fs/autofs4/dev-ioctl.c

   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
  43 typedef int (*ioctl_fn)(struct file *, struct autofs_sb_info *,
  44                         struct autofs_dev_ioctl *);
  45
  46 static 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  */
  57 static 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  */
  71 static 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(0x%08x)\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  */
  96 static 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
 117 static 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  */
 126 static 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;
 155 out:
 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  */
 163 static 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 dev ioctl version */
 176 static int autofs_dev_ioctl_version(struct file *fp,
 177                                     struct autofs_sb_info *sbi,
 178                                     struct autofs_dev_ioctl *param)
 179 {
 180         /* This should have already been set. */
 181         param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
 182         param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;
 183         return 0;
 184 }
 185
 186 /* Return autofs module protocol version */
 187 static int autofs_dev_ioctl_protover(struct file *fp,
 188                                      struct autofs_sb_info *sbi,
 189                                      struct autofs_dev_ioctl *param)
 190 {
 191         param->protover.version = sbi->version;
 192         return 0;
 193 }
 194
 195 /* Return autofs module protocol sub version */
 196 static int autofs_dev_ioctl_protosubver(struct file *fp,
 197                                         struct autofs_sb_info *sbi,
 198                                         struct autofs_dev_ioctl *param)
 199 {
 200         param->protosubver.sub_version = sbi->sub_version;
 201         return 0;
 202 }
 203
 204 /* Find the topmost mount satisfying test() */
 205 static int find_autofs_mount(const char *pathname,
 206                              struct path *res,
 207                              int test(struct path *path, void *data),
 208                              void *data)
 209 {
 210         struct path path;
 211         int err;
 212
 213         err = kern_path_mountpoint(AT_FDCWD, pathname, &path, 0);
 214         if (err)
 215                 return err;
 216         err = -ENOENT;
 217         while (path.dentry == path.mnt->mnt_root) {
 218                 if (path.dentry->d_sb->s_magic == AUTOFS_SUPER_MAGIC) {
 219                         if (test(&path, data)) {
 220                                 path_get(&path);
 221                                 *res = path;
 222                                 err = 0;
 223                                 break;
 224                         }
 225                 }
 226                 if (!follow_up(&path))
 227                         break;
 228         }
 229         path_put(&path);
 230         return err;
 231 }
 232
 233 static int test_by_dev(struct path *path, void *p)
 234 {
 235         return path->dentry->d_sb->s_dev == *(dev_t *)p;
 236 }
 237
 238 static int test_by_type(struct path *path, void *p)
 239 {
 240         struct autofs_info *ino = autofs4_dentry_ino(path->dentry);
 241
 242         return ino && ino->sbi->type & *(unsigned *)p;
 243 }
 244
 245 /*
 246  * Open a file descriptor on the autofs mount point corresponding
 247  * to the given path and device number (aka. new_encode_dev(sb->s_dev)).
 248  */
 249 static int autofs_dev_ioctl_open_mountpoint(const char *name, dev_t devid)
 250 {
 251         int err, fd;
 252
 253         fd = get_unused_fd_flags(O_CLOEXEC);
 254         if (likely(fd >= 0)) {
 255                 struct file *filp;
 256                 struct path path;
 257
 258                 err = find_autofs_mount(name, &path, test_by_dev, &devid);
 259                 if (err)
 260                         goto out;
 261
 262                 /*
 263                  * Find autofs super block that has the device number
 264                  * corresponding to the autofs fs we want to open.
