vhost/vsock: fix vhost virtio_vsock_pkt use-after-free

Stash the packet length in a local variable before handing over
ownership of the packet to virtio_transport_recv_pkt() or
virtio_transport_free_pkt().

This patch solves the use-after-free since pkt is no longer guaranteed
to be alive.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 0ddf3a2dbfc4..e3b30ea9ece5 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -307,6 +307,8 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 
         vhost_disable_notify(&vsock->dev, vq);
         for (;;) {
+                u32 len;
+
                 if (!vhost_vsock_more_replies(vsock)) {
                         /* Stop tx until the device processes already
                          * pending replies.  Leave tx virtqueue
@@ -334,13 +336,15 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
                         continue;
                 }
 
+                len = pkt->len;
+
                 /* Only accept correctly addressed packets */
                 if (le64_to_cpu(pkt->hdr.src_cid) == vsock->guest_cid)
                         virtio_transport_recv_pkt(pkt);
                 else
                         virtio_transport_free_pkt(pkt);
 
-                vhost_add_used(vq, head, sizeof(pkt->hdr) + pkt->len);
+                vhost_add_used(vq, head, sizeof(pkt->hdr) + len);
                 added = true;
         }