drm: Don't call drm_for_each_crtc with a non-KMS driver
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@google.com>
Fixes: f837297ad824 ("drm: Add DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags v2")
Cc: stable@vger.kernel.org
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161130083002.1520-1-michel@daenzer.net
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 @@
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:
