fs/notify/fanotify/fanotify_user.c

   1 #include <linux/fanotify.h>
   2 #include <linux/fcntl.h>
   3 #include <linux/file.h>
   4 #include <linux/fs.h>
   5 #include <linux/anon_inodes.h>
   6 #include <linux/fsnotify_backend.h>
   7 #include <linux/init.h>
   8 #include <linux/mount.h>
   9 #include <linux/namei.h>
  10 #include <linux/poll.h>
  11 #include <linux/security.h>
  12 #include <linux/syscalls.h>
  13 #include <linux/slab.h>
  14 #include <linux/types.h>
  15 #include <linux/uaccess.h>
  16 #include <linux/compat.h>
  17
  18 #include <asm/ioctls.h>
  19
  20 #include "../../mount.h"
  21 #include "../fdinfo.h"
  22
  23 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
  24 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
  25 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
  26
  27 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  28
  29 static struct kmem_cache *fanotify_mark_cache __read_mostly;
  30 static struct kmem_cache *fanotify_response_event_cache __read_mostly;
  31
  32 struct fanotify_response_event {
  33         struct list_head list;
  34         __s32 fd;
  35         struct fsnotify_event *event;
  36 };
  37
  38 /*
  39  * Get an fsnotify notification event if one exists and is small
  40  * enough to fit in "count". Return an error pointer if the count
  41  * is not large enough.
  42  *
  43  * Called with the group->notification_mutex held.
  44  */
  45 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  46                                             size_t count)
  47 {
  48         BUG_ON(!mutex_is_locked(&group->notification_mutex));
  49
  50         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  51
  52         if (fsnotify_notify_queue_is_empty(group))
  53                 return NULL;
  54
  55         if (FAN_EVENT_METADATA_LEN > count)
  56                 return ERR_PTR(-EINVAL);
  57
  58         /* held the notification_mutex the whole time, so this is the
  59          * same event we peeked above */
  60         return fsnotify_remove_notify_event(group);
  61 }
  62
  63 static int create_fd(struct fsnotify_group *group,
  64                         struct fsnotify_event *event,
  65                         struct file **file)
  66 {
  67         int client_fd;
  68         struct file *new_file;
  69
  70         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  71
  72         client_fd = get_unused_fd();
  73         if (client_fd < 0)
  74                 return client_fd;
  75
  76         if (event->data_type != FSNOTIFY_EVENT_PATH) {
  77                 WARN_ON(1);
  78                 put_unused_fd(client_fd);
  79                 return -EINVAL;
  80         }
  81
  82         /*
  83          * we need a new file handle for the userspace program so it can read even if it was
  84          * originally opened O_WRONLY.
  85          */
  86         /* it's possible this event was an overflow event.  in that case dentry and mnt
  87          * are NULL;  That's fine, just don't call dentry open */
  88         if (event->path.dentry && event->path.mnt)
  89                 new_file = dentry_open(&event->path,
  90                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
  91                                        current_cred());
  92         else
  93                 new_file = ERR_PTR(-EOVERFLOW);
  94         if (IS_ERR(new_file)) {
  95                 /*
  96                  * we still send an event even if we can't open the file.  this
  97                  * can happen when say tasks are gone and we try to open their
  98                  * /proc files or we try to open a WRONLY file like in sysfs
  99                  * we just send the errno to userspace since there isn't much
 100                  * else we can do.
 101                  */
 102                 put_unused_fd(client_fd);
 103                 client_fd = PTR_ERR(new_file);
 104         } else {
 105                 *file = new_file;
 106         }
 107
 108         return client_fd;
 109 }
 110
 111 static int fill_event_metadata(struct fsnotify_group *group,
 112                                    struct fanotify_event_metadata *metadata,
 113                                    struct fsnotify_event *event,
 114                                    struct file **file)
 115 {
 116         int ret = 0;
 117
 118         pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
 119                  group, metadata, event);
 120
 121         *file = NULL;
 122         metadata->event_len = FAN_EVENT_METADATA_LEN;
 123         metadata->metadata_len = FAN_EVENT_METADATA_LEN;
 124         metadata->vers = FANOTIFY_METADATA_VERSION;
 125         metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
 126         metadata->pid = pid_vnr(event->tgid);
 127         if (unlikely(event->mask & FAN_Q_OVERFLOW))
 128                 metadata->fd = FAN_NOFD;
 129         else {
 130                 metadata->fd = create_fd(group, event, file);
 131                 if (metadata->fd < 0)
 132                         ret = metadata->fd;
 133         }
 134
 135         return ret;
 136 }
 137
 138 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 139 static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
 140                                                   __s32 fd)
 141 {
 142         struct fanotify_response_event *re, *return_re = NULL;
 143
 144         mutex_lock(&group->fanotify_data.access_mutex);
 145         list_for_each_entry(re, &group->fanotify_data.access_list, list) {
 146                 if (re->fd != fd)
 147                         continue;
 148
 149                 list_del_init(&re->list);
 150                 return_re = re;
 151                 break;
 152         }
 153         mutex_unlock(&group->fanotify_data.access_mutex);
 154
 155         pr_debug("%s: found return_re=%p\n", __func__, return_re);
 156
 157         return return_re;
 158 }
 159
 160 static int process_access_response(struct fsnotify_group *group,
 161                                    struct fanotify_response *response_struct)
 162 {
 163         struct fanotify_response_event *re;
 164         __s32 fd = response_struct->fd;
 165         __u32 response = response_struct->response;
 166
 167         pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
 168                  fd, response);
 169         /*
 170          * make sure the response is valid, if invalid we do nothing and either
 171          * userspace can send a valid response or we will clean it up after the
 172          * timeout
 173          */
 174         switch (response) {
 175         case FAN_ALLOW:
 176         case FAN_DENY:
 177                 break;
 178         default:
 179                 return -EINVAL;
 180         }
 181
 182         if (fd < 0)
 183                 return -EINVAL;
 184
 185         re = dequeue_re(group, fd);
 186         if (!re)
 187                 return -ENOENT;
 188
 189         re->event->response = response;
 190
 191         wake_up(&group->fanotify_data.access_waitq);
 192
 193         kmem_cache_free(fanotify_response_event_cache, re);
 194
 195         return 0;
 196 }
 197
 198 static int prepare_for_access_response(struct fsnotify_group *group,
 199                                        struct fsnotify_event *event,
 200                                        __s32 fd)
 201 {
 202         struct fanotify_response_event *re;
 203
 204         if (!(event->mask & FAN_ALL_PERM_EVENTS))
 205                 return 0;
 206
 207         re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
 208         if (!re)
 209                 return -ENOMEM;
 210
 211         re->event = event;
 212         re->fd = fd;
 213
 214         mutex_lock(&group->fanotify_data.access_mutex);
 215
 216         if (atomic_read(&group->fanotify_data.bypass_perm)) {
 217                 mutex_unlock(&group->fanotify_data.access_mutex);
 218                 kmem_cache_free(fanotify_response_event_cache, re);
 219                 event->response = FAN_ALLOW;
 220                 return 0;
 221         }
 222
 223         list_add_tail(&re->list, &group->fanotify_data.access_list);
 224         mutex_unlock(&group->fanotify_data.access_mutex);
 225
 226         return 0;
 227 }
 228
 229 #else
 230 static int prepare_for_access_response(struct fsnotify_group *group,
 231                                        struct fsnotify_event *event,
 232                                        __s32 fd)
 233 {
 234         return 0;
 235 }
 236
 237 #endif
 238
 239 static ssize_t copy_event_to_user(struct fsnotify_group *group,
