Re: [PATCH] vsock/virtio: fix potential unbounded skb queue

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, May 15, 2026 at 05:10:39PM +0200, Greg KH wrote:
> On Fri, May 15, 2026 at 04:23:53PM +0200, Luigi Leonardi wrote:
> > On Fri, May 15, 2026 at 04:22:12PM +0200, Luigi Leonardi wrote:
> > > From: Eric Dumazet <edumazet@google.com>
> > > 
> > > Upstream commit 059b7dbd20a6f0c539a45ddff1573cb8946685b5
> > > 
> > > 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 <edumazet@google.com>
> > > Cc: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
> > > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > > Cc: Stefano Garzarella <sgarzare@redhat.com>
> > > Cc: Michael S. Tsirkin <mst@redhat.com>
> > > Cc: Jason Wang <jasowang@redhat.com>
> > > Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > Cc: Eugenio Pérez <eperezma@redhat.com>
> > > Cc: virtualization@lists.linux.dev
> > > Link: https://patch.msgid.link/20260430122653.554058-1-edumazet@google.com
> > > Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> > > [LL: Fixed conflict since this tree does not use buf_used added by commit
> > > 45ca7e9f0730 ("vsock/virtio: fix `rx_bytes` accounting for stream sockets")]
> > > Signed-off-by: Luigi Leonardi <leonardi@redhat.com>
> > > ---
> > > 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 4c374c36c29d..86e3051d000e 100644
> > > --- a/net/vmw_vsock/virtio_transport_common.c
> > > +++ b/net/vmw_vsock/virtio_transport_common.c
> > > @@ -283,7 +283,9 @@ 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->rx_bytes + len > vvs->buf_alloc)
> > > +	u64 skb_overhead = (skb_queue_len(&vvs->rx_queue) + 1) * SKB_TRUESIZE(0);
> > > +
> > > +	if (skb_overhead + vvs->rx_bytes + len > vvs->buf_alloc)
> > > 		return false;
> > > 
> > > 	vvs->rx_bytes += len;
> > > 
> > > ---
> > > base-commit: 3b9f64db049687c0d38b4b3ef2f297f0642179af
> > > change-id: 20260515-dumazet-07c0c855a9e2
> > > 
> > > Best regards,
> > > --
> > > Luigi Leonardi <leonardi@redhat.com>
> > > 
> > 
> > Forgot to add this is material for 6.6.y stable tree.
> 
> What about all of the newer stable trees?  You can't just apply a patch
> to an old branch :(

Ah, is this due to your other email?  that makes more sense, sorry for
the noise.

greg "drowning in email" k-h