virtio: fix indirect descriptor buffer overflow

We were previously allowing arbitrarily-long indirect descriptors, which
could lead to a buffer overflow in qemu-kvm process.

CVE-2011-2212

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

diff --git a/hw/virtio.c b/hw/virtio.c
index cc47a06a4e16d5ad91927514d419be4206e51e7b..a8f4940da2263c998b6d2373aeb24f3d1f4a0790 100644 (file)
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -449,9 +449,17 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)
         struct iovec *sg;
 
         if (vring_desc_flags(desc_pa, i) & VRING_DESC_F_WRITE) {
+            if (elem->in_num >= ARRAY_SIZE(elem->in_sg)) {
+                error_report("Too many write descriptors in indirect table");
+                exit(1);
+            }
             elem->in_addr[elem->in_num] = vring_desc_addr(desc_pa, i);
             sg = &elem->in_sg[elem->in_num++];
         } else {
+            if (elem->out_num >= ARRAY_SIZE(elem->out_sg)) {
+                error_report("Too many read descriptors in indirect table");
+                exit(1);
+            }
             elem->out_addr[elem->out_num] = vring_desc_addr(desc_pa, i);
             sg = &elem->out_sg[elem->out_num++];
         }