[PATCH 9/9] perf/thunder_x2: Avoid explicit cpumask var allocation from stack

From: Dawei Li
Date: Tue Apr 02 2024 - 07:01:25 EST


For CONFIG_CPUMASK_OFFSTACK=y kernel, explicit allocation of cpumask
variable on stack is not recommended since it can cause potential stack
overflow.

Instead, kernel code should always use *cpumask_var API(s) to allocate
cpumask var in config- neutral way, leaving allocation strategy to
CONFIG_CPUMASK_OFFSTACK.

Use *cpumask_var API(s) to address it.

Signed-off-by: Dawei Li <dawei.li@xxxxxxxxxxxx>
---
drivers/perf/thunderx2_pmu.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/perf/thunderx2_pmu.c b/drivers/perf/thunderx2_pmu.c
index e16d10c763de..8a02a4533b32 100644
--- a/drivers/perf/thunderx2_pmu.c
+++ b/drivers/perf/thunderx2_pmu.c
@@ -932,9 +932,9 @@ static int tx2_uncore_pmu_online_cpu(unsigned int cpu,
static int tx2_uncore_pmu_offline_cpu(unsigned int cpu,
struct hlist_node *hpnode)
{
- int new_cpu;
+ cpumask_var_t cpu_online_mask_temp;
struct tx2_uncore_pmu *tx2_pmu;
- struct cpumask cpu_online_mask_temp;
+ int new_cpu;

tx2_pmu = hlist_entry_safe(hpnode,
struct tx2_uncore_pmu, hpnode);
@@ -945,17 +945,21 @@ static int tx2_uncore_pmu_offline_cpu(unsigned int cpu,
if (tx2_pmu->hrtimer_callback)
hrtimer_cancel(&tx2_pmu->hrtimer);

- cpumask_copy(&cpu_online_mask_temp, cpu_online_mask);
- cpumask_clear_cpu(cpu, &cpu_online_mask_temp);
- new_cpu = cpumask_any_and(
- cpumask_of_node(tx2_pmu->node),
- &cpu_online_mask_temp);
+ if (!alloc_cpumask_var(&cpu_online_mask_temp, GFP_KERNEL))
+ return 0;
+
+ cpumask_copy(cpu_online_mask_temp, cpu_online_mask);
+ cpumask_clear_cpu(cpu, cpu_online_mask_temp);
+ new_cpu = cpumask_any_and(cpumask_of_node(tx2_pmu->node),
+ cpu_online_mask_temp);

tx2_pmu->cpu = new_cpu;
if (new_cpu >= nr_cpu_ids)
- return 0;
+ goto __free_cpumask;
perf_pmu_migrate_context(&tx2_pmu->pmu, cpu, new_cpu);

+__free_cpumask:
+ free_cpumask_var(cpu_online_mask_temp);
return 0;
}

--
2.27.0