On Mon, Jul 14, 2025 at 04:20:56PM +0100, Will Deacon wrote:

When receiving a vsock packet in the guest, only the virtqueue buffer size is validated prior to virtio_vsock_skb_rx_put(). Unfortunately, virtio_vsock_skb_rx_put() uses the length from the packet header as the length argument to skb_put(), potentially resulting in SKB overflow if the host has gone wonky.

Validate the length as advertised by the packet header before calling virtio_vsock_skb_rx_put().

Cc: stable@vger.kernel.org Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") Signed-off-by: Will Deacon will@kernel.org

---

net/vmw_vsock/virtio_transport.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c index f0e48e6911fc..bd2c6aaa1a93 100644 --- a/net/vmw_vsock/virtio_transport.c +++ b/net/vmw_vsock/virtio_transport.c @@ -624,8 +624,9 @@ static void virtio_transport_rx_work(struct work_struct *work) do { virtqueue_disable_cb(vq); for (;;) {

• 	unsigned int len, payload_len;
  

• 	struct virtio_vsock_hdr *hdr;
  struct sk_buff *skb;
  

• 	unsigned int len;
  
  if (!virtio_transport_more_replies(vsock)) {
  	/* Stop rx until the device processes already
  

@@ -642,12 +643,19 @@ static void virtio_transport_rx_work(struct work_struct *work) vsock->rx_buf_nr--;

	/* Drop short/long packets */

• 	if (unlikely(len < sizeof(struct virtio_vsock_hdr) ||
  

• 	if (unlikely(len < sizeof(*hdr) ||
  

pre-existing: in some part we use sizeof(*hdr) in other VIRTIO_VSOCK_SKB_HEADROOM, I think we should try to uniform that, but of course not for this series!

		     len > virtio_vsock_skb_len(skb))) {
		kfree_skb(skb);
		continue;
	}

• 	hdr = virtio_vsock_hdr(skb);
  

• 	payload_len = le32_to_cpu(hdr->len);
  

• 	if (payload_len > len - sizeof(*hdr)) {
  

Since this is an hot path, should we use `unlikely`, like in the previous check, to instruct the branch predictor?

The rest LGTM!

Thanks, Stefano

• 		kfree_skb(skb);
  

• 		continue;
  

• 	}
  

• virtio_vsock_skb_rx_put(skb);
  virtio_transport_deliver_tap_pkt(skb);
  virtio_transport_recv_pkt(&virtio_transport, skb);
  

-- 2.50.0.727.gbf7dc18ff4-goog