[PATCH] sched: fair: avoid integer overflow

[Michal Nazarewicz <mpn@google.com>]

From: Michal Nazarewicz <mina86@mina86.com>

sa->runnable_avg_sum is of type u32 but after shifting it by NICE_0_SHIFT
bits it is promoted to u64.  This of course makes no sense, since the
result will never be more then 32-bit long.  Casting sa->runnable_avg_sum
to u64 before it is shifted, fixes this problem.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index df77c60..50f1e170 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2153,7 +2153,7 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa,
 	long contrib;
 
 	/* The fraction of a cpu used by this cfs_rq */
-	contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
+	contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
 			  sa->runnable_avg_period + 1);
 	contrib -= cfs_rq->tg_runnable_contrib;
 
-- 
1.8.3.2