Re: [PATCH] cpufreq: amd-pstate: add check for cpufreq_cpu_get's return value

From: Anastasia Belova
Date: Thu Aug 08 2024 - 09:35:21 EST


Hello,

06/06/24 12:55, Gautham R. Shenoy пишет:
Hello,

On Mon, Jun 03, 2024 at 02:07:41PM +0300, Anastasia Belova wrote:
cpufreq_cpu_get may return NULL. To avoid NULL-dereference check it
and return in case of error.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Anastasia Belova <abelova@xxxxxxxxxxxxx>
Thank you for the patch. Indeed we should be checking if the policy is
valid before dereferencing it.

---
drivers/cpufreq/amd-pstate.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 1b7e82a0ad2e..672cb6c280a4 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -621,6 +621,8 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
unsigned long max_perf, min_perf, des_perf,
cap_perf, lowest_nonlinear_perf, max_freq;
struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+ if (!policy)
+ return;
This patch mixes code and declarations. While I personally don't
prefer that, since we have moved to using C99, the compiler does
not complain, nor does checkpatch complain.

So is this ok for cpufreq, Rafael?

Should I form the second version without mixing code and declarations?
Or it is better to wait for Rafael's answer?


Or would you prefer something like:

unsigned long cap_perf, lowest_nonlinear_perf;
unsigned long max_perf, min_perf, des_perf;
struct cpufreq_policy *policy;
struct amd_cpudata *cpudata;
unsigned int target_freq;
unsigned long max_freq;

policy = cpufreq_cpu_get(cpu);
if (!policy)
return;

cpudata = policy->driver_data;



struct amd_cpudata *cpudata = policy->driver_data;
unsigned int target_freq;
@@ -777,6 +779,8 @@ static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
static void amd_pstate_update_limits(unsigned int cpu)
{
struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+ if (!policy)
+ return;
Ditto.

struct amd_cpudata *cpudata = policy->driver_data;
u32 prev_high = 0, cur_high = 0;
int ret;
--
2.30.2

--
Thanks and Regards
gautham.

Thanks,
Anastasia Belova