linux-kernel - [PATCH] posix-timers: CLOCK_MONOTONIC_RAW: fix the usage of ->it

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Date:	Sat, 20 Dec 2008 18:48:17 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Eric Sesterhenn <snakebyte@....de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] posix-timers: CLOCK_MONOTONIC_RAW: fix the usage of
	->it_clock

(compile tested)

common_timer_create() and common_timer_set() blindly pass ->it_clock to
hrtimer_init() as clock_id. This used to work until CLOCK_MONOTONIC_RAW
was introduced, now we should be careful.

Perhaps it makes sense to add BUG_ON(clock_id >= HRTIMER_MAX_CLOCK_BASES)
to __hrtimer_init(), the wrong clock_id leads to catastrophe.

Reported-by: Eric Sesterhenn <snakebyte@....de>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>

--- K-28/kernel/posix-timers.c~CLOCK_MONOTONIC_RAW	2008-12-02 17:12:40.000000000 +0100
+++ K-28/kernel/posix-timers.c	2008-12-20 18:23:28.000000000 +0100
@@ -191,12 +191,20 @@ static inline int common_clock_set(const
 	return do_sys_settimeofday(tp, NULL);
 }
 
-static int common_timer_create(struct k_itimer *new_timer)
+static inline int
+__common_timer_init(struct k_itimer *timer, enum hrtimer_mode mode)
 {
-	hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
+	clockid_t clock_id = timer->it_clock ?
+				CLOCK_MONOTONIC : CLOCK_REALTIME;
+	hrtimer_init(&timer->it.real.timer, clock_id, mode);
 	return 0;
 }
 
+static int common_timer_create(struct k_itimer *new_timer)
+{
+	return __common_timer_init(new_timer, HRTIMER_MODE_ABS);
+}
+
 /*
  * Return nonzero if we know a priori this clockid_t value is bogus.
  */
@@ -730,7 +738,7 @@ common_timer_set(struct k_itimer *timr, 
 		return 0;
 
 	mode = flags & TIMER_ABSTIME ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
-	hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
+	__common_timer_init(timr, mode);
 	timr->it.real.timer.function = posix_timer_fn;
 
 	hrtimer_set_expires(timer, timespec_to_ktime(new_setting->it_value));

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