From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33383) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bkUwR-00007d-AH for qemu-devel@nongnu.org; Thu, 15 Sep 2016 07:34:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bkUwL-0002us-Cj for qemu-devel@nongnu.org; Thu, 15 Sep 2016 07:34:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51160) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bkUwL-0002uE-6Q for qemu-devel@nongnu.org; Thu, 15 Sep 2016 07:34:49 -0400 From: P J P Date: Thu, 15 Sep 2016 17:04:42 +0530 Message-Id: <1473939282-3596-1-git-send-email-ppandit@redhat.com> Subject: [Qemu-devel] [PATCH] virtio: add check for descriptor's mapped address List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Qemu Developers Cc: "Michael S. Tsirkin" , Qinghao Tang , Prasad J Pandit From: Prasad J Pandit 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 Signed-off-by: Prasad J Pandit --- hw/virtio/virtio.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 15ee3a7..0a4c5b6 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -472,12 +472,14 @@ 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); - iov[num_sg].iov_len = len; - addr[num_sg] = pa; + if (iov[num_sg].iov_base) { + iov[num_sg].iov_len = len; + addr[num_sg] = pa; + pa += len; + num_sg++; + } sz -= len; - pa += len; - num_sg++; } *p_num_sg = num_sg; } -- 2.5.5