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@yandex-team.ru>
---

V1 -> V2: Added Fixes section

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

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

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 11 Dec 2023 19:23:17 +0300 you 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@yandex-team.ru>
> 
> [...]

Here is the summary with links:
  - [v2] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()
    https://git.kernel.org/netdev/net/c/60316d7f10b1

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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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@yandex-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@redhat.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
>
>