Commit 85b088e9 authored Nov 10, 2013 by Michal Nazarewicz Committed by Ingo Molnar Nov 13, 2013

sched/fair: Avoid integer overflow



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.

Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384112521-25177-1-git-send-email-mpn@google.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 911b2898

kernel/sched/fair.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2178,7 +2178,7 @@ 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;