From 1723b5e7962eb077353bab0772ca8114774b6c60 Mon Sep 17 00:00:00 2001 From: Prasad J Pandit Date: Mon, 19 Sep 2016 23:55:45 +0530 Subject: [PATCH 4/7] 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 Signed-off-by: Prasad J Pandit Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Laszlo Ersek --- 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; -- 2.1.4