From: Quentin Perret <qperret@xxxxxxxxxx>
[ Upstream commit 6d2f8909a5fabb73fe2a63918117943986c39b6c ]
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
Signed-off-by: Sasha Levin <sashal@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 3c3554d9ee50..57b236251884 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -936,7 +936,7 @@ 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)
--
2.30.2
