From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx>
Closes: https://syzkaller.appspot.com/bug?extid=2ab700fe1829880a2ec6
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Tested-by: syzbot <syzbot+2ab700fe1829880a2ec6@xxxxxxxxxxxxxxxxxxxxxxxxx>
Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Cc: stable@xxxxxxxxxxxxxxx # v6.1+
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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)
