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    Subject[PATCH 5.4 455/475] perf: qcom_l2_pmu: fix an incorrect NULL check on list iterator
    Date
    From: Xiaomeng Tong <xiam0nd.tong@gmail.com>

    commit 2012a9e279013933885983cbe0a5fe828052563b upstream.

    The bug is here:
    return cluster;

    The list iterator value 'cluster' will *always* be set and non-NULL
    by list_for_each_entry(), so it is incorrect to assume that the
    iterator value will be NULL if the list is empty or no element
    is found.

    To fix the bug, return 'cluster' when found, otherwise return NULL.

    Cc: stable@vger.kernel.org
    Fixes: 21bdbb7102ed ("perf: add qcom l2 cache perf events driver")
    Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
    Link: https://lore.kernel.org/r/20220327055733.4070-1-xiam0nd.tong@gmail.com
    Signed-off-by: Will Deacon <will@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/perf/qcom_l2_pmu.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    --- a/drivers/perf/qcom_l2_pmu.c
    +++ b/drivers/perf/qcom_l2_pmu.c
    @@ -781,7 +781,7 @@ static struct cluster_pmu *l2_cache_asso
    {
    u64 mpidr;
    int cpu_cluster_id;
    - struct cluster_pmu *cluster = NULL;
    + struct cluster_pmu *cluster;

    /*
    * This assumes that the cluster_id is in MPIDR[aff1] for
    @@ -803,10 +803,10 @@ static struct cluster_pmu *l2_cache_asso
    cluster->cluster_id);
    cpumask_set_cpu(cpu, &cluster->cluster_cpus);
    *per_cpu_ptr(l2cache_pmu->pmu_cluster, cpu) = cluster;
    - break;
    + return cluster;
    }

    - return cluster;
    + return NULL;
    }

    static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)

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