ubd: fix missing lock around request issue

axboe · axboe · commit 6961cd4d0fde · 2018-11-07T14:34:05.000-07:00
We need to hold the device lock (and disable interrupts) while writing new commands, or we could be interrupted while that is happening and read invalid requests in the completion path. Fixes: 4e6da0f ("um: Convert ubd driver to blk-mq") Tested-by: Richard Weinberger <richard@nod.at> Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
@@ -1341,11 +1341,14 @@ static int ubd_queue_one_vec(struct blk_mq_hw_ctx *hctx, struct request *req,
 static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
 				 const struct blk_mq_queue_data *bd)
 {
+	struct ubd *ubd_dev = hctx->queue->queuedata;
 	struct request *req = bd->rq;
 	int ret = 0;
 
 	blk_mq_start_request(req);
 
+	spin_lock_irq(&ubd_dev->lock);
+
 	if (req_op(req) == REQ_OP_FLUSH) {
 		ret = ubd_queue_one_vec(hctx, req, 0, NULL);
 	} else {
@@ -1361,9 +1364,11 @@ static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
 		}
 	}
 out:
-	if (ret < 0) {
+	spin_unlock_irq(&ubd_dev->lock);
+
+	if (ret < 0)
 		blk_mq_requeue_request(req, true);
-	}
+
 	return BLK_STS_OK;
 }
 
