linux-kernel - [PATCH 3/9] perf/arm_cspmu: Avoid explicit cpumask var allocation from stack

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Date: Tue,  2 Apr 2024 18:56:04 +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 3/9] perf/arm_cspmu: 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/arm_cspmu/arm_cspmu.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
index b9a252272f1e..8fa7c26aec28 100644
--- a/drivers/perf/arm_cspmu/arm_cspmu.c
+++ b/drivers/perf/arm_cspmu/arm_cspmu.c
@@ -1322,8 +1322,8 @@ static int arm_cspmu_cpu_online(unsigned int cpu, struct hlist_node *node)
 
 static int arm_cspmu_cpu_teardown(unsigned int cpu, struct hlist_node *node)
 {
+	cpumask_var_t online_supported;
 	int dst;
-	struct cpumask online_supported;
 
 	struct arm_cspmu *cspmu =
 		hlist_entry_safe(node, struct arm_cspmu, cpuhp_node);
@@ -1332,17 +1332,22 @@ static int arm_cspmu_cpu_teardown(unsigned int cpu, struct hlist_node *node)
 	if (!cpumask_test_and_clear_cpu(cpu, &cspmu->active_cpu))
 		return 0;
 
+	if (!alloc_cpumask_var(&online_supported, GFP_KERNEL))
+		return 0;
+
 	/* Choose a new CPU to migrate ownership of the PMU to */
-	cpumask_and(&online_supported, &cspmu->associated_cpus,
+	cpumask_and(online_supported, &cspmu->associated_cpus,
 		    cpu_online_mask);
-	dst = cpumask_any_but(&online_supported, cpu);
+	dst = cpumask_any_but(online_supported, cpu);
 	if (dst >= nr_cpu_ids)
-		return 0;
+		goto __free_cpumask;
 
 	/* Use this CPU for event counting */
 	perf_pmu_migrate_context(&cspmu->pmu, cpu, dst);
 	arm_cspmu_set_active_cpu(dst, cspmu);
 
+__free_cpumask:
+	free_cpumask_var(online_supported);
 	return 0;
 }
 
-- 
2.27.0