1// SPDX-License-Identifier: GPL-2.0-or-later 2/* 3 * Copyright 2008 Red Hat, Inc. All rights reserved. 4 * Copyright 2008 Ian Kent <raven@themaw.net> 5 */ 6 7#include <linux/miscdevice.h> 8#include <linux/compat.h> 9#include <linux/syscalls.h> 10#include <linux/magic.h> 11#include <linux/nospec.h> 12 13#include "autofs_i.h" 14 15/* 16 * This module implements an interface for routing autofs ioctl control 17 * commands via a miscellaneous device file. 18 * 19 * The alternate interface is needed because we need to be able open 20 * an ioctl file descriptor on an autofs mount that may be covered by 21 * another mount. This situation arises when starting automount(8) 22 * or other user space daemon which uses direct mounts or offset 23 * mounts (used for autofs lazy mount/umount of nested mount trees), 24 * which have been left busy at service shutdown. 25 */ 26 27typedef int (*ioctl_fn)(struct file *, struct autofs_sb_info *, 28 struct autofs_dev_ioctl *); 29 30static int check_name(const char *name) 31{ 32 if (!strchr(name, '/')) 33 return -EINVAL; 34 return 0; 35} 36 37/* 38 * Check a string doesn't overrun the chunk of 39 * memory we copied from user land. 40 */ 41static int invalid_str(char *str, size_t size) 42{ 43 if (memchr(str, 0, size)) 44 return 0; 45 return -EINVAL; 46} 47 48/* 49 * Check that the user compiled against correct version of autofs 50 * misc device code. 51 * 52 * As well as checking the version compatibility this always copies 53 * the kernel interface version out. 54 */ 55static int check_dev_ioctl_version(int cmd, struct autofs_dev_ioctl *param) 56{ 57 int err = 0; 58 59 if ((param->ver_major != AUTOFS_DEV_IOCTL_VERSION_MAJOR) || 60 (param->ver_minor > AUTOFS_DEV_IOCTL_VERSION_MINOR)) { 61 pr_warn("ioctl control interface version mismatch: " 62 "kernel(%u.%u), user(%u.%u), cmd(0x%08x)\n", 63 AUTOFS_DEV_IOCTL_VERSION_MAJOR, 64 AUTOFS_DEV_IOCTL_VERSION_MINOR, 65 param->ver_major, param->ver_minor, cmd); 66 err = -EINVAL; 67 } 68 69 /* Fill in the kernel version. */ 70 param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR; 71 param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR; 72 73 return err; 74} 75 76/* 77 * Copy parameter control struct, including a possible path allocated 78 * at the end of the struct. 79 */ 80static struct autofs_dev_ioctl * 81copy_dev_ioctl(struct autofs_dev_ioctl __user *in) 82{ 83 struct autofs_dev_ioctl tmp, *res; 84 85 if (copy_from_user(&tmp, in, AUTOFS_DEV_IOCTL_SIZE)) 86 return ERR_PTR(-EFAULT); 87 88 if (tmp.size < AUTOFS_DEV_IOCTL_SIZE) 89 return ERR_PTR(-EINVAL); 90 91 if (tmp.size > AUTOFS_DEV_IOCTL_SIZE + PATH_MAX) 92 return ERR_PTR(-ENAMETOOLONG); 93 94 res = memdup_user(in, tmp.size); 95 if (!IS_ERR(res)) 96 res->size = tmp.size; 97 98 return res; 99} 100 101static inline void free_dev_ioctl(struct autofs_dev_ioctl *param) 102{ 103 kfree(param); 104} 105 106/* 107 * Check sanity of parameter control fields and if a path is present 108 * check that it is terminated and contains at least one "/". 