linux-kernel - Re: [PATCH v2] staging: greybus: lights: avoid NULL deref

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Message-Id: <DFJ5Q0E4QQ0F.1A6G2J04HJNH1@linaro.com>
Date: Thu, 08 Jan 2026 11:05:09 +0000
From: Rui Miguel Silva <rui.silva@...aro.org>
To: "Chaitanya Mishra" <chaitanyamishra.ai@...il.com>, <rmfrfs@...il.com>,
 <johan@...nel.org>, <elder@...nel.org>, <gregkh@...uxfoundation.org>
Cc: <greybus-dev@...ts.linaro.org>, <linux-staging@...ts.linux.dev>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] staging: greybus: lights: avoid NULL deref

Hey Chaitanya,
Thanks for the patch.

On Thu Jan 8, 2026 at 10:49 AM WET, Chaitanya Mishra wrote:

> gb_lights_light_config() stores channel_count before allocating the
> channels array. If kcalloc() fails, gb_lights_release() iterates the
> non-zero count and dereferences light->channels, which is NULL.
>
> Allocate channels first and only then publish channels_count so the
> cleanup path can't walk a NULL pointer.

Good catch, going through the error path, does looks this fix the issue.

But you need to add the changes between versions bellow --  and maybe a
link to the first version.

Reviewed-by: Rui Miguel Silva <rui.silva@...aro.org>

Cheers,
    Rui
>
> Fixes: 2870b52bae4c ("greybus: lights: add lights implementation")
> Signed-off-by: Chaitanya Mishra <chaitanyamishra.ai@...il.com>
> ---
>  drivers/staging/greybus/light.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c
> index e509fdc715db..38c233a706c4 100644
> --- a/drivers/staging/greybus/light.c
> +++ b/drivers/staging/greybus/light.c
> @@ -1008,14 +1008,18 @@ static int gb_lights_light_config(struct gb_lights *glights, u8 id)
>  	if (!strlen(conf.name))
>  		return -EINVAL;
>  
> -	light->channels_count = conf.channel_count;
>  	light->name = kstrndup(conf.name, NAMES_MAX, GFP_KERNEL);
>  	if (!light->name)
>  		return -ENOMEM;
> -	light->channels = kcalloc(light->channels_count,
> +	light->channels = kcalloc(conf.channel_count,
>  				  sizeof(struct gb_channel), GFP_KERNEL);
>  	if (!light->channels)
>  		return -ENOMEM;
> +	/*
> +	 * Publish channels_count only after channels allocation so cleanup
> +	 * doesn't walk a NULL channels pointer on allocation failure.
> +	 */
> +	light->channels_count = conf.channel_count;
>  
>  	/* First we collect all the configurations for all channels */
>  	for (i = 0; i < light->channels_count; i++) {
> -- 
> 2.50.1 (Apple Git-155)