From: Prasad J Pandit <pjp@fedoraproject.org>

Date: Mon, 19 Sep 2016 23:55:45 +0530

Subject: [PATCH] virtio: add check for descriptor's mapped address

virtio back end uses set of buffers to facilitate I/O operations.

If its size is too large, 'cpu_physical_memory_map' could return

a null address. This would result in a null dereference while

un-mapping descriptors. Add check to avoid it.

Reported-by: Qinghao Tang <luodalongde@gmail.com>

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

(cherry picked from commit 973e7170dddefb491a48df5cba33b2ae151013a0)

---

 hw/virtio/virtio.c | 5 +++++

 1 file changed, 5 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c

index 74c085c..eabe573 100644

--- a/hw/virtio/virtio.c

+++ b/hw/virtio/virtio.c

@@ -473,6 +473,11 @@ static void virtqueue_map_desc(unsigned int *p_num_sg, hwaddr *addr, struct iove

         }

         iov[num_sg].iov_base = cpu_physical_memory_map(pa, &len, is_write);

+        if (!iov[num_sg].iov_base) {

+            error_report("virtio: bogus descriptor or out of resources");

+            exit(1);

+        }

+

         iov[num_sg].iov_len = len;

         addr[num_sg] = pa;