[PATCH] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()

[PATCH] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()

[Nikolay Kuratov]

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

Signed-off-by: Nikolay Kuratov <kniv@yandex-team.ru>
---
 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

Re: [PATCH] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()

[Stefano Garzarella]

On Mon, Dec 11, 2023 at 05:25:05PM +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
>

We should add:

Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko")

>Signed-off-by: Nikolay Kuratov <kniv@yandex-team.ru>
>---
> 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 we respect the credit, this should not happen. It can happen, though,
that the receiver changes its buffer size while we're communicating,
and if it reduces it, this could happen. So yes, we need to fix it!

Thanks!

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

> 	if (bytes < 0)
> 		bytes = 0;
>
>-- 
>2.34.1
>

[PATCH v2] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()

[Nikolay Kuratov]

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

Re: [PATCH v2] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()

[Stefano Garzarella]

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
>
>

Re: [PATCH v2] vsock/virtio: Fix unsigned integer wrap around in virtio_transport_has_space()

[patchwork-bot+netdevbpf]

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!
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