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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>
This commit is contained in:
Michal Nazarewicz 2013-11-10 20:42:01 +01:00 committed by Ingo Molnar
parent 911b2898b3
commit 85b088e934
1 changed files with 1 additions and 1 deletions
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kernel/sched/fair.c
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@ -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;