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sched: Defend cfs and rt bandwidth quota against overflow

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When users write some huge number into cpu.cfs_quota_us or
cpu.rt_runtime_us, overflow might happen during to_ratio() shifts of
schedulable checks.

to_ratio() could be altered to avoid unnecessary internal overflow, but
min_cfs_quota_period is less than 1 << BW_SHIFT, so a cutoff would still
be needed. Set a cap MAX_BW for cfs_quota_us and rt_runtime_us to
prevent overflow.

Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Link: https://lkml.kernel.org/r/20200425105248.60093-1-changhuaixin@linux.alibaba.com
This commit is contained in:
Huaixin Chang 2020-04-25 18:52:48 +08:00 committed by Peter Zijlstra
parent dbe9337109
commit d505b8af58
3 changed files with 21 additions and 1 deletions
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8
kernel/sched/core.c
View File

@ -7379,6 +7379,8 @@ static DEFINE_MUTEX(cfs_constraints_mutex);
const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
/* More than 203 days if BW_SHIFT equals 20. */
static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
@ -7406,6 +7408,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
if (period > max_cfs_quota_period)
return -EINVAL;
/*
* Bound quota to defend quota against overflow during bandwidth shift.
*/
if (quota != RUNTIME_INF && quota > max_cfs_runtime)
return -EINVAL;
/*
* Prevent race between setting of cfs_rq->runtime_enabled and
* unthrottle_offline_cfs_rqs().

12
kernel/sched/rt.c
View File

@ -9,6 +9,8 @@
int sched_rr_timeslice = RR_TIMESLICE;
int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
/* More than 4 hours if BW_SHIFT equals 20. */
static const u64 max_rt_runtime = MAX_BW;
static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
@ -2585,6 +2587,12 @@ static int tg_set_rt_bandwidth(struct task_group *tg,
if (rt_period == 0)
return -EINVAL;
/*
* Bound quota to defend quota against overflow during bandwidth shift.
*/
if (rt_runtime != RUNTIME_INF && rt_runtime > max_rt_runtime)
return -EINVAL;
mutex_lock(&rt_constraints_mutex);
err = __rt_schedulable(tg, rt_period, rt_runtime);
if (err)
@ -2702,7 +2710,9 @@ static int sched_rt_global_validate(void)
return -EINVAL;
if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
(sysctl_sched_rt_runtime > sysctl_sched_rt_period))
((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
((u64)sysctl_sched_rt_runtime *
NSEC_PER_USEC > max_rt_runtime)))
return -EINVAL;
return 0;

2
kernel/sched/sched.h
View File

@ -1915,6 +1915,8 @@ extern void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se);
#define BW_SHIFT 20
#define BW_UNIT (1 << BW_SHIFT)
#define RATIO_SHIFT 8
#define MAX_BW_BITS (64 - BW_SHIFT)
#define MAX_BW ((1ULL << MAX_BW_BITS) - 1)
unsigned long to_ratio(u64 period, u64 runtime);
extern void init_entity_runnable_average(struct sched_entity *se);