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1/*
2 * Copyright 2008 Red Hat, Inc. All rights reserved.
3 * Copyright 2008 Ian Kent <raven@themaw.net>
4 *
5 * This file is part of the Linux kernel and is made available under
6 * the terms of the GNU General Public License, version 2, or at your
7 * option, any later version, incorporated herein by reference.
8 */
9
10#include <linux/module.h>
11#include <linux/vmalloc.h>
12#include <linux/miscdevice.h>
13#include <linux/init.h>
14#include <linux/wait.h>
15#include <linux/namei.h>
16#include <linux/fcntl.h>
17#include <linux/file.h>
18#include <linux/fdtable.h>
19#include <linux/sched.h>
20#include <linux/cred.h>
21#include <linux/compat.h>
22#include <linux/syscalls.h>
23#include <linux/magic.h>
24#include <linux/dcache.h>
25#include <linux/uaccess.h>
26#include <linux/slab.h>
27
28#include "autofs_i.h"
29
30/*
31 * This module implements an interface for routing autofs ioctl control
32 * commands via a miscellaneous device file.
33 *
34 * The alternate interface is needed because we need to be able open
35 * an ioctl file descriptor on an autofs mount that may be covered by
36 * another mount. This situation arises when starting automount(8)
37 * or other user space daemon which uses direct mounts or offset
38 * mounts (used for autofs lazy mount/umount of nested mount trees),
39 * which have been left busy at at service shutdown.
40 */
41
42typedef int (*ioctl_fn)(struct file *, struct autofs_sb_info *,
43 struct autofs_dev_ioctl *);
44
45static int check_name(const char *name)
46{
47 if (!strchr(name, '/'))
48 return -EINVAL;
49 return 0;
50}
51
52/*
53 * Check a string doesn't overrun the chunk of
54 * memory we copied from user land.
55 */
56static int invalid_str(char *str, size_t size)
57{
58 if (memchr(str, 0, size))
59 return 0;
60 return -EINVAL;
61}
62
63/*
64 * Check that the user compiled against correct version of autofs
65 * misc device code.
66 *
67 * As well as checking the version compatibility this always copies
68 * the kernel interface version out.
69 */
70static int check_dev_ioctl_version(int cmd, struct autofs_dev_ioctl *param)
71{
72 int err = 0;
73
74 if ((param->ver_major != AUTOFS_DEV_IOCTL_VERSION_MAJOR) ||
75 (param->ver_minor > AUTOFS_DEV_IOCTL_VERSION_MINOR)) {
76 pr_warn("ioctl control interface version mismatch: "
77 "kernel(%u.%u), user(%u.%u), cmd(0x%08x)\n",
78 AUTOFS_DEV_IOCTL_VERSION_MAJOR,
79 AUTOFS_DEV_IOCTL_VERSION_MINOR,
80 param->ver_major, param->ver_minor, cmd);
81 err = -EINVAL;
82 }
83
84 /* Fill in the kernel version. */
85 param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
86 param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;
87
88 return err;
89}
90
91/*
92 * Copy parameter control struct, including a possible path allocated
93 * at the end of the struct.
94 */
95static struct autofs_dev_ioctl *
96copy_dev_ioctl(struct autofs_dev_ioctl __user *in)
97{
98 struct autofs_dev_ioctl tmp, *res;
99
100 if (copy_from_user(&tmp, in, AUTOFS_DEV_IOCTL_SIZE))
101 return ERR_PTR(-EFAULT);
102
103 if (tmp.size < AUTOFS_DEV_IOCTL_SIZE)
104 return ERR_PTR(-EINVAL);
105
106 if (tmp.size > AUTOFS_DEV_IOCTL_SIZE + PATH_MAX)
107 return ERR_PTR(-ENAMETOOLONG);
108
109 res = memdup_user(in, tmp.size);
110 if (!IS_ERR(res))
111 res->size = tmp.size;
112
113 return res;
114}
115
116static inline void free_dev_ioctl(struct autofs_dev_ioctl *param)
117{
118 kfree(param);
119}
120
121/*
122 * Check sanity of parameter control fields and if a path is present
123 * check that it is terminated and contains at least one "/".
