syzbot

======================================================
WARNING: possible circular locking dependency detected
6.4.0-rc2-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor259/5009 is trying to acquire lock:
ffffffff8c6409f0 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_slow_inc+0x13/0x30 kernel/jump_label.c:185

but task is already holding lock:
ffffffff8c7ec468 (freezer_mutex){+.+.}-{3:3}, at: freezer_css_online+0x55/0x170 kernel/cgroup/legacy_freezer.c:111

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (freezer_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747
       freezer_change_state kernel/cgroup/legacy_freezer.c:389 [inline]
       freezer_write+0xa1/0xb50 kernel/cgroup/legacy_freezer.c:429
       cgroup_file_write+0x1e2/0x7b0 kernel/cgroup/cgroup.c:4071
       kernfs_fop_write_iter+0x3f1/0x600 fs/kernfs/file.c:334
       call_write_iter include/linux/fs.h:1868 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x945/0xd50 fs/read_write.c:584
       ksys_write+0x12b/0x250 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (cpu_hotplug_lock){++++}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3108 [inline]
       check_prevs_add kernel/locking/lockdep.c:3227 [inline]
       validate_chain kernel/locking/lockdep.c:3842 [inline]
       __lock_acquire+0x2f21/0x5df0 kernel/locking/lockdep.c:5074
       lock_acquire kernel/locking/lockdep.c:5691 [inline]
       lock_acquire+0x1b1/0x520 kernel/locking/lockdep.c:5656
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       cpus_read_lock+0x42/0x160 kernel/cpu.c:310
       static_key_slow_inc+0x13/0x30 kernel/jump_label.c:185
       freezer_css_online+0x102/0x170 kernel/cgroup/legacy_freezer.c:117
       online_css+0xaf/0x2a0 kernel/cgroup/cgroup.c:5491
       css_create kernel/cgroup/cgroup.c:5562 [inline]
       cgroup_apply_control_enable+0x69b/0xc00 kernel/cgroup/cgroup.c:3249
       cgroup_mkdir+0x5b9/0x10b0 kernel/cgroup/cgroup.c:5758
       kernfs_iop_mkdir+0x14a/0x1d0 fs/kernfs/dir.c:1219
       vfs_mkdir+0x242/0x460 fs/namei.c:4115
       do_mkdirat+0x28d/0x310 fs/namei.c:4138
       __do_sys_mkdirat fs/namei.c:4153 [inline]
       __se_sys_mkdirat fs/namei.c:4151 [inline]
       __x64_sys_mkdirat+0x119/0x170 fs/namei.c:4151
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(freezer_mutex);
                               lock(cpu_hotplug_lock);
                               lock(freezer_mutex);
  rlock(cpu_hotplug_lock);

 *** DEADLOCK ***

4 locks held by syz-executor259/5009:
 #0: ffff88807df46460 (sb_writers#10){.+.+}-{0:0}, at: filename_create+0xf5/0x4a0 fs/namei.c:3877
 #1: ffff888075698b70 (&type->i_mutex_dir_key#7/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:810 [inline]
 #1: ffff888075698b70 (&type->i_mutex_dir_key#7/1){+.+.}-{3:3}, at: filename_create+0x1ae/0x4a0 fs/namei.c:3884
 #2: ffffffff8c7e1748 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:370 [inline]
 #2: ffffffff8c7e1748 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0x138/0x520 kernel/cgroup/cgroup.c:1683
 #3: ffffffff8c7ec468 (freezer_mutex){+.+.}-{3:3}, at: freezer_css_online+0x55/0x170 kernel/cgroup/legacy_freezer.c:111

stack backtrace:
CPU: 1 PID: 5009 Comm: syz-executor259 Not tainted 6.4.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2188
 check_prev_add kernel/locking/lockdep.c:3108 [inline]
 check_prevs_add kernel/locking/lockdep.c:3227 [inline]
 validate_chain kernel/locking/lockdep.c:3842 [inline]
 __lock_acquire+0x2f21/0x5df0 kernel/locking/lockdep.c:5074
 lock_acquire kernel/locking/lockdep.c:5691 [inline]
 lock_acquire+0x1b1/0x520 kernel/locking/lockdep.c:5656
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 cpus_read_lock+0x42/0x160 kernel/cpu.c:310
 static_key_slow_inc+0x13/0x30 kernel/jump_label.c:185
 freezer_css_online+0x102/0x170 kernel/cgroup/legacy_freezer.c:117
 online_css+0xaf/0x2a0 kernel/cgroup/cgroup.c:5491
 css_create kernel/cgroup/cgroup.c:5562 [inline]
 cgroup_apply_control_enable+0x69b/0xc00 kernel/cgroup/cgroup.c:3249
 cgroup_mkdir+0x5b9/0x10b0 kernel/cgroup/cgroup.c:5758
 kernfs_iop_mkdir+0x14a/0x1d0 fs/kernfs/dir.c:1219
 vfs_mkdir+0x242/0x460 fs/namei.c:4115
 do_mkdirat+0x28d/0x310 fs/namei.c:4138
 __do_sys_mkdirat fs/namei.c:4153 [inline]
 __se_sys_mkdirat fs/namei.c:4151 [inline]
 __x64_sys_mkdirat+0x119/0x170 fs/namei.c:4151
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f8e68d07e09
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcbb7f7d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8e68d07e09
RDX: 00000000000001ff RSI: 0000000020000180 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffcbb7f7db0 R09: 00007ffcbb7f7db0
R10: 00007ffcbb7f7db0 R11: 0000000000000246 R12: 00007ffcbb7f7dac
R13: 00007ffcbb7f7dc0 R14: 00007ffcbb7f7e00 R15: 0000000000000000
 </TASK>