linux-kernel - Re: [PATCH] staging/media/imx: fix null pointer dereference

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Message-ID: <0d496695-ce20-4774-8e86-4d5c98dc220b@stanley.mountain>
Date: Thu, 10 Apr 2025 09:17:40 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Siddarth G <siddarthsgml@...il.com>
Cc: slongerbeam@...il.com, p.zabel@...gutronix.de, mchehab@...nel.org,
	gregkh@...uxfoundation.org, shawnguo@...nel.org,
	s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
	linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, skhan@...uxfoundation.org
Subject: Re: [PATCH] staging/media/imx: fix null pointer dereference

On Thu, Apr 10, 2025 at 02:47:27AM +0530, Siddarth G wrote:
> Cppcheck warnings:
> 
> drivers/staging/media/imx/imx-media-fim.c:79:6:
> error: Null pointer dereference: fi [ctunullpointer]
>   if (fi->denominator == 0) {
> 
> drivers/staging/media/imx/imx-media-csi.c:795:27:
> note: Calling function imx_media_fim_set_stream, 2nd argument is null
>   imx_media_fim_set_stream(priv->fim, NULL, false);
                                              ^^^^^
This is a false positive.  The false means that we don't call
update_fim_nominal().  Btw, Smatch parses this one correctly.

> 
> drivers/staging/media/imx/imx-media-fim.c:388:3:
> note: Calling function update_fim_nominal, 2nd argument is null
>   update_fim_nominal(fim, fi);
> 
> drivers/staging/media/imx/imx-media-fim.c:79:6:
> note: Dereferencing argument fi that is null
>   if (fi->denominator == 0) {
> 
> To fix the issue, add a check to validate that the 'fi' is not
> null before accessing its members.
> 
> Signed-off-by: Siddarth G <siddarthsgml@...il.com>

Don't resend because we just ignore false positives instead of
trying to silence them.  But if this were a real bug then it
would need a Fixes tag.

> ---
>  drivers/staging/media/imx/imx-media-fim.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/staging/media/imx/imx-media-fim.c b/drivers/staging/media/imx/imx-media-fim.c
> index ccbc0371fba2..25f79d0f87b9 100644
> --- a/drivers/staging/media/imx/imx-media-fim.c
> +++ b/drivers/staging/media/imx/imx-media-fim.c
> @@ -76,6 +76,9 @@ static bool icap_enabled(struct imx_media_fim *fim)
>  static void update_fim_nominal(struct imx_media_fim *fim,
>  			       const struct v4l2_fract *fi)
>  {
> +	if (!fi)
> +		return;

If this were a real bug, then probably the NULL check would be better in
the caller.

regards,
dan carpenter

> +
>  	if (fi->denominator == 0) {
>  		dev_dbg(fim->sd->dev, "no frame interval, FIM disabled\n");
>  		fim->enabled = false;
> -- 
> 2.43.0
>