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    Subject[PATCH 4.11 158/197] cpuidle: check dev before usage in cpuidle_use_deepest_state()
    Date
    4.11-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Li, Fei <fei.li@intel.com>

    commit 41dc750ea67f317c0deedde713d1728425524ef2 upstream.

    In case of there is no cpuidle devices registered, dev will be null, and
    panic will be triggered like below;
    In this patch, add checking of dev before usage, like that done in
    cpuidle_idle_call.

    Panic without fix:
    [ 184.961328] BUG: unable to handle kernel NULL pointer dereference at
    (null)
    [ 184.961328] IP: cpuidle_use_deepest_state+0x30/0x60
    ...
    [ 184.961328] play_idle+0x8d/0x210
    [ 184.961328] ? __schedule+0x359/0x8e0
    [ 184.961328] ? _raw_spin_unlock_irqrestore+0x28/0x50
    [ 184.961328] ? kthread_queue_delayed_work+0x41/0x80
    [ 184.961328] clamp_idle_injection_func+0x64/0x1e0

    Fixes: bb8313b603eb8 (cpuidle: Allow enforcing deepest idle state selection)
    Signed-off-by: Li, Fei <fei.li@intel.com>
    Tested-by: Shi, Feng <fengx.shi@intel.com>
    Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/cpuidle/cpuidle.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/drivers/cpuidle/cpuidle.c
    +++ b/drivers/cpuidle/cpuidle.c
    @@ -111,7 +111,8 @@ void cpuidle_use_deepest_state(bool enab

    preempt_disable();
    dev = cpuidle_get_device();
    - dev->use_deepest_state = enable;
    + if (dev)
    + dev->use_deepest_state = enable;
    preempt_enable();
    }


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