linux-kernel - [PATCH 4/9] perf/arm_dsu: Avoid explicit cpumask var allocation from stack

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Date: Tue,  2 Apr 2024 18:56:05 +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 4/9] perf/arm_dsu: 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_dsu_pmu.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c
index bae3ca37f846..87efdca05807 100644
--- a/drivers/perf/arm_dsu_pmu.c
+++ b/drivers/perf/arm_dsu_pmu.c
@@ -230,13 +230,21 @@ static const struct attribute_group *dsu_pmu_attr_groups[] = {
 	NULL,
 };
 
-static int dsu_pmu_get_online_cpu_any_but(struct dsu_pmu *dsu_pmu, int cpu)
+static unsigned int dsu_pmu_get_online_cpu_any_but(struct dsu_pmu *dsu_pmu, int cpu)
 {
-	struct cpumask online_supported;
+	cpumask_var_t online_supported;
+	unsigned int ret;
 
-	cpumask_and(&online_supported,
-			 &dsu_pmu->associated_cpus, cpu_online_mask);
-	return cpumask_any_but(&online_supported, cpu);
+	if (!alloc_cpumask_var(&online_supported, GFP_KERNEL))
+		return -ENOMEM;
+
+	cpumask_and(online_supported,
+		    &dsu_pmu->associated_cpus, cpu_online_mask);
+	ret = cpumask_any_but(&online_supported, cpu);
+
+	free_cpumask_var(online_supported);
+
+	return ret;
 }
 
 static inline bool dsu_pmu_counter_valid(struct dsu_pmu *dsu_pmu, u32 idx)
-- 
2.27.0