Re: [PATCH] greybus: lights: check return of get_channel_from_mode

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Mar 07, 2024 at 09:48:13AM +0000, Rui Miguel Silva wrote:
> If channel for the given node is not found we return null from
> get_channel_from_mode. Make sure we validate the return pointer
> before using it in two of the missing places.
> 
> This was originally reported in [0]:
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> [0] https://lore.kernel.org/all/20240301190425.120605-1-m.lobanov@rosalinux.ru
> 
> Fixes: 2870b52bae4c ("greybus: lights: add lights implementation")
> Reported-by: Mikhail Lobanov <m.lobanov@rosalinux.ru>
> Suggested-by: Mikhail Lobanov <m.lobanov@rosalinux.ru>
> Suggested-by: Alex Elder <elder@ieee.org>
> Signed-off-by: Rui Miguel Silva <rmfrfs@gmail.com>
> ---
>  drivers/staging/greybus/light.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c
> index c6bd86a5335a..6f10b9e2c053 100644
> --- a/drivers/staging/greybus/light.c
> +++ b/drivers/staging/greybus/light.c
> @@ -147,6 +147,9 @@ static int __gb_lights_flash_brightness_set(struct gb_channel *channel)
>  		channel = get_channel_from_mode(channel->light,
>  						GB_CHANNEL_MODE_TORCH);
>  
> +	if (!channel)
> +		return -EINVAL;
> +
>  	/* For not flash we need to convert brightness to intensity */
>  	intensity = channel->intensity_uA.min +
>  			(channel->intensity_uA.step * channel->led->brightness);
> @@ -549,7 +552,8 @@ static int gb_lights_light_v4l2_register(struct gb_light *light)
>  	}
>  
>  	channel_flash = get_channel_from_mode(light, GB_CHANNEL_MODE_FLASH);
> -	WARN_ON(!channel_flash);
> +	if (WARN_ON(!channel_flash))
> +		return -EINVAL;

We should NOT crash machines just because of this, the WARN_ON() should
be removed and just properly handle the error please.

thanks,

greg k-h