linux-kernel - [PATCH v3] PM: EM: Fix potential division-by-zero error in em_compute

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tencent_6D2374392DB66C9D23BF6E2546638A42EC08@qq.com>
Date: Mon, 14 Apr 2025 17:04:06 +0800
From: Yaxiong Tian <iambestgod@...com>
To: lukasz.luba@....com,
	rafael@...nel.org
Cc: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yaxiong Tian <tianyaxiong@...inos.cn>
Subject: [PATCH v3] PM: EM: Fix potential division-by-zero error in em_compute_costs()

From: Yaxiong Tian <tianyaxiong@...inos.cn>

When the device is of a non-CPU type, table[i].performance won't be
initialized in the previous em_init_performance(), resulting in division
by zero when calculating costs in em_compute_costs().

Since the 'cost' algorithm is only used for EAS energy efficiency
calculations and is currently not utilized by other device drivers, we
should add the _is_cpu_device(dev) check to prevent this division-by-zero
issue.

Fixes: <1b600da51073> ("PM: EM: Optimize em_cpu_energy() and remove division")
Signed-off-by: Yaxiong Tian <tianyaxiong@...inos.cn>
---
 kernel/power/energy_model.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index d9b7e2b38c7a..fc972cc1fc12 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -235,7 +235,7 @@ static int em_compute_costs(struct device *dev, struct em_perf_state *table,
 
 	/* Compute the cost of each performance state. */
 	for (i = nr_states - 1; i >= 0; i--) {
-		unsigned long power_res, cost;
+		unsigned long power_res, cost = 0;
 
 		if ((flags & EM_PERF_DOMAIN_ARTIFICIAL) && cb->get_cost) {
 			ret = cb->get_cost(dev, table[i].frequency, &cost);
@@ -244,7 +244,7 @@ static int em_compute_costs(struct device *dev, struct em_perf_state *table,
 					cost, ret);
 				return -EINVAL;
 			}
-		} else {
+		} else if (_is_cpu_device(dev)) {
 			/* increase resolution of 'cost' precision */
 			power_res = table[i].power * 10;
 			cost = power_res / table[i].performance;
-- 
2.25.1