Re: [PATCH v2] kernel: drm/vmwgfx: limit the number of mip levels in vmw_gb_surface_define_ioctl()

[Sinclair Yeh <syeh@vmware.com>]

Thanks Vladis!

Reviewed-by: Sinclair Yeh <syeh@vmware.com>

On Thu, Apr 06, 2017 at 02:33:40PM +0200, Vladis Dronov wrote:
> The 'req->mip_levels' parameter in vmw_gb_surface_define_ioctl() is
> a user-controlled 'uint32_t' value which is used as a loop count limit.
> This can lead to a kernel lockup and DoS. Add check for 'req->mip_levels'.
> 
> References:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugzilla.redhat.com_show-5Fbug.cgi-3Fid-3D1437431&d=DwIBAg&c=uilaK90D4TOVoH58JNXRgQ&r=HaJ2a6NYExoV0cntAYcoqA&m=D9ZabTkAbhTqB-puuJ1a4SnWKUIGw0oXestkhJG6dCQ&s=6PZxBQ8MQjy-uc5pd6vyZg3D5yrG0jlSPi5pPE0oFK4&e= 
> Signed-off-by: Vladis Dronov <vdronov@redhat.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> index b445ce9..e0d7ff9 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> @@ -1281,6 +1281,9 @@ int vmw_gb_surface_define_ioctl(struct drm_device *dev, void *data,
>  	if (req->multisample_count != 0)
>  		return -EINVAL;
>  
> +	if (req->mip_levels > DRM_VMW_MAX_MIP_LEVELS)
> +		return -EINVAL;
> +
>  	if (unlikely(vmw_user_surface_size == 0))
>  		vmw_user_surface_size = ttm_round_pot(sizeof(*user_srf)) +
>  			128;
> -- 
> 2.9.3
>