virtio-net: fix unmap leak

virtio_net_handle_ctrl() and other functions that process control vq
request call iov_discard_front() which will shorten the iov. This will
lead unmapping in virtqueue_push() leaks mapping.

Fixes this by keeping the original iov untouched and using a temp variable
in those functions.

Cc: Wen Congyang <[email protected]>
Cc: Stefano Stabellini <[email protected]>
Cc: [email protected]
Signed-off-by: Jason Wang <[email protected]>
Reviewed-by: Stefano Stabellini <[email protected]>
Reviewed-by: Fam Zheng <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Message-id: [email protected]
Signed-off-by: Peter Maydell <[email protected]>
(cherry picked from commit 771b6ed)
Signed-off-by: Michael Roth <[email protected]>

Author: jasowang

hw/net/virtio-net.c

@@ -798,7 +798,7 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
     virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
     VirtQueueElement elem;
     size_t s;
-    struct iovec *iov;
+    struct iovec *iov, *iov2;
     unsigned int iov_cnt;
 
     while (virtqueue_pop(vq, &elem)) {
@@ -808,8 +808,8 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
             exit(1);
         }
 
-        iov = elem.out_sg;
         iov_cnt = elem.out_num;
+        iov2 = iov = g_memdup(elem.out_sg, sizeof(struct iovec) * elem.out_num);
         s = iov_to_buf(iov, iov_cnt, 0, &ctrl, sizeof(ctrl));
         iov_discard_front(&iov, &iov_cnt, sizeof(ctrl));
         if (s != sizeof(ctrl)) {
@@ -833,6 +833,7 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
 
         virtqueue_push(vq, &elem, sizeof(status));
         virtio_notify(vdev, vq);
+        g_free(iov2);
     }
 }