[PATCH] drm/locking: Allow NULL crtc in drm_modeset_legacy_acquire_ctx

[Daniel Vetter]

I've missed checking this and so didn't notice that there's a NULL
check missing. Since depending upon calling context the crtc might not
even be there (disable-me-harder does happen around planes, especially
in cleanup code) we need to dodge the oops and look at the global
acquire ctx.

Reported-by: "Jasper St. Pierre" <jstpierre at mecheye.net>
Cc: "Jasper St. Pierre" <jstpierre at mecheye.net>
Cc: Rob Clark <robdclark at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/drm_modeset_lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c
index 474e4d12a2d8..93d28269e3bd 100644
--- a/drivers/gpu/drm/drm_modeset_lock.c
+++ b/drivers/gpu/drm/drm_modeset_lock.c
@@ -209,7 +209,7 @@ EXPORT_SYMBOL(drm_modeset_lock_crtc);
 struct drm_modeset_acquire_ctx *
 drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc)
 {
-	if (crtc->acquire_ctx)
+	if (crtc && crtc->acquire_ctx)
 		return crtc->acquire_ctx;
 
 	WARN_ON(!crtc->dev->mode_config.acquire_ctx);
-- 
2.1.1