linux-kernel - Re: [PATCH] gpu-drm-tiny-cirrus: Add NULL check of pointer pipe->plane.state->fb in cirrus_pipe

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Date:   Fri, 17 Feb 2023 11:14:24 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Alexander Sapozhnikov <alsp705@...il.com>
Cc:     linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org,
        Jani Nikula <jani.nikula@...el.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] gpu-drm-tiny-cirrus: Add NULL check of pointer
 pipe->plane.state->fb in cirrus_pipe_update()

Hi

Am 15.02.23 um 18:15 schrieb Alexander Sapozhnikov:
> From: Alexandr Sapozhnikov <alsp705@...il.com>
> 
> After having been compared to NULL value at cirrus.c:455, pointer 'pipe->plane.state->fb' is passed as
> 1st parameter in call to function 'cirrus_fb_blit_rect' at cirrus.c:461, where it is dereferenced at cirrus.c:316.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Alexandr Sapozhnikov <alsp705@...il.com>

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

I'll add you patch to drm-misc-fixes.

Best regards
Thomas

> ---
>   drivers/gpu/drm/tiny/cirrus.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
> index 678c2ef..ffa7e61 100644
> --- a/drivers/gpu/drm/tiny/cirrus.c
> +++ b/drivers/gpu/drm/tiny/cirrus.c
> @@ -455,7 +455,7 @@ static void cirrus_pipe_update(struct drm_simple_display_pipe *pipe,
>   	if (state->fb && cirrus->cpp != cirrus_cpp(state->fb))
>   		cirrus_mode_set(cirrus, &crtc->mode, state->fb);
>   
> -	if (drm_atomic_helper_damage_merged(old_state, state, &rect))
> +	if (state->fb && drm_atomic_helper_damage_merged(old_state, state, &rect))
>   		cirrus_fb_blit_rect(state->fb, &shadow_plane_state->data[0], &rect);
>   }
>   

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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