Patch "nbd: fix race between timeout and normal completion" has been added to the 6.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nbd: fix race between timeout and normal completion

to the 6.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nbd-fix-race-between-timeout-and-normal-completion.patch
and it can be found in the queue-6.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3f8644d330dea27d13c39d6ebf4191bb7f56df16
Author: Ming Lei <ming.lei@xxxxxxxxxx>
Date:   Fri Aug 30 11:41:45 2024 +0800

    nbd: fix race between timeout and normal completion
    
    [ Upstream commit c9ea57c91f03bcad415e1a20113bdb2077bcf990 ]
    
    If request timetout is handled by nbd_requeue_cmd(), normal completion
    has to be stopped for avoiding to complete this requeued request, other
    use-after-free can be triggered.
    
    Fix the race by clearing NBD_CMD_INFLIGHT in nbd_requeue_cmd(), meantime
    make sure that cmd->lock is grabbed for clearing the flag and the
    requeue.
    
    Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
    Cc: Yu Kuai <yukuai3@xxxxxxxxxx>
    Fixes: 2895f1831e91 ("nbd: don't clear 'NBD_CMD_INFLIGHT' flag if request is not completed")
    Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
    Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240830034145.1827742-1-ming.lei@xxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index b87aa80a46dda..0e8ddf30563d0 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -181,6 +181,17 @@ static void nbd_requeue_cmd(struct nbd_cmd *cmd)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
 
+	lockdep_assert_held(&cmd->lock);
+
+	/*
+	 * Clear INFLIGHT flag so that this cmd won't be completed in
+	 * normal completion path
+	 *
+	 * INFLIGHT flag will be set when the cmd is queued to nbd next
+	 * time.
+	 */
+	__clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
+
 	if (!test_and_set_bit(NBD_CMD_REQUEUED, &cmd->flags))
 		blk_mq_requeue_request(req, true);
 }
@@ -480,8 +491,8 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req)
 					nbd_mark_nsock_dead(nbd, nsock, 1);
 				mutex_unlock(&nsock->tx_lock);
 			}
-			mutex_unlock(&cmd->lock);
 			nbd_requeue_cmd(cmd);
+			mutex_unlock(&cmd->lock);
 			nbd_config_put(nbd);
 			return BLK_EH_DONE;
 		}