[PATCH 1/2] drm: Don't call drm_for_each_crtc with a non-KMS driver

[Daniel Vetter]

On Wed, Nov 30, 2016 at 05:30:01PM +0900, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer at amd.com>
> 
> Fixes oops if userspace calls DRM_IOCTL_GET_CAP for
>  DRM_CAP_PAGE_FLIP_TARGET on a non-KMS device node. (Normal userspace
> doesn't do that, discovered by syzkaller)
> 
> Reported-by: Dmitry Vyukov <dvyukov at google.com>
> Fixes: f837297ad824 ("drm: Add DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags v2")
> Cc: stable at vger.kernel.org
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>

Applied to drm-misc-fixes, thanks.
-Daniel

> ---
>  drivers/gpu/drm/drm_ioctl.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 0ad2c47..71c3473 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -254,10 +254,12 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
>  		req->value = dev->mode_config.async_page_flip;
>  		break;
>  	case DRM_CAP_PAGE_FLIP_TARGET:
> -		req->value = 1;
> -		drm_for_each_crtc(crtc, dev) {
> -			if (!crtc->funcs->page_flip_target)
> -				req->value = 0;
> +		if (drm_core_check_feature(dev, DRIVER_MODESET)) {
> +			req->value = 1;
> +			drm_for_each_crtc(crtc, dev) {
> +				if (!crtc->funcs->page_flip_target)
> +					req->value = 0;
> +			}
>  		}
>  		break;
>  	case DRM_CAP_CURSOR_WIDTH:
> -- 
> 2.10.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch