linux-kernel - Re: [PATCH] platform/x86: ISST: Check for admin capability for write commands

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Message-ID: <b402fa2b-0cc8-d39a-6f35-3680ff54407b@linux.intel.com>
Date: Tue, 6 Jan 2026 11:49:13 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
cc: Hans de Goede <hansg@...nel.org>, platform-driver-x86@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: ISST: Check for admin capability for write
 commands

On Mon, 29 Dec 2025, Srinivas Pandruvada wrote:

> In some SST deployments, administrators want to allow reading SST
> capabilities for non-root users. This can be achieved by changing file
> permissions for "/dev/isst_interface", but they still want to prevent
> any changes to the SST configuration by non-root users.
> 
> This capability was available before for non-TPMI SST. Extend the same
> capability for TPMI SST by adding a check for CAP_SYS_ADMIN for all
> write commands.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
>  .../x86/intel/speed_select_if/isst_tpmi_core.c        | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> index 47026bb3e1af..a624e0b2991f 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> @@ -612,7 +612,7 @@ static long isst_if_core_power_state(void __user *argp)
>  		return -EINVAL;
>  
>  	if (core_power.get_set) {
> -		if (power_domain_info->write_blocked)
> +		if (power_domain_info->write_blocked || !capable(CAP_SYS_ADMIN))

Hi,

This check doesn't exist in my tree, you seem to have mis-submitted this 
independently of the other series that adds the check.

-- 
 i.

>  			return -EPERM;
>  
>  		_write_cp_info("cp_enable", core_power.enable, SST_CP_CONTROL_OFFSET,
> @@ -659,7 +659,7 @@ static long isst_if_clos_param(void __user *argp)
>  		return -EINVAL;
>  
>  	if (clos_param.get_set) {
> -		if (power_domain_info->write_blocked)
> +		if (power_domain_info->write_blocked || !capable(CAP_SYS_ADMIN))
>  			return -EPERM;
>  
>  		_write_cp_info("clos.min_freq", clos_param.min_freq_mhz,
> @@ -751,7 +751,8 @@ static long isst_if_clos_assoc(void __user *argp)
>  
>  		power_domain_info = &sst_inst->power_domain_info[part][punit_id];
>  
> -		if (assoc_cmds.get_set && power_domain_info->write_blocked)
> +		if (assoc_cmds.get_set && (power_domain_info->write_blocked ||
> +					   !capable(CAP_SYS_ADMIN)))
>  			return -EPERM;
>  
>  		offset = SST_CLOS_ASSOC_0_OFFSET +
> @@ -928,7 +929,7 @@ static int isst_if_set_perf_level(void __user *argp)
>  	if (!power_domain_info)
>  		return -EINVAL;
>  
> -	if (power_domain_info->write_blocked)
> +	if (power_domain_info->write_blocked || !capable(CAP_SYS_ADMIN))
>  		return -EPERM;
>  
>  	if (!(power_domain_info->pp_header.allowed_level_mask & BIT(perf_level.level)))
> @@ -988,7 +989,7 @@ static int isst_if_set_perf_feature(void __user *argp)
>  	if (!power_domain_info)
>  		return -EINVAL;
>  
> -	if (power_domain_info->write_blocked)
> +	if (power_domain_info->write_blocked || !capable(CAP_SYS_ADMIN))
>  		return -EPERM;
>  
>  	_write_pp_info("perf_feature", perf_feature.feature, SST_PP_CONTROL_OFFSET,
>