1 files changed, 14 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index d46a951bd541..bd2f4c68506a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -659,12 +659,21 @@ int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
                 return 0;
         mnt = real_mount(bastard);
         mnt_add_count(mnt, 1);
+        smp_mb();                       // see mntput_no_expire()
         if (likely(!read_seqretry(&mount_lock, seq)))
                 return 0;
         if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
                 mnt_add_count(mnt, -1);
                 return 1;
         }
+        lock_mount_hash();
+        if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
+                mnt_add_count(mnt, -1);
+                unlock_mount_hash();
+                return 1;
+        }
+        unlock_mount_hash();
+        /* caller will mntput() */
         return -1;
 }
 
@@ -1210,6 +1219,11 @@ static void mntput_no_expire(struct mount *mnt)
                 return;
         }
         lock_mount_hash();
+        /*
+         * make sure that if __legitimize_mnt() has not seen us grab
+         * mount_lock, we'll see their refcount increment here.
+         */
+        smp_mb();
         mnt_add_count(mnt, -1);
         if (mnt_get_count(mnt)) {
                 rcu_read_unlock();