On Wed, May 27, 2026 at 07:10:46PM +0200, Stefano Garzarella wrote: > From: Stefano Garzarella <[email protected]> > > 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 <[email protected]> > Closes: https://lore.kernel.org/netdev/20260523173557.5cc4f4f6@pumpkin > Suggested-by: "Michael S. Tsirkin" <[email protected]> > Signed-off-by: Stefano Garzarella <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]> > --- > 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 b143290a311d..d4d26fba9e37 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 = ((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 > -- > 2.54.0
