linux-kernel - Re: [PATCH] media: staging/imx: Fix NULL deref in find_pipeline

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Message-ID: <20190627070452.GA19308@kadam>
Date:   Thu, 27 Jun 2019 10:04:52 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Steve Longerbeam <slongerbeam@...il.com>
Cc:     linux-media@...r.kernel.org,
        "open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        open list <linux-kernel@...r.kernel.org>,
        NXP Linux Team <linux-imx@....com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] media: staging/imx: Fix NULL deref in
 find_pipeline_entity()

On Wed, Jun 26, 2019 at 11:52:25AM -0700, Steve Longerbeam wrote:
> Fix a cut&paste error in find_pipeline_entity(). The start entity must be
> passed to media_entity_to_video_device() in find_pipeline_entity(), not
> pad->entity. The pad is only put to use later, after determining the start
> entity is not the entity being searched for.
> 
> Fixes: 3ef46bc97ca2 ("media: staging/imx: Improve pipeline searching")
> 
> Reported-by: Colin Ian King <colin.king@...onical.com>
> Signed-off-by: Steve Longerbeam <slongerbeam@...il.com>
> ---
>  drivers/staging/media/imx/imx-media-utils.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/media/imx/imx-media-utils.c b/drivers/staging/media/imx/imx-media-utils.c
> index b5b8a3b7730a..6fb88c22ee27 100644
> --- a/drivers/staging/media/imx/imx-media-utils.c
> +++ b/drivers/staging/media/imx/imx-media-utils.c
> @@ -842,7 +842,7 @@ find_pipeline_entity(struct media_entity *start, u32 grp_id,
>  		if (sd->grp_id & grp_id)
>  			return &sd->entity;
>  	} else if (buftype && is_media_entity_v4l2_video_device(start)) {
> -		vfd = media_entity_to_video_device(pad->entity);
> +		vfd = media_entity_to_video_device(start);

Can we also remove the "pad = NULL" assignment at the start of the
function?  Otherwise static checkers and new versions of GCC will warn
that the assignment isn't used.  Plus removing the initialization will
prevent bugs like this in the future.

regards,
dan carpenter