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

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Message-ID: <2026010814-displease-jawed-688e@gregkh>
Date: Thu, 8 Jan 2026 11:46:26 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Chaitanya Mishra <chaitanyamishra.ai@...il.com>
Cc: rmfrfs@...il.com, johan@...nel.org, elder@...nel.org,
	greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: greybus: lights: avoid NULL deref

On Thu, Jan 08, 2026 at 04:07:00PM +0530, 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.

How was this issue found?  How was the fix generated?  How was it
tested?

> 
> Fixes: 2870b52bae4c ("greybus: lights: add lights implementation")
> Signed-off-by: Chaitanya Mishra <chaitanyamishra.ai@...il.com>
> ---
>  drivers/staging/greybus/light.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c
> index e509fdc715db..4c9ad9ea8827 100644
> --- a/drivers/staging/greybus/light.c
> +++ b/drivers/staging/greybus/light.c
> @@ -1008,14 +1008,14 @@ 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;
> +	light->channels_count = conf.channel_count;

This is "tricky", perhaps add a comment here as to why you are only
assigning this now and not before?

thanks,

greg k-h