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 #include "fanotify.h"
  23
  24 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
  25 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
  26 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
  27
  28 /*
  29  * All flags that may be specified in parameter event_f_flags of fanotify_init.
  30  *
  31  * Internal and external open flags are stored together in field f_flags of
  32  * struct file. Only external open flags shall be allowed in event_f_flags.
  33  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
  34  * excluded.
  35  */
  36 #define FANOTIFY_INIT_ALL_EVENT_F_BITS                          ( \
  37                 O_ACCMODE       | O_APPEND      | O_NONBLOCK    | \
  38                 __O_SYNC        | O_DSYNC       | O_CLOEXEC     | \
  39                 O_LARGEFILE     | O_NOATIME     )
  40
  41 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  42
  43 static struct kmem_cache *fanotify_mark_cache __read_mostly;
  44 struct kmem_cache *fanotify_event_cachep __read_mostly;
  45 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
  46
  47 /*
  48  * Get an fsnotify notification event if one exists and is small
  49  * enough to fit in "count". Return an error pointer if the count
  50  * is not large enough.
  51  *
  52  * Called with the group->notification_mutex held.
  53  */
  54 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  55                                             size_t count)
  56 {
  57         BUG_ON(!mutex_is_locked(&group->notification_mutex));
  58
  59         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  60
  61         if (fsnotify_notify_queue_is_empty(group))
  62                 return NULL;
  63
  64         if (FAN_EVENT_METADATA_LEN > count)
  65                 return ERR_PTR(-EINVAL);
  66
  67         /* held the notification_mutex the whole time, so this is the
  68          * same event we peeked above */
  69         return fsnotify_remove_first_event(group);
  70 }
  71
  72 static int create_fd(struct fsnotify_group *group,
  73                      struct fanotify_event_info *event,
  74                      struct file **file)
  75 {
  76         int client_fd;
  77         struct file *new_file;
  78
  79         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  80
  81         client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
  82         if (client_fd < 0)
  83                 return client_fd;
  84
  85         /*
  86          * we need a new file handle for the userspace program so it can read even if it was
  87          * originally opened O_WRONLY.
  88          */
  89         /* it's possible this event was an overflow event.  in that case dentry and mnt
  90          * are NULL;  That's fine, just don't call dentry open */
  91         if (event->path.dentry && event->path.mnt)
  92                 new_file = dentry_open(&event->path,
  93                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
  94                                        current_cred());
  95         else
  96                 new_file = ERR_PTR(-EOVERFLOW);
  97         if (IS_ERR(new_file)) {
  98                 /*
  99                  * we still send an event even if we can't open the file.  this
 100                  * can happen when say tasks are gone and we try to open their
 101                  * /proc files or we try to open a WRONLY file like in sysfs
 102                  * we just send the errno to userspace since there isn't much
 103                  * else we can do.
 104                  */
 105                 put_unused_fd(client_fd);
 106                 client_fd = PTR_ERR(new_file);
 107         } else {
 108                 *file = new_file;
 109         }
 110
 111         return client_fd;
 112 }
 113
 114 static int fill_event_metadata(struct fsnotify_group *group,
 115                                struct fanotify_event_metadata *metadata,
 116                                struct fsnotify_event *fsn_event,
 117                                struct file **file)
 118 {
 119         int ret = 0;
 120         struct fanotify_event_info *event;
 121
 122         pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
 123                  group, metadata, fsn_event);
 124
 125         *file = NULL;
 126         event = container_of(fsn_event, struct fanotify_event_info, fse);
 127         metadata->event_len = FAN_EVENT_METADATA_LEN;
 128         metadata->metadata_len = FAN_EVENT_METADATA_LEN;
 129         metadata->vers = FANOTIFY_METADATA_VERSION;
 130         metadata->reserved = 0;
 131         metadata->mask = fsn_event->mask & FAN_ALL_OUTGOING_EVENTS;
 132         metadata->pid = pid_vnr(event->tgid);
 133         if (unlikely(fsn_event->mask & FAN_Q_OVERFLOW))
 134                 metadata->fd = FAN_NOFD;
 135         else {
 136                 metadata->fd = create_fd(group, event, file);
 137                 if (metadata->fd < 0)
 138                         ret = metadata->fd;
 139         }
 140
 141         return ret;
 142 }
 143
 144 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 145 static struct fanotify_perm_event_info *dequeue_event(
 146                                 struct fsnotify_group *group, int fd)
 147 {
 148         struct fanotify_perm_event_info *event, *return_e = NULL;
 149
 150         spin_lock(&group->fanotify_data.access_lock);
 151         list_for_each_entry(event, &group->fanotify_data.access_list,
 152                             fae.fse.list) {
 153                 if (event->fd != fd)
 154                         continue;
 155
 156                 list_del_init(&event->fae.fse.list);
 157                 return_e = event;
 158                 break;
 159         }
 160         spin_unlock(&group->fanotify_data.access_lock);
 161
 162         pr_debug("%s: found return_re=%p\n", __func__, return_e);
 163
 164         return return_e;
 165 }
 166
 167 static int process_access_response(struct fsnotify_group *group,
 168                                    struct fanotify_response *response_struct)
 169 {
 170         struct fanotify_perm_event_info *event;
 171         int fd = response_struct->fd;
 172         int response = response_struct->response;
 173
 174         pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
 175                  fd, response);
 176         /*
 177          * make sure the response is valid, if invalid we do nothing and either
 178          * userspace can send a valid response or we will clean it up after the
 179          * timeout
 180          */
 181         switch (response) {
 182         case FAN_ALLOW:
 183         case FAN_DENY:
 184                 break;
 185         default:
 186                 return -EINVAL;
 187         }
 188
 189         if (fd < 0)
 190                 return -EINVAL;
 191
 192         event = dequeue_event(group, fd);
 193         if (!event)
 194                 return -ENOENT;
 195
 196         event->response = response;
 197         wake_up(&group->fanotify_data.access_waitq);
 198
 199         return 0;
 200 }
 201 #endif
 202
 203 static ssize_t copy_event_to_user(struct fsnotify_group *group,
 204                                   struct fsnotify_event *event,
 205                                   char __user *buf)
 206 {
 207         struct fanotify_event_metadata fanotify_event_metadata;
 208         struct file *f;
 209         int fd, ret;
 210
 211         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 212
 213         ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
 214         if (ret < 0)
 215                 return ret;
 216
 217         fd = fanotify_event_metadata.fd;
 218         ret = -EFAULT;
 219         if (copy_to_user(buf, &fanotify_event_metadata,
 220                          fanotify_event_metadata.event_len))
 221                 goto out_close_fd;
 222
 223 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 224         if (event->mask & FAN_ALL_PERM_EVENTS)
 225                 FANOTIFY_PE(event)->fd = fd;
 226 #endif
 227
 228         if (fd != FAN_NOFD)
 229                 fd_install(fd, f);
 230         return fanotify_event_metadata.event_len;
 231
 232 out_close_fd:
 233         if (fd != FAN_NOFD) {
 234                 put_unused_fd(fd);
 235                 fput(f);
 236         }
 237         return ret;
 238 }
 239
 240 /* intofiy userspace file descriptor functions */
 241 static unsigned int fanotify_poll(struct file *file, poll_table *wait)
 242 {
 243         struct fsnotify_group *group = file->private_data;
 244         int ret = 0;
 245
 246         poll_wait(file, &group->notification_waitq, wait);
 247         mutex_lock(&group->notification_mutex);
 248         if (!fsnotify_notify_queue_is_empty(group))
 249                 ret = POLLIN | POLLRDNORM;
 250         mutex_unlock(&group->notification_mutex);
 251
 252         return ret;
 253 }
 254
 255 static ssize_t fanotify_read(struct file *file, char __user *buf,
 256                              size_t count, loff_t *pos)
 257 {
 258         struct fsnotify_group *group;
 259         struct fsnotify_event *kevent;
 260         char __user *start;
 261         int ret;
 262         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 263
 264         start = buf;
 265         group = file->private_data;
 266
 267         pr_debug("%s: group=%p\n", __func__, group);
 268
 269         add_wait_queue(&group->notification_waitq, &wait);
 270         while (1) {
 271                 mutex_lock(&group->notification_mutex);
 272                 kevent = get_one_event(group, count);
 273                 mutex_unlock(&group->notification_mutex);
 274
 275                 if (IS_ERR(kevent)) {
 276                         ret = PTR_ERR(kevent);
 277                         break;
 278                 }
 279
 280                 if (!kevent) {
 281                         ret = -EAGAIN;
 282                         if (file->f_flags & O_NONBLOCK)
 283                                 break;
 284
 285                         ret = -ERESTARTSYS;
 286                         if (signal_pending(current))
 287                                 break;
 288
 289                         if (start != buf)
 290                                 break;
 291
 292                         wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 293                         continue;
 294                 }
 295
 296                 ret = copy_event_to_user(group, kevent, buf);
 297                 /*
 298                  * Permission events get queued to wait for response.  Other
 299                  * events can be destroyed now.
