[PATCH 0/9] perf: Avoid explicit cpumask var allocation from stack

[Dawei Li <dawei.li@xxxxxxxxxxxx>]

Hi,

This series try to eliminate direct cpumask var allocation from stack
for perf subsystem.

Direct/explicit allocation of cpumask on stack could be dangerous since
it can lead to stack overflow for systems with big NR_CPUS or
CONFIG_CPUMASK_OFFSTACK=y.

For arm64, it's more urgent since commit 3fbd56f0e7c1 ("ARM64: Dynamically
allocate cpumasks and increase supported CPUs to 512").

It's sort of a pattern that almost every cpumask var in perf subystem
occurs in teardown callback of cpuhp. In which case, if dynamic
allocation failed(which is unlikely), we choose return 0 rather than
-ENOMEM to caller cuz:
@teardown is not supposed to fail and if it does, system crashes:

static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
                            struct hlist_node *node)
{
        struct cpuhp_step *sp = cpuhp_get_step(state);
        int ret;

        /*
         * If there's nothing to do, we done.
         * Relies on the union for multi_instance.
         */
        if (cpuhp_step_empty(bringup, sp))
                return 0;
        /*
         * The non AP bound callbacks can fail on bringup. On teardown
         * e.g. module removal we crash for now.
         */
	#ifdef CONFIG_SMP
        if (cpuhp_is_ap_state(state))
                ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
        else
                ret = cpuhp_invoke_callback(cpu, state, bringup, node,
		NULL);
	#else
        ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
	#endif
        BUG_ON(ret && !bringup);
        return ret;
}

Dawei Li (9):
  perf/alibaba_uncore_drw: Avoid explicit cpumask var allocation from
    stack
  perf/arm-cmn: Avoid explicit cpumask var allocation from stack
  perf/arm_cspmu: Avoid explicit cpumask var allocation from stack
  perf/arm_dsu: Avoid explicit cpumask var allocation from stack
  perf/dwc_pcie: Avoid explicit cpumask var allocation from stack
  perf/hisi_pcie: Avoid explicit cpumask var allocation from stack
  perf/hisi_uncore: Avoid explicit cpumask var allocation from stack
  perf/qcom_l2: Avoid explicit cpumask var allocation from stack
  perf/thunder_x2: Avoid explicit cpumask var allocation from stack

 drivers/perf/alibaba_uncore_drw_pmu.c    | 13 +++++++++----
 drivers/perf/arm-cmn.c                   | 13 +++++++++----
 drivers/perf/arm_cspmu/arm_cspmu.c       | 13 +++++++++----
 drivers/perf/arm_dsu_pmu.c               | 18 +++++++++++++-----
 drivers/perf/dwc_pcie_pmu.c              | 17 +++++++++++------
 drivers/perf/hisilicon/hisi_pcie_pmu.c   | 15 ++++++++++-----
 drivers/perf/hisilicon/hisi_uncore_pmu.c | 13 +++++++++----
 drivers/perf/qcom_l2_pmu.c               | 15 ++++++++++-----
 drivers/perf/thunderx2_pmu.c             | 20 ++++++++++++--------
 9 files changed, 92 insertions(+), 45 deletions(-)


Thanks,

    Dawei

-- 
2.27.0