[PATCH -next] cpufreq: CPPC: Fix wrong return value in cppc_get_cpu_cost()

From: Jinjie Ruan
Date: Tue Nov 05 2024 - 20:13:50 EST


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@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/c4765377-7830-44c2-84fa-706b6e304e10@stanley.mountain/
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
Suggested-by: Quentin Perret <qperret@xxxxxxxxxx>
---
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