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Re: [PATCH] vhost: svq: fix uninitialized variable
From: |
Eugenio Perez Martin |
Subject: |
Re: [PATCH] vhost: svq: fix uninitialized variable |
Date: |
Fri, 17 Feb 2023 12:24:51 +0100 |
On Fri, Feb 17, 2023 at 11:42 AM Laurent Vivier <lvivier@redhat.com> wrote:
>
> The problem has been reported by gcc with CFLAGS=-O3:
>
> .../hw/virtio/vhost-shadow-virtqueue.c: In function ‘vhost_svq_poll’:
> .../hw/virtio/vhost-shadow-virtqueue.c:538:12:
> error: ‘len’ may be used uninitialized [-Werror=maybe-uninitialized]
> 538 | return len;
> | ^~~
>
> vhost_svq_get_buf() returns NULL if SVQ is empty but doesn't set len to 0,
> and vhost_svq_poll() returns len without checking the return of
> vhost_svq_get_buf(). So if the SVQ is empty vhost_svq_poll() can return
> an random value.
>
s/an random/a random/.
I think this solves the same as
https://www.mail-archive.com/qemu-devel@nongnu.org/msg939383.html ?
Thanks!
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> hw/virtio/vhost-shadow-virtqueue.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c
> b/hw/virtio/vhost-shadow-virtqueue.c
> index 430729635815..31cf642db267 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -420,6 +420,7 @@ static VirtQueueElement
> *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
> vring_used_elem_t used_elem;
> uint16_t last_used, last_used_chain, num;
>
> + *len = 0;
> if (!vhost_svq_more_used(svq)) {
> return NULL;
> }
> --
> 2.39.1
>