linux-kernel - Re: [PATCH v2] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has

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Date:   Mon, 11 Dec 2023 17:33:39 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Nikolay Kuratov <kniv@...dex-team.ru>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        virtualization@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v2] vsock/virtio: Fix unsigned integer wrap around in
 virtio_transport_has_space()

On Mon, Dec 11, 2023 at 07:23:17PM +0300, Nikolay Kuratov wrote:
>We need to do signed arithmetic if we expect condition
>`if (bytes < 0)` to be possible
>
>Found by Linux Verification Center (linuxtesting.org) with SVACE
>
>Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko")
>Signed-off-by: Nikolay Kuratov <kniv@...dex-team.ru>
>---
>
>V1 -> V2: Added Fixes section

Please, next time carry also R-b tags.

>
> net/vmw_vsock/virtio_transport_common.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

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

Thanks,
Stefano

>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index c8e162c9d1df..6df246b53260 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -843,7 +843,7 @@ static s64 virtio_transport_has_space(struct vsock_sock *vsk)
> 	struct virtio_vsock_sock *vvs = vsk->trans;
> 	s64 bytes;
>
>-	bytes = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);
>+	bytes = (s64)vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);
> 	if (bytes < 0)
> 		bytes = 0;
>
>-- 
>2.34.1
>
>