124 */
125static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param)
126{
127 int err;
128
129 err = check_dev_ioctl_version(cmd, param);
130 if (err) {
131 pr_warn("invalid device control module version "
132 "supplied for cmd(0x%08x)\n", cmd);
133 goto out;
134 }
135
136 if (param->size > AUTOFS_DEV_IOCTL_SIZE) {
137 err = invalid_str(param->path, param->size - AUTOFS_DEV_IOCTL_SIZE);
138 if (err) {
139 pr_warn(
140 "path string terminator missing for cmd(0x%08x)\n",
141 cmd);
142 goto out;
143 }
144
145 err = check_name(param->path);
146 if (err) {
147 pr_warn("invalid path supplied for cmd(0x%08x)\n",
148 cmd);
149 goto out;
150 }
151 }
152
153 err = 0;
154out:
155 return err;
156}
157
158/*
159 * Get the autofs super block info struct from the file opened on
160 * the autofs mount point.
161 */
162static struct autofs_sb_info *autofs_dev_ioctl_sbi(struct file *f)
163{
164 struct autofs_sb_info *sbi = NULL;
165 struct inode *inode;
166
167 if (f) {
168 inode = file_inode(f);
169 sbi = autofs4_sbi(inode->i_sb);
170 }
171 return sbi;
172}
173
174/* Return autofs dev ioctl version */
175static int autofs_dev_ioctl_version(struct file *fp,
176 struct autofs_sb_info *sbi,
177 struct autofs_dev_ioctl *param)
178{
179 /* This should have already been set. */
180 param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
181 param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;
182 return 0;
183}
184
185/* Return autofs module protocol version */
186static int autofs_dev_ioctl_protover(struct file *fp,
187 struct autofs_sb_info *sbi,
188 struct autofs_dev_ioctl *param)
189{
190 param->protover.version = sbi->version;
191 return 0;
192}
193
194/* Return autofs module protocol sub version */
195static int autofs_dev_ioctl_protosubver(struct file *fp,
196 struct autofs_sb_info *sbi,
197 struct autofs_dev_ioctl *param)
198{
199 param->protosubver.sub_version = sbi->sub_version;
200 return 0;
201}
202
203/* Find the topmost mount satisfying test() */
204static int find_autofs_mount(const char *pathname,
205 struct path *res,
206 int test(const struct path *path, void *data),
207 void *data)
208{
209 struct path path;
210 int err;
211
212 err = kern_path_mountpoint(AT_FDCWD, pathname, &path, 0);
213 if (err)
214 return err;
215 err = -ENOENT;
216 while (path.dentry == path.mnt->mnt_root) {
217 if (path.dentry->d_sb->s_magic == AUTOFS_SUPER_MAGIC) {
218 if (test(&path, data)) {
219 path_get(&path);
220 *res = path;
221 err = 0;
222 break;
223 }
224 }
225 if (!follow_up(&path))
226 break;
227 }
228 path_put(&path);
229 return err;
230}
231
232static int test_by_dev(const struct path *path, void *p)
233{
234 return path->dentry->d_sb->s_dev == *(dev_t *)p;
235}
236
237static int test_by_type(const struct path *path, void *p)
238{
239 struct autofs_info *ino = autofs4_dentry_ino(path->dentry);
240
241 return ino && ino->sbi->type & *(unsigned *)p;
242}
243
244/*
245 * Open a file descriptor on the autofs mount point corresponding
246 * to the given path and device number (aka. new_encode_dev(sb->s_dev)).
