linux-cve-announce - CVE-2023-53522: cgroup,freezer: hold cpu_hotplug_lock before freezer

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Message-ID: <2025100133-CVE-2023-53522-4e19@gregkh>
Date: Wed,  1 Oct 2025 13:46:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53522: cgroup,freezer: hold cpu_hotplug_lock before freezer_mutex

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

cgroup,freezer: hold cpu_hotplug_lock before freezer_mutex

syzbot is reporting circular locking dependency between cpu_hotplug_lock
and freezer_mutex, for commit f5d39b020809 ("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().

The Linux kernel CVE team has assigned CVE-2023-53522 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.1 with commit f5d39b020809146cc28e6e73369bf8065e0310aa and fixed in 6.1.25 with commit 3756171b97c307d9df8b8ded1d883eec30172085
	Issue introduced in 6.1 with commit f5d39b020809146cc28e6e73369bf8065e0310aa and fixed in 6.2.12 with commit 34fbb7b45bae20b551dda24337c7761ca13ce69d
	Issue introduced in 6.1 with commit f5d39b020809146cc28e6e73369bf8065e0310aa and fixed in 6.3 with commit 57dcd64c7e036299ef526b400a8d12b8a2352f26

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2023-53522
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/cgroup/legacy_freezer.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/3756171b97c307d9df8b8ded1d883eec30172085
	https://git.kernel.org/stable/c/34fbb7b45bae20b551dda24337c7761ca13ce69d
	https://git.kernel.org/stable/c/57dcd64c7e036299ef526b400a8d12b8a2352f26