From: Xiubo Li xiubli@redhat.com
stable inclusion from linux-4.19.155 commit 2ef6f4bd60411934e3fc2715442c2afe70f84bf3
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[ Upstream commit 87aac3a80af5cbad93e63250e8a1e19095ba0d30 ]
There has one race case for ceph's rbd-nbd tool. When do mapping it may fail with EBUSY from ioctl(nbd, NBD_DO_IT), but actually the nbd device has already unmaped.
It dues to if just after the wake_up(), the recv_work() is scheduled out and defers calling the nbd_config_put(), though the map process has exited the "nbd->recv_task" is not cleared.
Signed-off-by: Xiubo Li xiubli@redhat.com Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/block/nbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 816188aa841f..bebb6ed71731 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -757,9 +757,9 @@ static void recv_work(struct work_struct *work)
blk_mq_complete_request(blk_mq_rq_from_pdu(cmd)); } + nbd_config_put(nbd); atomic_dec(&config->recv_threads); wake_up(&config->recv_wq); - nbd_config_put(nbd); kfree(args); }