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

This reverts commit 4157501b9a8f ("vsock/virtio: fix skb overhead
overflow on 32-bit builds"). The fix was semantically correct (although
it would have been better to use mul_u32_u32(), as David pointed out),
but in practice we are estimating the memory used to allocate the SKBs,
and this will never cause a 32-bit variable to overflow on a 32-bit
system, since the memory would have run out long before that. On 64-bit,
SKB_TRUESIZE() already evaluates to size_t, so the multiplication is
already in 64-bit arithmetic without the cast.

Let's revert this to avoid unnecessary 64-bit multiplies on the
per-packet receive path on 32-bit systems.

Reported-by: David Laight <david.laight.linux@gmail.com>
Closes: https://lore.kernel.org/netdev/20260523173557.5cc4f4f6@pumpkin
Suggested-by: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Laight <david.laight.linux@gmail.com>
Link: https://patch.msgid.link/20260527171046.130211-1-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 b143290a311d1ffac6c181aa6ae45ac58703a23f..d4d26fba9e3721ea06fed490514f4b906f345ed4 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 = ((u64)skb_queue_len(&vvs->rx_queue) + 1) * SKB_TRUESIZE(0);
+       u64 skb_overhead = (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