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Groups > linux.kernel > #1289541

[PATCH] sched/fair: fix mul overflow on 32-bit systems

From Andrey Ryabinin <aryabinin@virtuozzo.com>
Newsgroups linux.kernel
Subject [PATCH] sched/fair: fix mul overflow on 32-bit systems
Date 2015-12-11 14:00 +0100
Message-ID <qEvsL-4sJ-27@gated-at.bofh.it> (permalink)
Organization linux.* mail to news gateway

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Make 'r' 64-bit type to avoid overflow in 'r * LOAD_AVG_MAX'
on 32-bit systems:
	UBSAN: Undefined behaviour in kernel/sched/fair.c:2785:18
	signed integer overflow:
	87950 * 47742 cannot be represented in type 'int'

Fixes: 9d89c257dfb9 ("sched/fair: Rewrite runnable load and utilization average tracking")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e3266eb..733f0b8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2780,14 +2780,14 @@ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 	int decayed, removed = 0;
 
 	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
-		long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
+		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
 		sa->load_avg = max_t(long, sa->load_avg - r, 0);
 		sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
 		removed = 1;
 	}
 
 	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
-		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
+		s64 r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
 		sa->util_avg = max_t(long, sa->util_avg - r, 0);
 		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
 	}
-- 
2.4.10

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[PATCH] sched/fair: fix mul overflow on 32-bit systems Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-12-11 14:00 +0100
  Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Peter Zijlstra <peterz@infradead.org> - 2015-12-11 14:30 +0100
    Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Peter Zijlstra <peterz@infradead.org> - 2015-12-11 14:40 +0100
      Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-12-11 15:00 +0100
        Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Morten Rasmussen <morten.rasmussen@arm.com> - 2015-12-11 19:00 +0100
          Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-12-11 19:40 +0100
            Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems bsegall@google.com - 2015-12-11 20:20 +0100
              Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Yuyang Du <yuyang.du@intel.com> - 2015-12-14 05:50 +0100
              Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Morten Rasmussen <morten.rasmussen@arm.com> - 2015-12-14 13:40 +0100
                Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems bsegall@google.com - 2015-12-14 19:00 +0100
          Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Yuyang Du <yuyang.du@intel.com> - 2015-12-14 07:30 +0100
            Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Peter Zijlstra <peterz@infradead.org> - 2015-12-14 13:00 +0100
              Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Morten Rasmussen <morten.rasmussen@arm.com> - 2015-12-14 14:10 +0100
                Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Peter Zijlstra <peterz@infradead.org> - 2015-12-14 15:30 +0100
                Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Morten Rasmussen <morten.rasmussen@arm.com> - 2015-12-14 15:50 +0100
              Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Yuyang Du <yuyang.du@intel.com> - 2015-12-15 11:10 +0100
                Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Steve Muckle <steve.muckle@linaro.org> - 2015-12-15 23:00 +0100
                Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems Yuyang Du <yuyang.du@intel.com> - 2015-12-18 11:20 +0100
        Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems bsegall@google.com - 2015-12-11 19:00 +0100

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