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

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

[Luigi Leonardi]

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>

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

[Luigi Leonardi]

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.

Luigi

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

[Greg KH]

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 :(

thanks,

greg k-h

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

[Greg KH]

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

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

[Michael S. Tsirkin]

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>


I am not sure we should queue this for stable yet. It causes regressions
that we are now trying to fix.

-- 
MST