 265                  */
 266
 267                 filp = dentry_open(&path, O_RDONLY, current_cred());
 268                 path_put(&path);
 269                 if (IS_ERR(filp)) {
 270                         err = PTR_ERR(filp);
 271                         goto out;
 272                 }
 273
 274                 fd_install(fd, filp);
 275         }
 276
 277         return fd;
 278
 279 out:
 280         put_unused_fd(fd);
 281         return err;
 282 }
 283
 284 /* Open a file descriptor on an autofs mount point */
 285 static int autofs_dev_ioctl_openmount(struct file *fp,
 286                                       struct autofs_sb_info *sbi,
 287                                       struct autofs_dev_ioctl *param)
 288 {
 289         const char *path;
 290         dev_t devid;
 291         int err, fd;
 292
 293         /* param->path has already been checked */
 294         if (!param->openmount.devid)
 295                 return -EINVAL;
 296
 297         param->ioctlfd = -1;
 298
 299         path = param->path;
 300         devid = new_decode_dev(param->openmount.devid);
 301
 302         err = 0;
 303         fd = autofs_dev_ioctl_open_mountpoint(path, devid);
 304         if (unlikely(fd < 0)) {
 305                 err = fd;
 306                 goto out;
 307         }
 308
 309         param->ioctlfd = fd;
 310 out:
 311         return err;
 312 }
 313
 314 /* Close file descriptor allocated above (user can also use close(2)). */
 315 static int autofs_dev_ioctl_closemount(struct file *fp,
 316                                        struct autofs_sb_info *sbi,
 317                                        struct autofs_dev_ioctl *param)
 318 {
 319         return sys_close(param->ioctlfd);
 320 }
 321
 322 /*
 323  * Send "ready" status for an existing wait (either a mount or an expire
 324  * request).
 325  */
 326 static int autofs_dev_ioctl_ready(struct file *fp,
 327                                   struct autofs_sb_info *sbi,
 328                                   struct autofs_dev_ioctl *param)
 329 {
 330         autofs_wqt_t token;
 331
 332         token = (autofs_wqt_t) param->ready.token;
 333         return autofs4_wait_release(sbi, token, 0);
 334 }
 335
 336 /*
 337  * Send "fail" status for an existing wait (either a mount or an expire
 338  * request).
 339  */
 340 static int autofs_dev_ioctl_fail(struct file *fp,
 341                                  struct autofs_sb_info *sbi,
 342                                  struct autofs_dev_ioctl *param)
 343 {
 344         autofs_wqt_t token;
 345         int status;
 346
 347         token = (autofs_wqt_t) param->fail.token;
 348         status = param->fail.status ? param->fail.status : -ENOENT;
 349         return autofs4_wait_release(sbi, token, status);
 350 }
 351
 352 /*
 353  * Set the pipe fd for kernel communication to the daemon.
 354  *
 355  * Normally this is set at mount using an option but if we
 356  * are reconnecting to a busy mount then we need to use this
 357  * to tell the autofs mount about the new kernel pipe fd. In
 358  * order to protect mounts against incorrectly setting the
 359  * pipefd we also require that the autofs mount be catatonic.
 360  *
 361  * This also sets the process group id used to identify the
 362  * controlling process (eg. the owning automount(8) daemon).
 363  */
 364 static int autofs_dev_ioctl_setpipefd(struct file *fp,
 365                                       struct autofs_sb_info *sbi,
 366                                       struct autofs_dev_ioctl *param)
 367 {
 368         int pipefd;
 369         int err = 0;
 370         struct pid *new_pid = NULL;
 371
 372         if (param->setpipefd.pipefd == -1)
 373                 return -EINVAL;
 374
 375         pipefd = param->setpipefd.pipefd;
 376
 377         mutex_lock(&sbi->wq_mutex);
 378         if (!sbi->catatonic) {
 379                 mutex_unlock(&sbi->wq_mutex);
 380                 return -EBUSY;
 381         } else {
 382                 struct file *pipe;
 383
 384                 new_pid = get_task_pid(current, PIDTYPE_PGID);
 385
 386                 if (ns_of_pid(new_pid) != ns_of_pid(sbi->oz_pgrp)) {
 387                         pr_warn("not allowed to change PID namespace\n");
 388                         err = -EINVAL;
 389                         goto out;
 390                 }
 391
 392                 pipe = fget(pipefd);
 393                 if (!pipe) {
 394                         err = -EBADF;
 395                         goto out;
 396                 }
 397                 if (autofs_prepare_pipe(pipe) < 0) {
 398                         err = -EPIPE;
 399                         fput(pipe);
 400                         goto out;
 401                 }
 402                 swap(sbi->oz_pgrp, new_pid);
 403                 sbi->pipefd = pipefd;
 404                 sbi->pipe = pipe;
 405                 sbi->catatonic = 0;
 406         }
 407 out:
 408         put_pid(new_pid);
 409         mutex_unlock(&sbi->wq_mutex);
 410         return err;
 411 }
 412
 413 /*
 414  * Make the autofs mount point catatonic, no longer responsive to
 415  * mount requests. Also closes the kernel pipe file descriptor.
