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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/compat.h>
21#include <linux/syscalls.h>
22#include <linux/magic.h>
23#include <linux/dcache.h>
24#include <linux/uaccess.h>
25#include <linux/slab.h>
26
27#include "autofs_i.h"
28
29/*
30 * This module implements an interface for routing autofs ioctl control
31 * commands via a miscellaneous device file.
32 *
33 * The alternate interface is needed because we need to be able open
34 * an ioctl file descriptor on an autofs mount that may be covered by
35 * another mount. This situation arises when starting automount(8)
36 * or other user space daemon which uses direct mounts or offset
37 * mounts (used for autofs lazy mount/umount of nested mount trees),
38 * which have been left busy at at service shutdown.
39 */
40
41#define AUTOFS_DEV_IOCTL_SIZE sizeof(struct autofs_dev_ioctl)
42
43typedef int (*ioctl_fn)(struct file *, struct autofs_sb_info *,
44 struct autofs_dev_ioctl *);
45
46static int check_name(const char *name)
47{
48 if (!strchr(name, '/'))
49 return -EINVAL;
50 return 0;
51}
52
53/*
54 * Check a string doesn't overrun the chunk of
55 * memory we copied from user land.
56 */
57static int invalid_str(char *str, size_t size)
58{
59 if (memchr(str, 0, size))
60 return 0;
61 return -EINVAL;
62}
63
64/*
65 * Check that the user compiled against correct version of autofs
66 * misc device code.
67 *
68 * As well as checking the version compatibility this always copies
69 * the kernel interface version out.
70 */
71static int check_dev_ioctl_version(int cmd, struct autofs_dev_ioctl *param)
72{
73 int err = 0;
74
75 if ((param->ver_major != AUTOFS_DEV_IOCTL_VERSION_MAJOR) ||
76 (param->ver_minor > AUTOFS_DEV_IOCTL_VERSION_MINOR)) {
77 pr_warn("ioctl control interface version mismatch: "
78 "kernel(%u.%u), user(%u.%u), cmd(%d)\n",
79 AUTOFS_DEV_IOCTL_VERSION_MAJOR,
80 AUTOFS_DEV_IOCTL_VERSION_MINOR,
81 param->ver_major, param->ver_minor, cmd);
82 err = -EINVAL;
83 }
84
85 /* Fill in the kernel version. */
86 param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
87 param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;
88
89 return err;
90}
91
92/*
93 * Copy parameter control struct, including a possible path allocated
94 * at the end of the struct.
95 */
96static struct autofs_dev_ioctl *
97 copy_dev_ioctl(struct autofs_dev_ioctl __user *in)
98{
99 struct autofs_dev_ioctl tmp, *res;
100
101 if (copy_from_user(&tmp, in, sizeof(tmp)))
102 return ERR_PTR(-EFAULT);
103
104 if (tmp.size < sizeof(tmp))
105 return ERR_PTR(-EINVAL);
106
107 if (tmp.size > (PATH_MAX + sizeof(tmp)))
108 return ERR_PTR(-ENAMETOOLONG);
109
110 res = memdup_user(in, tmp.size);
111 if (!IS_ERR(res))
112 res->size = tmp.size;
113
114 return res;
115}
116
117static inline void free_dev_ioctl(struct autofs_dev_ioctl *param)
118{
119 kfree(param);
120}
121
122/*
123 * Check sanity of parameter control fields and if a path is present
124 * check that it is terminated and contains at least one "/".
125 */
126static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param)
127{
128 int err;
129
130 err = check_dev_ioctl_version(cmd, param);
131 if (err) {
132 pr_warn("invalid device control module version "
133 "supplied for cmd(0x%08x)\n", cmd);
134 goto out;
135 }
136
137 if (param->size > sizeof(*param)) {
138 err = invalid_str(param->path, param->size - sizeof(*param));
139 if (err) {
140 pr_warn(
141 "path string terminator missing for cmd(0x%08x)\n",
142 cmd);
143 goto out;
144 }
145
146 err = check_name(param->path);
147 if (err) {
148 pr_warn("invalid path supplied for cmd(0x%08x)\n",
149 cmd);
150 goto out;
151 }
152 }
153
154 err = 0;
155out:
156 return err;
157}
158
159/*
160 * Get the autofs super block info struct from the file opened on
161 * the autofs mount point.
