case NS_GET_USERNS:
216 return open_related_ns(ns, ns_get_owner);
217 case NS_GET_PARENT:
218 if (!ns->ops->get_parent)
219 return -EINVAL;
220 return open_related_ns(ns, ns->ops->get_parent);
221 case NS_GET_NSTYPE:
222 return ns->ns_type;
223 case NS_GET_OWNER_UID:
224 if (ns->ns_type != CLONE_NEWUSER)
225 return -EINVAL;
226 user_ns = container_of(ns, struct user_namespace, ns);
227 argp = (uid_t __user *) arg;
228 uid = from_kuid_munged(current_user_ns(), user_ns->owner);
229 return put_user(uid, argp);
230 case NS_GET_PID_FROM_PIDNS:
231 fallthrough;
232 case NS_GET_TGID_FROM_PIDNS:
233 fallthrough;
234 case NS_GET_PID_IN_PIDNS:
235 fallthrough;
236 case NS_GET_TGID_IN_PIDNS: {
237 if (ns->ns_type != CLONE_NEWPID)
238 return -EINVAL;
239
240 ret = -ESRCH;
241 pid_ns = container_of(ns, struct pid_namespace, ns);
242
243 guard(rcu)();
244
245 if (ioctl == NS_GET_PID_IN_PIDNS ||
246 ioctl == NS_GET_TGID_IN_PIDNS)
247 tsk = find_task_by_vpid(arg);
248 else
249 tsk = find_task_by_pid_ns(arg, pid_ns);
250 if (!tsk)
251 break;
252
253 switch (ioctl) {
254 case NS_GET_PID_FROM_PIDNS:
255 ret = task_pid_vnr(tsk);
256 break;
257 case NS_GET_TGID_FROM_PIDNS:
258 ret = task_tgid_vnr(tsk);
259 break;
260 case NS_GET_PID_IN_PIDNS:
261 ret = task_pid_nr_ns(tsk, pid_ns);
262 break;
263 case NS_GET_TGID_IN_PIDNS:
264 ret = task_tgid_nr_ns(tsk, pid_ns);
265 break;
266 default:
267 ret = 0;
268 break;
269 }
270
271 if (!ret)
272 ret = -ESRCH;
273 return ret;
274 }
275 case NS_GET_MNTNS_ID:
276 if (ns->ns_type != CLONE_NEWNS)
277 return -EINVAL;
278 fallthrough;
279 case NS_GET_ID: {
280 __u64 __user *idp;
281 __u64 id;
282
283 idp = (__u64 __user *)arg;
284 id = ns->ns_id;
285 return put_user(id, idp);
286 }
287 }
288
289 /* extensible ioctls */
290 switch (_IOC_NR(ioctl)) {
291 case _IOC_NR(NS_MNT_GET_INFO): {
292 struct mnt_ns_info kinfo = {};
293 struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
294 size_t usize = _IOC_SIZE(ioctl);
295
296 if (ns->ns_type != CLONE_NEWNS)
297 return -EINVAL;
298
299 if (!uinfo)
300 return -EINVAL;
301
302 if (usize < MNT_NS_INFO_SIZE_VER0)
303 return -EINVAL;
304
305 return copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
306 }
307 case _IOC_NR(NS_MNT_GET_PREV):
308 previous = true;
309 fallthrough;
310 case _IOC_NR(NS_MNT_GET_NEXT): {
311 struct mnt_ns_info kinfo = {};
312 struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
313 struct path path __free(path_put) = {};
314 struct file *f __free(fput) = NULL;
315 size_t usize = _IOC_SIZE(ioctl);
316
317 if (ns->ns_type != CLONE_NEWNS)
318 return -EINVAL;
319
320 if (usize < MNT_NS_INFO_SIZE_VER0)
321 return -EINVAL;
322
323 mnt_ns = get_sequential_mnt_ns(to_mnt_ns(ns), previous);
324 if (IS_ERR(mnt_ns))
325 return PTR_ERR(mnt_ns);
326
327 ns = to_ns_common(mnt_ns);
328 /* Transfer ownership of @mnt_ns reference to @path. */
329 ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
330 if (ret)
331 return ret;
332
333 CLASS(get_unused_fd, fd)(O_CLOEXEC);
334 if (fd < 0)
335 return fd;
336
337 f = dentry_open(&path, O_RDONLY, current_cred());
338 if (IS_ERR(f))
339 return PTR_ERR(f);
340
341 if (uinfo) {
342 /*
343 * If @uinfo is passed return all information about the
344 * mount namespace as well.