 300                  */
 301                 if (!(kevent->mask & FAN_ALL_PERM_EVENTS)) {
 302                         fsnotify_destroy_event(group, kevent);
 303                         if (ret < 0)
 304                                 break;
 305                 } else {
 306 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 307                         if (ret < 0) {
 308                                 FANOTIFY_PE(kevent)->response = FAN_DENY;
 309                                 wake_up(&group->fanotify_data.access_waitq);
 310                                 break;
 311                         }
 312                         spin_lock(&group->fanotify_data.access_lock);
 313                         list_add_tail(&kevent->list,
 314                                       &group->fanotify_data.access_list);
 315                         spin_unlock(&group->fanotify_data.access_lock);
 316 #endif
 317                 }
 318                 buf += ret;
 319                 count -= ret;
 320         }
 321         remove_wait_queue(&group->notification_waitq, &wait);
 322
 323         if (start != buf && ret != -EFAULT)
 324                 ret = buf - start;
 325         return ret;
 326 }
 327
 328 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 329 {
 330 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 331         struct fanotify_response response = { .fd = -1, .response = -1 };
 332         struct fsnotify_group *group;
 333         int ret;
 334
 335         group = file->private_data;
 336
 337         if (count > sizeof(response))
 338                 count = sizeof(response);
 339
 340         pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
 341
 342         if (copy_from_user(&response, buf, count))
 343                 return -EFAULT;
 344
 345         ret = process_access_response(group, &response);
 346         if (ret < 0)
 347                 count = ret;
 348
 349         return count;
 350 #else
 351         return -EINVAL;
 352 #endif
 353 }
 354
 355 static int fanotify_release(struct inode *ignored, struct file *file)
 356 {
 357         struct fsnotify_group *group = file->private_data;
 358
 359 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 360         struct fanotify_perm_event_info *event, *next;
 361
 362         /*
 363          * There may be still new events arriving in the notification queue
 364          * but since userspace cannot use fanotify fd anymore, no event can
 365          * enter or leave access_list by now.
 366          */
 367         spin_lock(&group->fanotify_data.access_lock);
 368
 369         atomic_inc(&group->fanotify_data.bypass_perm);
 370
 371         list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
 372                                  fae.fse.list) {
 373                 pr_debug("%s: found group=%p event=%p\n", __func__, group,
 374                          event);
 375
 376                 list_del_init(&event->fae.fse.list);
 377                 event->response = FAN_ALLOW;
 378         }
 379         spin_unlock(&group->fanotify_data.access_lock);
 380
 381         /*
 382          * Since bypass_perm is set, newly queued events will not wait for
 383          * access response. Wake up the already sleeping ones now.
 384          * synchronize_srcu() in fsnotify_destroy_group() will wait for all
 385          * processes sleeping in fanotify_handle_event() waiting for access
 386          * response and thus also for all permission events to be freed.
 387          */
 388         wake_up(&group->fanotify_data.access_waitq);
 389 #endif
 390
 391         /* matches the fanotify_init->fsnotify_alloc_group */
 392         fsnotify_destroy_group(group);
 393
 394         return 0;
 395 }
 396
 397 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 398 {
 399         struct fsnotify_group *group;
 400         struct fsnotify_event *fsn_event;
 401         void __user *p;
 402         int ret = -ENOTTY;
 403         size_t send_len = 0;
 404
 405         group = file->private_data;
 406
 407         p = (void __user *) arg;
 408
 409         switch (cmd) {
 410         case FIONREAD:
 411                 mutex_lock(&group->notification_mutex);
 412                 list_for_each_entry(fsn_event, &group->notification_list, list)
 413                         send_len += FAN_EVENT_METADATA_LEN;
 414                 mutex_unlock(&group->notification_mutex);
 415                 ret = put_user(send_len, (int __user *) p);
 416                 break;
 417         }
 418
 419         return ret;
 420 }
 421
 422 static const struct file_operations fanotify_fops = {
 423         .show_fdinfo    = fanotify_show_fdinfo,
 424         .poll           = fanotify_poll,
 425         .read           = fanotify_read,
 426         .write          = fanotify_write,
 427         .fasync         = NULL,
 428         .release        = fanotify_release,
 429         .unlocked_ioctl = fanotify_ioctl,
 430         .compat_ioctl   = fanotify_ioctl,
 431         .llseek         = noop_llseek,
 432 };
 433
 434 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
 435 {
 436         kmem_cache_free(fanotify_mark_cache, fsn_mark);
 437 }
 438
 439 static int fanotify_find_path(int dfd, const char __user *filename,
 440                               struct path *path, unsigned int flags)
 441 {
 442         int ret;
 443
 444         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
 445                  dfd, filename, flags);
 446
 447         if (filename == NULL) {
 448                 struct fd f = fdget(dfd);
 449
 450                 ret = -EBADF;
 451                 if (!f.file)
 452                         goto out;
 453
 454                 ret = -ENOTDIR;
 455                 if ((flags & FAN_MARK_ONLYDIR) &&
 456                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
 457                         fdput(f);
 458                         goto out;
 459                 }
 460
 461                 *path = f.file->f_path;
 462                 path_get(path);
 463                 fdput(f);
 464         } else {
 465                 unsigned int lookup_flags = 0;
 466
 467                 if (!(flags & FAN_MARK_DONT_FOLLOW))
 468                         lookup_flags |= LOOKUP_FOLLOW;
 469                 if (flags & FAN_MARK_ONLYDIR)
 470                         lookup_flags |= LOOKUP_DIRECTORY;
 471
 472                 ret = user_path_at(dfd, filename, lookup_flags, path);
 473                 if (ret)
 474                         goto out;
 475         }
 476
 477         /* you can only watch an inode if you have read permissions on it */
 478         ret = inode_permission(path->dentry->d_inode, MAY_READ);
 479         if (ret)
 480                 path_put(path);
 481 out:
 482         return ret;
 483 }
 484
 485 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 486                                             __u32 mask,
 487                                             unsigned int flags,
 488                                             int *destroy)
 489 {
 490         __u32 oldmask = 0;
 491
 492         spin_lock(&fsn_mark->lock);
 493         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 494                 __u32 tmask = fsn_mark->mask & ~mask;
 495
 496                 if (flags & FAN_MARK_ONDIR)
 497                         tmask &= ~FAN_ONDIR;
 498
 499                 oldmask = fsn_mark->mask;
 500                 fsnotify_set_mark_mask_locked(fsn_mark, tmask);
 501         } else {
 502                 __u32 tmask = fsn_mark->ignored_mask & ~mask;
 503                 if (flags & FAN_MARK_ONDIR)
 504                         tmask &= ~FAN_ONDIR;
 505
 506                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
 507         }
 508         *destroy = !(fsn_mark->mask | fsn_mark->ignored_mask);
 509         spin_unlock(&fsn_mark->lock);
 510
 511         return mask & oldmask;
 512 }
 513
 514 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
 515                                          struct vfsmount *mnt, __u32 mask,
 516                                          unsigned int flags)
 517 {
 518         struct fsnotify_mark *fsn_mark = NULL;
 519         __u32 removed;
 520         int destroy_mark;
 521
 522         mutex_lock(&group->mark_mutex);
 523         fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
 524         if (!fsn_mark) {
 525                 mutex_unlock(&group->mark_mutex);
 526                 return -ENOENT;
 527         }
 528
 529         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 530                                                  &destroy_mark);