162 */
163static struct autofs_sb_info *autofs_dev_ioctl_sbi(struct file *f)
164{
165 struct autofs_sb_info *sbi = NULL;
166 struct inode *inode;
167
168 if (f) {
169 inode = file_inode(f);
170 sbi = autofs4_sbi(inode->i_sb);
171 }
172 return sbi;
173}
174
175/* Return autofs module protocol version */
176static int autofs_dev_ioctl_protover(struct file *fp,
177 struct autofs_sb_info *sbi,
178 struct autofs_dev_ioctl *param)
179{
180 param->protover.version = sbi->version;
181 return 0;
182}
183
184/* Return autofs module protocol sub version */
185static int autofs_dev_ioctl_protosubver(struct file *fp,
186 struct autofs_sb_info *sbi,
187 struct autofs_dev_ioctl *param)
188{
189 param->protosubver.sub_version = sbi->sub_version;
190 return 0;
191}
192
193/* Find the topmost mount satisfying test() */
194static int find_autofs_mount(const char *pathname,
195 struct path *res,
196 int test(struct path *path, void *data),
197 void *data)
198{
199 struct path path;
200 int err;
201
202 err = kern_path_mountpoint(AT_FDCWD, pathname, &path, 0);
203 if (err)
204 return err;
205 err = -ENOENT;
206 while (path.dentry == path.mnt->mnt_root) {
207 if (path.dentry->d_sb->s_magic == AUTOFS_SUPER_MAGIC) {
208 if (test(&path, data)) {
209 path_get(&path);
210 *res = path;
211 err = 0;
212 break;
213 }
214 }
215 if (!follow_up(&path))
216 break;
217 }
218 path_put(&path);
219 return err;
220}
221
222static int test_by_dev(struct path *path, void *p)
223{
224 return path->dentry->d_sb->s_dev == *(dev_t *)p;
225}
226
227static int test_by_type(struct path *path, void *p)
228{
229 struct autofs_info *ino = autofs4_dentry_ino(path->dentry);
230
231 return ino && ino->sbi->type & *(unsigned *)p;
232}
233
234/*
235 * Open a file descriptor on the autofs mount point corresponding
236 * to the given path and device number (aka. new_encode_dev(sb->s_dev)).
237 */
238static int autofs_dev_ioctl_open_mountpoint(const char *name, dev_t devid)
239{
240 int err, fd;
241
242 fd = get_unused_fd_flags(O_CLOEXEC);
243 if (likely(fd >= 0)) {
244 struct file *filp;
245 struct path path;
246
247 err = find_autofs_mount(name, &path, test_by_dev, &devid);
248 if (err)
249 goto out;
250
251 /*
252 * Find autofs super block that has the device number
253 * corresponding to the autofs fs we want to open.
254 */
255
256 filp = dentry_open(&path, O_RDONLY, current_cred());
257 path_put(&path);
258 if (IS_ERR(filp)) {
259 err = PTR_ERR(filp);
260 goto out;
261 }
262
263 fd_install(fd, filp);
264 }
265
266 return fd;
267
268out:
269 put_unused_fd(fd);
270 return err;
271}
272
273/* Open a file descriptor on an autofs mount point */
274static int autofs_dev_ioctl_openmount(struct file *fp,
275 struct autofs_sb_info *sbi,
276 struct autofs_dev_ioctl *param)
277{
278 const char *path;
279 dev_t devid;
280 int err, fd;
281
282 /* param->path has already been checked */
283 if (!param->openmount.devid)
284 return -EINVAL;
285
286 param->ioctlfd = -1;
287
288 path = param->path;
289 devid = new_decode_dev(param->openmount.devid);
290
291 err = 0;
292 fd = autofs_dev_ioctl_open_mountpoint(path, devid);
293 if (unlikely(fd < 0)) {
294 err = fd;
295 goto out;
296 }
297
298 param->ioctlfd = fd;
299out:
300 return err;
301}
302
303/* Close file descriptor allocated above (user can also use close(2)). */
304static int autofs_dev_ioctl_closemount(struct file *fp,
305 struct autofs_sb_info *sbi,
306 struct autofs_dev_ioctl *param)
307{
308 return sys_close(param->ioctlfd);
309}
310
311/*
312 * Send "ready" status for an existing wait (either a mount or an expire
313 * request).
