Re: [PATCH v2] vduse: Validate vq_num in vduse_validate_config()

[Stefano Garzarella]

On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
> Add a limit to 'config->vq_num' which is user controlled data which
> comes from an vduse_ioctl to prevent large memory allocations.
>
> This is found using static analysis with smatch.
>
> Suggested-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>
> ---
> v1->v2: Change title of the commit and description, add a limit to
> 	vq_num.
>
> Note: I think here 0xffff is the max size of vring =  no: of vqueues.
> Only compile and boot tested.
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 35dceee3ed56..31017ebc4d7c 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
> 	if (config->config_size > PAGE_SIZE)
> 		return false;
>
> +	if (config->vq_num > 0xffff)

What about using U16_MAX here?

Thanks,
Stefano

> +		return false;
> +
> 	if (!device_is_allowed(config->device_id))
> 		return false;
>
> --
> 2.38.1