linux-kernel - [PATCH 5/9] perf/dwc_pcie: Avoid explicit cpumask var allocation from stack

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Message-Id: <20240402105610.1695644-6-dawei.li@shingroup.cn>
Date: Tue,  2 Apr 2024 18:56:06 +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 5/9] perf/dwc_pcie: 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/dwc_pcie_pmu.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/perf/dwc_pcie_pmu.c b/drivers/perf/dwc_pcie_pmu.c
index 957058ad0099..97037b6aaa97 100644
--- a/drivers/perf/dwc_pcie_pmu.c
+++ b/drivers/perf/dwc_pcie_pmu.c
@@ -690,33 +690,38 @@ static int dwc_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *cpuhp_n
 {
 	struct dwc_pcie_pmu *pcie_pmu;
 	struct pci_dev *pdev;
-	int node;
-	cpumask_t mask;
 	unsigned int target;
+	cpumask_var_t mask;
+	int node;
 
 	pcie_pmu = hlist_entry_safe(cpuhp_node, struct dwc_pcie_pmu, cpuhp_node);
 	/* Nothing to do if this CPU doesn't own the PMU */
 	if (cpu != pcie_pmu->on_cpu)
 		return 0;
 
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		return 0;
+
 	pcie_pmu->on_cpu = -1;
 	pdev = pcie_pmu->pdev;
 	node = dev_to_node(&pdev->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) {
 		pci_err(pdev, "There is no CPU to set\n");
-		return 0;
+		goto __free_cpumask;
 	}
 
 	/* This PMU does NOT support interrupt, just migrate context. */
 	perf_pmu_migrate_context(&pcie_pmu->pmu, cpu, target);
 	pcie_pmu->on_cpu = target;
 
+__free_cpumask:
+	free_cpumask_var(mask);
 	return 0;
 }
 
-- 
2.27.0