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Commit 5a7780e7 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

hrtimer: check relative timeouts for overflow 



Various user space callers ask for relative timeouts. While we fixed
that overflow issue in hrtimer_start(), the sites which convert
relative user space values to absolute timeouts themself were uncovered.

Instead of putting overflow checks into each place add a function
which does the sanity checking and convert all affected callers to use
it.

Thanks to Frans Pop, who reported the problem and tested the fixes.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Tested-by: default avatarFrans Pop <elendil@planet.nl>
parent e760e716

include/linux/ktime.h

+2 −0
Original line number Diff line number Diff line
@@ -310,6 +310,8 @@ static inline ktime_t ktime_sub_us(const ktime_t kt, const u64 usec) 
	return ktime_sub_ns(kt, usec * 1000);

}



extern ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs);



/*

 * The resolution of the clocks. The resolution value is returned in

 * the clock_getres() system call to give application programmers an

kernel/futex.c

+1 −1
Original line number Diff line number Diff line
@@ -2116,7 +2116,7 @@ asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val, 


		t = timespec_to_ktime(ts);

		if (cmd == FUTEX_WAIT)

			t = ktime_add(ktime_get(), t);

			t = ktime_add_safe(ktime_get(), t);

		tp = &t;

	}

	/*

kernel/futex_compat.c

+1 −1
Original line number Diff line number Diff line
@@ -176,7 +176,7 @@ asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val, 


		t = timespec_to_ktime(ts);

		if (cmd == FUTEX_WAIT)

			t = ktime_add(ktime_get(), t);

			t = ktime_add_safe(ktime_get(), t);

		tp = &t;

	}

	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)

kernel/hrtimer.c

+20 −17
Original line number Diff line number Diff line
@@ -325,6 +325,23 @@ u64 ktime_divns(const ktime_t kt, s64 div) 
}

#endif /* BITS_PER_LONG >= 64 */



/*

 * Add two ktime values and do a safety check for overflow:

 */

ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)

{

	ktime_t res = ktime_add(lhs, rhs);



	/*

	 * We use KTIME_SEC_MAX here, the maximum timeout which we can

	 * return to user space in a timespec:

	 */

	if (res.tv64 < 0 || res.tv64 < lhs.tv64 || res.tv64 < rhs.tv64)

		res = ktime_set(KTIME_SEC_MAX, 0);



	return res;

}



/*

 * Check, whether the timer is on the callback pending list

 */
@@ -682,13 +699,7 @@ u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval) 
		 */

		orun++;

	}

	timer->expires = ktime_add(timer->expires, interval);

	/*

	 * Make sure, that the result did not wrap with a very large

	 * interval.

	 */

	if (timer->expires.tv64 < 0)

		timer->expires = ktime_set(KTIME_SEC_MAX, 0);

	timer->expires = ktime_add_safe(timer->expires, interval);



	return orun;

}
@@ -839,7 +850,7 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode) 
	new_base = switch_hrtimer_base(timer, base);



	if (mode == HRTIMER_MODE_REL) {

		tim = ktime_add(tim, new_base->get_time());

		tim = ktime_add_safe(tim, new_base->get_time());

		/*

		 * CONFIG_TIME_LOW_RES is a temporary way for architectures

		 * to signal that they simply return xtime in
@@ -848,16 +859,8 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode) 
		 * timeouts. This will go away with the GTOD framework.

		 */

#ifdef CONFIG_TIME_LOW_RES

		tim = ktime_add(tim, base->resolution);

		tim = ktime_add_safe(tim, base->resolution);

#endif

		/*

		 * Careful here: User space might have asked for a

		 * very long sleep, so the add above might result in a

		 * negative number, which enqueues the timer in front

		 * of the queue.

		 */

		if (tim.tv64 < 0)

			tim.tv64 = KTIME_MAX;

	}

	timer->expires = tim;

kernel/posix-timers.c

+5 −3
Original line number Diff line number Diff line
@@ -767,9 +767,11 @@ common_timer_set(struct k_itimer *timr, int flags, 
	/* SIGEV_NONE timers are not queued ! See common_timer_get */

	if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {

		/* Setup correct expiry time for relative timers */

		if (mode == HRTIMER_MODE_REL)

			timer->expires = ktime_add(timer->expires,

		if (mode == HRTIMER_MODE_REL) {

			timer->expires =

				ktime_add_safe(timer->expires,

					       timer->base->get_time());

		}

		return 0;

	}