Commit 6fec64e1 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

posix-timers: Make forward callback return s64 



The posix timer ti_overrun handling is broken because the forwarding
functions can return a huge number of overruns which does not fit in an
int. As a consequence timer_getoverrun(2) and siginfo::si_overrun can turn
into random number generators.

As a first step to address that let the timer_forward() callbacks return
the full 64 bit value.

Cast it to (int) temporarily until k_itimer::ti_overrun is converted to
64bit and the conversion to user space visible values is sanitized.

Reported-by: default avatarTeam OWL337 <icytxw@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarJohn Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Link: https://lkml.kernel.org/r/20180626132704.922098090@linutronix.de
parent 6ff84735

kernel/time/alarmtimer.c

+2 −2
Original line number Diff line number Diff line
@@ -581,11 +581,11 @@ static void alarm_timer_rearm(struct k_itimer *timr) 
 * @timr:	Pointer to the posixtimer data struct

 * @now:	Current time to forward the timer against

 */

static int alarm_timer_forward(struct k_itimer *timr, ktime_t now)

static s64 alarm_timer_forward(struct k_itimer *timr, ktime_t now)

{

	struct alarm *alarm = &timr->it.alarm.alarmtimer;



	return (int) alarm_forward(alarm, timr->it_interval, now);

	return alarm_forward(alarm, timr->it_interval, now);

}



/**

kernel/time/posix-timers.c

+3 −3
Original line number Diff line number Diff line
@@ -645,11 +645,11 @@ static ktime_t common_hrtimer_remaining(struct k_itimer *timr, ktime_t now) 
	return __hrtimer_expires_remaining_adjusted(timer, now);

}



static int common_hrtimer_forward(struct k_itimer *timr, ktime_t now)

static s64 common_hrtimer_forward(struct k_itimer *timr, ktime_t now)

{

	struct hrtimer *timer = &timr->it.real.timer;



	return (int)hrtimer_forward(timer, now, timr->it_interval);

	return hrtimer_forward(timer, now, timr->it_interval);

}



/*
@@ -702,7 +702,7 @@ void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting) 
	 * expiry time forward by intervals, so expiry is > now.

	 */

	if (iv && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none))

		timr->it_overrun += kc->timer_forward(timr, now);

		timr->it_overrun += (int)kc->timer_forward(timr, now);



	remaining = kc->timer_remaining(timr, now);

	/* Return 0 only, when the timer is expired and not pending */

kernel/time/posix-timers.h

+1 −1
Original line number Diff line number Diff line
@@ -19,7 +19,7 @@ struct k_clock { 
	void	(*timer_get)(struct k_itimer *timr,

			     struct itimerspec64 *cur_setting);

	void	(*timer_rearm)(struct k_itimer *timr);

	int	(*timer_forward)(struct k_itimer *timr, ktime_t now);

	s64	(*timer_forward)(struct k_itimer *timr, ktime_t now);

	ktime_t	(*timer_remaining)(struct k_itimer *timr, ktime_t now);

	int	(*timer_try_to_cancel)(struct k_itimer *timr);

	void	(*timer_arm)(struct k_itimer *timr, ktime_t expires,

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