virtio_blk: Fix signedness bug in virtblk_prep_rq()

The virtblk_map_data() function returns negative error codes, however, the
'nents' field of vbr->sg_table is an unsigned int, which causes the error
handling not to work correctly.

Cc: stable@vger.kernel.org
Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Message-Id: <20221021204126.927603-1-rafaelmendsr@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Suwan Kim <suwan.kim027@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index dcbf86cd2155e196b40a4faae4bbfd3e9ef9d55f..6a77fa9174288089f803e3a698c0382e2d128381 100644 (file)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -334,14 +334,16 @@ static blk_status_t virtblk_prep_rq(struct blk_mq_hw_ctx *hctx,
                                        struct virtblk_req *vbr)
 {
        blk_status_t status;
+       int num;
 
        status = virtblk_setup_cmd(vblk->vdev, req, vbr);
        if (unlikely(status))
                return status;
 
-       vbr->sg_table.nents = virtblk_map_data(hctx, req, vbr);
-       if (unlikely(vbr->sg_table.nents < 0))
+       num = virtblk_map_data(hctx, req, vbr);
+       if (unlikely(num < 0))
                return virtblk_fail_to_queue(req, -ENOMEM);
+       vbr->sg_table.nents = num;
 
        blk_mq_start_request(req);