From: Ming Lei Date: Tue, 21 Apr 2015 02:00:19 +0000 (+0800) Subject: blk-mq: fix race between timeout and CPU hotplug X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=f054b56c951bf1731ba7314a4c7f1cc0b2977cc9;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git blk-mq: fix race between timeout and CPU hotplug Firstly during CPU hotplug, even queue is freezed, timeout handler still may come and access hctx->tags, which may cause use after free, so this patch deactivates timeout handler inside CPU hotplug notifier. Secondly, tags can be shared by more than one queues, so we have to check if the hctx has been unmapped, otherwise still use-after-free on tags can be triggered. Cc: Reported-by: Dongsu Park Tested-by: Dongsu Park Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- diff --git a/block/blk-mq.c b/block/blk-mq.c index ade8a2d1b0aa..1fccb98aa28f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -677,8 +677,11 @@ static void blk_mq_rq_timer(unsigned long priv) data.next = blk_rq_timeout(round_jiffies_up(data.next)); mod_timer(&q->timeout, data.next); } else { - queue_for_each_hw_ctx(q, hctx, i) - blk_mq_tag_idle(hctx); + queue_for_each_hw_ctx(q, hctx, i) { + /* the hctx may be unmapped, so check it here */ + if (blk_mq_hw_queue_mapped(hctx)) + blk_mq_tag_idle(hctx); + } } } @@ -2090,9 +2093,16 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb, */ list_for_each_entry(q, &all_q_list, all_q_node) blk_mq_freeze_queue_start(q); - list_for_each_entry(q, &all_q_list, all_q_node) + list_for_each_entry(q, &all_q_list, all_q_node) { blk_mq_freeze_queue_wait(q); + /* + * timeout handler can't touch hw queue during the + * reinitialization + */ + del_timer_sync(&q->timeout); + } + list_for_each_entry(q, &all_q_list, all_q_node) blk_mq_queue_reinit(q);