vfs: fix NULL pointer dereference in fsync_buffers_list()

Fix NULL pointer dereference in fsync_buffers_list() introduced by recent fix
of races in private_list handling.  Since bh->b_assoc_map has been cleared in
__remove_assoc_queue() we should really use original value stored in the
'mapping' variable.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 897cd7477b34..ddfdd2c80bf9 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -835,7 +835,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
                 smp_mb();
                 if (buffer_dirty(bh)) {
                         list_add(&bh->b_assoc_buffers,
-                                 &bh->b_assoc_map->private_list);
+                                 &mapping->private_list);
                         bh->b_assoc_map = mapping;
                 }
                 spin_unlock(lock);