109 */ 110static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param) 111{ 112 int err; 113 114 err = check_dev_ioctl_version(cmd, param); 115 if (err) { 116 pr_warn("invalid device control module version " 117 "supplied for cmd(0x%08x)\n", cmd); 118 goto out; 119 } 120 121 if (param->size > AUTOFS_DEV_IOCTL_SIZE) { 122 err = invalid_str(param->path, param->size - AUTOFS_DEV_IOCTL_SIZE); 123 if (err) { 124 pr_warn( 125 "path string terminator missing for cmd(0x%08x)\n", 126 cmd); 127 goto out; 128 } 129 130 err = check_name(param->path); 131 if (err) { 132 pr_warn("invalid path supplied for cmd(0x%08x)\n", 133 cmd); 134 goto out; 135 } 136 } else { 137 unsigned int inr = _IOC_NR(cmd); 138 139 if (inr == AUTOFS_DEV_IOCTL_OPENMOUNT_CMD || 140 inr == AUTOFS_DEV_IOCTL_REQUESTER_CMD || 141 inr == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD) { 142 err = -EINVAL; 143 goto out; 144 } 145 } 146 147 err = 0; 148out: 149 return err; 150} 151 152/* Return autofs dev ioctl version */ 153static int autofs_dev_ioctl_version(struct file *fp, 154 struct autofs_sb_info *sbi, 155 struct autofs_dev_ioctl *param) 156{ 157 /* This should have already been set. */ 158 param->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR; 159 param->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR; 160 return 0; 161} 162 163/* Return autofs module protocol version */ 164static int autofs_dev_ioctl_protover(struct file *fp, 165 struct autofs_sb_info *sbi, 166 struct autofs_dev_ioctl *param) 167{ 168 param->protover.version = sbi->version; 169 return 0; 170} 171 172/* Return autofs module protocol sub version */ 173static int autofs_dev_ioctl_protosubver(struct file *fp, 174 struct autofs_sb_info *sbi, 175 struct autofs_dev_ioctl *param) 176{ 177 param->protosubver.sub_version = sbi->sub_version; 178 return 0; 179} 180 181/* Find the topmost mount satisfying test() */ 182static int find_autofs_mount(const char *pathname, 183 struct path *res, 184 int test(const struct path *path, void *data), 185 void *data) 186{ 187 struct path path; 188 int err; 189 190 err = kern_path(pathname, LOOKUP_MOUNTPOINT, &path); 191 if (err) 192 return err; 193 err = -ENOENT; 194 while (path.dentry == path.mnt->mnt_root) { 195 if (path.dentry->d_sb->s_magic == AUTOFS_SUPER_MAGIC) { 196 if (test(&path, data)) { 197 path_get(&path); 198 *res = path; 199 err = 0; 200 break; 201 } 202 } 203 if (!follow_up(&path)) 204 break; 205 } 206 path_put(&path); 207 return err; 208} 209 210static int test_by_dev(const struct path *path, void *p) 211{ 212 return path->dentry->d_sb->s_dev == *(dev_t *)p; 213} 214 215static int test_by_type(const struct path *path, void *p) 216{ 217 struct autofs_info *ino = autofs_dentry_ino(path->dentry); 218 219 return ino && ino->sbi->type & *(unsigned *)p; 220} 221 222/* 223 * Open a file descriptor on the autofs mount point corresponding 224 * to the given path and device number (aka. new_encode_dev(sb->s_dev)). 225 */ 226static int autofs_dev_ioctl_open_mountpoint(const char *name, dev_t devid) 227{ 228 int err, fd; 229 230 fd = get_unused_fd_flags(O_CLOEXEC); 231 if (likely(fd >= 0)) { 232 struct file *filp; 233 struct path path; 234 235 err = find_autofs_mount(name, &path, test_by_dev, &devid); 236 if (err) 237 goto out; 238 239 filp = dentry_open(&path, O_RDONLY, current_cred()); 240 path_put(&path); 241 if (IS_ERR(filp)) { 242 err = PTR_ERR(filp); 243 goto out; 244 } 245 246 fd_install(fd, filp); 247 } 248 249 return fd; 250 251out: 252 put_unused_fd(fd); 