linux-kernel - Re: [PATCH] virtio_blk: Fix signedness bug in virtblk_prep

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Date:   Mon, 24 Oct 2022 15:33:46 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Rafael Mendonca <rafaelmendsr@...il.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Jens Axboe <axboe@...nel.dk>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Suwan Kim <suwan.kim027@...il.com>,
        virtualization@...ts.linux-foundation.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_blk: Fix signedness bug in virtblk_prep_rq()

On Fri, Oct 21, 2022 at 05:41:26PM -0300, Rafael Mendonca wrote:
>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.
>
>Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
>Signed-off-by: Rafael Mendonca <rafaelmendsr@...il.com>
>---
> drivers/block/virtio_blk.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)

Good catch!

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

>
>diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
>index 19da5defd734..291f705e61a8 100644
>--- a/drivers/block/virtio_blk.c
>+++ b/drivers/block/virtio_blk.c
>@@ -321,16 +321,18 @@ 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)) {
> 		virtblk_cleanup_cmd(req);
> 		return BLK_STS_RESOURCE;
> 	}
>+	vbr->sg_table.nents = num;
>
> 	blk_mq_start_request(req);
>
>-- 
>2.34.1
>