Commit d505b8af authored by Huaixin Chang's avatar Huaixin Chang Committed by Peter Zijlstra

sched: Defend cfs and rt bandwidth quota against overflow

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: default avatarHuaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarBen Segall <bsegall@google.com>
Link: https://lkml.kernel.org/r/20200425105248.60093-1-changhuaixin@linux.alibaba.com
parent dbe93371
...@@ -7379,6 +7379,8 @@ static DEFINE_MUTEX(cfs_constraints_mutex); ...@@ -7379,6 +7379,8 @@ static DEFINE_MUTEX(cfs_constraints_mutex);
const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */ const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */ 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); 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) ...@@ -7406,6 +7408,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
if (period > max_cfs_quota_period) if (period > max_cfs_quota_period)
return -EINVAL; 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 * Prevent race between setting of cfs_rq->runtime_enabled and
* unthrottle_offline_cfs_rqs(). * unthrottle_offline_cfs_rqs().
......
...@@ -9,6 +9,8 @@ ...@@ -9,6 +9,8 @@
int sched_rr_timeslice = RR_TIMESLICE; int sched_rr_timeslice = RR_TIMESLICE;
int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * 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); 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, ...@@ -2585,6 +2587,12 @@ static int tg_set_rt_bandwidth(struct task_group *tg,
if (rt_period == 0) if (rt_period == 0)
return -EINVAL; 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); mutex_lock(&rt_constraints_mutex);
err = __rt_schedulable(tg, rt_period, rt_runtime); err = __rt_schedulable(tg, rt_period, rt_runtime);
if (err) if (err)
...@@ -2702,7 +2710,9 @@ static int sched_rt_global_validate(void) ...@@ -2702,7 +2710,9 @@ static int sched_rt_global_validate(void)
return -EINVAL; return -EINVAL;
if ((sysctl_sched_rt_runtime != RUNTIME_INF) && 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 -EINVAL;
return 0; return 0;
......
...@@ -1915,6 +1915,8 @@ extern void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se); ...@@ -1915,6 +1915,8 @@ extern void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se);
#define BW_SHIFT 20 #define BW_SHIFT 20
#define BW_UNIT (1 << BW_SHIFT) #define BW_UNIT (1 << BW_SHIFT)
#define RATIO_SHIFT 8 #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); unsigned long to_ratio(u64 period, u64 runtime);
extern void init_entity_runnable_average(struct sched_entity *se); extern void init_entity_runnable_average(struct sched_entity *se);
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment