git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From f0cc749254d12c78e93dae3b27b21dc9546843d0 Mon Sep 17 00:00:00 2001
   2 From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
   3 Date: Sun, 11 Jun 2023 22:48:12 +0900
   4 Subject: cgroup,freezer: hold cpu_hotplug_lock before freezer_mutex in freezer_css_{online,offline}()
   5
   6 From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
   7
   8 commit f0cc749254d12c78e93dae3b27b21dc9546843d0 upstream.
   9
  10 syzbot is again reporting circular locking dependency between
  11 cpu_hotplug_lock and freezer_mutex. Do like what we did with
  12 commit 57dcd64c7e036299 ("cgroup,freezer: hold cpu_hotplug_lock
  13 before freezer_mutex").
  14
  15 Reported-by: syzbot <syzbot+2ab700fe1829880a2ec6@syzkaller.appspotmail.com>
  16 Closes: https://syzkaller.appspot.com/bug?extid=2ab700fe1829880a2ec6
  17 Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
  18 Tested-by: syzbot <syzbot+2ab700fe1829880a2ec6@syzkaller.appspotmail.com>
  19 Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
  20 Cc: stable@vger.kernel.org # v6.1+
  21 Signed-off-by: Tejun Heo <tj@kernel.org>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23 ---
  24  kernel/cgroup/legacy_freezer.c |    8 ++++++--
  25  1 file changed, 6 insertions(+), 2 deletions(-)
  26
  27 --- a/kernel/cgroup/legacy_freezer.c
  28 +++ b/kernel/cgroup/legacy_freezer.c
  29 @@ -108,16 +108,18 @@ static int freezer_css_online(struct cgr
  30         struct freezer *freezer = css_freezer(css);
  31         struct freezer *parent = parent_freezer(freezer);
  32
  33 +       cpus_read_lock();
  34         mutex_lock(&freezer_mutex);
  35
  36         freezer->state |= CGROUP_FREEZER_ONLINE;
  37
  38         if (parent && (parent->state & CGROUP_FREEZING)) {
  39                 freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN;
  40 -               static_branch_inc(&freezer_active);
  41 +               static_branch_inc_cpuslocked(&freezer_active);
  42         }
  43
  44         mutex_unlock(&freezer_mutex);
  45 +       cpus_read_unlock();
  46         return 0;
  47  }
  48
  49 @@ -132,14 +134,16 @@ static void freezer_css_offline(struct c
  50  {
  51         struct freezer *freezer = css_freezer(css);
  52
  53 +       cpus_read_lock();
  54         mutex_lock(&freezer_mutex);
  55
  56         if (freezer->state & CGROUP_FREEZING)
  57 -               static_branch_dec(&freezer_active);
  58 +               static_branch_dec_cpuslocked(&freezer_active);
  59
  60         freezer->state = 0;
  61
  62         mutex_unlock(&freezer_mutex);
  63 +       cpus_read_unlock();
  64  }
  65
  66  static void freezer_css_free(struct cgroup_subsys_state *css)