 240                                   struct fsnotify_event *event,
 241                                   char __user *buf)
 242 {
 243         struct fanotify_event_metadata fanotify_event_metadata;
 244         struct file *f;
 245         int fd, ret;
 246
 247         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 248
 249         ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
 250         if (ret < 0)
 251                 goto out;
 252
 253         fd = fanotify_event_metadata.fd;
 254         ret = -EFAULT;
 255         if (copy_to_user(buf, &fanotify_event_metadata,
 256                          fanotify_event_metadata.event_len))
 257                 goto out_close_fd;
 258
 259         ret = prepare_for_access_response(group, event, fd);
 260         if (ret)
 261                 goto out_close_fd;
 262
 263         if (fd != FAN_NOFD)
 264                 fd_install(fd, f);
 265         return fanotify_event_metadata.event_len;
 266
 267 out_close_fd:
 268         if (fd != FAN_NOFD) {
 269                 put_unused_fd(fd);
 270                 fput(f);
 271         }
 272 out:
 273 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 274         if (event->mask & FAN_ALL_PERM_EVENTS) {
 275                 event->response = FAN_DENY;
 276                 wake_up(&group->fanotify_data.access_waitq);
 277         }
 278 #endif
 279         return ret;
 280 }
 281
 282 /* intofiy userspace file descriptor functions */
 283 static unsigned int fanotify_poll(struct file *file, poll_table *wait)
 284 {
 285         struct fsnotify_group *group = file->private_data;
 286         int ret = 0;
 287
 288         poll_wait(file, &group->notification_waitq, wait);
 289         mutex_lock(&group->notification_mutex);
 290         if (!fsnotify_notify_queue_is_empty(group))
 291                 ret = POLLIN | POLLRDNORM;
 292         mutex_unlock(&group->notification_mutex);
 293
 294         return ret;
 295 }
 296
 297 static ssize_t fanotify_read(struct file *file, char __user *buf,
 298                              size_t count, loff_t *pos)
 299 {
 300         struct fsnotify_group *group;
 301         struct fsnotify_event *kevent;
 302         char __user *start;
 303         int ret;
 304         DEFINE_WAIT(wait);
 305
 306         start = buf;
 307         group = file->private_data;
 308
 309         pr_debug("%s: group=%p\n", __func__, group);
 310
 311         while (1) {
 312                 prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
 313
 314                 mutex_lock(&group->notification_mutex);
 315                 kevent = get_one_event(group, count);
 316                 mutex_unlock(&group->notification_mutex);
 317
 318                 if (kevent) {
 319                         ret = PTR_ERR(kevent);
 320                         if (IS_ERR(kevent))
 321                                 break;
 322                         ret = copy_event_to_user(group, kevent, buf);
 323                         fsnotify_put_event(kevent);
 324                         if (ret < 0)
 325                                 break;
 326                         buf += ret;
 327                         count -= ret;
 328                         continue;
 329                 }
 330
 331                 ret = -EAGAIN;
 332                 if (file->f_flags & O_NONBLOCK)
 333                         break;
 334                 ret = -ERESTARTSYS;
 335                 if (signal_pending(current))
 336                         break;
 337
 338                 if (start != buf)
 339                         break;
 340
 341                 schedule();
 342         }
 343
 344         finish_wait(&group->notification_waitq, &wait);
 345         if (start != buf && ret != -EFAULT)
 346                 ret = buf - start;
 347         return ret;
 348 }
 349
 350 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 351 {
 352 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 353         struct fanotify_response response = { .fd = -1, .response = -1 };
 354         struct fsnotify_group *group;
 355         int ret;
 356
 357         group = file->private_data;
 358
 359         if (count > sizeof(response))
 360                 count = sizeof(response);
 361
 362         pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
 363
 364         if (copy_from_user(&response, buf, count))
 365                 return -EFAULT;
 366
 367         ret = process_access_response(group, &response);
 368         if (ret < 0)
 369                 count = ret;
 370
 371         return count;
 372 #else
 373         return -EINVAL;
 374 #endif
 375 }
 376
 377 static int fanotify_release(struct inode *ignored, struct file *file)
 378 {
 379         struct fsnotify_group *group = file->private_data;
 380
 381 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 382         struct fanotify_response_event *re, *lre;
 383
 384         mutex_lock(&group->fanotify_data.access_mutex);
 385
 386         atomic_inc(&group->fanotify_data.bypass_perm);
 387
 388         list_for_each_entry_safe(re, lre, &group->fanotify_data.access_list, list) {
 389                 pr_debug("%s: found group=%p re=%p event=%p\n", __func__, group,
 390                          re, re->event);
 391
 392                 list_del_init(&re->list);
 393                 re->event->response = FAN_ALLOW;
 394
 395                 kmem_cache_free(fanotify_response_event_cache, re);
 396         }
 397         mutex_unlock(&group->fanotify_data.access_mutex);
 398
 399         wake_up(&group->fanotify_data.access_waitq);
 400 #endif
 401
 402         if (file->f_flags & FASYNC)
 403                 fsnotify_fasync(-1, file, 0);
 404
 405         /* matches the fanotify_init->fsnotify_alloc_group */
 406         fsnotify_destroy_group(group);
 407
 408         return 0;
 409 }
 410
 411 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 412 {
 413         struct fsnotify_group *group;
 414         struct fsnotify_event_holder *holder;
 415         void __user *p;
 416         int ret = -ENOTTY;
 417         size_t send_len = 0;
 418
 419         group = file->private_data;
 420
 421         p = (void __user *) arg;
 422
 423         switch (cmd) {
 424         case FIONREAD:
 425                 mutex_lock(&group->notification_mutex);
 426                 list_for_each_entry(holder, &group->notification_list, event_list)
 427                         send_len += FAN_EVENT_METADATA_LEN;
 428                 mutex_unlock(&group->notification_mutex);
 429                 ret = put_user(send_len, (int __user *) p);
 430                 break;
 431         }
 432
 433         return ret;
 434 }
 435
 436 static const struct file_operations fanotify_fops = {
 437         .show_fdinfo    = fanotify_show_fdinfo,
 438         .poll           = fanotify_poll,
 439         .read           = fanotify_read,
 440         .write          = fanotify_write,
 441         .fasync         = NULL,
 442         .release        = fanotify_release,
 443         .unlocked_ioctl = fanotify_ioctl,
 444         .compat_ioctl   = fanotify_ioctl,
 445         .llseek         = noop_llseek,
 446 };
 447
 448 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
 449 {
 450         kmem_cache_free(fanotify_mark_cache, fsn_mark);
 451 }
 452
 453 static int fanotify_find_path(int dfd, const char __user *filename,
 454                               struct path *path, unsigned int flags)
 455 {
 456         int ret;
 457
 458         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
 459                  dfd, filename, flags);
 460
 461         if (filename == NULL) {
 462                 struct fd f = fdget(dfd);
 463
 464                 ret = -EBADF;
 465                 if (!f.file)
 466                         goto out;
 467
 468                 ret = -ENOTDIR;
 469                 if ((flags & FAN_MARK_ONLYDIR) &&
 470                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
 471                         fdput(f);
 472                         goto out;
 473                 }
 474
 475                 *path = f.file->f_path;
 476                 path_get(path);
 477                 fdput(f);
 478         } else {
 479                 unsigned int lookup_flags = 0;
 480
 481                 if (!(flags & FAN_MARK_DONT_FOLLOW))
 482                         lookup_flags |= LOOKUP_FOLLOW;
 483                 if (flags & FAN_MARK_ONLYDIR)
 484                         lookup_flags |= LOOKUP_DIRECTORY;
 485
 486                 ret = user_path_at(dfd, filename, lookup_flags, path);
 487                 if (ret)
 488                         goto out;
 489         }
 490
 491         /* you can only watch an inode if you have read permissions on it */
 492         ret = inode_permission(path->dentry->d_inode, MAY_READ);
 493         if (ret)
 494                 path_put(path);
 495 out:
 496         return ret;
 497 }
 498
 499 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 500                                             __u32 mask,
 501                                             unsigned int flags,
 502                                             int *destroy)
 503 {
 504         __u32 oldmask;
 505
 506         spin_lock(&fsn_mark->lock);
 507         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 508                 oldmask = fsn_mark->mask;
 509                 fsnotify_set_mark_mask_locked(fsn_mark, (oldmask & ~mask));
 510         } else {
 511                 oldmask = fsn_mark->ignored_mask;
 512                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, (oldmask & ~mask));
 513         }
 514         spin_unlock(&fsn_mark->lock);
 515
 516         *destroy = !(oldmask & ~mask);
 517
 518         return mask & oldmask;
 519 }
 520
 521 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
 522                                          struct vfsmount *mnt, __u32 mask,
 523                                          unsigned int flags)
 524 {
 525         struct fsnotify_mark *fsn_mark = NULL;
 526         __u32 removed;
 527         int destroy_mark;
 528
 529         fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
 530         if (!fsn_mark)
 531                 return -ENOENT;
 532
 533         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 534                                                  &destroy_mark);
 535         if (destroy_mark)
 536                 fsnotify_destroy_mark(fsn_mark, group);
 537
 538         fsnotify_put_mark(fsn_mark);
 539         if (removed & real_mount(mnt)->mnt_fsnotify_mask)
 540                 fsnotify_recalc_vfsmount_mask(mnt);
 541
 542         return 0;
 543 }
 544
 545 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
 546                                       struct inode *inode, __u32 mask,
 547                                       unsigned int flags)
 548 {
 549         struct fsnotify_mark *fsn_mark = NULL;
 550         __u32 removed;
 551         int destroy_mark;
 552
 553         fsn_mark = fsnotify_find_inode_mark(group, inode);
 554         if (!fsn_mark)
 555                 return -ENOENT;
 556
 557         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 558                                                  &destroy_mark);
 559         if (destroy_mark)
 560                 fsnotify_destroy_mark(fsn_mark, group);
 561         /* matches the fsnotify_find_inode_mark() */
 562         fsnotify_put_mark(fsn_mark);
 563         if (removed & inode->i_fsnotify_mask)
 564                 fsnotify_recalc_inode_mask(inode);
 565
 566         return 0;
 567 }
 568
 569 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 570                                        __u32 mask,
 571                                        unsigned int flags)
 572 {
 573         __u32 oldmask = -1;
 574
 575         spin_lock(&fsn_mark->lock);
 576         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 577                 oldmask = fsn_mark->mask;
 578                 fsnotify_set_mark_mask_locked(fsn_mark, (oldmask | mask));
 579         } else {
 580                 __u32 tmask = fsn_mark->ignored_mask | mask;
 581                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
 582                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
 583                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 584         }
 585
 586         if (!(flags & FAN_MARK_ONDIR)) {
 587                 __u32 tmask = fsn_mark->ignored_mask | FAN_ONDIR;
 588                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
 589         }
 590
 591         spin_unlock(&fsn_mark->lock);
 592
 593         return mask & ~oldmask;
 594 }
 595
 596 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
 597                                       struct vfsmount *mnt, __u32 mask,
 598                                       unsigned int flags)
 599 {
 600         struct fsnotify_mark *fsn_mark;
 601         __u32 added;
 602         int ret = 0;
 603
 604         fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
 605         if (!fsn_mark) {
 606                 if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 607                         return -ENOSPC;
 608
 609                 fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 610                 if (!fsn_mark)
 611                         return -ENOMEM;
 612
 613                 fsnotify_init_mark(fsn_mark, fanotify_free_mark);
 614                 ret = fsnotify_add_mark(fsn_mark, group, NULL, mnt, 0);
 615                 if (ret)
 616                         goto err;
 617         }
 618         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 619
 620         if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
 621                 fsnotify_recalc_vfsmount_mask(mnt);
 622 err:
 623         fsnotify_put_mark(fsn_mark);
 624         return ret;
 625 }
 626
 627 static int fanotify_add_inode_mark(struct fsnotify_group *group,
 628                                    struct inode *inode, __u32 mask,
 629                                    unsigned int flags)
 630 {
 631         struct fsnotify_mark *fsn_mark;
 632         __u32 added;
 633         int ret = 0;
 634
 635         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 636
 637         /*
 638          * If some other task has this inode open for write we should not add
 639          * an ignored mark, unless that ignored mark is supposed to survive
 640          * modification changes anyway.
 641          */
 642         if ((flags & FAN_MARK_IGNORED_MASK) &&
 643             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 644             (atomic_read(&inode->i_writecount) > 0))
 645                 return 0;
 646
 647         fsn_mark = fsnotify_find_inode_mark(group, inode);
 648         if (!fsn_mark) {
 649                 if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 650                         return -ENOSPC;
 651
 652                 fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 653                 if (!fsn_mark)
 654                         return -ENOMEM;
 655
 656                 fsnotify_init_mark(fsn_mark, fanotify_free_mark);
 657                 ret = fsnotify_add_mark(fsn_mark, group, inode, NULL, 0);
 658                 if (ret)
 659                         goto err;
 660         }
 661         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 662
 663         if (added & ~inode->i_fsnotify_mask)
 664                 fsnotify_recalc_inode_mask(inode);
 665 err:
 666         fsnotify_put_mark(fsn_mark);
 667         return ret;
 668 }
 669
 670 /* fanotify syscalls */
 671 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 672 {
 673         struct fsnotify_group *group;
 674         int f_flags, fd;
 675         struct user_struct *user;
 676
 677         pr_debug("%s: flags=%d event_f_flags=%d\n",
 678                 __func__, flags, event_f_flags);
 679
 680         if (!capable(CAP_SYS_ADMIN))
 681                 return -EPERM;
 682
 683         if (flags & ~FAN_ALL_INIT_FLAGS)
 684                 return -EINVAL;
 685
 686         user = get_current_user();
 687         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
 688                 free_uid(user);
 689                 return -EMFILE;
 690         }
 691
 692         f_flags = O_RDWR | FMODE_NONOTIFY;
 693         if (flags & FAN_CLOEXEC)
 694                 f_flags |= O_CLOEXEC;
 695         if (flags & FAN_NONBLOCK)
 696                 f_flags |= O_NONBLOCK;
 697
 698         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
 699         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
 700         if (IS_ERR(group)) {
 701                 free_uid(user);
 702                 return PTR_ERR(group);
 703         }
 704
 705         group->fanotify_data.user = user;
 706         atomic_inc(&user->fanotify_listeners);
 707
 708         group->fanotify_data.f_flags = event_f_flags;
 709 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 710         mutex_init(&group->fanotify_data.access_mutex);
 711         init_waitqueue_head(&group->fanotify_data.access_waitq);
 712         INIT_LIST_HEAD(&group->fanotify_data.access_list);
 713         atomic_set(&group->fanotify_data.bypass_perm, 0);
 714 #endif
 715         switch (flags & FAN_ALL_CLASS_BITS) {
 716         case FAN_CLASS_NOTIF:
 717                 group->priority = FS_PRIO_0;
 718                 break;
 719         case FAN_CLASS_CONTENT:
 720                 group->priority = FS_PRIO_1;
 721                 break;
 722         case FAN_CLASS_PRE_CONTENT:
 723                 group->priority = FS_PRIO_2;
 724                 break;
 725         default:
 726                 fd = -EINVAL;
 727                 goto out_destroy_group;
 728         }
 729
 730         if (flags & FAN_UNLIMITED_QUEUE) {
 731                 fd = -EPERM;
 732                 if (!capable(CAP_SYS_ADMIN))
 733                         goto out_destroy_group;
 734                 group->max_events = UINT_MAX;
 735         } else {
 736                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 737         }
 738
 739         if (flags & FAN_UNLIMITED_MARKS) {
 740                 fd = -EPERM;
 741                 if (!capable(CAP_SYS_ADMIN))
 742                         goto out_destroy_group;
 743                 group->fanotify_data.max_marks = UINT_MAX;
 744         } else {
 745                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
 746         }
 747
 748         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 749         if (fd < 0)
 750                 goto out_destroy_group;
 751
 752         return fd;
 753
 754 out_destroy_group:
 755         fsnotify_destroy_group(group);
 756         return fd;
 757 }
 758
 759 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
 760                               __u64, mask, int, dfd,
 761                               const char  __user *, pathname)
 762 {
 763         struct inode *inode = NULL;
 764         struct vfsmount *mnt = NULL;
 765         struct fsnotify_group *group;
 766         struct fd f;
