On 2024/5/16 14:27, Cheng Yu wrote:

From: Zhao Wenhui zhaowenhui8@huawei.com

hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I9PR8C CVE: NA

---

sched/fair: limit burst to zero when cfs bandwidth is toggled off

When the quota value in CFS bandwidth is set to -1, that imples the cfs bandwidth is toggled off. So the burst feature is supposed to be disable as well.

Currently, when quota is -1, burst will not be check, so that it can be set to almost arbitery value. Examples: mkdir /sys/fs/cgroup/cpu/test echo -1 > /sys/fs/cgroup/cpu/test/cpu.cfs_quota_us echo 10000000000000000 > /sys/fs/cgroup/cpu/test/cpu.cfs_burst_us

Moreover, after the burst modified by this way, quota can't be set to any value: echo 100000 > cpu.cfs_quota_us -bash: echo: write error: Invalid argument

This patch can ensure the burst value being zero and unalterable, when quota is set to -1.

Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller") Signed-off-by: Zhao Wenhui zhaowenhui8@huawei.com Signed-off-by: Cheng Yu serein.chengyu@huawei.com

---

kernel/sched/core.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9e7a99947de6..5441afe18953 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11051,6 +11051,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota, burst + quota > max_cfs_runtime)) return -EINVAL;

• /*

• * Ensure burst equals to zero when quota is -1.
  

• */
  

• if (quota == RUNTIME_INF && burst)

• return -EINVAL;
  

How about put this forward， before  the first quota check?

+ /* + * Ensure burst equals to zero when quota is -1. + */ + if (quota == RUNTIME_INF && burst) + return -EINVAL; +

/*      * Ensure we have at some amount of bandwidth every period.  This is      * to prevent reaching a state of large arrears when throttled via      * entity_tick() resulting in prolonged exit starvation.      */     if (quota < min_cfs_quota_period || period < min_cfs_quota_period)         return -EINVAL;

Besides，burst already been set to zero when cfs_quota_us < 0,  the check of non-zone burst is meaningless.

/* * Prevent race between setting of cfs_rq->runtime_enabled and * unthrottle_offline_cfs_rqs(). @@ -11110,8 +11116,10 @@ static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)

period = ktime_to_ns(tg->cfs_bandwidth.period); burst = tg->cfs_bandwidth.burst;

• if (cfs_quota_us < 0)

• if (cfs_quota_us < 0) { quota = RUNTIME_INF;

• burst = 0;
  

• } else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC) quota = (u64)cfs_quota_us * NSEC_PER_USEC; else

*}* and *else* on same line.