[tip:timers/urgent] timers: Fix overflow in get_next_timer_interrupt

[tip-bot for Matija Glavinic Pecotic]

Commit-ID:  34f41c0316ed52b0b44542491d89278efdaa70e4
Gitweb:     http://git.kernel.org/tip/34f41c0316ed52b0b44542491d89278efdaa70e4
Author:     Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@xxxxxxxxx>
AuthorDate: Tue, 1 Aug 2017 09:11:52 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 1 Aug 2017 14:20:53 +0200

timers: Fix overflow in get_next_timer_interrupt

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@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
Cc: khilman@xxxxxxxxxxxx
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/a7900f04-2a21-c9fd-67be-ab334d459ee5@xxxxxxxxx
---
 kernel/time/timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 71ce3f4..8f5d1bf 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1495,7 +1495,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
 		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:
 		 */