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From: Laszlo Ersek <lersek@redhat.com>
Message-ID: <87fdb7dd-34a6-6b6f-0119-afc483c8604e@redhat.com>
Date: Mon, 19 Sep 2016 12:37:16 +0200
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Subject: Re: [Qemu-devel] [PATCH v2] virtio: add check for descriptor's
 mapped address
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To: P J P <ppandit@redhat.com>, Qemu Developers <qemu-devel@nongnu.org>
Cc: Qinghao Tang <luodalongde@gmail.com>, "Michael S. Tsirkin" <mst@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Prasad J Pandit <pjp@fedoraproject.org>

On 09/19/16 11:06, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> 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>
> ---
>  hw/virtio/virtio.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> Update per:
>   -> https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg03889.html
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 15ee3a7..311dd0b 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -472,6 +472,11 @@ 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(EXIT_FAILURE);
> +        }
> +
>          iov[num_sg].iov_len = len;
>          addr[num_sg] = pa;
>  
> 

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