Re: [PATCH net] vsock/virtio: fix skb overhead overflow on 32-bit builds
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2026-05-21 13:09:43
Also in:
kvm, lkml, stable, virtualization
On Thu, May 21, 2026 at 02:47:32PM +0200, Stefano Garzarella wrote:
From: Stefano Garzarella <sgarzare@redhat.com>
On 32-bit architectures, both skb_queue_len() and SKB_TRUESIZE(0) evaluate
to 32-bit values. The multiplication can overflow before being assigned to
the u64 skb_overhead variable, making the skb overhead check ineffective.
Cast skb_queue_len() to u64 so the multiplication is always performed in
64-bit arithmetic.
This issue was reported by Sashiko while reviewing another patch.
Fixes: 059b7dbd20a6 ("vsock/virtio: fix potential unbounded skb queue")
Closes: https://sashiko.dev/#/patchset/20260518090656.134588-1-sgarzare%40redhat.com
Cc: stable@vger.kernel.org
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>Acked-by: Michael S. Tsirkin <mst@redhat.com>
quoted hunk ↗ jump to hunk
--- 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 df3b418e0392..71198bf23fc4 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c@@ -417,7 +417,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, u32 len) { - u64 skb_overhead = (skb_queue_len(&vvs->rx_queue) + 1) * SKB_TRUESIZE(0); + u64 skb_overhead = ((u64)skb_queue_len(&vvs->rx_queue) + 1) * SKB_TRUESIZE(0); /* Allow at most buf_alloc * 2 total budget (payload + overhead), * similar to how SO_RCVBUF is doubled to reserve space for sk_buff-- 2.54.0