syzbot

INFO: task syz.0.516:11424 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.516       state:D stack:26704 pid:11424 tgid:11423 ppid:10994  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x145f/0x5070 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7241
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1dfe/0x25e0 kernel/locking/rtmutex.c:1760
 __rwbase_read_lock+0xbc/0x180 kernel/locking/rwbase_rt.c:114
 rwbase_read_lock kernel/locking/rwbase_rt.c:147 [inline]
 __down_read kernel/locking/rwsem.c:1466 [inline]
 down_read+0x127/0x1f0 kernel/locking/rwsem.c:1539
 __super_lock fs/super.c:59 [inline]
 super_lock+0x2a9/0x3b0 fs/super.c:121
 user_get_super+0xc8/0x120 fs/super.c:998
 quotactl_block fs/quota/quota.c:890 [inline]
 __do_sys_quotactl fs/quota/quota.c:955 [inline]
 __se_sys_quotactl+0x4da/0x950 fs/quota/quota.c:917
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fce19f2f749
RSP: 002b:00007fce1818e038 EFLAGS: 00000246 ORIG_RAX: 00000000000000b3
RAX: ffffffffffffffda RBX: 00007fce1a185fa0 RCX: 00007fce19f2f749
RDX: 0000000000000000 RSI: 00002000000000c0 RDI: ffffffff80000802
RBP: 00007fce19fb3f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000000140 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fce1a186038 R14: 00007fce1a185fa0 R15: 00007ffd2d79d028
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/38:
 #0: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
2 locks held by getty/5553:
 #0: ffff88814d7aa0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e8b2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x44f/0x1460 drivers/tty/n_tty.c:2211
5 locks held by syz-executor/5806:
1 lock held by syz.0.516/11424:
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: __super_lock fs/super.c:59 [inline]
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: super_lock+0x2a9/0x3b0 fs/super.c:121
1 lock held by syz.9.611/12603:
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: __super_lock fs/super.c:59 [inline]
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: super_lock+0x2a9/0x3b0 fs/super.c:121
1 lock held by syz.9.611/12604:
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: __super_lock fs/super.c:59 [inline]
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: super_lock+0x2a9/0x3b0 fs/super.c:121
1 lock held by syz.9.611/12605:
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: __super_lock fs/super.c:59 [inline]
 #0: ffff8880280f00d0 (&type->s_umount_key#67){++++}-{4:4}, at: super_lock+0x2a9/0x3b0 fs/super.c:121
3 locks held by syz.1.676/13301:
2 locks held by syz.3.678/13332:
1 lock held by sed/13338:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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:160 [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:346 [inline]
 watchdog+0xf95/0xfe0 kernel/hung_task.c:515
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 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 10/25/2025
RIP: 0010:remove_class_from_lock_chain kernel/locking/lockdep.c:6197 [inline]
RIP: 0010:remove_class_from_lock_chains kernel/locking/lockdep.c:6236 [inline]
RIP: 0010:zap_class+0xcf/0x340 kernel/locking/lockdep.c:6281
Code: 49 81 fc 00 00 08 00 0f 84 a4 01 00 00 4e 8b 2c e5 c0 b3 76 92 4d 85 ed 0f 94 c0 49 83 c5 f8 0f 94 c1 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 90 b3 bb 91
RSP: 0000:ffffc90000087bc8 EFLAGS: 00000046
RAX: 0000000000074400 RBX: ffffffff91ca3c08 RCX: 0000000000074400
RDX: ffffffff9276b3b8 RSI: 0000000000000006 RDI: 0000000000171495
RBP: ffffffff92bab830 R08: ffffffff81a9df28 R09: ffffffff8d5ae940
R10: dffffc0000000000 R11: fffffbfff1db668f R12: 0000000000030e44
R13: ffffffff9328aaf0 R14: 000000000eabc624 R15: 00000000000011b5
FS:  0000000000000000(0000) GS:ffff888126cef000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005596d07fe950 CR3: 0000000078f8a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __lockdep_free_key_range kernel/locking/lockdep.c:6407 [inline]
 lockdep_unregister_key+0x1c4/0x350 kernel/locking/lockdep.c:6609
 wq_unregister_lockdep kernel/workqueue.c:4852 [inline]
 pwq_release_workfn+0x6d2/0x870 kernel/workqueue.c:5148
 kthread_worker_fn+0x4f0/0xb20 kernel/kthread.c:1005
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>