314 */
315static int autofs_dev_ioctl_ready(struct file *fp,
316 struct autofs_sb_info *sbi,
317 struct autofs_dev_ioctl *param)
318{
319 autofs_wqt_t token;
320
321 token = (autofs_wqt_t) param->ready.token;
322 return autofs4_wait_release(sbi, token, 0);
323}
324
325/*
326 * Send "fail" status for an existing wait (either a mount or an expire
327 * request).
328 */
329static int autofs_dev_ioctl_fail(struct file *fp,
330 struct autofs_sb_info *sbi,
331 struct autofs_dev_ioctl *param)
332{
333 autofs_wqt_t token;
334 int status;
335
336 token = (autofs_wqt_t) param->fail.token;
337 status = param->fail.status ? param->fail.status : -ENOENT;
338 return autofs4_wait_release(sbi, token, status);
339}
340
341/*
342 * Set the pipe fd for kernel communication to the daemon.
343 *
344 * Normally this is set at mount using an option but if we
345 * are reconnecting to a busy mount then we need to use this
346 * to tell the autofs mount about the new kernel pipe fd. In
347 * order to protect mounts against incorrectly setting the
348 * pipefd we also require that the autofs mount be catatonic.
349 *
350 * This also sets the process group id used to identify the
351 * controlling process (eg. the owning automount(8) daemon).
352 */
353static int autofs_dev_ioctl_setpipefd(struct file *fp,
354 struct autofs_sb_info *sbi,
355 struct autofs_dev_ioctl *param)
356{
357 int pipefd;
358 int err = 0;
359 struct pid *new_pid = NULL;
360
361 if (param->setpipefd.pipefd == -1)
362 return -EINVAL;
363
364 pipefd = param->setpipefd.pipefd;
365
366 mutex_lock(&sbi->wq_mutex);
367 if (!sbi->catatonic) {
368 mutex_unlock(&sbi->wq_mutex);
369 return -EBUSY;
370 } else {
371 struct file *pipe;
372
373 new_pid = get_task_pid(current, PIDTYPE_PGID);
374
375 if (ns_of_pid(new_pid) != ns_of_pid(sbi->oz_pgrp)) {
376 pr_warn("not allowed to change PID namespace\n");
377 err = -EINVAL;
378 goto out;
379 }
380
381 pipe = fget(pipefd);
382 if (!pipe) {
383 err = -EBADF;
384 goto out;
385 }
386 if (autofs_prepare_pipe(pipe) < 0) {
387 err = -EPIPE;
388 fput(pipe);
389 goto out;
390 }
391 swap(sbi->oz_pgrp, new_pid);
392 sbi->pipefd = pipefd;
393 sbi->pipe = pipe;
394 sbi->catatonic = 0;
395 }
396out:
397 put_pid(new_pid);
398 mutex_unlock(&sbi->wq_mutex);
399 return err;
400}
401
402/*
403 * Make the autofs mount point catatonic, no longer responsive to
404 * mount requests. Also closes the kernel pipe file descriptor.
405 */
406static int autofs_dev_ioctl_catatonic(struct file *fp,
407 struct autofs_sb_info *sbi,
408 struct autofs_dev_ioctl *param)
409{
410 autofs4_catatonic_mode(sbi);
411 return 0;
412}
413
414/* Set the autofs mount timeout */
415static int autofs_dev_ioctl_timeout(struct file *fp,
416 struct autofs_sb_info *sbi,
417 struct autofs_dev_ioctl *param)
418{
419 unsigned long timeout;
420
421 timeout = param->timeout.timeout;
422 param->timeout.timeout = sbi->exp_timeout / HZ;
423 sbi->exp_timeout = timeout * HZ;
424 return 0;
425}
426
427/*
428 * Return the uid and gid of the last request for the mount
429 *
430 * When reconstructing an autofs mount tree with active mounts
431 * we need to re-connect to mounts that may have used the original
432 * process uid and gid (or string variations of them) for mount
433 * lookups within the map entry.
