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clockevents/drivers/cs5535: Improve resilience to spurious interrupts 

The interrupt handler mfgpt_tick() is not robust versus spurious interrupts
which happen before the clock event device is registered and fully
initialized.

The reason is that the safe guard against spurious interrupts solely checks
for the clockevents shutdown state, but lacks a check for detached
state. If the interrupt hits while the device is in detached state it
passes the safe guard and dereferences the event handler call back which is
NULL.

Add the missing state check.

Fixes: 8f9327cbb6 ("clockevents/drivers/cs5535: Migrate to new 'set-state' interface")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Kozub <zub@linux.fjfi.cvut.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20171020093103.3317F6004D@linux.fjfi.cvut.cz
zero-colors
David Kozub 2017-10-19 22:57:02 +02:00 committed by Thomas Gleixner
parent 33d930e59a
commit eb39a7c035
1 changed files with 2 additions and 1 deletions
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3
drivers/clocksource/cs5535-clockevt.c
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@ -117,7 +117,8 @@ static irqreturn_t mfgpt_tick(int irq, void *dev_id)
/* Turn off the clock (and clear the event) */
disable_timer(cs5535_event_clock);
if (clockevent_state_shutdown(&cs5535_clockevent))
if (clockevent_state_detached(&cs5535_clockevent) ||
clockevent_state_shutdown(&cs5535_clockevent))
return IRQ_HANDLED;
/* Clear the counter */