On Thu, Apr 30, 2026 at 12:26:52PM +0000, Eric Dumazet wrote:
virtio_transport_inc_rx_pkt() checks vvs->rx_bytes + len > vvs->buf_alloc.
virtio_transport_recv_enqueue() skips coalescing for packets
with VIRTIO_VSOCK_SEQ_EOM.
If fed with packets with len == 0 and VIRTIO_VSOCK_SEQ_EOM,
a very large number of packets can be queued
because vvs->rx_bytes stays at 0.
Fix this by estimating the skb metadata size:
(Number of skbs in the queue) * SKB_TRUESIZE(0)
Fixes: 077706165717 ("virtio/vsock: don't use skbuff state to account credit")
Signed-off-by: Eric Dumazet <[email protected]>
Cc: Arseniy Krasnov <[email protected]>
Cc: Stefan Hajnoczi <[email protected]>
Cc: Stefano Garzarella <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Xuan Zhuo <[email protected]>
Cc: "Eugenio Pérez" <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
net/vmw_vsock/virtio_transport_common.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c
b/net/vmw_vsock/virtio_transport_common.c
index
416d533f493d7b07e9c77c43f741d28cfcd0953e..9b8014516f4fb1130ae184635fbba4dfee58bd64
100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -447,7 +447,9 @@ 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)
{
- if (vvs->buf_used + len > vvs->buf_alloc)
+ u64 skb_overhead = (skb_queue_len(&vvs->rx_queue) + 1) *
SKB_TRUESIZE(0);
+
+ if (skb_overhead + vvs->buf_used + len > vvs->buf_alloc)
return false;
I'm not sure about this fix, I mean that maybe this is incomplete.
In virtio-vsock, there is a credit mechanism between the two peers:
https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.html#x1-4850003
This takes only the payload into account, so it’s true that this problem
exists; however, perhaps we should also inform the other peer of a lower
credit balance, otherwise the other peer will believe it has much more
credit than it actually does, send a large payload, and then the packet
will be discarded and the data lost (there are no retransmissions,
etc.).
Thanks,
Stefano