434 */
435static int autofs_dev_ioctl_requester(struct file *fp,
436 struct autofs_sb_info *sbi,
437 struct autofs_dev_ioctl *param)
438{
439 struct autofs_info *ino;
440 struct path path;
441 dev_t devid;
442 int err = -ENOENT;
443
444 if (param->size <= sizeof(*param)) {
445 err = -EINVAL;
446 goto out;
447 }
448
449 devid = sbi->sb->s_dev;
450
451 param->requester.uid = param->requester.gid = -1;
452
453 err = find_autofs_mount(param->path, &path, test_by_dev, &devid);
454 if (err)
455 goto out;
456
457 ino = autofs4_dentry_ino(path.dentry);
458 if (ino) {
459 err = 0;
460 autofs4_expire_wait(path.dentry, 0);
461 spin_lock(&sbi->fs_lock);
462 param->requester.uid =
463 from_kuid_munged(current_user_ns(), ino->uid);
464 param->requester.gid =
465 from_kgid_munged(current_user_ns(), ino->gid);
466 spin_unlock(&sbi->fs_lock);
467 }
468 path_put(&path);
469out:
470 return err;
471}
472
473/*
474 * Call repeatedly until it returns -EAGAIN, meaning there's nothing
475 * more that can be done.
476 */
477static int autofs_dev_ioctl_expire(struct file *fp,
478 struct autofs_sb_info *sbi,
479 struct autofs_dev_ioctl *param)
480{
481 struct vfsmount *mnt;
482 int how;
483
484 how = param->expire.how;
485 mnt = fp->f_path.mnt;
486
487 return autofs4_do_expire_multi(sbi->sb, mnt, sbi, how);
488}
489
490/* Check if autofs mount point is in use */
491static int autofs_dev_ioctl_askumount(struct file *fp,
492 struct autofs_sb_info *sbi,
493 struct autofs_dev_ioctl *param)
494{
495 param->askumount.may_umount = 0;
496 if (may_umount(fp->f_path.mnt))
497 param->askumount.may_umount = 1;
498 return 0;
499}
500
501/*
502 * Check if the given path is a mountpoint.
503 *
504 * If we are supplied with the file descriptor of an autofs
505 * mount we're looking for a specific mount. In this case
506 * the path is considered a mountpoint if it is itself a
507 * mountpoint or contains a mount, such as a multi-mount
508 * without a root mount. In this case we return 1 if the
509 * path is a mount point and the super magic of the covering
510 * mount if there is one or 0 if it isn't a mountpoint.
511 *
512 * If we aren't supplied with a file descriptor then we
513 * lookup the path and check if it is the root of a mount.
514 * If a type is given we are looking for a particular autofs
515 * mount and if we don't find a match we return fail. If the
516 * located path is the root of a mount we return 1 along with
517 * the super magic of the mount or 0 otherwise.
518 *
519 * In both cases the the device number (as returned by
520 * new_encode_dev()) is also returned.
