[3.13.y-ckt stable] Patch "clockevent: sun4i: Fix race condition in the probe code" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    clockevent: sun4i: Fix race condition in the probe code

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From fcbd19bed6af03838ca54af8b86323f4904a10c9 Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime.ripard at free-electrons.com>
Date: Tue, 18 Nov 2014 23:59:33 +0100
Subject: clockevent: sun4i: Fix race condition in the probe code

commit 6bab4a8a1888729f17f4923cc5867e4674f66333 upstream.

The interrupts were activated and the handler registered before the clockevent
was registered in the probe function.

The interrupt handler, however, was making the assumption that the clockevent
device was registered.

That could cause a null pointer dereference if the timer interrupt was firing
during this narrow window.

Fix that by moving the clockevent registration before the interrupt is enabled.

Reported-by: Roman Byshko <rbyshko at gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano at linaro.org>
[ kamal: backport to 3.13-stable ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/clocksource/sun4i_timer.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/clocksource/sun4i_timer.c b/drivers/clocksource/sun4i_timer.c
index a4f6119..aff7a7c 100644
--- a/drivers/clocksource/sun4i_timer.c
+++ b/drivers/clocksource/sun4i_timer.c
@@ -182,6 +182,11 @@ static void __init sun4i_timer_init(struct device_node *node)
 	/* Make sure timer is stopped before playing with interrupts */
 	sun4i_clkevt_time_stop(0);

+	sun4i_clockevent.cpumask = cpumask_of(0);
+
+	clockevents_config_and_register(&sun4i_clockevent, rate,
+					TIMER_SYNC_TICKS, 0xffffffff);
+
 	ret = setup_irq(irq, &sun4i_timer_irq);
 	if (ret)
 		pr_warn("failed to setup irq %d\n", irq);
@@ -189,11 +194,6 @@ static void __init sun4i_timer_init(struct device_node *node)
 	/* Enable timer0 interrupt */
 	val = readl(timer_base + TIMER_IRQ_EN_REG);
 	writel(val | TIMER_IRQ_EN(0), timer_base + TIMER_IRQ_EN_REG);
-
-	sun4i_clockevent.cpumask = cpumask_of(0);
-
-	clockevents_config_and_register(&sun4i_clockevent, rate,
-					TIMER_SYNC_TICKS, 0xffffffff);
 }
 CLOCKSOURCE_OF_DECLARE(sun4i, "allwinner,sun4i-timer",
 		       sun4i_timer_init);
--
1.9.1