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

[Daniel Vetter]

On Wed, May 28, 2014 at 04:16:42PM +0100, Chris Wilson wrote:
> 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;

Yeah, nicely completes our set of WARN checks. Also merged the other patch
for sigbus instead of loud WARN to dinq.

Thanks, Daniel
> +
>  	WARN_ON(!pll->refcount);
>  	if (pll->active == 0) {
>  		DRM_DEBUG_DRIVER("setting up %s\n", pll->name);
> -- 
> 1.7.9.5
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch