linux-kernel - Re: [PATCH] drm/gma500: Fix end of loop tests for list_for_each

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Message-ID: <YOgDpQKxRfNxqhLm@phenom.ffwll.local>
Date:   Fri, 9 Jul 2021 10:07:01 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Harshvardhan Jha <harshvardhan.jha@...cle.com>
Cc:     patrik.r.jakobsson@...il.com, airlied@...ux.ie, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dan.carpenter@...cle.com
Subject: Re: [PATCH] drm/gma500: Fix end of loop tests for list_for_each_entry

On Fri, Jul 09, 2021 at 01:09:59PM +0530, Harshvardhan Jha wrote:
> The list_for_each_entry() iterator, "connector" in this code, can never be
> NULL.  If we exit the loop without finding the correct  connector then
> "connector" points invalid memory that is an offset from the list head.
> This will eventually lead to memory corruption and presumably a kernel
> crash.
> 
> Fixes: 9bd81acdb648 ("gma500: Convert Oaktrail to work with new output handling")
> Signed-off-by: Harshvardhan Jha <harshvardhan.jha@...cle.com>
>  ---

The space here before the --- tripped the tooling, but I caught it :-)

Thanks for the patch, applied to drm-misc-next for 5.15.
-Daniel

> From static analysis.  Not tested.
> ---
>  drivers/gpu/drm/gma500/oaktrail_lvds.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/gma500/oaktrail_lvds.c b/drivers/gpu/drm/gma500/oaktrail_lvds.c
> index 432bdcc57ac9..a1332878857b 100644
> --- a/drivers/gpu/drm/gma500/oaktrail_lvds.c
> +++ b/drivers/gpu/drm/gma500/oaktrail_lvds.c
> @@ -117,7 +117,7 @@ static void oaktrail_lvds_mode_set(struct drm_encoder *encoder,
>  			continue;
>  	}
>  
> -	if (!connector) {
> +	if (list_entry_is_head(connector, &mode_config->connector_list, head)) {
>  		DRM_ERROR("Couldn't find connector when setting mode");
>  		gma_power_end(dev);
>  		return;
> -- 
> 2.32.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch