releases/4.14.123/sched-core-handle-overflow-in-cpu_shares_write_u64.patch

   1 From a242e1c718700bb869747ef8bd9868a6d0e6601d Mon Sep 17 00:00:00 2001
   2 From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
   3 Date: Wed, 27 Feb 2019 11:10:18 +0300
   4 Subject: sched/core: Handle overflow in cpu_shares_write_u64
   5
   6 [ Upstream commit 5b61d50ab4ef590f5e1d4df15cd2cea5f5715308 ]
   7
   8 Bit shift in scale_load() could overflow shares. This patch saturates
   9 it to MAX_SHARES like following sched_group_set_shares().
  10
  11 Example:
  12
  13  # echo 9223372036854776832 > cpu.shares
  14  # cat cpu.shares
  15
  16 Before patch: 1024
  17 After pattch: 262144
  18
  19 Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
  20 Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
  21 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  22 Cc: Peter Zijlstra <peterz@infradead.org>
  23 Cc: Thomas Gleixner <tglx@linutronix.de>
  24 Link: http://lkml.kernel.org/r/155125501891.293431.3345233332801109696.stgit@buzz
  25 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  26 Signed-off-by: Sasha Levin <sashal@kernel.org>
  27 ---
  28  kernel/sched/core.c | 2 ++
  29  1 file changed, 2 insertions(+)
  30
  31 diff --git a/kernel/sched/core.c b/kernel/sched/core.c
  32 index 2464a242d6c9d..b3ff73d6a4c23 100644
  33 --- a/kernel/sched/core.c
  34 +++ b/kernel/sched/core.c
  35 @@ -6380,6 +6380,8 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
  36  static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
  37                                 struct cftype *cftype, u64 shareval)
  38  {
  39 +       if (shareval > scale_load_down(ULONG_MAX))
  40 +               shareval = MAX_SHARES;
  41         return sched_group_set_shares(css_tg(css), scale_load(shareval));
  42  }
  43
  44 --
  45 2.20.1
  46