253 return err; 254} 255 256/* Open a file descriptor on an autofs mount point */ 257static int autofs_dev_ioctl_openmount(struct file *fp, 258 struct autofs_sb_info *sbi, 259 struct autofs_dev_ioctl *param) 260{ 261 const char *path; 262 dev_t devid; 263 int err, fd; 264 265 /* param->path has been checked in validate_dev_ioctl() */ 266 267 if (!param->openmount.devid) 268 return -EINVAL; 269 270 param->ioctlfd = -1; 271 272 path = param->path; 273 devid = new_decode_dev(param->openmount.devid); 274 275 err = 0; 276 fd = autofs_dev_ioctl_open_mountpoint(path, devid); 277 if (unlikely(fd < 0)) { 278 err = fd; 279 goto out; 280 } 281 282 param->ioctlfd = fd; 283out: 284 return err; 285} 286 287/* Close file descriptor allocated above (user can also use close(2)). */ 288static int autofs_dev_ioctl_closemount(struct file *fp, 289 struct autofs_sb_info *sbi, 290 struct autofs_dev_ioctl *param) 291{ 292 return ksys_close(param->ioctlfd); 293} 294 295/* 296 * Send "ready" status for an existing wait (either a mount or an expire 297 * request). 298 */ 299static int autofs_dev_ioctl_ready(struct file *fp, 300 struct autofs_sb_info *sbi, 301 struct autofs_dev_ioctl *param) 302{ 303 autofs_wqt_t token; 304 305 token = (autofs_wqt_t) param->ready.token; 306 return autofs_wait_release(sbi, token, 0); 307} 308 309/* 310 * Send "fail" status for an existing wait (either a mount or an expire 311 * request). 312 */ 313static int autofs_dev_ioctl_fail(struct file *fp, 314 struct autofs_sb_info *sbi, 315 struct autofs_dev_ioctl *param) 316{ 317 autofs_wqt_t token; 318 int status; 319 320 token = (autofs_wqt_t) param->fail.token; 321 status = param->fail.status < 0 ? param->fail.status : -ENOENT; 322 return autofs_wait_release(sbi, token, status); 323} 324 325/* 326 * Set the pipe fd for kernel communication to the daemon. 327 * 328 * Normally this is set at mount using an option but if we 329 * are reconnecting to a busy mount then we need to use this 330 * to tell the autofs mount about the new kernel pipe fd. In 331 * order to protect mounts against incorrectly setting the 332 * pipefd we also require that the autofs mount be catatonic. 333 * 334 * This also sets the process group id used to identify the 335 * controlling process (eg. the owning automount(8) daemon). 336 */ 337static int autofs_dev_ioctl_setpipefd(struct file *fp, 338 struct autofs_sb_info *sbi, 339 struct autofs_dev_ioctl *param) 340{ 341 int pipefd; 342 int err = 0; 343 struct pid *new_pid = NULL; 344 345 if (param->setpipefd.pipefd == -1) 346 return -EINVAL; 347 348 pipefd = param->setpipefd.pipefd; 349 350 mutex_lock(&sbi->wq_mutex); 351 if (!(sbi->flags & AUTOFS_SBI_CATATONIC)) { 352 mutex_unlock(&sbi->wq_mutex); 353 return -EBUSY; 354 } else { 355 struct file *pipe; 356 357 new_pid = get_task_pid(current, PIDTYPE_PGID); 358 359 if (ns_of_pid(new_pid) != ns_of_pid(sbi->oz_pgrp)) { 360 pr_warn("not allowed to change PID namespace\n"); 361 err = -EINVAL; 362 goto out; 363 } 364 365 pipe = fget(pipefd); 366 if (!pipe) { 367 err = -EBADF; 368 goto out; 369 } 370 if (autofs_prepare_pipe(pipe) < 0) { 371 err = -EPIPE; 372 fput(pipe); 373 goto out; 374 } 375 swap(sbi->oz_pgrp, new_pid); 376 sbi->pipefd = pipefd; 377 sbi->pipe = pipe; 378 sbi->flags &= ~AUTOFS_SBI_CATATONIC; 379 } 380out: 381 put_pid(new_pid); 382 mutex_unlock(&sbi->wq_mutex); 383 return err; 384} 385 386/* 387 * Make the autofs mount point catatonic, no longer responsive to 388 * mount requests. Also closes the kernel pipe file descriptor. 