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    Subject[PATCH 5.15 037/121] sched/debug: fix dentry leak in update_sched_domain_debugfs
    Date
    From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    commit c2e406596571659451f4b95e37ddfd5a8ef1d0dc upstream.

    Kuyo reports that the pattern of using debugfs_remove(debugfs_lookup())
    leaks a dentry and with a hotplug stress test, the machine eventually
    runs out of memory.

    Fix this up by using the newly created debugfs_lookup_and_remove() call
    instead which properly handles the dentry reference counting logic.

    Cc: Major Chen <major.chen@samsung.com>
    Cc: stable <stable@kernel.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Juri Lelli <juri.lelli@redhat.com>
    Cc: Vincent Guittot <vincent.guittot@linaro.org>
    Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Ben Segall <bsegall@google.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
    Cc: Valentin Schneider <vschneid@redhat.com>
    Cc: Matthias Brugger <matthias.bgg@gmail.com>
    Reported-by: Kuyo Chang <kuyo.chang@mediatek.com>
    Tested-by: Kuyo Chang <kuyo.chang@mediatek.com>
    Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lore.kernel.org/r/20220902123107.109274-2-gregkh@linuxfoundation.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/sched/debug.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/sched/debug.c
    +++ b/kernel/sched/debug.c
    @@ -416,7 +416,7 @@ void update_sched_domain_debugfs(void)
    char buf[32];

    snprintf(buf, sizeof(buf), "cpu%d", cpu);
    - debugfs_remove(debugfs_lookup(buf, sd_dentry));
    + debugfs_lookup_and_remove(buf, sd_dentry);
    d_cpu = debugfs_create_dir(buf, sd_dentry);

    i = 0;

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