 531         if (destroy_mark)
 532                 fsnotify_detach_mark(fsn_mark);
 533         mutex_unlock(&group->mark_mutex);
 534         if (destroy_mark)
 535                 fsnotify_free_mark(fsn_mark);
 536
 537         fsnotify_put_mark(fsn_mark);
 538         if (removed & real_mount(mnt)->mnt_fsnotify_mask)
 539                 fsnotify_recalc_vfsmount_mask(mnt);
 540
 541         return 0;
 542 }
 543
 544 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
 545                                       struct inode *inode, __u32 mask,
 546                                       unsigned int flags)
 547 {
 548         struct fsnotify_mark *fsn_mark = NULL;
 549         __u32 removed;
 550         int destroy_mark;
 551
 552         mutex_lock(&group->mark_mutex);
 553         fsn_mark = fsnotify_find_inode_mark(group, inode);
 554         if (!fsn_mark) {
 555                 mutex_unlock(&group->mark_mutex);
 556                 return -ENOENT;
 557         }
 558
 559         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 560                                                  &destroy_mark);
 561         if (destroy_mark)
 562                 fsnotify_detach_mark(fsn_mark);
 563         mutex_unlock(&group->mark_mutex);
 564         if (destroy_mark)
 565                 fsnotify_free_mark(fsn_mark);
 566
 567         /* matches the fsnotify_find_inode_mark() */
 568         fsnotify_put_mark(fsn_mark);
 569         if (removed & inode->i_fsnotify_mask)
 570                 fsnotify_recalc_inode_mask(inode);
 571
 572         return 0;
 573 }
 574
 575 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 576                                        __u32 mask,
 577                                        unsigned int flags)
 578 {
 579         __u32 oldmask = -1;
 580
 581         spin_lock(&fsn_mark->lock);
 582         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 583                 __u32 tmask = fsn_mark->mask | mask;
 584
 585                 if (flags & FAN_MARK_ONDIR)
 586                         tmask |= FAN_ONDIR;
 587
 588                 oldmask = fsn_mark->mask;
 589                 fsnotify_set_mark_mask_locked(fsn_mark, tmask);
 590         } else {
 591                 __u32 tmask = fsn_mark->ignored_mask | mask;
 592                 if (flags & FAN_MARK_ONDIR)
 593                         tmask |= FAN_ONDIR;
 594
 595                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
 596                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
 597                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 598         }
 599         spin_unlock(&fsn_mark->lock);
 600
 601         return mask & ~oldmask;
 602 }
 603
 604 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
 605                                                    struct inode *inode,
 606                                                    struct vfsmount *mnt)
 607 {
 608         struct fsnotify_mark *mark;
 609         int ret;
 610
 611         if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 612                 return ERR_PTR(-ENOSPC);
 613
 614         mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 615         if (!mark)
 616                 return ERR_PTR(-ENOMEM);
 617
 618         fsnotify_init_mark(mark, fanotify_free_mark);
 619         ret = fsnotify_add_mark_locked(mark, group, inode, mnt, 0);
 620         if (ret) {
 621                 fsnotify_put_mark(mark);
 622                 return ERR_PTR(ret);
 623         }
 624
 625         return mark;
 626 }
 627
 628
 629 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
 630                                       struct vfsmount *mnt, __u32 mask,
 631                                       unsigned int flags)
 632 {
 633         struct fsnotify_mark *fsn_mark;
 634         __u32 added;
 635
 636         mutex_lock(&group->mark_mutex);
 637         fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
 638         if (!fsn_mark) {
 639                 fsn_mark = fanotify_add_new_mark(group, NULL, mnt);
 640                 if (IS_ERR(fsn_mark)) {
 641                         mutex_unlock(&group->mark_mutex);
 642                         return PTR_ERR(fsn_mark);
 643                 }
 644         }
 645         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 646         mutex_unlock(&group->mark_mutex);
 647
 648         if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
 649                 fsnotify_recalc_vfsmount_mask(mnt);
 650
 651         fsnotify_put_mark(fsn_mark);
 652         return 0;
 653 }
 654
 655 static int fanotify_add_inode_mark(struct fsnotify_group *group,
 656                                    struct inode *inode, __u32 mask,
 657                                    unsigned int flags)
 658 {
 659         struct fsnotify_mark *fsn_mark;
 660         __u32 added;
 661
 662         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 663
 664         /*
 665          * If some other task has this inode open for write we should not add
 666          * an ignored mark, unless that ignored mark is supposed to survive
 667          * modification changes anyway.
