From dd24f87f65c957f30e605e44961d2fd53a44c780 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Fri, 16 May 2025 00:26:01 +0800 Subject: [PATCH] ublk: fix dead loop when canceling io command Commit: f40139fde527 ("ublk: fix race between io_uring_cmd_complete_in_task and ublk_cancel_cmd") adds a request state check in ublk_cancel_cmd(), and if the request is started, skips canceling this uring_cmd. However, the current uring_cmd may be in ACTIVE state, without block request coming to the uring command. Meantime, if the cached request in tag_set.tags[tag] has been delivered to ublk server and reycycled, then this uring_cmd can't be canceled. ublk requests are aborted in ublk char device release handler, which depends on canceling all ACTIVE uring_cmd. So it causes a dead loop. Fix this issue by not taking a stale request into account when canceling uring_cmd in ublk_cancel_cmd(). Reported-by: Shinichiro Kawasaki Closes: https://lore.kernel.org/linux-block/mruqwpf4tqenkbtgezv5oxwq7ngyq24jzeyqy4ixzvivatbbxv@4oh2wzz4e6qn/ Fixes: f40139fde527 ("ublk: fix race between io_uring_cmd_complete_in_task and ublk_cancel_cmd") Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20250515162601.77346-1-ming.lei@redhat.com [axboe: rewording of commit message] Signed-off-by: Jens Axboe --- drivers/block/ublk_drv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index f9032076bc061..dc104c025cd56 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -1708,7 +1708,7 @@ static void ublk_cancel_cmd(struct ublk_queue *ubq, unsigned tag, * that ublk_dispatch_req() is always called */ req = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], tag); - if (req && blk_mq_request_started(req)) + if (req && blk_mq_request_started(req) && req->tag == tag) return; spin_lock(&ubq->cancel_lock); -- 2.39.5