Re: [Qemu-devel] [PATCH v2] virtio: add check for descriptor's mapped address

[Stefan Hajnoczi]

On Mon, Sep 19, 2016 at 02:36:11PM +0530, P J P wrote:
> From: Prasad J Pandit <address@hidden>
> 
> 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 <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
>  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);

exit(1) is used everywhere else in the file (including just a few lines
above in the same function).  Please use exit(1) for consistency.

Looks fine otherwise.

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