345 */
346 ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
347 if (ret)
348 return ret;
349 }
350
351 /* Transfer reference of @f to caller's fdtable. */
352 fd_install(fd, no_free_ptr(f));
353 /* File descriptor is live so hand it off to the caller. */
354 return take_fd(fd);
355 }
356 default:
357 ret = -ENOTTY;
358 }
359
360 return ret;
361 }
362
ns_get_name(char * buf,size_t size,struct task_struct * task,const struct proc_ns_operations * ns_ops)363 int ns_get_name(char *buf, size_t size, struct task_struct *task,
364 const struct proc_ns_operations *ns_ops)
365 {
366 struct ns_common *ns;
367 int res = -ENOENT;
368 const char *name;
369 ns = ns_ops->get(task);
370 if (ns) {
371 name = ns_ops->real_ns_name ? : ns_ops->name;
372 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
373 ns_ops->put(ns);
374 }
375 return res;
376 }
377
proc_ns_file(const struct file * file)378 bool proc_ns_file(const struct file *file)
379 {
380 return file->f_op == &ns_file_operations;
381 }
382
383 /**
384 * ns_match() - Returns true if current namespace matches dev/ino provided.
385 * @ns: current namespace
386 * @dev: dev_t from nsfs that will be matched against current nsfs
387 * @ino: ino_t from nsfs that will be matched against current nsfs
388 *
389 * Return: true if dev and ino matches the current nsfs.
390 */
ns_match(const struct ns_common * ns,dev_t dev,ino_t ino)391 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
392 {
393 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
394 }
395
396
nsfs_show_path(struct seq_file * seq,struct dentry * dentry)397 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
398 {
399 struct inode *inode = d_inode(dentry);
400 const struct ns_common *ns = inode->i_private;
401 const struct proc_ns_operations *ns_ops = ns->ops;
402
403 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
404 return 0;
405 }
406
407 static const struct super_operations nsfs_ops = {
408 .statfs = simple_statfs,
409 .evict_inode = nsfs_evict,
410 .show_path = nsfs_show_path,
411 };
412
nsfs_init_inode(struct inode * inode,void * data)413 static int nsfs_init_inode(struct inode *inode, void *data)
414 {
415 struct ns_common *ns = data;
416
417 inode->i_private = data;
418 inode->i_mode |= S_IRUGO;
419 inode->i_fop = &ns_file_operations;
420 inode->i_ino = ns->inum;
421 return 0;
422 }
423
nsfs_put_data(void * data)424 static void nsfs_put_data(void *data)
425 {
426 struct ns_common *ns = data;
427 ns->ops->put(ns);
428 }
429
430 static const struct stashed_operations nsfs_stashed_ops = {
431 .init_inode = nsfs_init_inode,
432 .put_data = nsfs_put_data,
433 };
434
435 #define NSFS_FID_SIZE_U32_VER0 (NSFS_FILE_HANDLE_SIZE_VER0 / sizeof(u32))
436 #define NSFS_FID_SIZE_U32_LATEST (NSFS_FILE_HANDLE_SIZE_LATEST / sizeof(u32))
437
nsfs_encode_fh(struct inode * inode,u32 * fh,int * max_len,struct inode * parent)438 static int nsfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
439 struct inode *parent)
440 {
441 struct nsfs_file_handle *fid = (struct nsfs_file_handle *)fh;
442 struct ns_common *ns = inode->i_private;
443 int len = *max_len;
444
445 if (parent)
446 return FILEID_INVALID;
447
448 if (len < NSFS_FID_SIZE_U32_VER0) {
449 *max_len = NSFS_FID_SIZE_U32_LATEST;
450 return FILEID_INVALID;
451 } else if (len > NSFS_FID_SIZE_U32_LATEST) {
452 *max_len = NSFS_FID_SIZE_U32_LATEST;
453 }
454
455 fid->ns_id = ns->ns_id;
456 fid->ns_type = ns->ns_type;
457 fid->ns_inum = inode->i_ino;
458 return FILEID_NSFS;
459 }
460
nsfs_fh_to_dentry(struct super_block * sb,struct fid * fh,int fh_len,int fh_type)461 static struct dentry *nsfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
462 int fh_len, int fh_type)
463 {
464 struct path path __free(path_put) = {};
465 struct nsfs_file_handle *fid = (struct nsfs_file_handle *)fh;
466 struct user_namespace *owning_ns = NULL;
467 struct ns_common *ns;
468 int ret;
469
470 if (fh_len < NSFS_FID_SIZE_U32_VER0)
