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From: Konstantin Khlebnikov <>
To: Peter Zijlstra <>,
	Ingo Molnar <>,
Subject: [PATCH 2/3] sched/core: handle overflow in cpu_shares_write_u64
Date: Wed, 27 Feb 2019 11:10:18 +0300
Message-ID: <155125501891.293431.3345233332801109696.stgit@buzz> (raw)
In-Reply-To: <155125501739.293431.5252197504404771496.stgit@buzz>

Bit shift in scale_load() could overflow shares. This patch saturates
it to MAX_SHARES like following sched_group_set_shares().

# echo 9223372036854776832 > cpu.shares
# cat cpu.shares

Before patch: 1024
After pattch: 262144

Signed-off-by: Konstantin Khlebnikov <>
 kernel/sched/core.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d8d76a65cfdd..a626fbd9fdc7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6502,6 +6502,8 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
 				struct cftype *cftype, u64 shareval)
+	if (shareval > scale_load_down(ULONG_MAX))
+		shareval = MAX_SHARES;
 	return sched_group_set_shares(css_tg(css), scale_load(shareval));

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-27  8:10 [PATCH 1/3] sched/rt: check integer overflow at usec to nsec conversion Konstantin Khlebnikov
2019-02-27  8:10 ` Konstantin Khlebnikov [this message]
2019-04-19 12:16   ` [tip:sched/core] sched/core: Handle overflow in cpu_shares_write_u64 tip-bot for Konstantin Khlebnikov
2019-02-27  8:10 ` [PATCH 3/3] sched/core: check quota and period overflow at usec to nsec conversion Konstantin Khlebnikov
2019-04-19 12:17   ` [tip:sched/core] sched/core: Check " tip-bot for Konstantin Khlebnikov
2019-04-19 12:16 ` [tip:sched/core] sched/rt: Check integer " tip-bot for Konstantin Khlebnikov

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