syzbot

======================================================
WARNING: possible circular locking dependency detected
6.1.34-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor190/3540 is trying to acquire lock:
ffffffff8cdc4970 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_slow_inc+0xe/0x20 kernel/jump_label.c:158

but task is already holding lock:
ffffffff8cf5a608 (freezer_mutex){+.+.}-{3:3}, at: freezer_css_online+0x4b/0x140 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}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       __mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
       freezer_change_state kernel/cgroup/legacy_freezer.c:389 [inline]
       freezer_write+0xa4/0x3f0 kernel/cgroup/legacy_freezer.c:429
       cgroup_file_write+0x2c6/0x690 kernel/cgroup/cgroup.c:4057
       kernfs_fop_write_iter+0x3a2/0x4f0 fs/kernfs/file.c:330
       call_write_iter include/linux/fs.h:2205 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x7ae/0xba0 fs/read_write.c:584
       ksys_write+0x19c/0x2c0 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/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:3098 [inline]
       check_prevs_add kernel/locking/lockdep.c:3217 [inline]
       validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       cpus_read_lock+0x3e/0x150 kernel/cpu.c:310
       static_key_slow_inc+0xe/0x20 kernel/jump_label.c:158
       freezer_css_online+0xc2/0x140 kernel/cgroup/legacy_freezer.c:117
       online_css+0xba/0x260 kernel/cgroup/cgroup.c:5476
       css_create kernel/cgroup/cgroup.c:5547 [inline]
       cgroup_apply_control_enable+0x7d1/0xae0 kernel/cgroup/cgroup.c:3235
       cgroup_mkdir+0xd8b/0xff0 kernel/cgroup/cgroup.c:5743
       kernfs_iop_mkdir+0x275/0x400 fs/kernfs/dir.c:1196
       vfs_mkdir+0x3b6/0x590 fs/namei.c:4036
       do_mkdirat+0x260/0x520 fs/namei.c:4061
       __do_sys_mkdirat fs/namei.c:4076 [inline]
       __se_sys_mkdirat fs/namei.c:4074 [inline]
       __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4074
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/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);
  lock(cpu_hotplug_lock);

 *** DEADLOCK ***

4 locks held by syz-executor190/3540:
 #0: ffff888076982460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393
 #1: ffff8880728b8b70 (&type->i_mutex_dir_key#7/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:791 [inline]
 #1: ffff8880728b8b70 (&type->i_mutex_dir_key#7/1){+.+.}-{3:3}, at: filename_create+0x256/0x530 fs/namei.c:3807
 #2: ffffffff8cf4f6a8 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xe5/0x290 kernel/cgroup/cgroup.c:1667
 #3: ffffffff8cf5a608 (freezer_mutex){+.+.}-{3:3}, at: freezer_css_online+0x4b/0x140 kernel/cgroup/legacy_freezer.c:111

stack backtrace:
CPU: 0 PID: 3540 Comm: syz-executor190 Not tainted 6.1.34-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3098 [inline]
 check_prevs_add kernel/locking/lockdep.c:3217 [inline]
 validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
 lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 cpus_read_lock+0x3e/0x150 kernel/cpu.c:310
 static_key_slow_inc+0xe/0x20 kernel/jump_label.c:158
 freezer_css_online+0xc2/0x140 kernel/cgroup/legacy_freezer.c:117
 online_css+0xba/0x260 kernel/cgroup/cgroup.c:5476
 css_create kernel/cgroup/cgroup.c:5547 [inline]
 cgroup_apply_control_enable+0x7d1/0xae0 kernel/cgroup/cgroup.c:3235
 cgroup_mkdir+0xd8b/0xff0 kernel/cgroup/cgroup.c:5743
 kernfs_iop_mkdir+0x275/0x400 fs/kernfs/dir.c:1196
 vfs_mkdir+0x3b6/0x590 fs/namei.c:4036
 do_mkdirat+0x260/0x520 fs/namei.c:4061
 __do_sys_mkdirat fs/namei.c:4076 [inline]
 __se_sys_mkdirat fs/namei.c:4074 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4074
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f111fe22dc9
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:00007ffca07fb858 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f111fe22dc9
RDX: 00000000000001ff RSI: 0000000020000180 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffca07fb880 R09: 00007ffca07fb880
R10: 00007ffca07fb880 R11: 0000000000000246 R12: 00007ffca07fb87c
R13: 00007ffca07fb890 R14: 00007ffca07fb8d0 R15: 0000000000000000
 </TASK>