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

[Etienne Carriere]

Hello Cristian,

On Mon, 23 May 2022 at 19:17, Cristian Marussi <cristian.marussi at arm.com> 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 at gmail.com>
> Cc: Etienne Carriere <etienne.carriere at linaro.org>
> Cc: Sudeep Holla <sudeep.holla at arm.com>
> Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>

Acked-by: Etienne Carriere <etienne.carriere at linaro.org>

Best regards,
etienne

> ---
>  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++)
> --
> 2.36.1
>