 668          */
 669         if ((flags & FAN_MARK_IGNORED_MASK) &&
 670             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 671             (atomic_read(&inode->i_writecount) > 0))
 672                 return 0;
 673
 674         mutex_lock(&group->mark_mutex);
 675         fsn_mark = fsnotify_find_inode_mark(group, inode);
 676         if (!fsn_mark) {
 677                 fsn_mark = fanotify_add_new_mark(group, inode, NULL);
 678                 if (IS_ERR(fsn_mark)) {
 679                         mutex_unlock(&group->mark_mutex);
 680                         return PTR_ERR(fsn_mark);
 681                 }
 682         }
 683         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 684         mutex_unlock(&group->mark_mutex);
 685
 686         if (added & ~inode->i_fsnotify_mask)
 687                 fsnotify_recalc_inode_mask(inode);
 688
 689         fsnotify_put_mark(fsn_mark);
 690         return 0;
 691 }
 692
 693 /* fanotify syscalls */
 694 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 695 {
 696         struct fsnotify_group *group;
 697         int f_flags, fd;
 698         struct user_struct *user;
 699         struct fanotify_event_info *oevent;
 700
 701         pr_debug("%s: flags=%d event_f_flags=%d\n",
 702                 __func__, flags, event_f_flags);
 703
 704         if (!capable(CAP_SYS_ADMIN))
 705                 return -EPERM;
 706
 707         if (flags & ~FAN_ALL_INIT_FLAGS)
 708                 return -EINVAL;
 709
 710         if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
 711                 return -EINVAL;
 712
 713         switch (event_f_flags & O_ACCMODE) {
 714         case O_RDONLY:
 715         case O_RDWR:
 716         case O_WRONLY:
 717                 break;
 718         default:
 719                 return -EINVAL;
 720         }
 721
 722         user = get_current_user();
 723         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
 724                 free_uid(user);
 725                 return -EMFILE;
 726         }
 727
 728         f_flags = O_RDWR | FMODE_NONOTIFY;
 729         if (flags & FAN_CLOEXEC)
 730                 f_flags |= O_CLOEXEC;
 731         if (flags & FAN_NONBLOCK)
 732                 f_flags |= O_NONBLOCK;
 733
 734         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
 735         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
 736         if (IS_ERR(group)) {
 737                 free_uid(user);
 738                 return PTR_ERR(group);
 739         }
 740
 741         group->fanotify_data.user = user;
 742         atomic_inc(&user->fanotify_listeners);
 743
 744         oevent = fanotify_alloc_event(NULL, FS_Q_OVERFLOW, NULL);
 745         if (unlikely(!oevent)) {
 746                 fd = -ENOMEM;
 747                 goto out_destroy_group;
 748         }
 749         group->overflow_event = &oevent->fse;
 750
 751         if (force_o_largefile())
 752                 event_f_flags |= O_LARGEFILE;
 753         group->fanotify_data.f_flags = event_f_flags;
 754 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 755         spin_lock_init(&group->fanotify_data.access_lock);
 756         init_waitqueue_head(&group->fanotify_data.access_waitq);
 757         INIT_LIST_HEAD(&group->fanotify_data.access_list);
 758         atomic_set(&group->fanotify_data.bypass_perm, 0);
 759 #endif
 760         switch (flags & FAN_ALL_CLASS_BITS) {
 761         case FAN_CLASS_NOTIF:
 762                 group->priority = FS_PRIO_0;
 763                 break;
 764         case FAN_CLASS_CONTENT:
 765                 group->priority = FS_PRIO_1;
 766                 break;
 767         case FAN_CLASS_PRE_CONTENT:
 768                 group->priority = FS_PRIO_2;
 769                 break;
 770         default:
 771                 fd = -EINVAL;
 772                 goto out_destroy_group;
 773         }
 774
 775         if (flags & FAN_UNLIMITED_QUEUE) {
 776                 fd = -EPERM;
 777                 if (!capable(CAP_SYS_ADMIN))
 778                         goto out_destroy_group;
 779                 group->max_events = UINT_MAX;
 780         } else {
 781                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 782         }
 783
 784         if (flags & FAN_UNLIMITED_MARKS) {
 785                 fd = -EPERM;
 786                 if (!capable(CAP_SYS_ADMIN))
 787                         goto out_destroy_group;
 788                 group->fanotify_data.max_marks = UINT_MAX;
 789         } else {
 790                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
 791         }
 792
 793         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 794         if (fd < 0)
 795                 goto out_destroy_group;
 796
 797         return fd;
 798
 799 out_destroy_group:
 800         fsnotify_destroy_group(group);
 801         return fd;
 802 }
 803
 804 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
 805                               __u64, mask, int, dfd,
 806                               const char  __user *, pathname)
 807 {
 808         struct inode *inode = NULL;