521 */
522static int autofs_dev_ioctl_ismountpoint(struct file *fp,
523 struct autofs_sb_info *sbi,
524 struct autofs_dev_ioctl *param)
525{
526 struct path path;
527 const char *name;
528 unsigned int type;
529 unsigned int devid, magic;
530 int err = -ENOENT;
531
532 if (param->size <= sizeof(*param)) {
533 err = -EINVAL;
534 goto out;
535 }
536
537 name = param->path;
538 type = param->ismountpoint.in.type;
539
540 param->ismountpoint.out.devid = devid = 0;
541 param->ismountpoint.out.magic = magic = 0;
542
543 if (!fp || param->ioctlfd == -1) {
544 if (autofs_type_any(type))
545 err = kern_path_mountpoint(AT_FDCWD,
546 name, &path, LOOKUP_FOLLOW);
547 else
548 err = find_autofs_mount(name, &path,
549 test_by_type, &type);
550 if (err)
551 goto out;
552 devid = new_encode_dev(path.dentry->d_sb->s_dev);
553 err = 0;
554 if (path.mnt->mnt_root == path.dentry) {
555 err = 1;
556 magic = path.dentry->d_sb->s_magic;
557 }
558 } else {
559 dev_t dev = sbi->sb->s_dev;
560
561 err = find_autofs_mount(name, &path, test_by_dev, &dev);
562 if (err)
563 goto out;
564
565 devid = new_encode_dev(dev);
566
567 err = have_submounts(path.dentry);
568
569 if (follow_down_one(&path))
570 magic = path.dentry->d_sb->s_magic;
571 }
572
573 param->ismountpoint.out.devid = devid;
574 param->ismountpoint.out.magic = magic;
575 path_put(&path);
576out:
577 return err;
578}
579
580/*
581 * Our range of ioctl numbers isn't 0 based so we need to shift
582 * the array index by _IOC_NR(AUTOFS_CTL_IOC_FIRST) for the table
583 * lookup.
584 */
585#define cmd_idx(cmd) (cmd - _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST))
586
587static ioctl_fn lookup_dev_ioctl(unsigned int cmd)
588{
589 static struct {
590 int cmd;
591 ioctl_fn fn;
592 } _ioctls[] = {
593 {cmd_idx(AUTOFS_DEV_IOCTL_VERSION_CMD), NULL},
594 {cmd_idx(AUTOFS_DEV_IOCTL_PROTOVER_CMD),
595 autofs_dev_ioctl_protover},
596 {cmd_idx(AUTOFS_DEV_IOCTL_PROTOSUBVER_CMD),
597 autofs_dev_ioctl_protosubver},
598 {cmd_idx(AUTOFS_DEV_IOCTL_OPENMOUNT_CMD),
599 autofs_dev_ioctl_openmount},
600 {cmd_idx(AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD),
601 autofs_dev_ioctl_closemount},
602 {cmd_idx(AUTOFS_DEV_IOCTL_READY_CMD),
603 autofs_dev_ioctl_ready},
604 {cmd_idx(AUTOFS_DEV_IOCTL_FAIL_CMD),
605 autofs_dev_ioctl_fail},
606 {cmd_idx(AUTOFS_DEV_IOCTL_SETPIPEFD_CMD),
607 autofs_dev_ioctl_setpipefd},
608 {cmd_idx(AUTOFS_DEV_IOCTL_CATATONIC_CMD),
609 autofs_dev_ioctl_catatonic},
610 {cmd_idx(AUTOFS_DEV_IOCTL_TIMEOUT_CMD),
611 autofs_dev_ioctl_timeout},
612 {cmd_idx(AUTOFS_DEV_IOCTL_REQUESTER_CMD),
613 autofs_dev_ioctl_requester},
614 {cmd_idx(AUTOFS_DEV_IOCTL_EXPIRE_CMD),
615 autofs_dev_ioctl_expire},
616 {cmd_idx(AUTOFS_DEV_IOCTL_ASKUMOUNT_CMD),
617 autofs_dev_ioctl_askumount},
618 {cmd_idx(AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD),
619 autofs_dev_ioctl_ismountpoint}
620 };
621 unsigned int idx = cmd_idx(cmd);
622
623 return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx].fn;
624}
625
626/* ioctl dispatcher */
627static int _autofs_dev_ioctl(unsigned int command,
628 struct autofs_dev_ioctl __user *user)
629{
630 struct autofs_dev_ioctl *param;
631 struct file *fp;
632 struct autofs_sb_info *sbi;
633 unsigned int cmd_first, cmd;
634 ioctl_fn fn = NULL;
635 int err = 0;
636
637 /* only root can play with this */
638 if (!capable(CAP_SYS_ADMIN))
639 return -EPERM;
640
641 cmd_first = _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST);
642 cmd = _IOC_NR(command);
643
644 if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) ||
645 cmd - cmd_first >= AUTOFS_DEV_IOCTL_IOC_COUNT) {
646 return -ENOTTY;
647 }
648
649 /* Copy the parameters into kernel space. */
650 param = copy_dev_ioctl(user);
651 if (IS_ERR(param))
652 return PTR_ERR(param);
653
654 err = validate_dev_ioctl(command, param);
655 if (err)
656 goto out;
657
658 /* The validate routine above always sets the version */
659 if (cmd == AUTOFS_DEV_IOCTL_VERSION_CMD)
660 goto done;
661
662 fn = lookup_dev_ioctl(cmd);
663 if (!fn) {
664 pr_warn("unknown command 0x%08x\n", command);
665 return -ENOTTY;
666 }
667
668 fp = NULL;
669 sbi = NULL;
670
671 /*
672 * For obvious reasons the openmount can't have a file
673 * descriptor yet. We don't take a reference to the
674 * file during close to allow for immediate release.
675 */
676 if (cmd != AUTOFS_DEV_IOCTL_OPENMOUNT_CMD &&
677 cmd != AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD) {
678 fp = fget(param->ioctlfd);
679 if (!fp) {
680 if (cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD)
681 goto cont;
682 err = -EBADF;
683 goto out;
684 }
685
686 sbi = autofs_dev_ioctl_sbi(fp);
687 if (!sbi || sbi->magic != AUTOFS_SBI_MAGIC) {
688 err = -EINVAL;
689 fput(fp);
690 goto out;
691 }
692
693 /*
694 * Admin needs to be able to set the mount catatonic in
695 * order to be able to perform the re-open.
696 */
697 if (!autofs4_oz_mode(sbi) &&
698 cmd != AUTOFS_DEV_IOCTL_CATATONIC_CMD) {
699 err = -EACCES;
700 fput(fp);
701 goto out;
702 }
703 }
704cont:
705 err = fn(fp, sbi, param);
706
707 if (fp)
708 fput(fp);
709done:
710 if (err >= 0 && copy_to_user(user, param, AUTOFS_DEV_IOCTL_SIZE))
711 err = -EFAULT;
712out:
713 free_dev_ioctl(param);
714 return err;
715}
716
717static long autofs_dev_ioctl(struct file *file, uint command, ulong u)
718{
719 int err;
720
721 err = _autofs_dev_ioctl(command, (struct autofs_dev_ioctl __user *) u);
722 return (long) err;
723}
724
725#ifdef CONFIG_COMPAT
726static long autofs_dev_ioctl_compat(struct file *file, uint command, ulong u)
727{
728 return (long) autofs_dev_ioctl(file, command, (ulong) compat_ptr(u));
729}
730#else
731#define autofs_dev_ioctl_compat NULL
732#endif
733
734static const struct file_operations _dev_ioctl_fops = {
735 .unlocked_ioctl = autofs_dev_ioctl,
736 .compat_ioctl = autofs_dev_ioctl_compat,
737 .owner = THIS_MODULE,
738 .llseek = noop_llseek,
739};
740
741static struct miscdevice _autofs_dev_ioctl_misc = {
742 .minor = AUTOFS_MINOR,
743 .name = AUTOFS_DEVICE_NAME,
744 .fops = &_dev_ioctl_fops
745};
746
747MODULE_ALIAS_MISCDEV(AUTOFS_MINOR);
748MODULE_ALIAS("devname:autofs");
749
750/* Register/deregister misc character device */
751int __init autofs_dev_ioctl_init(void)
752{
753 int r;
754
755 r = misc_register(&_autofs_dev_ioctl_misc);
756 if (r) {
757 pr_err("misc_register failed for control device\n");
758 return r;
759 }
760
761 return 0;
762}
763
764void autofs_dev_ioctl_exit(void)
765{
766 misc_deregister(&_autofs_dev_ioctl_misc);
767}