471 return NULL;
472
473 /* Check that any trailing bytes are zero. */
474 if ((fh_len > NSFS_FID_SIZE_U32_LATEST) &&
475 memchr_inv((void *)fid + NSFS_FID_SIZE_U32_LATEST, 0,
476 fh_len - NSFS_FID_SIZE_U32_LATEST))
477 return NULL;
478
479 switch (fh_type) {
480 case FILEID_NSFS:
481 break;
482 default:
483 return NULL;
484 }
485
486 scoped_guard(rcu) {
487 ns = ns_tree_lookup_rcu(fid->ns_id, fid->ns_type);
488 if (!ns)
489 return NULL;
490
491 VFS_WARN_ON_ONCE(ns->ns_id != fid->ns_id);
492 VFS_WARN_ON_ONCE(ns->ns_type != fid->ns_type);
493 VFS_WARN_ON_ONCE(ns->inum != fid->ns_inum);
494
495 if (!__ns_ref_get(ns))
496 return NULL;
497 }
498
499 switch (ns->ns_type) {
500 #ifdef CONFIG_CGROUPS
501 case CLONE_NEWCGROUP:
502 if (!current_in_namespace(to_cg_ns(ns)))
503 owning_ns = to_cg_ns(ns)->user_ns;
504 break;
505 #endif
506 #ifdef CONFIG_IPC_NS
507 case CLONE_NEWIPC:
508 if (!current_in_namespace(to_ipc_ns(ns)))
509 owning_ns = to_ipc_ns(ns)->user_ns;
510 break;
511 #endif
512 case CLONE_NEWNS:
513 if (!current_in_namespace(to_mnt_ns(ns)))
514 owning_ns = to_mnt_ns(ns)->user_ns;
515 break;
516 #ifdef CONFIG_NET_NS
517 case CLONE_NEWNET:
518 if (!current_in_namespace(to_net_ns(ns)))
519 owning_ns = to_net_ns(ns)->user_ns;
520 break;
521 #endif
522 #ifdef CONFIG_PID_NS
523 case CLONE_NEWPID:
524 if (!current_in_namespace(to_pid_ns(ns))) {
525 owning_ns = to_pid_ns(ns)->user_ns;
526 } else if (!READ_ONCE(to_pid_ns(ns)->child_reaper)) {
527 ns->ops->put(ns);
528 return ERR_PTR(-EPERM);
529 }
530 break;
531 #endif
532 #ifdef CONFIG_TIME_NS
533 case CLONE_NEWTIME:
534 if (!current_in_namespace(to_time_ns(ns)))
535 owning_ns = to_time_ns(ns)->user_ns;
536 break;
537 #endif
538 #ifdef CONFIG_USER_NS
539 case CLONE_NEWUSER:
540 if (!current_in_namespace(to_user_ns(ns)))
541 owning_ns = to_user_ns(ns);
542 break;
543 #endif
544 #ifdef CONFIG_UTS_NS
545 case CLONE_NEWUTS:
546 if (!current_in_namespace(to_uts_ns(ns)))
547 owning_ns = to_uts_ns(ns)->user_ns;
548 break;
549 #endif
550 default:
551 return ERR_PTR(-EOPNOTSUPP);
552 }
553
554 if (owning_ns && !ns_capable(owning_ns, CAP_SYS_ADMIN)) {
555 ns->ops->put(ns);
556 return ERR_PTR(-EPERM);
557 }
558
559 /* path_from_stashed() unconditionally consumes the reference. */
560 ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
561 if (ret)
562 return ERR_PTR(ret);
563
564 return no_free_ptr(path.dentry);
565 }
566
nsfs_export_permission(struct handle_to_path_ctx * ctx,unsigned int oflags)567 static int nsfs_export_permission(struct handle_to_path_ctx *ctx,
568 unsigned int oflags)
569 {
570 /* nsfs_fh_to_dentry() performs all permission checks. */
571 return 0;
572 }
573
nsfs_export_open(const struct path * path,unsigned int oflags)574 static struct file *nsfs_export_open(const struct path *path, unsigned int oflags)
575 {
576 return file_open_root(path, "", oflags, 0);
577 }
578
579 static const struct export_operations nsfs_export_operations = {
580 .encode_fh = nsfs_encode_fh,
581 .fh_to_dentry = nsfs_fh_to_dentry,
582 .open = nsfs_export_open,
583 .permission = nsfs_export_permission,
584 };
585
nsfs_init_fs_context(struct fs_context * fc)586 static int nsfs_init_fs_context(struct fs_context *fc)
587 {
588 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
589 if (!ctx)
590 return -ENOMEM;
591 ctx->ops = &nsfs_ops;
592 ctx->eops = &nsfs_export_operations;
593 ctx->dops = &ns_dentry_operations;
594 fc->s_fs_info = (void *)&nsfs_stashed_ops;
595 return 0;
596 }
597
598 static struct file_system_type nsfs = {
599 .name = "nsfs",
600 .init_fs_context = nsfs_init_fs_context,
601 .kill_sb = kill_anon_super,
602 };
603
nsfs_init(void)604 void __init nsfs_init(void)
605 {
606 nsfs_mnt = kern_mount(&nsfs);
607 if (IS_ERR(nsfs_mnt))
608 panic("can't set nsfs up\n");
609 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
610 nsfs_root_path.mnt = nsfs_mnt;
611 nsfs_root_path.dentry = nsfs_mnt->mnt_root;
612 }
613