247 */
248static int autofs_dev_ioctl_open_mountpoint(const char *name, dev_t devid)
249{
250 int err, fd;
251
252 fd = get_unused_fd_flags(O_CLOEXEC);
253 if (likely(fd >= 0)) {
254 struct file *filp;
255 struct path path;
256
257 err = find_autofs_mount(name, &path, test_by_dev, &devid);
258 if (err)
259 goto out;
260
261 filp = dentry_open(&path, O_RDONLY, current_cred());
262 path_put(&path);
263 if (IS_ERR(filp)) {
264 err = PTR_ERR(filp);
265 goto out;
266 }
267
268 fd_install(fd, filp);
269 }
270
271 return fd;
272
273out:
274 put_unused_fd(fd);
275 return err;
276}
277
278/* Open a file descriptor on an autofs mount point */
279static int autofs_dev_ioctl_openmount(struct file *fp,
280 struct autofs_sb_info *sbi,
281 struct autofs_dev_ioctl *param)
282{
283 const char *path;
284 dev_t devid;
285 int err, fd;
286
287 /* param->path has already been checked */
288 if (!param->openmount.devid)
289 return -EINVAL;
290
291 param->ioctlfd = -1;
292
293 path = param->path;
294 devid = new_decode_dev(param->openmount.devid);
295
296 err = 0;
297 fd = autofs_dev_ioctl_open_mountpoint(path, devid);
298 if (unlikely(fd < 0)) {
299 err = fd;
300 goto out;
301 }
302
303 param->ioctlfd = fd;
304out:
305 return err;
306}
307
308/* Close file descriptor allocated above (user can also use close(2)). */
309static int autofs_dev_ioctl_closemount(struct file *fp,
310 struct autofs_sb_info *sbi,
311 struct autofs_dev_ioctl *param)
312{
313 return ksys_close(param->ioctlfd);
314}
315
316/*
317 * Send "ready" status for an existing wait (either a mount or an expire
318 * request).
319 */
320static int autofs_dev_ioctl_ready(struct file *fp,
321 struct autofs_sb_info *sbi,
322 struct autofs_dev_ioctl *param)
323{
324 autofs_wqt_t token;
325
326 token = (autofs_wqt_t) param->ready.token;
327 return autofs4_wait_release(sbi, token, 0);
328}
329
330/*
331 * Send "fail" status for an existing wait (either a mount or an expire
332 * request).
333 */
334static int autofs_dev_ioctl_fail(struct file *fp,
335 struct autofs_sb_info *sbi,
336 struct autofs_dev_ioctl *param)
337{
338 autofs_wqt_t token;
339 int status;
340
341 token = (autofs_wqt_t) param->fail.token;
342 status = param->fail.status < 0 ? param->fail.status : -ENOENT;
343 return autofs4_wait_release(sbi, token, status);
344}
345
346/*
347 * Set the pipe fd for kernel communication to the daemon.
348 *
349 * Normally this is set at mount using an option but if we
350 * are reconnecting to a busy mount then we need to use this
351 * to tell the autofs mount about the new kernel pipe fd. In
352 * order to protect mounts against incorrectly setting the
353 * pipefd we also require that the autofs mount be catatonic.
354 *
355 * This also sets the process group id used to identify the
356 * controlling process (eg. the owning automount(8) daemon).
357 */
358static int autofs_dev_ioctl_setpipefd(struct file *fp,
359 struct autofs_sb_info *sbi,
360 struct autofs_dev_ioctl *param)
361{
362 int pipefd;
363 int err = 0;
364 struct pid *new_pid = NULL;
365
366 if (param->setpipefd.pipefd == -1)
367 return -EINVAL;
368
369 pipefd = param->setpipefd.pipefd;
370
371 mutex_lock(&sbi->wq_mutex);
372 if (!sbi->catatonic) {
373 mutex_unlock(&sbi->wq_mutex);
374 return -EBUSY;
375 } else {
376 struct file *pipe;
377
378 new_pid = get_task_pid(current, PIDTYPE_PGID);
379
380 if (ns_of_pid(new_pid) != ns_of_pid(sbi->oz_pgrp)) {
381 pr_warn("not allowed to change PID namespace\n");
382 err = -EINVAL;
383 goto out;
384 }
385
386 pipe = fget(pipefd);
387 if (!pipe) {
388 err = -EBADF;
389 goto out;
390 }
391 if (autofs_prepare_pipe(pipe) < 0) {
392 err = -EPIPE;
393 fput(pipe);
394 goto out;
395 }
396 swap(sbi->oz_pgrp, new_pid);
397 sbi->pipefd = pipefd;
398 sbi->pipe = pipe;
399 sbi->catatonic = 0;
400 }
401out:
402 put_pid(new_pid);
403 mutex_unlock(&sbi->wq_mutex);
404 return err;
405}
406
407/*
408 * Make the autofs mount point catatonic, no longer responsive to
409 * mount requests. Also closes the kernel pipe file descriptor.