 416  */
 417 static int autofs_dev_ioctl_catatonic(struct file *fp,
 418                                       struct autofs_sb_info *sbi,
 419                                       struct autofs_dev_ioctl *param)
 420 {
 421         autofs4_catatonic_mode(sbi);
 422         return 0;
 423 }
 424
 425 /* Set the autofs mount timeout */
 426 static int autofs_dev_ioctl_timeout(struct file *fp,
 427                                     struct autofs_sb_info *sbi,
 428                                     struct autofs_dev_ioctl *param)
 429 {
 430         unsigned long timeout;
 431
 432         timeout = param->timeout.timeout;
 433         param->timeout.timeout = sbi->exp_timeout / HZ;
 434         sbi->exp_timeout = timeout * HZ;
 435         return 0;
 436 }
 437
 438 /*
 439  * Return the uid and gid of the last request for the mount
 440  *
 441  * When reconstructing an autofs mount tree with active mounts
 442  * we need to re-connect to mounts that may have used the original
 443  * process uid and gid (or string variations of them) for mount
 444  * lookups within the map entry.
 445  */
 446 static int autofs_dev_ioctl_requester(struct file *fp,
 447                                       struct autofs_sb_info *sbi,
 448                                       struct autofs_dev_ioctl *param)
 449 {
 450         struct autofs_info *ino;
 451         struct path path;
 452         dev_t devid;
 453         int err = -ENOENT;
 454
 455         if (param->size <= sizeof(*param)) {
 456                 err = -EINVAL;
 457                 goto out;
 458         }
 459
 460         devid = sbi->sb->s_dev;
 461
 462         param->requester.uid = param->requester.gid = -1;
 463
 464         err = find_autofs_mount(param->path, &path, test_by_dev, &devid);
 465         if (err)
 466                 goto out;
 467
 468         ino = autofs4_dentry_ino(path.dentry);
 469         if (ino) {
 470                 err = 0;
 471                 autofs4_expire_wait(path.dentry, 0);
 472                 spin_lock(&sbi->fs_lock);
 473                 param->requester.uid =
 474                         from_kuid_munged(current_user_ns(), ino->uid);
 475                 param->requester.gid =
 476                         from_kgid_munged(current_user_ns(), ino->gid);
 477                 spin_unlock(&sbi->fs_lock);
 478         }
 479         path_put(&path);
 480 out:
 481         return err;
 482 }
 483
 484 /*
 485  * Call repeatedly until it returns -EAGAIN, meaning there's nothing
 486  * more that can be done.
 487  */
 488 static int autofs_dev_ioctl_expire(struct file *fp,
 489                                    struct autofs_sb_info *sbi,
 490                                    struct autofs_dev_ioctl *param)
 491 {
 492         struct vfsmount *mnt;
 493         int how;
 494
 495         how = param->expire.how;
 496         mnt = fp->f_path.mnt;
 497
 498         return autofs4_do_expire_multi(sbi->sb, mnt, sbi, how);
 499 }
 500
 501 /* Check if autofs mount point is in use */
 502 static int autofs_dev_ioctl_askumount(struct file *fp,
 503                                       struct autofs_sb_info *sbi,
 504                                       struct autofs_dev_ioctl *param)
 505 {
 506         param->askumount.may_umount = 0;
 507         if (may_umount(fp->f_path.mnt))
 508                 param->askumount.may_umount = 1;
 509         return 0;
 510 }
 511
 512 /*
 513  * Check if the given path is a mountpoint.
 514  *
 515  * If we are supplied with the file descriptor of an autofs
 516  * mount we're looking for a specific mount. In this case
 517  * the path is considered a mountpoint if it is itself a
 518  * mountpoint or contains a mount, such as a multi-mount
 519  * without a root mount. In this case we return 1 if the
 520  * path is a mount point and the super magic of the covering
 521  * mount if there is one or 0 if it isn't a mountpoint.
