linux

mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-12-28 11:24:07 -05:00

Files

Tetsuo Handa 57dcd64c7e cgroup,freezer: hold cpu_hotplug_lock before freezer_mutex

syzbot is reporting circular locking dependency between cpu_hotplug_lock
and freezer_mutex, for commit f5d39b0208 ("freezer,sched: Rewrite core
freezer logic") replaced atomic_inc() in freezer_apply_state() with
static_branch_inc() which holds cpu_hotplug_lock.

cpu_hotplug_lock => cgroup_threadgroup_rwsem => freezer_mutex

  cgroup_file_write() {
    cgroup_procs_write() {
      __cgroup_procs_write() {
        cgroup_procs_write_start() {
          cgroup_attach_lock() {
            cpus_read_lock() {
              percpu_down_read(&cpu_hotplug_lock);
            }
            percpu_down_write(&cgroup_threadgroup_rwsem);
          }
        }
        cgroup_attach_task() {
          cgroup_migrate() {
            cgroup_migrate_execute() {
              freezer_attach() {
                mutex_lock(&freezer_mutex);
                (...snipped...)
              }
            }
          }
        }
        (...snipped...)
      }
    }
  }

freezer_mutex => cpu_hotplug_lock

  cgroup_file_write() {
    freezer_write() {
      freezer_change_state() {
        mutex_lock(&freezer_mutex);
        freezer_apply_state() {
          static_branch_inc(&freezer_active) {
            static_key_slow_inc() {
              cpus_read_lock();
              static_key_slow_inc_cpuslocked();
              cpus_read_unlock();
            }
          }
        }
        mutex_unlock(&freezer_mutex);
      }
    }
  }

Swap locking order by moving cpus_read_lock() in freezer_apply_state()
to before mutex_lock(&freezer_mutex) in freezer_change_state().

Reported-by: syzbot <syzbot+c39682e86c9d84152f93@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?extid=c39682e86c9d84152f93
Suggested-by: Hillf Danton <hdanton@sina.com>
Fixes: f5d39b0208 ("freezer,sched: Rewrite core freezer logic")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

2023-04-12 07:30:28 -10:00

cgroup-internal.h

memcg: fix possible use-after-free in memcg_write_event_control()

2022-12-09 18:41:17 -08:00

cgroup-v1.c

cgroup: Use cgroup_attach_{lock,unlock}() from cgroup_attach_task_all()

2022-08-26 11:14:34 -10:00

cgroup.c

fs: port ->permission() to pass mnt_idmap

2023-01-19 09:24:28 +01:00

cpuset.c

cgroup/cpuset: Fix partition root's cpuset.cpus update bug