389 */ 390static int autofs_dev_ioctl_catatonic(struct file *fp, 391 struct autofs_sb_info *sbi, 392 struct autofs_dev_ioctl *param) 393{ 394 autofs_catatonic_mode(sbi); 395 return 0; 396} 397 398/* Set the autofs mount timeout */ 399static int autofs_dev_ioctl_timeout(struct file *fp, 400 struct autofs_sb_info *sbi, 401 struct autofs_dev_ioctl *param) 402{ 403 unsigned long timeout; 404 405 timeout = param->timeout.timeout; 406 param->timeout.timeout = sbi->exp_timeout / HZ; 407 sbi->exp_timeout = timeout * HZ; 408 return 0; 409} 410 411/* 412 * Return the uid and gid of the last request for the mount 413 * 414 * When reconstructing an autofs mount tree with active mounts 415 * we need to re-connect to mounts that may have used the original 416 * process uid and gid (or string variations of them) for mount 417 * lookups within the map entry. 418 */ 419static int autofs_dev_ioctl_requester(struct file *fp, 420 struct autofs_sb_info *sbi, 421 struct autofs_dev_ioctl *param) 422{ 423 struct autofs_info *ino; 424 struct path path; 425 dev_t devid; 426 int err = -ENOENT; 427 428 /* param->path has been checked in validate_dev_ioctl() */ 429 430 devid = sbi->sb->s_dev; 431 432 param->requester.uid = param->requester.gid = -1; 433 434 err = find_autofs_mount(param->path, &path, test_by_dev, &devid); 435 if (err) 436 goto out; 437 438 ino = autofs_dentry_ino(path.dentry); 439 if (ino) { 440 err = 0; 441 autofs_expire_wait(&path, 0); 442 spin_lock(&sbi->fs_lock); 443 param->requester.uid = 444 from_kuid_munged(current_user_ns(), ino->uid); 445 param->requester.gid = 446 from_kgid_munged(current_user_ns(), ino->gid); 447 spin_unlock(&sbi->fs_lock); 448 } 449 path_put(&path); 450out: 451 return err; 452} 453 454/* 455 * Call repeatedly until it returns -EAGAIN, meaning there's nothing 456 * more that can be done. 457 */ 458static int autofs_dev_ioctl_expire(struct file *fp, 459 struct autofs_sb_info *sbi, 460 struct autofs_dev_ioctl *param) 461{ 462 struct vfsmount *mnt; 463 int how; 464 465 how = param->expire.how; 466 mnt = fp->f_path.mnt; 467 468 return autofs_do_expire_multi(sbi->sb, mnt, sbi, how); 469} 470 471/* Check if autofs mount point is in use */ 472static int autofs_dev_ioctl_askumount(struct file *fp, 473 struct autofs_sb_info *sbi, 474 struct autofs_dev_ioctl *param) 475{ 476 param->askumount.may_umount = 0; 477 if (may_umount(fp->f_path.mnt)) 478 param->askumount.may_umount = 1; 479 return 0; 480} 481 482/* 483 * Check if the given path is a mountpoint. 484 * 485 * If we are supplied with the file descriptor of an autofs 486 * mount we're looking for a specific mount. In this case 487 * the path is considered a mountpoint if it is itself a 488 * mountpoint or contains a mount, such as a multi-mount 489 * without a root mount. In this case we return 1 if the 490 * path is a mount point and the super magic of the covering 491 * mount if there is one or 0 if it isn't a mountpoint. 492 * 493 * If we aren't supplied with a file descriptor then we 494 * lookup the path and check if it is the root of a mount. 