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

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Message-ID: <2026010842-disown-reminder-752d@gregkh>
Date: Thu, 8 Jan 2026 12:01:55 +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 v2] staging: greybus: lights: avoid NULL deref

On Thu, Jan 08, 2026 at 04:19:47PM +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.
> 
> 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)
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot