inotify: Do not drop mark reference under idr_lock

Dropping mark reference can result in mark being freed. Although it
should not happen in inotify_remove_from_idr() since caller should hold
another reference, just don't risk lock up just after WARN_ON
unnecessarily. Also fold do_inotify_remove_from_idr() into the single
callsite as that function really is just two lines of real code.

Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 6 insertions, 18 deletions

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index b82a507a5367..f9113e57ef33 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -395,21 +395,6 @@ static struct inotify_inode_mark *inotify_idr_find(struct fsnotify_group *group,
         return i_mark;
 }
 
-static void do_inotify_remove_from_idr(struct fsnotify_group *group,
-                                       struct inotify_inode_mark *i_mark)
-{
-        struct idr *idr = &group->inotify_data.idr;
-        spinlock_t *idr_lock = &group->inotify_data.idr_lock;
-        int wd = i_mark->wd;
-
-        assert_spin_locked(idr_lock);
-
-        idr_remove(idr, wd);
-
-        /* removed from the idr, drop that ref */
-        fsnotify_put_mark(&i_mark->fsn_mark);
-}
-
 /*
  * Remove the mark from the idr (if present) and drop the reference
  * on the mark because it was in the idr.
@@ -417,6 +402,7 @@ static void do_inotify_remove_from_idr(struct fsnotify_group *group,
 static void inotify_remove_from_idr(struct fsnotify_group *group,
                                     struct inotify_inode_mark *i_mark)
 {
+        struct idr *idr = &group->inotify_data.idr;
         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
         struct inotify_inode_mark *found_i_mark = NULL;
         int wd;
@@ -468,13 +454,15 @@ static void inotify_remove_from_idr(struct fsnotify_group *group,
                 BUG();
         }
 
-        do_inotify_remove_from_idr(group, i_mark);
+        idr_remove(idr, wd);
+        /* Removed from the idr, drop that ref. */
+        fsnotify_put_mark(&i_mark->fsn_mark);
 out:
+        i_mark->wd = -1;
+        spin_unlock(idr_lock);
         /* match the ref taken by inotify_idr_find_locked() */
         if (found_i_mark)
                 fsnotify_put_mark(&found_i_mark->fsn_mark);
-        i_mark->wd = -1;
-        spin_unlock(idr_lock);
 }
 
 /*