Re: [PATCH] firmware: arm_scmi: Relax BASE protocol sanity checks on protocol list

[Michael Riesch <michael.riesch@wolfvision.net>]

Hi Cristian,

On 5/23/22 19:15, Cristian Marussi wrote:
> Even though malformed replies from firmware must be treated carefully to
> avoid memory corruption Kernel side, some out-of-spec SCMI replies can
> be tolerated to avoid breaking existing deployed system, as long as they
> won't cause memory issues.
> 
> Reported-by: Nicolas Frattaroli <frattaroli.nicolas@gmail.com>
> Cc: Etienne Carriere <etienne.carriere@linaro.org>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>

Thanks a lot, without this fix the Mali G52 GPU won't probe on my RK3568
EVB1 in vanilla v5.19-rc1.

I guess this patch should have a Fixes: tag, right?

Would be great to have this in v5.19. AFAIC:

Acked-by: Michael Riesch <michael.riesch@wolfvision.net>

Best regards,
Michael

> ---
>  drivers/firmware/arm_scmi/base.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c
> index 20fba7370f4e..d0ac96da1ddf 100644
> --- a/drivers/firmware/arm_scmi/base.c
> +++ b/drivers/firmware/arm_scmi/base.c
> @@ -221,11 +221,17 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph,
>  		calc_list_sz = (1 + (loop_num_ret - 1) / sizeof(u32)) *
>  				sizeof(u32);
>  		if (calc_list_sz != real_list_sz) {
> -			dev_err(dev,
> -				"Malformed reply - real_sz:%zd  calc_sz:%u\n",
> -				real_list_sz, calc_list_sz);
> -			ret = -EPROTO;
> -			break;
> +			dev_warn(dev,
> +				 "Malformed reply - real_sz:%zd  calc_sz:%u  (loop_num_ret:%d)\n",
> +				 real_list_sz, calc_list_sz, loop_num_ret);
> +			/*
> +			 * Bail out if the expected list size is bigger than the
> +			 * total payload size of the received reply.
> +			 */
> +			if (calc_list_sz > real_list_sz) {
> +				ret = -EPROTO;
> +				break;
> +			}
>  		}
>  
>  		for (loop = 0; loop < loop_num_ret; loop++)