linux-kernel - [PATCH 4.9 19/93] timers: Fix overflow in get_next_timer

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Date:   Wed,  9 Aug 2017 11:13:12 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@...ia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        khilman@...libre.com, akpm@...ux-foundation.org
Subject: [PATCH 4.9 19/93] timers: Fix overflow in get_next_timer_interrupt

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@...ia.com>

commit 34f41c0316ed52b0b44542491d89278efdaa70e4 upstream.

For e.g. HZ=100, timer being 430 jiffies in the future, and 32 bit
unsigned int, there is an overflow on unsigned int right-hand side
of the expression which results with wrong values being returned.

Type cast the multiplier to 64bit to avoid that issue.

Fixes: 46c8f0b077a8 ("timers: Fix get_next_timer_interrupt() computation")
Signed-off-by: Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@...ia.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
Cc: khilman@...libre.com
Cc: akpm@...ux-foundation.org
Link: http://lkml.kernel.org/r/a7900f04-2a21-c9fd-67be-ab334d459ee5@nokia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/time/timer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1536,7 +1536,7 @@ u64 get_next_timer_interrupt(unsigned lo
 		base->is_idle = false;
 	} else {
 		if (!is_max_delta)
-			expires = basem + (nextevt - basej) * TICK_NSEC;
+			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
 		/*
 		 * If we expect to sleep more than a tick, mark the base idle:
 		 */