The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 6d2f8909a5fabb73fe2a63918117943986c39b6c Gitweb: https://git.kernel.org/tip/6d2f8909a5fabb73fe2a63918117943986c39b6c Author: Quentin Perret <qperret@xxxxxxxxxx> AuthorDate: Fri, 30 Apr 2021 15:14:12 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Thu, 06 May 2021 15:33:26 +02:00 sched: Fix out-of-bound access in uclamp Util-clamp places tasks in different buckets based on their clamp values for performance reasons. However, the size of buckets is currently computed using a rounding division, which can lead to an off-by-one error in some configurations. For instance, with 20 buckets, the bucket size will be 1024/20=51. A task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly, correct indexes are in range [0,19], hence leading to an out of bound memory access. Clamp the bucket id to fix the issue. Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") Suggested-by: Qais Yousef <qais.yousef@xxxxxxx> Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Link: https://lkml.kernel.org/r/20210430151412.160913-1-qperret@xxxxxxxxxx --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9143163..5226cc2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -938,7 +938,7 @@ DEFINE_STATIC_KEY_FALSE(sched_uclamp_used); static inline unsigned int uclamp_bucket_id(unsigned int clamp_value) { - return clamp_value / UCLAMP_BUCKET_DELTA; + return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1); } static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
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