ublk: don't queue request if the associated uring_cmd is canceled

Commit 524346e9d79f ("ublk: build batch from IOs in same io_ring_ctx and io task")
need to dereference `io->cmd` for checking if the IO can be added to current
batch, see ublk_belong_to_same_batch() and io_uring_cmd_ctx_handle(). However,
`io->cmd` may become invalid after the uring_cmd is canceled.

Fixes it by only allowing to queue this IO in case that ublk_prep_req()
returns `BLK_STS_OK`, when 'io->cmd' is guaranteed to be valid.

Reported-by: Changhui Zhong <czhong@redhat.com>
Fixes: 524346e9d79f ("ublk: build batch from IOs in same io_ring_ctx and io task")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250701072325.1458109-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index c3e3c3b65a6d4d3990822897845c5ce438a7c111..9fd284fa76dcd71f97acef149275f643b26c70d9 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1442,15 +1442,16 @@ static void ublk_queue_rqs(struct rq_list *rqlist)
                struct ublk_queue *this_q = req->mq_hctx->driver_data;
                struct ublk_io *this_io = &this_q->ios[req->tag];
 
+               if (ublk_prep_req(this_q, req, true) != BLK_STS_OK) {
+                       rq_list_add_tail(&requeue_list, req);
+                       continue;
+               }
+
                if (io && !ublk_belong_to_same_batch(io, this_io) &&
                                !rq_list_empty(&submit_list))
                        ublk_queue_cmd_list(io, &submit_list);
                io = this_io;
-
-               if (ublk_prep_req(this_q, req, true) == BLK_STS_OK)
-                       rq_list_add_tail(&submit_list, req);
-               else
-                       rq_list_add_tail(&requeue_list, req);
+               rq_list_add_tail(&submit_list, req);
        }
 
        if (!rq_list_empty(&submit_list))