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 PĂ©rez" <[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;
 
        vvs->rx_bytes += len;
-- 
2.54.0.545.g6539524ca2-goog


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