[PATCH] platform/x86: ISST: Check for admin capability for write commands

[PATCH] platform/x86: ISST: Check for admin capability for write commands

[Srinivas Pandruvada]

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@linux.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))
 			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,
-- 
2.52.0

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

[Ilpo Järvinen]

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@linux.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,
> 

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

[srinivas pandruvada]

On Tue, 2026-01-06 at 11:49 +0200, Ilpo Järvinen wrote:
> 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@linux.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.

Hi llpo,

This was part of the series, which was submitted as bug fix before.
[PATCH 0/2] platform/x86: ISST: Fix for write lock and suspend/resume

I should have added this as dependency.

Thanks,
Srinivas