Merge tag 'fsnotify_for_v5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify updates from Jan Kara:
 "This contains cleanups of the fsnotify name removal hook and also a
  patch to disable fanotify permission events for 'proc' filesystem"

* tag 'fsnotify_for_v5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fsnotify: get rid of fsnotify_nameremove()
  fsnotify: move fsnotify_nameremove() hook out of d_delete()
  configfs: call fsnotify_rmdir() hook
  debugfs: call fsnotify_{unlink,rmdir}() hooks
  debugfs: simplify __debugfs_remove_file()
  devpts: call fsnotify_unlink() hook
  tracefs: call fsnotify_{unlink,rmdir}() hooks
  rpc_pipefs: call fsnotify_{unlink,rmdir}() hooks
  btrfs: call fsnotify_rmdir() hook
  fsnotify: add empty fsnotify_{unlink,rmdir}() hooks
  fanotify: Disallow permission events for proc filesystem

1 files changed, 22 insertions, 0 deletions

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index a90bb19dcfa2..91006f47e420 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -920,6 +920,22 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
 	return 0;
 }
 
+static int fanotify_events_supported(struct path *path, __u64 mask)
+{
+	/*
+	 * Some filesystems such as 'proc' acquire unusual locks when opening
+	 * files. For them fanotify permission events have high chances of
+	 * deadlocking the system - open done when reporting fanotify event
+	 * blocks on this "unusual" lock while another process holding the lock
+	 * waits for fanotify permission event to be answered. Just disallow
+	 * permission events for such filesystems.
+	 */
+	if (mask & FANOTIFY_PERM_EVENTS &&
+	    path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
+		return -EINVAL;
+	return 0;
+}
+
 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 			    int dfd, const char  __user *pathname)
 {
@@ -1018,6 +1034,12 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	if (ret)
 		goto fput_and_out;
 
+	if (flags & FAN_MARK_ADD) {
+		ret = fanotify_events_supported(&path, mask);
+		if (ret)
+			goto path_put_and_out;
+	}
+
 	if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
 		ret = fanotify_test_fid(&path, &__fsid);
 		if (ret)