410 */
411static int autofs_dev_ioctl_catatonic(struct file *fp,
412 struct autofs_sb_info *sbi,
413 struct autofs_dev_ioctl *param)
414{
415 autofs4_catatonic_mode(sbi);
416 return 0;
417}
418
419/* Set the autofs mount timeout */
420static int autofs_dev_ioctl_timeout(struct file *fp,
421 struct autofs_sb_info *sbi,
422 struct autofs_dev_ioctl *param)
423{
424 unsigned long timeout;
425
426 timeout = param->timeout.timeout;
427 param->timeout.timeout = sbi->exp_timeout / HZ;
428 sbi->exp_timeout = timeout * HZ;
429 return 0;
430}
431
432/*
433 * Return the uid and gid of the last request for the mount
434 *
435 * When reconstructing an autofs mount tree with active mounts
436 * we need to re-connect to mounts that may have used the original
437 * process uid and gid (or string variations of them) for mount
438 * lookups within the map entry.
439 */
440static int autofs_dev_ioctl_requester(struct file *fp,
441 struct autofs_sb_info *sbi,
442 struct autofs_dev_ioctl *param)
443{
444 struct autofs_info *ino;
445 struct path path;
446 dev_t devid;
447 int err = -ENOENT;
448
449 if (param->size <= AUTOFS_DEV_IOCTL_SIZE) {
450 err = -EINVAL;
451 goto out;
452 }
453
454 devid = sbi->sb->s_dev;
455
456 param->requester.uid = param->requester.gid = -1;
457
458 err = find_autofs_mount(param->path, &path, test_by_dev, &devid);
459 if (err)
460 goto out;
461
462 ino = autofs4_dentry_ino(path.dentry);
463 if (ino) {
464 err = 0;
465 autofs4_expire_wait(&path, 0);
466 spin_lock(&sbi->fs_lock);
467 param->requester.uid =
468 from_kuid_munged(current_user_ns(), ino->uid);
469 param->requester.gid =
470 from_kgid_munged(current_user_ns(), ino->gid);
471 spin_unlock(&sbi->fs_lock);
472 }
473 path_put(&path);
474out:
475 return err;
476}
477
478/*
479 * Call repeatedly until it returns -EAGAIN, meaning there's nothing
480 * more that can be done.
481 */
482static int autofs_dev_ioctl_expire(struct file *fp,
483 struct autofs_sb_info *sbi,
484 struct autofs_dev_ioctl *param)
485{
486 struct vfsmount *mnt;
487 int how;
488
489 how = param->expire.how;
490 mnt = fp->f_path.mnt;
491
492 return autofs4_do_expire_multi(sbi->sb, mnt, sbi, how);
493}
494
495/* Check if autofs mount point is in use */
496static int autofs_dev_ioctl_askumount(struct file *fp,
497 struct autofs_sb_info *sbi,
498 struct autofs_dev_ioctl *param)
499{
500 param->askumount.may_umount = 0;
501 if (may_umount(fp->f_path.mnt))
502 param->askumount.may_umount = 1;
503 return 0;
504}
505
506/*
507 * Check if the given path is a mountpoint.
508 *
509 * If we are supplied with the file descriptor of an autofs
510 * mount we're looking for a specific mount. In this case
511 * the path is considered a mountpoint if it is itself a
512 * mountpoint or contains a mount, such as a multi-mount
513 * without a root mount. In this case we return 1 if the
514 * path is a mount point and the super magic of the covering
515 * mount if there is one or 0 if it isn't a mountpoint.
