[Qemu-devel] [PATCH] virtio: check vring descriptor buffer length

[P J P <ppandit@redhat.com>]

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

virtio back end uses set of buffers to facilitate I/O operations.
An infinite loop unfolds in virtqueue_pop() if a buffer was
of zero size. Add check to avoid it.

Reported-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/virtio/virtio.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 30ede3d..8de896c 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -457,6 +457,11 @@ static void virtqueue_map_desc(unsigned int *p_num_sg, hwaddr *addr, struct iove
     unsigned num_sg = *p_num_sg;
     assert(num_sg <= max_num_sg);
 
+    if (!sz) {
+        error_report("virtio: zero sized buffers are not allowed");
+        exit(1);
+    }
+
     while (sz) {
         hwaddr len = sz;
 
-- 
2.5.5