On Mon, Feb 10, 2020 at 10:13:22AM +0800, yukuai (C) wrote: > On 2020/2/10 9:00, Bart Van Assche wrote: > > Have you already noticed patch "[PATCH] blktrace: Protect q->blk_trace > > with RCU"? If not, have you already tried to verify whether that patch > > fixes the use-after-free detected by syzbot? > > I just tested and confirmed the patch didn't fix the problem. Right, the two are for fixing different issue. > > By the way, I think Ming is right about "So release not by wq just > reduces the chance, instead of fixing it completely.", and "move > blk_mq_debugfs_unregister() into blk_unregister_queue()" is a good > choice. However, blk_trace_shutdown() and blk_mq_exit_queue() also > remove some files or dirs, and they may need to move to > blk_unregister_queue(). Right. Fortunately, we hold sysfs_dir_lock in blk_unregister_queue(), so the issue can be fixed by check & remove with holding the same lock in blk_trace_free(). Thanks, Ming
