linux-kernel - Re: [PATCH] drm/i915: Fix NULL ptr deref in intel_async_flip_check

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Message-ID: <ZrPlbBGFAGLVfGf3@ashyti-mobl2.lan>
Date: Wed, 7 Aug 2024 22:21:48 +0100
From: Andi Shyti <andi.shyti@...ux.intel.com>
To: Ma Ke <make24@...as.ac.cn>
Cc: jani.nikula@...ux.intel.com, rodrigo.vivi@...el.com,
	joonas.lahtinen@...ux.intel.com, tursulin@...ulin.net,
	airlied@...il.com, daniel@...ll.ch, ville.syrjala@...ux.intel.com,
	stanislav.lisovskiy@...el.com, intel-gfx@...ts.freedesktop.org,
	intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] drm/i915: Fix NULL ptr deref in
 intel_async_flip_check_uapi()

Hi Ma,

> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index c2c388212e2e..9dd7b5985d57 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -6115,7 +6115,7 @@ static int intel_async_flip_check_uapi(struct intel_atomic_state *state,
>  		return -EINVAL;
>  	}
>  
> -	if (intel_crtc_needs_modeset(new_crtc_state)) {
> +	if (new_crtc_state && intel_crtc_needs_modeset(new_crtc_state)) {

new_crtc_state is used also earlier. If it was NULL you wouldn't
have reached this state.

Have you experienced a null pointer dereference or is it some
code analyzer that reported this? Can you explain how
intel_atomic_get_new_crtc_state() can return NULL?

For now this is nacked.

Thanks,
Andi