 522  *
 523  * If we aren't supplied with a file descriptor then we
 524  * lookup the path and check if it is the root of a mount.
 525  * If a type is given we are looking for a particular autofs
 526  * mount and if we don't find a match we return fail. If the
 527  * located path is the root of a mount we return 1 along with
 528  * the super magic of the mount or 0 otherwise.
 529  *
 530  * In both cases the the device number (as returned by
 531  * new_encode_dev()) is also returned.
 532  */
 533 static int autofs_dev_ioctl_ismountpoint(struct file *fp,
 534                                          struct autofs_sb_info *sbi,
 535                                          struct autofs_dev_ioctl *param)
 536 {
 537         struct path path;
 538         const char *name;
 539         unsigned int type;
 540         unsigned int devid, magic;
 541         int err = -ENOENT;
 542
 543         if (param->size <= sizeof(*param)) {
 544                 err = -EINVAL;
 545                 goto out;
 546         }
 547
 548         name = param->path;
 549         type = param->ismountpoint.in.type;
 550
 551         param->ismountpoint.out.devid = devid = 0;
 552         param->ismountpoint.out.magic = magic = 0;
 553
 554         if (!fp || param->ioctlfd == -1) {
 555                 if (autofs_type_any(type))
 556                         err = kern_path_mountpoint(AT_FDCWD,
 557                                                    name, &path, LOOKUP_FOLLOW);
 558                 else
 559                         err = find_autofs_mount(name, &path,
 560                                                 test_by_type, &type);
 561                 if (err)
 562                         goto out;
 563                 devid = new_encode_dev(path.dentry->d_sb->s_dev);
 564                 err = 0;
 565                 if (path.mnt->mnt_root == path.dentry) {
 566                         err = 1;
 567                         magic = path.dentry->d_sb->s_magic;
 568                 }
 569         } else {
 570                 dev_t dev = sbi->sb->s_dev;
 571
 572                 err = find_autofs_mount(name, &path, test_by_dev, &dev);
 573                 if (err)
 574                         goto out;
 575
 576                 devid = new_encode_dev(dev);
 577
 578                 err = have_submounts(path.dentry);
 579
 580                 if (follow_down_one(&path))
 581                         magic = path.dentry->d_sb->s_magic;
 582         }
 583
 584         param->ismountpoint.out.devid = devid;
 585         param->ismountpoint.out.magic = magic;
 586         path_put(&path);
 587 out:
 588         return err;
 589 }
 590
 591 /*
 592  * Our range of ioctl numbers isn't 0 based so we need to shift
 593  * the array index by _IOC_NR(AUTOFS_CTL_IOC_FIRST) for the table
 594  * lookup.
 595  */
 596 #define cmd_idx(cmd)    (cmd - _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST))
 597
 598 static ioctl_fn lookup_dev_ioctl(unsigned int cmd)
 599 {
 600         static ioctl_fn _ioctls[] = {
 601                 autofs_dev_ioctl_version,
 602                 autofs_dev_ioctl_protover,
 603                 autofs_dev_ioctl_protosubver,
 604                 autofs_dev_ioctl_openmount,
 605                 autofs_dev_ioctl_closemount,
 606                 autofs_dev_ioctl_ready,
 607                 autofs_dev_ioctl_fail,
 608                 autofs_dev_ioctl_setpipefd,
 609                 autofs_dev_ioctl_catatonic,
 610                 autofs_dev_ioctl_timeout,
 611                 autofs_dev_ioctl_requester,
 612                 autofs_dev_ioctl_expire,
 613                 autofs_dev_ioctl_askumount,
 614                 autofs_dev_ioctl_ismountpoint,
 615         };
 616         unsigned int idx = cmd_idx(cmd);
 617
 618         return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx];
 619 }
 620
 621 /* ioctl dispatcher */
 622 static int _autofs_dev_ioctl(unsigned int command,
 623                              struct autofs_dev_ioctl __user *user)
 624 {
 625         struct autofs_dev_ioctl *param;
 626         struct file *fp;
 627         struct autofs_sb_info *sbi;
 628         unsigned int cmd_first, cmd;
 629         ioctl_fn fn = NULL;
 630         int err = 0;
 631
 632         /* only root can play with this */
 633         if (!capable(CAP_SYS_ADMIN))
 634                 return -EPERM;
 635
 636         cmd_first = _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST);
 637         cmd = _IOC_NR(command);
 638
 639         if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) ||
 640             cmd - cmd_first > AUTOFS_DEV_IOCTL_IOC_COUNT) {
 641                 return -ENOTTY;
 642         }
 643
 644         /* Copy the parameters into kernel space. */
 645         param = copy_dev_ioctl(user);
 646         if (IS_ERR(param))
 647                 return PTR_ERR(param);
 648
 649         err = validate_dev_ioctl(command, param);
 650         if (err)
 651                 goto out;
 652
 653         fn = lookup_dev_ioctl(cmd);
 654         if (!fn) {
 655                 pr_warn("unknown command 0x%08x\n", command);
 656                 err = -ENOTTY;
 657                 goto out;
 658         }
 659
 660         fp = NULL;
 661         sbi = NULL;
 662
 663         /*
 664          * For obvious reasons the openmount can't have a file
 665          * descriptor yet. We don't take a reference to the
 666          * file during close to allow for immediate release,
 667          * and the same for retrieving ioctl version.
