From: Huaixin Chang <changhuaixin@linux.alibaba.com>
To: linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@redhat.com, bsegall@google.com,
chiluk+linux@indeed.com, vincent.guittot@linaro.org,
pauld@redhead.com, Huaixin Chang <changhuaixin@linux.alibaba.com>
Subject: [PATCH 1/2] sched: Defend cfs and rt bandwidth quota against overflow
Date: Mon, 20 Apr 2020 10:44:20 +0800 [thread overview]
Message-ID: <20200420024421.22442-2-changhuaixin@linux.alibaba.com> (raw)
In-Reply-To: <20200420024421.22442-1-changhuaixin@linux.alibaba.com>
Kernel limitation on cpu.cfs_quota_us is insufficient. Some large
numbers might cause overflow in to_ratio() calculation and produce
unexpected results.
For example, if we make two cpu cgroups and then write a reasonable
value and a large value into child's and parent's cpu.cfs_quota_us. This
will cause a write error.
cd /sys/fs/cgroup/cpu
mkdir parent; mkdir parent/child
echo 8000 > parent/child/cpu.cfs_quota_us
# 17592186044416 is (1UL << 44)
echo 17592186044416 > parent/cpu.cfs_quota_us
In this case, quota will overflow and thus fail the __cfs_schedulable
check. Similar overflow also affects rt bandwidth.
Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com>
---
kernel/sched/core.c | 8 ++++++++
kernel/sched/rt.c | 9 +++++++++
kernel/sched/sched.h | 2 ++
3 files changed, 19 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3a61a3b8eaa9..f0a74e35c3f0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7390,6 +7390,8 @@ 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_USEC * NSEC_PER_USEC;
static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
@@ -7417,6 +7419,12 @@ 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().
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index df11d88c9895..f5eea19d68c4 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2569,6 +2569,9 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
return ret;
}
+/* More than 203 days if BW_SHIFT equals 20. */
+static const u64 max_rt_runtime = MAX_BW_USEC * NSEC_PER_USEC;
+
static int tg_set_rt_bandwidth(struct task_group *tg,
u64 rt_period, u64 rt_runtime)
{
@@ -2585,6 +2588,12 @@ 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)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index db3a57675ccf..6f6b7f545557 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1918,6 +1918,8 @@ 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_USEC ((1UL << MAX_BW_BITS) - 1)
unsigned long to_ratio(u64 period, u64 runtime);
extern void init_entity_runnable_average(struct sched_entity *se);
--
2.14.4.44.g2045bb6
next prev parent reply other threads:[~2020-04-20 2:45 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-20 2:44 [PATCH 0/2] Two small fixes for bandwidth controller Huaixin Chang
2020-04-20 2:44 ` Huaixin Chang [this message]
2020-04-20 17:50 ` [PATCH 1/2] sched: Defend cfs and rt bandwidth quota against overflow bsegall
2020-04-22 3:36 ` changhuaixin
2020-04-22 18:44 ` bsegall
2020-04-23 13:37 ` [PATCH] " Huaixin Chang
2020-04-23 20:33 ` bsegall
2020-04-25 10:52 ` [PATCH v2] " Huaixin Chang
2020-04-27 18:29 ` bsegall
2020-05-11 13:03 ` Peter Zijlstra
2020-05-19 18:44 ` [tip: sched/core] " tip-bot2 for Huaixin Chang
2020-04-22 8:38 ` [PATCH 1/2] " kbuild test robot
2020-04-24 6:35 ` kbuild test robot
2020-04-20 2:44 ` [PATCH 2/2] sched/fair: Refill bandwidth before scaling Huaixin Chang
2020-04-20 17:54 ` bsegall
2020-04-21 15:09 ` Phil Auld
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Huaixin Chang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200420024421.22442-2-changhuaixin@linux.alibaba.com \
--to=changhuaixin@linux.alibaba.com \
--cc=bsegall@google.com \
--cc=chiluk+linux@indeed.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pauld@redhead.com \
--cc=peterz@infradead.org \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).