 767         struct path path;
 768         int ret;
 769
 770         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
 771                  __func__, fanotify_fd, flags, dfd, pathname, mask);
 772
 773         /* we only use the lower 32 bits as of right now. */
 774         if (mask & ((__u64)0xffffffff << 32))
 775                 return -EINVAL;
 776
 777         if (flags & ~FAN_ALL_MARK_FLAGS)
 778                 return -EINVAL;
 779         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 780         case FAN_MARK_ADD:              /* fallthrough */
 781         case FAN_MARK_REMOVE:
 782                 if (!mask)
 783                         return -EINVAL;
 784         case FAN_MARK_FLUSH:
 785                 break;
 786         default:
 787                 return -EINVAL;
 788         }
 789
 790         if (mask & FAN_ONDIR) {
 791                 flags |= FAN_MARK_ONDIR;
 792                 mask &= ~FAN_ONDIR;
 793         }
 794
 795 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 796         if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
 797 #else
 798         if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
 799 #endif
 800                 return -EINVAL;
 801
 802         f = fdget(fanotify_fd);
 803         if (unlikely(!f.file))
 804                 return -EBADF;
 805
 806         /* verify that this is indeed an fanotify instance */
 807         ret = -EINVAL;
 808         if (unlikely(f.file->f_op != &fanotify_fops))
 809                 goto fput_and_out;
 810         group = f.file->private_data;
 811
 812         /*
 813          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
 814          * allowed to set permissions events.
 815          */
 816         ret = -EINVAL;
 817         if (mask & FAN_ALL_PERM_EVENTS &&
 818             group->priority == FS_PRIO_0)
 819                 goto fput_and_out;
 820
 821         ret = fanotify_find_path(dfd, pathname, &path, flags);
 822         if (ret)
 823                 goto fput_and_out;
 824
 825         /* inode held in place by reference to path; group by fget on fd */
 826         if (!(flags & FAN_MARK_MOUNT))
 827                 inode = path.dentry->d_inode;
 828         else
 829                 mnt = path.mnt;
 830
 831         /* create/update an inode mark */
 832         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 833         case FAN_MARK_ADD:
 834                 if (flags & FAN_MARK_MOUNT)
 835                         ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
 836                 else
 837                         ret = fanotify_add_inode_mark(group, inode, mask, flags);
 838                 break;
 839         case FAN_MARK_REMOVE:
 840                 if (flags & FAN_MARK_MOUNT)
 841                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
 842                 else
 843                         ret = fanotify_remove_inode_mark(group, inode, mask, flags);
 844                 break;
 845         case FAN_MARK_FLUSH:
 846                 if (flags & FAN_MARK_MOUNT)
 847                         fsnotify_clear_vfsmount_marks_by_group(group);
 848                 else
 849                         fsnotify_clear_inode_marks_by_group(group);
 850                 break;
 851         default:
 852                 ret = -EINVAL;
 853         }
 854
 855         path_put(&path);
 856 fput_and_out:
 857         fdput(f);
 858         return ret;
 859 }
 860
 861 #ifdef CONFIG_COMPAT
 862 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
 863                                 int, fanotify_fd, unsigned int, flags,
 864                                 __u32, mask0, __u32, mask1, int, dfd,
 865                                 const char  __user *, pathname)
 866 {
 867         return sys_fanotify_mark(fanotify_fd, flags,
 868 #ifdef __BIG_ENDIAN
 869                                 ((__u64)mask1 << 32) | mask0,
 870 #else
 871                                 ((__u64)mask0 << 32) | mask1,
 872 #endif
 873                                  dfd, pathname);
 874 }
 875 #endif
 876
 877 /*
 878  * fanotify_user_setup - Our initialization function.  Note that we cannot return
 879  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
 880  * must result in panic().
 881  */
 882 static int __init fanotify_user_setup(void)
 883 {
 884         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
 885         fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
 886                                                    SLAB_PANIC);
 887
 888         return 0;
 889 }
 890 device_initcall(fanotify_user_setup);