 668          */
 669         if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD &&
 670             cmd != AUTOFS_DEV_IOCTL_OPENMOUNT_CMD &&
 671             cmd != AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD) {
 672                 fp = fget(param->ioctlfd);
 673                 if (!fp) {
 674                         if (cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD)
 675                                 goto cont;
 676                         err = -EBADF;
 677                         goto out;
 678                 }
 679
 680                 sbi = autofs_dev_ioctl_sbi(fp);
 681                 if (!sbi || sbi->magic != AUTOFS_SBI_MAGIC) {
 682                         err = -EINVAL;
 683                         fput(fp);
 684                         goto out;
 685                 }
 686
 687                 /*
 688                  * Admin needs to be able to set the mount catatonic in
 689                  * order to be able to perform the re-open.
 690                  */
 691                 if (!autofs4_oz_mode(sbi) &&
 692                     cmd != AUTOFS_DEV_IOCTL_CATATONIC_CMD) {
 693                         err = -EACCES;
 694                         fput(fp);
 695                         goto out;
 696                 }
 697         }
 698 cont:
 699         err = fn(fp, sbi, param);
 700
 701         if (fp)
 702                 fput(fp);
 703         if (err >= 0 && copy_to_user(user, param, AUTOFS_DEV_IOCTL_SIZE))
 704                 err = -EFAULT;
 705 out:
 706         free_dev_ioctl(param);
 707         return err;
 708 }
 709
 710 static long autofs_dev_ioctl(struct file *file, uint command, ulong u)
 711 {
 712         int err;
 713
 714         err = _autofs_dev_ioctl(command, (struct autofs_dev_ioctl __user *) u);
 715         return (long) err;
 716 }
 717
 718 #ifdef CONFIG_COMPAT
 719 static long autofs_dev_ioctl_compat(struct file *file, uint command, ulong u)
 720 {
 721         return (long) autofs_dev_ioctl(file, command, (ulong) compat_ptr(u));
 722 }
 723 #else
 724 #define autofs_dev_ioctl_compat NULL
 725 #endif
 726
 727 static 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
 734 static struct miscdevice _autofs_dev_ioctl_misc = {
 735         .minor          = AUTOFS_MINOR,
 736         .name           = AUTOFS_DEVICE_NAME,
 737         .fops           = &_dev_ioctl_fops
 738 };
 739
 740 MODULE_ALIAS_MISCDEV(AUTOFS_MINOR);
 741 MODULE_ALIAS("devname:autofs");
 742
 743 /* Register/deregister misc character device */
 744 int __init autofs_dev_ioctl_init(void)
 745 {
 746         int r;
 747
 748         r = misc_register(&_autofs_dev_ioctl_misc);
 749         if (r) {
 750                 pr_err("misc_register failed for control device\n");
 751                 return r;
 752         }
 753
 754         return 0;
 755 }
 756
 757 void autofs_dev_ioctl_exit(void)
 758 {
 759         misc_deregister(&_autofs_dev_ioctl_misc);
 760 }