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* [PATCH v2] clockevents/drivers/cs5535: improve resilience to spurious interrupts
@ 2017-10-19 20:57 David Kozub
  2017-10-20 11:45 ` [tip:timers/urgent] clockevents/drivers/cs5535: Improve " tip-bot for David Kozub
  0 siblings, 1 reply; 2+ messages in thread
From: David Kozub @ 2017-10-19 20:57 UTC (permalink / raw)
  To: Daniel Lezcano, Thomas Gleixner; +Cc: linux-kernel

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.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Kozub <zub@linux.fjfi.cvut.cz>
---
Changes in v2:
  - Use commit message suggested by Thomas Gleixner
  - Fix formatting of multi-line if condition

 drivers/clocksource/cs5535-clockevt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/cs5535-clockevt.c b/drivers/clocksource/cs5535-clockevt.c
index a1df588343f2..1de8cac99a0e 100644
--- a/drivers/clocksource/cs5535-clockevt.c
+++ b/drivers/clocksource/cs5535-clockevt.c
@@ -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 */
-- 
2.14.2

^ permalink raw reply	[flat|nested] 2+ messages in thread

* [tip:timers/urgent] clockevents/drivers/cs5535: Improve resilience to spurious interrupts
  2017-10-19 20:57 [PATCH v2] clockevents/drivers/cs5535: improve resilience to spurious interrupts David Kozub
@ 2017-10-20 11:45 ` tip-bot for David Kozub
  0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for David Kozub @ 2017-10-20 11:45 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: tglx, hpa, daniel.lezcano, linux-kernel, zub, mingo

Commit-ID:  eb39a7c0355393c5a8d930f342ad7a6231b552c4
Gitweb:     https://git.kernel.org/tip/eb39a7c0355393c5a8d930f342ad7a6231b552c4
Author:     David Kozub <zub@linux.fjfi.cvut.cz>
AuthorDate: Thu, 19 Oct 2017 22:57:02 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 20 Oct 2017 13:41:52 +0200

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: 8f9327cbb6e8 ("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

---
 drivers/clocksource/cs5535-clockevt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/cs5535-clockevt.c b/drivers/clocksource/cs5535-clockevt.c
index a1df588..1de8cac 100644
--- a/drivers/clocksource/cs5535-clockevt.c
+++ b/drivers/clocksource/cs5535-clockevt.c
@@ -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 */

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2017-10-20 11:48 UTC | newest]

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2017-10-19 20:57 [PATCH v2] clockevents/drivers/cs5535: improve resilience to spurious interrupts David Kozub
2017-10-20 11:45 ` [tip:timers/urgent] clockevents/drivers/cs5535: Improve " tip-bot for David Kozub

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