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>

diff --git a/fs/buffer.c b/fs/buffer.c
index 897cd7477b34374b383b80d80144a57c5446ba98..ddfdd2c80bf9ba22c20901e5a74f9cd449d80ccd 100644 (file)
--- 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);