 809         struct vfsmount *mnt = NULL;
 810         struct fsnotify_group *group;
 811         struct fd f;
 812         struct path path;
 813         int ret;
 814
 815         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
 816                  __func__, fanotify_fd, flags, dfd, pathname, mask);
 817
 818         /* we only use the lower 32 bits as of right now. */
 819         if (mask & ((__u64)0xffffffff << 32))
 820                 return -EINVAL;
 821
 822         if (flags & ~FAN_ALL_MARK_FLAGS)
 823                 return -EINVAL;
 824         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 825         case FAN_MARK_ADD:              /* fallthrough */
 826         case FAN_MARK_REMOVE:
 827                 if (!mask)
 828                         return -EINVAL;
 829                 break;
 830         case FAN_MARK_FLUSH:
 831                 if (flags & ~(FAN_MARK_MOUNT | FAN_MARK_FLUSH))
 832                         return -EINVAL;
 833                 break;
 834         default:
 835                 return -EINVAL;
 836         }
 837
 838         if (mask & FAN_ONDIR) {
 839                 flags |= FAN_MARK_ONDIR;
 840                 mask &= ~FAN_ONDIR;
 841         }
 842
 843 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 844         if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
 845 #else
 846         if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
 847 #endif
 848                 return -EINVAL;
 849
 850         f = fdget(fanotify_fd);
 851         if (unlikely(!f.file))
 852                 return -EBADF;
 853
 854         /* verify that this is indeed an fanotify instance */
 855         ret = -EINVAL;
 856         if (unlikely(f.file->f_op != &fanotify_fops))
 857                 goto fput_and_out;
 858         group = f.file->private_data;
 859
 860         /*
 861          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
 862          * allowed to set permissions events.
 863          */
 864         ret = -EINVAL;
 865         if (mask & FAN_ALL_PERM_EVENTS &&
 866             group->priority == FS_PRIO_0)
 867                 goto fput_and_out;
 868
 869         if (flags & FAN_MARK_FLUSH) {
 870                 ret = 0;
 871                 if (flags & FAN_MARK_MOUNT)
 872                         fsnotify_clear_vfsmount_marks_by_group(group);
 873                 else
 874                         fsnotify_clear_inode_marks_by_group(group);
 875                 goto fput_and_out;
 876         }
 877
 878         ret = fanotify_find_path(dfd, pathname, &path, flags);
 879         if (ret)
 880                 goto fput_and_out;
 881
 882         /* inode held in place by reference to path; group by fget on fd */
 883         if (!(flags & FAN_MARK_MOUNT))
 884                 inode = path.dentry->d_inode;
 885         else
 886                 mnt = path.mnt;
 887
 888         /* create/update an inode mark */
 889         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
 890         case FAN_MARK_ADD:
 891                 if (flags & FAN_MARK_MOUNT)
 892                         ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
 893                 else
 894                         ret = fanotify_add_inode_mark(group, inode, mask, flags);
 895                 break;
 896         case FAN_MARK_REMOVE:
 897                 if (flags & FAN_MARK_MOUNT)
 898                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
 899                 else
 900                         ret = fanotify_remove_inode_mark(group, inode, mask, flags);
 901                 break;
 902         default:
 903                 ret = -EINVAL;
 904         }
 905
 906         path_put(&path);
 907 fput_and_out:
 908         fdput(f);
 909         return ret;
 910 }
 911
 912 #ifdef CONFIG_COMPAT
 913 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
 914                                 int, fanotify_fd, unsigned int, flags,
 915                                 __u32, mask0, __u32, mask1, int, dfd,
 916                                 const char  __user *, pathname)
 917 {
 918         return sys_fanotify_mark(fanotify_fd, flags,
 919 #ifdef __BIG_ENDIAN
 920                                 ((__u64)mask0 << 32) | mask1,
 921 #else
 922                                 ((__u64)mask1 << 32) | mask0,
 923 #endif
 924                                  dfd, pathname);
 925 }
 926 #endif
 927
 928 /*
 929  * fanotify_user_setup - Our initialization function.  Note that we cannot return
 930  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
 931  * must result in panic().
 932  */
 933 static int __init fanotify_user_setup(void)
 934 {
 935         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
 936         fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC);
 937 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 938         fanotify_perm_event_cachep = KMEM_CACHE(fanotify_perm_event_info,
 939                                                 SLAB_PANIC);
 940 #endif
 941
 942         return 0;
 943 }
 944 device_initcall(fanotify_user_setup);