linux-kernel - [PATCH 8/9] perf/qcom_l2: Avoid explicit cpumask var allocation from stack

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Date: Tue,  2 Apr 2024 18:56:09 +0800
From: Dawei Li <dawei.li@...ngroup.cn>
To: will@...nel.org,
	mark.rutland@....com
Cc: xueshuai@...ux.alibaba.com,
	renyu.zj@...ux.alibaba.com,
	yangyicong@...ilicon.com,
	jonathan.cameron@...wei.com,
	andersson@...nel.org,
	konrad.dybcio@...aro.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	Dawei Li <dawei.li@...ngroup.cn>
Subject: [PATCH 8/9] perf/qcom_l2: Avoid explicit cpumask var allocation from stack

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@...ngroup.cn>
---
 drivers/perf/qcom_l2_pmu.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c
index 148df5ae8ef8..8fe0c7557521 100644
--- a/drivers/perf/qcom_l2_pmu.c
+++ b/drivers/perf/qcom_l2_pmu.c
@@ -801,9 +801,9 @@ static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
 
 static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
 {
-	struct cluster_pmu *cluster;
+	cpumask_var_t cluster_online_cpus;
 	struct l2cache_pmu *l2cache_pmu;
-	cpumask_t cluster_online_cpus;
+	struct cluster_pmu *cluster;
 	unsigned int target;
 
 	l2cache_pmu = hlist_entry_safe(node, struct l2cache_pmu, node);
@@ -815,17 +815,20 @@ static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
 	if (cluster->on_cpu != cpu)
 		return 0;
 
+	if (!alloc_cpumask_var(&cluster_online_cpus, GFP_KERNEL))
+		return 0;
+
 	/* Give up ownership of cluster */
 	cpumask_clear_cpu(cpu, &l2cache_pmu->cpumask);
 	cluster->on_cpu = -1;
 
 	/* Any other CPU for this cluster which is still online */
-	cpumask_and(&cluster_online_cpus, &cluster->cluster_cpus,
+	cpumask_and(cluster_online_cpus, &cluster->cluster_cpus,
 		    cpu_online_mask);
-	target = cpumask_any_but(&cluster_online_cpus, cpu);
+	target = cpumask_any_but(cluster_online_cpus, cpu);
 	if (target >= nr_cpu_ids) {
 		disable_irq(cluster->irq);
-		return 0;
+		goto __free_cpumask;
 	}
 
 	perf_pmu_migrate_context(&l2cache_pmu->pmu, cpu, target);
@@ -833,6 +836,8 @@ static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
 	cpumask_set_cpu(target, &l2cache_pmu->cpumask);
 	WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(target)));
 
+__free_cpumask:
+	free_cpumask_var(cluster_online_cpus);
 	return 0;
 }
 
-- 
2.27.0