516 *
517 * If we aren't supplied with a file descriptor then we
518 * lookup the path and check if it is the root of a mount.
519 * If a type is given we are looking for a particular autofs
520 * mount and if we don't find a match we return fail. If the
521 * located path is the root of a mount we return 1 along with
522 * the super magic of the mount or 0 otherwise.
523 *
524 * In both cases the the device number (as returned by
525 * new_encode_dev()) is also returned.
526 */
527static int autofs_dev_ioctl_ismountpoint(struct file *fp,
528 struct autofs_sb_info *sbi,
529 struct autofs_dev_ioctl *param)
530{
531 struct path path;
532 const char *name;
533 unsigned int type;
534 unsigned int devid, magic;
535 int err = -ENOENT;
536
537 if (param->size <= AUTOFS_DEV_IOCTL_SIZE) {
538 err = -EINVAL;
539 goto out;
540 }
541
542 name = param->path;
543 type = param->ismountpoint.in.type;
544
545 param->ismountpoint.out.devid = devid = 0;
546 param->ismountpoint.out.magic = magic = 0;
547
548 if (!fp || param->ioctlfd == -1) {
549 if (autofs_type_any(type))
550 err = kern_path_mountpoint(AT_FDCWD,
551 name, &path, LOOKUP_FOLLOW);
552 else
553 err = find_autofs_mount(name, &path,
554 test_by_type, &type);
555 if (err)
556 goto out;
557 devid = new_encode_dev(path.dentry->d_sb->s_dev);
558 err = 0;
559 if (path.mnt->mnt_root == path.dentry) {
560 err = 1;
561 magic = path.dentry->d_sb->s_magic;
562 }
563 } else {
564 dev_t dev = sbi->sb->s_dev;
565
566 err = find_autofs_mount(name, &path, test_by_dev, &dev);
567 if (err)
568 goto out;
569
570 devid = new_encode_dev(dev);
571
572 err = path_has_submounts(&path);
573
574 if (follow_down_one(&path))
575 magic = path.dentry->d_sb->s_magic;
576 }
577
578 param->ismountpoint.out.devid = devid;
579 param->ismountpoint.out.magic = magic;
580 path_put(&path);
581out:
582 return err;
583}
584
585/*
586 * Our range of ioctl numbers isn't 0 based so we need to shift
587 * the array index by _IOC_NR(AUTOFS_CTL_IOC_FIRST) for the table
588 * lookup.
589 */
590#define cmd_idx(cmd) (cmd - _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST))
591
592static ioctl_fn lookup_dev_ioctl(unsigned int cmd)
593{
594 static ioctl_fn _ioctls[] = {
595 autofs_dev_ioctl_version,
596 autofs_dev_ioctl_protover,
597 autofs_dev_ioctl_protosubver,
598 autofs_dev_ioctl_openmount,
599 autofs_dev_ioctl_closemount,
600 autofs_dev_ioctl_ready,
601 autofs_dev_ioctl_fail,
602 autofs_dev_ioctl_setpipefd,
603 autofs_dev_ioctl_catatonic,
604 autofs_dev_ioctl_timeout,
605 autofs_dev_ioctl_requester,
606 autofs_dev_ioctl_expire,
607 autofs_dev_ioctl_askumount,
608 autofs_dev_ioctl_ismountpoint,
609 };
610 unsigned int idx = cmd_idx(cmd);
611
612 return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx];
613}
614
615/* ioctl dispatcher */
616static int _autofs_dev_ioctl(unsigned int command,
617 struct autofs_dev_ioctl __user *user)
618{
619 struct autofs_dev_ioctl *param;
620 struct file *fp;
621 struct autofs_sb_info *sbi;
622 unsigned int cmd_first, cmd;
623 ioctl_fn fn = NULL;
624 int err = 0;
625
626 cmd_first = _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST);
627 cmd = _IOC_NR(command);
628
629 if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) ||
630 cmd - cmd_first > AUTOFS_DEV_IOCTL_IOC_COUNT) {
631 return -ENOTTY;
632 }
633
634 /* Only root can use ioctls other than AUTOFS_DEV_IOCTL_VERSION_CMD
635 * and AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD
636 */
637 if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD &&
638 cmd != AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD &&
639 !capable(CAP_SYS_ADMIN))
640 return -EPERM;
641
642 /* Copy the parameters into kernel space. */
643 param = copy_dev_ioctl(user);
644 if (IS_ERR(param))
645 return PTR_ERR(param);
646
647 err = validate_dev_ioctl(command, param);
648 if (err)
649 goto out;
650
651 fn = lookup_dev_ioctl(cmd);
652 if (!fn) {
653 pr_warn("unknown command 0x%08x\n", command);
654 err = -ENOTTY;
655 goto out;
656 }
657
658 fp = NULL;
659 sbi = NULL;
660
661 /*
662 * For obvious reasons the openmount can't have a file
663 * descriptor yet. We don't take a reference to the
664 * file during close to allow for immediate release,
665 * and the same for retrieving ioctl version.
