From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
commit f0cc749254d12c78e93dae3b27b21dc9546843d0 upstream.
syzbot is again reporting circular locking dependency between cpu_hotplug_lock and freezer_mutex. Do like what we did with commit 57dcd64c7e036299 ("cgroup,freezer: hold cpu_hotplug_lock before freezer_mutex").
Reported-by: syzbot syzbot+2ab700fe1829880a2ec6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2ab700fe1829880a2ec6 Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Tested-by: syzbot syzbot+2ab700fe1829880a2ec6@syzkaller.appspotmail.com Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic") Cc: stable@vger.kernel.org # v6.1+ Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/cgroup/legacy_freezer.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/kernel/cgroup/legacy_freezer.c +++ b/kernel/cgroup/legacy_freezer.c @@ -108,16 +108,18 @@ static int freezer_css_online(struct cgr struct freezer *freezer = css_freezer(css); struct freezer *parent = parent_freezer(freezer);
+ cpus_read_lock(); mutex_lock(&freezer_mutex);
freezer->state |= CGROUP_FREEZER_ONLINE;
if (parent && (parent->state & CGROUP_FREEZING)) { freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN; - static_branch_inc(&freezer_active); + static_branch_inc_cpuslocked(&freezer_active); }
mutex_unlock(&freezer_mutex); + cpus_read_unlock(); return 0; }
@@ -132,14 +134,16 @@ static void freezer_css_offline(struct c { struct freezer *freezer = css_freezer(css);
+ cpus_read_lock(); mutex_lock(&freezer_mutex);
if (freezer->state & CGROUP_FREEZING) - static_branch_dec(&freezer_active); + static_branch_dec_cpuslocked(&freezer_active);
freezer->state = 0;
mutex_unlock(&freezer_mutex); + cpus_read_unlock(); }
static void freezer_css_free(struct cgroup_subsys_state *css)