linux-kernel - [PATCH -next] cpufreq: CPPC: Fix wrong return value in cppc_get_cpu

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Message-ID: <20241106011238.2407104-1-ruanjinjie@huawei.com>
Date: Wed, 6 Nov 2024 09:12:38 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <rafael@...nel.org>, <viresh.kumar@...aro.org>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <qperret@...gle.com>, <ruanjinjie@...wei.com>
Subject: [PATCH -next] cpufreq: CPPC: Fix wrong return value in cppc_get_cpu_cost()

cppc_get_cpu_cost() return 0 if the policy is NULL. Then in
em_compute_costs(), the later zero check for cost is not valid
as cost is uninitialized. As Quentin pointed out, kernel energy model
core check the return value of get_cost() first, so if the callback
failed it should tell the core. Return -EINVAL to fix it.

Fixes: 1a1374bb8c59 ("cpufreq: CPPC: Fix possible null-ptr-deref for cppc_get_cpu_cost()")
Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/all/c4765377-7830-44c2-84fa-706b6e304e10@stanley.mountain/
Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
Suggested-by: Quentin Perret <qperret@...gle.com>
---
 drivers/cpufreq/cppc_cpufreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index aa5dd194fc5b..cdc569cf7743 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -475,7 +475,7 @@ static int cppc_get_cpu_cost(struct device *cpu_dev, unsigned long KHz,
 
 	policy = cpufreq_cpu_get_raw(cpu_dev->id);
 	if (!policy)
-		return 0;
+		return -EINVAL;
 
 	cpu_data = policy->driver_data;
 	perf_caps = &cpu_data->perf_caps;
-- 
2.34.1