495 * If a type is given we are looking for a particular autofs 496 * mount and if we don't find a match we return fail. If the 497 * located path is the root of a mount we return 1 along with 498 * the super magic of the mount or 0 otherwise. 499 * 500 * In both cases the device number (as returned by 501 * new_encode_dev()) is also returned. 502 */ 503static int autofs_dev_ioctl_ismountpoint(struct file *fp, 504 struct autofs_sb_info *sbi, 505 struct autofs_dev_ioctl *param) 506{ 507 struct path path; 508 const char *name; 509 unsigned int type; 510 unsigned int devid, magic; 511 int err = -ENOENT; 512 513 /* param->path has been checked in validate_dev_ioctl() */ 514 515 name = param->path; 516 type = param->ismountpoint.in.type; 517 518 param->ismountpoint.out.devid = devid = 0; 519 param->ismountpoint.out.magic = magic = 0; 520 521 if (!fp || param->ioctlfd == -1) { 522 if (autofs_type_any(type)) 523 err = kern_path(name, LOOKUP_FOLLOW | LOOKUP_MOUNTPOINT, 524 &path); 525 else 526 err = find_autofs_mount(name, &path, 527 test_by_type, &type); 528 if (err) 529 goto out; 530 devid = new_encode_dev(path.dentry->d_sb->s_dev); 531 err = 0; 532 if (path.mnt->mnt_root == path.dentry) { 533 err = 1; 534 magic = path.dentry->d_sb->s_magic; 535 } 536 } else { 537 dev_t dev = sbi->sb->s_dev; 538 539 err = find_autofs_mount(name, &path, test_by_dev, &dev); 540 if (err) 541 goto out; 542 543 devid = new_encode_dev(dev); 544 545 err = path_has_submounts(&path); 546 547 if (follow_down_one(&path)) 548 magic = path.dentry->d_sb->s_magic; 549 } 550 551 param->ismountpoint.out.devid = devid; 552 param->ismountpoint.out.magic = magic; 553 path_put(&path); 554out: 555 return err; 556} 557 558/* 559 * Our range of ioctl numbers isn't 0 based so we need to shift 560 * the array index by _IOC_NR(AUTOFS_CTL_IOC_FIRST) for the table 561 * lookup. 562 */ 563#define cmd_idx(cmd) (cmd - _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST)) 564 565static ioctl_fn lookup_dev_ioctl(unsigned int cmd) 566{ 567 static const ioctl_fn _ioctls[] = { 568 autofs_dev_ioctl_version, 569 autofs_dev_ioctl_protover, 570 autofs_dev_ioctl_protosubver, 571 autofs_dev_ioctl_openmount, 572 autofs_dev_ioctl_closemount, 573 autofs_dev_ioctl_ready, 574 autofs_dev_ioctl_fail, 575 autofs_dev_ioctl_setpipefd, 576 autofs_dev_ioctl_catatonic, 577 autofs_dev_ioctl_timeout, 578 autofs_dev_ioctl_requester, 579 autofs_dev_ioctl_expire, 580 autofs_dev_ioctl_askumount, 581 autofs_dev_ioctl_ismountpoint, 582 }; 583 unsigned int idx = cmd_idx(cmd); 584 585 if (idx >= ARRAY_SIZE(_ioctls)) 586 return NULL; 587 idx = array_index_nospec(idx, ARRAY_SIZE(_ioctls)); 588 return _ioctls[idx]; 589} 590 591/* ioctl dispatcher */ 592static int _autofs_dev_ioctl(unsigned int command, 593 struct autofs_dev_ioctl __user *user) 594{ 595 struct autofs_dev_ioctl *param; 596 struct file *fp; 597 struct autofs_sb_info *sbi; 598 unsigned int cmd_first, cmd; 599 ioctl_fn fn = NULL; 600 int err = 0; 601 602 cmd_first = _IOC_NR(AUTOFS_DEV_IOCTL_IOC_FIRST); 603 cmd = _IOC_NR(command); 604 605 if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) || 606 cmd - cmd_first > AUTOFS_DEV_IOCTL_IOC_COUNT) { 607 return -ENOTTY; 608 } 609 610 /* Only root can use ioctls other than AUTOFS_DEV_IOCTL_VERSION_CMD 611 * and AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD 612 */ 613 if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD && 614 cmd != AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD && 615 !capable(CAP_SYS_ADMIN)) 616 return -EPERM; 617 618 /* Copy the parameters into kernel space. */ 619 param = copy_dev_ioctl(user); 620 if (IS_ERR(param)) 621 return PTR_ERR(param); 622 623 err = validate_dev_ioctl(command, param); 624 if (err) 625 goto out; 626 627 fn = lookup_dev_ioctl(cmd); 628 if (!fn) { 629 pr_warn("unknown command 0x%08x\n", command); 630 err = -ENOTTY; 631 goto out; 632 } 633 634 fp = NULL; 635 sbi = NULL; 636 637 /* 638 * For obvious reasons the openmount can't have a file 639 * descriptor yet. We don't take a reference to the 640 * file during close to allow for immediate release, 641 * and the same for retrieving ioctl version. 642 */ 643 if (cmd != AUTOFS_DEV_IOCTL_VERSION_CMD && 644 cmd != AUTOFS_DEV_IOCTL_OPENMOUNT_CMD && 645 cmd != AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD) { 646 struct super_block *sb; 647 648 fp = fget(param->ioctlfd); 649 if (!fp) { 650 if (cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD) 651 goto cont; 652 err = -EBADF; 653 goto out; 654 } 655 656 sb = file_inode(fp)->i_sb; 657 if (sb->s_type != &autofs_fs_type) { 658 err = -EINVAL; 659 fput(fp); 660 goto out; 661 } 662 sbi = autofs_sbi(sb); 663 664 /* 665 * Admin needs to be able to set the mount catatonic in 666 * order to be able to perform the re-open. 667 */ 668 if (!autofs_oz_mode(sbi) && 669 cmd != AUTOFS_DEV_IOCTL_CATATONIC_CMD) { 670 err = -EACCES; 671 fput(fp); 672 goto out; 673 } 674 } 675cont: 676 err = fn(fp, sbi, param); 677 678 if (fp) 679 fput(fp); 680 if (err >= 0 && copy_to_user(user, param, AUTOFS_DEV_IOCTL_SIZE)) 681 err = -EFAULT; 682out: 683 free_dev_ioctl(param); 684 return err; 685} 686 687static long autofs_dev_ioctl(struct file *file, unsigned int command, 688 unsigned long u) 689{ 690 int err; 691 692 err = _autofs_dev_ioctl(command, (struct autofs_dev_ioctl __user *) u); 693 return (long) err; 694} 695 696#ifdef CONFIG_COMPAT 697static long autofs_dev_ioctl_compat(struct file *file, unsigned int command, 698 unsigned long u) 699{ 700 return autofs_dev_ioctl(file, command, (unsigned long) compat_ptr(u)); 701} 702#else 703#define autofs_dev_ioctl_compat NULL 704#endif 705 706static const struct file_operations _dev_ioctl_fops = { 707 .unlocked_ioctl = autofs_dev_ioctl, 708 .compat_ioctl = autofs_dev_ioctl_compat, 709 .owner = THIS_MODULE, 710 .llseek = noop_llseek, 711}; 712 713static struct miscdevice _autofs_dev_ioctl_misc = { 714 .minor = AUTOFS_MINOR, 715 .name = AUTOFS_DEVICE_NAME, 716 .fops = &_dev_ioctl_fops, 717 .mode = 0644, 718}; 719 720MODULE_ALIAS_MISCDEV(AUTOFS_MINOR); 721MODULE_ALIAS("devname:autofs"); 722 723/* Register/deregister misc character device */ 724int __init autofs_dev_ioctl_init(void) 725{ 726 int r; 727 728 r = misc_register(&_autofs_dev_ioctl_misc); 729 if (r) { 730 pr_err("misc_register failed for control device\n"); 731 return r; 732 } 733 734 return 0; 735} 736 737void autofs_dev_ioctl_exit(void) 738{ 739 misc_deregister(&_autofs_dev_ioctl_misc); 740} 741