666 */
667 if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD &&
668 cmd != AUTOFS_DEV_IOCTL_OPENMOUNT_CMD &&
669 cmd != AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD) {
670 fp = fget(param->ioctlfd);
671 if (!fp) {
672 if (cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD)
673 goto cont;
674 err = -EBADF;
675 goto out;
676 }
677
678 sbi = autofs_dev_ioctl_sbi(fp);
679 if (!sbi || sbi->magic != AUTOFS_SBI_MAGIC) {
680 err = -EINVAL;
681 fput(fp);
682 goto out;
683 }
684
685 /*
686 * Admin needs to be able to set the mount catatonic in
687 * order to be able to perform the re-open.
688 */
689 if (!autofs4_oz_mode(sbi) &&
690 cmd != AUTOFS_DEV_IOCTL_CATATONIC_CMD) {
691 err = -EACCES;
692 fput(fp);
693 goto out;
694 }
695 }
696cont:
697 err = fn(fp, sbi, param);
698
699 if (fp)
700 fput(fp);
701 if (err >= 0 && copy_to_user(user, param, AUTOFS_DEV_IOCTL_SIZE))
702 err = -EFAULT;
703out:
704 free_dev_ioctl(param);
705 return err;
706}
707
708static long autofs_dev_ioctl(struct file *file, unsigned int command,
709 unsigned long u)
710{
711 int err;
712
713 err = _autofs_dev_ioctl(command, (struct autofs_dev_ioctl __user *) u);
714 return (long) err;
715}
716
717#ifdef CONFIG_COMPAT
718static long autofs_dev_ioctl_compat(struct file *file, unsigned int command,
719 unsigned long u)
720{
721 return autofs_dev_ioctl(file, command, (unsigned long) compat_ptr(u));
722}
723#else
724#define autofs_dev_ioctl_compat NULL
725#endif
726
727static const struct file_operations _dev_ioctl_fops = {
728 .unlocked_ioctl = autofs_dev_ioctl,
729 .compat_ioctl = autofs_dev_ioctl_compat,
730 .owner = THIS_MODULE,
731 .llseek = noop_llseek,
732};
733
734static struct miscdevice _autofs_dev_ioctl_misc = {
735 .minor = AUTOFS_MINOR,
736 .name = AUTOFS_DEVICE_NAME,
737 .fops = &_dev_ioctl_fops,
738 .mode = 0644,
739};
740
741MODULE_ALIAS_MISCDEV(AUTOFS_MINOR);
742MODULE_ALIAS("devname:autofs");
743
744/* Register/deregister misc character device */
745int __init autofs_dev_ioctl_init(void)
746{
747 int r;
748
749 r = misc_register(&_autofs_dev_ioctl_misc);
750 if (r) {
751 pr_err("misc_register failed for control device\n");
752 return r;
753 }
754
755 return 0;
756}
757
758void autofs_dev_ioctl_exit(void)
759{
760 misc_deregister(&_autofs_dev_ioctl_misc);
761}