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

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Message-ID: <20251229183652.823308-1-srinivas.pandruvada@linux.intel.com>
Date: Mon, 29 Dec 2025 10:36:52 -0800
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: hansg@...nel.org,
	ilpo.jarvinen@...ux.intel.com
Cc: platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: [PATCH] platform/x86: ISST: Check for admin capability for write commands

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))
 			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