From a2c5a95d599c9b4a864d97520df42baefbfdb822 Mon Sep 17 00:00:00 2001 From: Quentin Perret Date: Fri, 30 Apr 2021 15:14:12 +0000 Subject: [PATCH] UPSTREAM: 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. Bug: 186415778 Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") Suggested-by: Qais Yousef Signed-off-by: Quentin Perret Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Reviewed-by: Dietmar Eggemann Link: https://lkml.kernel.org/r/20210430151412.160913-1-qperret@google.com (cherry picked from commit 6d2f8909a5fabb73fe2a63918117943986c39b6c) Signed-off-by: Quentin Perret Change-Id: I8097f5ed34abcff36c5ed395643d65727ea969eb --- 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 6334ed78ed5a..d2bbb1e55bdf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -757,7 +757,7 @@ static struct uclamp_se uclamp_default[UCLAMP_CNT]; 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_bucket_base_value(unsigned int clamp_value)