locks: fix error in locks_move_blocks()

After moving all requests from
   fl->fl_blocked_requests
to
   new->fl_blocked_requests

it is nonsensical to do anything to all the remaining elements, there
aren't any.  This should do something to all the requests that have been
moved. For simplicity, it does it to all requests in the target list.

Setting "f->fl_blocker = new" to all members of new->fl_blocked_requests
is "obviously correct" as it preserves the invariant of the linkage
among requests.

Reported-by: syzbot+239d99847eb49ecb3899@syzkaller.appspotmail.com
Fixes: 9fe27999c4be ("fs/locks: allow a lock request to block other requests.")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

diff --git a/fs/locks.c b/fs/locks.c
index f0b24d98f36beeefeb4802e41604e44eb7d9782c..ff6af2c326012cb027378d6e909506fc7e687531 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -453,7 +453,7 @@ static void locks_move_blocks(struct file_lock *new, struct file_lock *fl)
                return;
        spin_lock(&blocked_lock_lock);
        list_splice_init(&fl->fl_blocked_requests, &new->fl_blocked_requests);
-       list_for_each_entry(f, &fl->fl_blocked_requests, fl_blocked_member)
+       list_for_each_entry(f, &new->fl_blocked_requests, fl_blocked_member)
                f->fl_blocker = new;
        spin_unlock(&blocked_lock_lock);
 }