[Intel-gfx] [PATCH 2/2] drm/i915: Check for a NULL shared dpll before dereferencing

[Chris Wilson]

This doesn't look possible but a little extra defense against the
improbable is worth it - an oops here could lockup the machine.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_display.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 62fac7e..61fd887 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1751,6 +1751,9 @@ static void intel_prepare_shared_dpll(struct intel_crtc *crtc)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_shared_dpll *pll = intel_crtc_to_shared_dpll(crtc);
 
+	if (WARN_ON(pll == NULL))
+		return;
+
 	WARN_ON(!pll->refcount);
 	if (pll->active == 0) {
 		DRM_DEBUG_DRIVER("setting up %s\n", pll->name);
-- 
1.7.9.5