linux-kernel - [PATCH 2/9] perf/arm-cmn: Avoid explicit cpumask var allocation from stack

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Date: Tue,  2 Apr 2024 18:56:03 +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 2/9] perf/arm-cmn: 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-cmn.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 7ef9c7e4836b..7278fd72d3da 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1949,21 +1949,26 @@ static int arm_cmn_pmu_offline_cpu(unsigned int cpu, struct hlist_node *cpuhp_no
 {
 	struct arm_cmn *cmn;
 	unsigned int target;
+	cpumask_var_t mask;
 	int node;
-	cpumask_t mask;
 
 	cmn = hlist_entry_safe(cpuhp_node, struct arm_cmn, cpuhp_node);
 	if (cpu != cmn->cpu)
 		return 0;
 
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		return 0;
+
 	node = dev_to_node(cmn->dev);
-	if (cpumask_and(&mask, cpumask_of_node(node), cpu_online_mask) &&
-	    cpumask_andnot(&mask, &mask, cpumask_of(cpu)))
-		target = cpumask_any(&mask);
+	if (cpumask_and(mask, cpumask_of_node(node), cpu_online_mask) &&
+	    cpumask_andnot(mask, mask, cpumask_of(cpu)))
+		target = cpumask_any(mask);
 	else
 		target = cpumask_any_but(cpu_online_mask, cpu);
 	if (target < nr_cpu_ids)
 		arm_cmn_migrate(cmn, target);
+
+	free_cpumask_var(mask);
 	return 0;
 }
 
-- 
2.27.0