vsock/virtio: fix skb overhead overflow on 32-bit builds

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>
Link: https://patch.msgid.link/20260521124732.125771-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index d4d26fba9e3721ea06fed490514f4b906f345ed4..b143290a311d1ffac6c181aa6ae45ac58703a23f 100644 (file)
--- 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