vsock/virtio: Validate length in packet header before skb_put()

willdeacon · gregkh · commit ee438c492b2e · 2025-08-28T16:28:36.000+02:00
commit 0dab924 upstream. 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: <stable@vger.kernel.org> Fixes: 71dc9ec ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") Signed-off-by: Will Deacon <will@kernel.org> Message-Id: <20250717090116.11987-3-will@kernel.org> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
@@ -497,8 +497,9 @@ 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
@@ -515,12 +516,19 @@ 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) ||
 				     len > virtio_vsock_skb_len(skb))) {
 				kfree_skb(skb);
 				continue;
 			}
 
+			hdr = virtio_vsock_hdr(skb);
+			payload_len = le32_to_cpu(hdr->len);
+			if (unlikely(payload_len > len - sizeof(*hdr))) {
+				kfree_skb(skb);
+				continue;
+			}
+
 			virtio_vsock_skb_rx_put(skb);
 			virtio_transport_deliver_tap_pkt(skb);
 			virtio_transport_recv_pkt(&virtio_transport, skb);
