Re: [PATCH v3 2/9] vsock/virtio: Validate length in packet header before skb_put()
From: Stefano Garzarella <sgarzare@redhat.com>
Date: 2025-07-15 09:53:30
Also in:
lkml, stable, virtualization
On Mon, Jul 14, 2025 at 04:20:56PM +0100, Will Deacon wrote:
quoted hunk ↗ jump to hunk
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: <redacted> 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