sched/core: Handle overflow in cpu_shares_write_u64

[ Upstream commit 5b61d50ab4ef590f5e1d4df15cd2cea5f5715308 ]

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

Example:

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

Before patch: 1024
After pattch: 262144

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/155125501891.293431.3345233332801109696.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 89c9c1d7d22c5a41ee75118365a93551f2d529cc..a75ad50b5e2ffc60293e0ee8b8ea279e623dd7e1 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6559,6 +6559,8 @@ 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));
 }