Messages in this thread Patch in this message | | | Date | Fri, 30 Apr 2021 15:14:12 +0000 | Subject | [PATCH v3] sched: Fix out-of-bound access in uclamp | From | Quentin Perret <> |
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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@arm.com> Signed-off-by: Quentin Perret <qperret@google.com> --- Changes in v3: - Keep rounding div to improve fairness (Vincent) --- 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 98191218d891..c12ec648423e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -928,7 +928,7 @@ 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) -- 2.31.1.527.g47e6f16901-goog
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