syzbot

INFO: task syz.0.973:14275 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.973       state:D stack:25592 pid:14275 tgid:14274 ppid:5597   task_flags:0x400140 flags:0x00080003
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5387 [inline]
 __schedule+0x1681/0x54c0 kernel/sched/core.c:7188
 __schedule_loop kernel/sched/core.c:7267 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7282
 schedule_timeout+0xc3/0x2c0 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common kernel/sched/completion.c:121 [inline]
 wait_for_common kernel/sched/completion.c:132 [inline]
 wait_for_completion+0x2cc/0x5e0 kernel/sched/completion.c:153
 kthread_flush_worker+0x138/0x1a0 kernel/kthread.c:1579
 __alloc_workqueue+0xfc1/0x1f30 kernel/workqueue.c:5895
 alloc_workqueue_noprof+0xe3/0x210 kernel/workqueue.c:5918
 btrfs_init_workqueues+0x25e/0x680 fs/btrfs/disk-io.c:1954
 open_ctree+0x1598/0x4190 fs/btrfs/disk-io.c:3444
 btrfs_fill_super fs/btrfs/super.c:981 [inline]
 btrfs_get_tree_super fs/btrfs/super.c:1944 [inline]
 btrfs_get_tree_subvol fs/btrfs/super.c:2087 [inline]
 btrfs_get_tree+0x1061/0x1910 fs/btrfs/super.c:2121
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3834
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4360
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff20212e04a
RSP: 002b:00007ff200385e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ff200385ee0 RCX: 00007ff20212e04a
RDX: 0000200000005100 RSI: 0000200000000040 RDI: 00007ff200385ea0
RBP: 0000200000005100 R08: 00007ff200385ee0 R09: 0000000000800810
R10: 0000000000800810 R11: 0000000000000246 R12: 0000200000000040
R13: 00007ff200385ea0 R14: 000000000000510a R15: 0000200000000140
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/37:
 #0: ffffffff8dfc8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8dfc8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8dfc8140 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
2 locks held by getty/5348:
 #0: ffff8880373330a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003cbe2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x462/0x13a0 drivers/tty/n_tty.c:2211
6 locks held by syz-executor/5599:
 #0: ffff88803fbd40d0 (&type->s_umount_key#68){++++}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88803fbd40d0 (&type->s_umount_key#68){++++}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff88803fbd40d0 (&type->s_umount_key#68){++++}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:508
 #1: ffff888033edb1d8 (btrfs_trans_completed){.+.+}-{0:0}, at: btrfs_commit_transaction+0x1a2/0x30e0 fs/btrfs/transaction.c:2239
 #2: ffff888033edb1b0 (btrfs_trans_super_committed){.+.+}-{0:0}, at: btrfs_commit_transaction+0x1a2/0x30e0 fs/btrfs/transaction.c:2239
 #3: ffff888033edb188 (btrfs_trans_unblocked){++++}-{0:0}, at: btrfs_commit_transaction+0x1a2/0x30e0 fs/btrfs/transaction.c:2239
 #4: ffff888033ed92b8 (&fs_info->reloc_mutex){+.+.}-{4:4}, at: btrfs_commit_transaction+0xf6b/0x30e0 fs/btrfs/transaction.c:2456
 #5: ffff88806496bda8 (&head_ref->mutex){+.+.}-{4:4}, at: btrfs_delayed_ref_lock+0x88/0x2b0 fs/btrfs/delayed-ref.c:381
4 locks held by kworker/u8:2/11715:
1 lock held by syz.0.973/14275:
 #0: ffff8880332f40d0 (&type->s_umount_key#60/1){+.+.}-{4:4}, at: alloc_super+0x28c/0xac0 fs/super.c:345
3 locks held by kworker/u8:6/15858:
4 locks held by syz.5.1135/16253:
2 locks held by syz.5.1135/16272:
 #0: ffff888034abc480 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: inode_lock include/linux/fs.h:1029 [inline]
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: open_last_lookups fs/namei.c:4608 [inline]
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: path_openat+0xb5e/0x38a0 fs/namei.c:4855
2 locks held by syz.5.1135/16273:
 #0: ffff888034abc480 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1074 [inline]
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2914 [inline]
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2938 [inline]
 #1: ffff888061e9e2a0 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:4950
2 locks held by udevadm/16255:
1 lock held by udevadm/16271:
2 locks held by udevadm/16274:

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd3/0x1030 kernel/hung_task.c:561
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 3 Comm: pool_workqueue_ Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:chain_hlock_class_idx kernel/locking/lockdep.c:438 [inline]
RIP: 0010:remove_class_from_lock_chain kernel/locking/lockdep.c:6198 [inline]
RIP: 0010:remove_class_from_lock_chains kernel/locking/lockdep.c:6236 [inline]
RIP: 0010:zap_class+0xf1/0x340 kernel/locking/lockdep.c:6281
Code: 08 c1 75 d7 45 8b 75 00 41 f6 c6 fc 0f 84 e1 00 00 00 41 c1 ee 08 4a 8d 1c 75 30 23 73 92 49 81 fe 00 00 50 00 73 2f 0f b7 03 <25> ff 1f 00 00 49 39 c7 74 33 49 ff c6 41 8b 45 00 89 c1 c1 e9 08
RSP: 0018:ffffc90000087c50 EFLAGS: 00000087
RAX: 0000000000002860 RBX: ffffffff927de30a RCX: 0000000000040600
RDX: ffffffff936e2378 RSI: ffffffff936e2378 RDI: ffffffff931d6f30
RBP: ffffffff937227d0 R08: ffffffff81adcd38 R09: ffffffff8dfc8140
R10: dffffc0000000000 R11: fffffbfff1f11c3f R12: 00000000000445d0
R13: ffffffff93936eb0 R14: 0000000000055fed R15: 0000000000000d2e
FS:  0000000000000000(0000) GS:ffff888126279000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5d52bd9d58 CR3: 0000000035b5e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __lockdep_free_key_range kernel/locking/lockdep.c:6407 [inline]
 lockdep_unregister_key+0x1c3/0x350 kernel/locking/lockdep.c:6609
 wq_unregister_lockdep kernel/workqueue.c:4929 [inline]
 pwq_release_workfn+0x6ce/0x8c0 kernel/workqueue.c:5225
 kthread_worker_fn+0x4ee/0xb20 kernel/kthread.c:1025
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>