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

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: 71dc9ec9ac7d ("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>

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index f0e48e6911fc46cba87f7dafeb8dbc21421df254..eb08a393413d456a5e82b9a98f12be8c553aebd1 100644 (file)
--- 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) ||
                                     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);