Commitd505b8a

changhuaixin

authored and

Peter Zijlstra

committed

sched: Defend cfs and rt bandwidth quota against overflow

When users write some huge number into cpu.cfs_quota_us orcpu.rt_runtime_us, overflow might happen during to_ratio() shifts ofschedulable checks.to_ratio() could be altered to avoid unnecessary internal overflow, butmin_cfs_quota_period is less than 1 << BW_SHIFT, so a cutoff would stillbe needed. Set a cap MAX_BW for cfs_quota_us and rt_runtime_us toprevent 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

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+21

-1

lines changed

kernel/sched

3 files changed

+21

-1

lines changed

`‎kernel/sched/core.c‎`

Lines changed: 8 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -7379,6 +7379,8 @@ static DEFINE_MUTEX(cfs_constraints_mutex);`
`7379`	`7379`
`7380`	`7380`	`constu64max_cfs_quota_period=1NSEC_PER_SEC;/ 1s */`
`7381`	`7381`	`staticconstu64min_cfs_quota_period=1NSEC_PER_MSEC;/ 1ms */`
	`7382`	`+/* More than 203 days if BW_SHIFT equals 20. */`
	`7383`	`+staticconstu64max_cfs_runtime=MAX_BW*NSEC_PER_USEC;`
`7382`	`7384`
`7383`	`7385`	`staticint__cfs_schedulable(structtask_group*tg,u64period,u64runtime);`
`7384`	`7386`
`@@ -7406,6 +7408,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)`
`7406`	`7408`	`if (period>max_cfs_quota_period)`
`7407`	`7409`	`return-EINVAL;`
`7408`	`7410`
	`7411`	`+/*`
	`7412`	`+ * Bound quota to defend quota against overflow during bandwidth shift.`
	`7413`	`+ */`
	`7414`	`+if (quota!=RUNTIME_INF&&quota>max_cfs_runtime)`
	`7415`	`+return-EINVAL;`
	`7416`	`+`
`7409`	`7417`	`/*`
`7410`	`7418`	`* Prevent race between setting of cfs_rq->runtime_enabled and`
`7411`	`7419`	`* unthrottle_offline_cfs_rqs().`

`‎kernel/sched/rt.c‎`

Lines changed: 11 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,8 @@`
`9`	`9`
`10`	`10`	`intsched_rr_timeslice=RR_TIMESLICE;`
`11`	`11`	`intsysctl_sched_rr_timeslice= (MSEC_PER_SEC /HZ)*RR_TIMESLICE;`
	`12`	`+/* More than 4 hours if BW_SHIFT equals 20. */`
	`13`	`+staticconstu64max_rt_runtime=MAX_BW;`
`12`	`14`
`13`	`15`	`staticintdo_sched_rt_period_timer(structrt_bandwidth*rt_b,intoverrun);`
`14`	`16`
`@@ -2585,6 +2587,12 @@ static int tg_set_rt_bandwidth(struct task_group *tg,`
`2585`	`2587`	`if (rt_period==0)`
`2586`	`2588`	`return-EINVAL;`
`2587`	`2589`
	`2590`	`+/*`
	`2591`	`+ * Bound quota to defend quota against overflow during bandwidth shift.`
	`2592`	`+ */`
	`2593`	`+if (rt_runtime!=RUNTIME_INF&&rt_runtime>max_rt_runtime)`
	`2594`	`+return-EINVAL;`
	`2595`	`+`
`2588`	`2596`	`mutex_lock(&rt_constraints_mutex);`
`2589`	`2597`	`err=__rt_schedulable(tg,rt_period,rt_runtime);`
`2590`	`2598`	`if (err)`
`@@ -2702,7 +2710,9 @@ static int sched_rt_global_validate(void)`
`2702`	`2710`	`return-EINVAL;`
`2703`	`2711`
`2704`	`2712`	`if ((sysctl_sched_rt_runtime!=RUNTIME_INF)&&`
`2705`		`-(sysctl_sched_rt_runtime>sysctl_sched_rt_period))`
	`2713`	`+((sysctl_sched_rt_runtime>sysctl_sched_rt_period)\|\|`
	`2714`	`+ ((u64)sysctl_sched_rt_runtime*`
	`2715`	`+NSEC_PER_USEC>max_rt_runtime)))`
`2706`	`2716`	`return-EINVAL;`
`2707`	`2717`
`2708`	`2718`	`return0;`

`‎kernel/sched/sched.h‎`

Lines changed: 2 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -1915,6 +1915,8 @@ extern void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se);`
`1915`	`1915`	`#defineBW_SHIFT20`
`1916`	`1916`	`#defineBW_UNIT(1 << BW_SHIFT)`
`1917`	`1917`	`#defineRATIO_SHIFT8`
	`1918`	`+#defineMAX_BW_BITS(64 - BW_SHIFT)`
	`1919`	`+#defineMAX_BW((1ULL << MAX_BW_BITS) - 1)`
`1918`	`1920`	`unsigned longto_ratio(u64period,u64runtime);`
`1919`	`1921`
`1920`	`1922`	`externvoidinit_entity_runnable_average(structsched_entity*se);`

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Commitd505b8a

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`‎kernel/sched/core.c‎`

`‎kernel/sched/rt.c‎`

`‎kernel/sched/sched.h‎`

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