syzbot

INFO: task syz.6.1064:11560 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.1064      state:D stack:26896 pid:11560 tgid:11558 ppid:6268   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0xfee/0x6120 kernel/sched/core.c:6908
 __schedule_loop kernel/sched/core.c:6990 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7005
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7062
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0xc9a/0x1b90 kernel/locking/mutex.c:776
 expkey_flush+0x18/0x90 fs/nfsd/export.c:250
 write_flush.isra.0+0x2af/0x3d0 net/sunrpc/cache.c:1551
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x240/0x330 fs/proc/inode.c:342
 do_loop_readv_writev fs/read_write.c:852 [inline]
 do_loop_readv_writev fs/read_write.c:837 [inline]
 vfs_writev+0x5ea/0xe10 fs/read_write.c:1061
 do_writev+0x13e/0x340 fs/read_write.c:1105
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2318f9c799
RSP: 002b:00007f2319ed0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f2319215fa0 RCX: 00007f2318f9c799
RDX: 000000000000000a RSI: 0000200000000240 RDI: 000000000000000a
RBP: 00007f2319032c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2319216038 R14: 00007f2319215fa0 R15: 00007ffeb3548758
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
 #0: ffffffff8e7e7460 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8e7e7460 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8e7e7460 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
4 locks held by kworker/u8:2/35:
 #0: ffff88801c6ae948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250
 #1: ffffc90000ab7d08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251
 #2: ffffffff905fac50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:675
 #3: ffffffff8e7f3078 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
2 locks held by getty/5584:
 #0: ffff888036ca30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211
2 locks held by kworker/1:3/5830:
 #0: ffff88813fe63148 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250
 #1: ffffc90004107d08 (free_ipc_work){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251
2 locks held by syz.7.85/6582:
2 locks held by syz.4.98/6696:
1 lock held by dhcpcd/7060:
 #0: ffff888062aa35c8 (&sb->s_type->i_mutex_key#14){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline]
 #0: ffff888062aa35c8 (&sb->s_type->i_mutex_key#14){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:661
2 locks held by syz.4.301/7913:
3 locks held by syz.7.404/8429:
2 locks held by syz.7.425/8520:
2 locks held by syz.7.465/8782:
 #0: ffff888035255900 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:536 [inline]
 #0: ffff888035255900 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x22c/0xa30 mm/mmap.c:1310
 #1: ffff88802d14fa08 (&anon_vma->rwsem){++++}-{4:4}, at: anon_vma_lock_write mm/internal.h:220 [inline]
 #1: ffff88802d14fa08 (&anon_vma->rwsem){++++}-{4:4}, at: unlink_anon_vmas+0xe1/0x8e0 mm/rmap.c:486
2 locks held by syz.4.584/9316:
2 locks held by syz.4.603/9399:
2 locks held by syz.7.649/9608:
 #0: ffff88807ba70f80 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:536 [inline]
 #0: ffff88807ba70f80 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x22c/0xa30 mm/mmap.c:1310
 #1: ffff88802d14fa08 (&anon_vma->rwsem){++++}-{4:4}, at: anon_vma_lock_write mm/internal.h:220 [inline]
 #1: ffff88802d14fa08 (&anon_vma->rwsem){++++}-{4:4}, at: unlink_anon_vmas+0xe1/0x8e0 mm/rmap.c:486
2 locks held by syz.4.741/10065:
2 locks held by syz.4.827/10430:
2 locks held by syz.4.839/10453:
1 lock held by syz.4.971/11065:
1 lock held by syz.4.1003/11200:
2 locks held by syz.5.999/11230:
 #0: ffffffff906bf810 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8ec579c8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_set_doit+0x6c1/0xc00 fs/nfsd/nfsctl.c:1597
1 lock held by syz.4.1032/11382:
3 locks held by syz.6.1064/11560:
 #0: ffff888036e55978 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1261
 #1: ffff88805c8a8420 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1105
 #2: ffffffff8ec579c8 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:250
2 locks held by syz-executor/11787:
 #0: ffff888062e000e0 (&type->s_umount_key#57){++++}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff888062e000e0 (&type->s_umount_key#57){++++}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff888062e000e0 (&type->s_umount_key#57){++++}-{4:4}, at: deactivate_super fs/super.c:508 [inline]
 #0: ffff888062e000e0 (&type->s_umount_key#57){++++}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:505
 #1: ffffffff8ec579c8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
2 locks held by syz.4.1157/12021:
2 locks held by syz.4.1165/12062:
2 locks held by syz.4.1169/12072:
1 lock held by syz.4.1182/12170:
2 locks held by syz-executor/12574:
 #0: ffff88803418e0e0 (&type->s_umount_key#57){++++}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88803418e0e0 (&type->s_umount_key#57){++++}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff88803418e0e0 (&type->s_umount_key#57){++++}-{4:4}, at: deactivate_super fs/super.c:508 [inline]
 #0: ffff88803418e0e0 (&type->s_umount_key#57){++++}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:505
 #1: ffffffff8ec579c8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
1 lock held by syz.8.1428/13477:
 #0: ffffffff8e7f3078 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
1 lock held by syz-executor/13755:
 #0: ffffffff906134a8 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline]
 #0: ffffffff906134a8 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x38/0x220 drivers/net/tun.c:3436
1 lock held by syz.7.1512/13960:
2 locks held by syz.4.1517/13991:
1 lock held by syz.4.1532/14107:
1 lock held by dhcpcd/14122:
 #0: ffff88807ca0a260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
 #0: ffff88807ca0a260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3197
1 lock held by dhcpcd/14123:
 #0: ffff8880619d0260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
 #0: ffff8880619d0260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3197
1 lock held by dhcpcd/14124:
 #0: ffff8880318c8260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
 #0: ffff8880318c8260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3197
1 lock held by dhcpcd/14125:
 #0: ffff8880619d2260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
 #0: ffff8880619d2260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3197
1 lock held by dhcpcd/14126:
 #0: ffff888035994260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
 #0: ffff888035994260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3197

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
 watchdog+0xd25/0x1050 kernel/hung_task.c:515
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 12695 Comm: kworker/0:0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
Workqueue: events_long defense_work_handler
RIP: 0010:hlock_class kernel/locking/lockdep.c:234 [inline]
RIP: 0010:mark_lock+0x52/0xa20 kernel/locking/lockdep.c:4731
Code: 89 d3 83 fa 08 74 6d 41 be 01 00 00 00 89 d9 41 d3 e6 4d 63 f6 41 0f b7 44 24 20 66 25 ff 1f 0f b7 c0 48 0f a3 05 3e dd 2f 14 <73> 5b 48 8d 04 80 48 8d 04 80 48 8d 04 c5 a0 0b 14 96 4c 89 f1 48
RSP: 0018:ffffc90000007c50 EFLAGS: 00000003
RAX: 0000000000000457 RBX: 0000000000000002 RCX: 0000000000000002
RDX: 0000000000000002 RSI: ffff88802f93c858 RDI: ffff88802f93bd00
RBP: ffffc90000007ce8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88802f93c858
R13: ffff88802f93bd00 R14: 0000000000000004 R15: 1ffff92000000fac
FS:  0000000000000000(0000) GS:ffff88812434d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005606b46d44b0 CR3: 0000000031370000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 mark_held_locks+0x40/0x70 kernel/locking/lockdep.c:4325
 __trace_hardirqs_on_caller kernel/locking/lockdep.c:4343 [inline]
 lockdep_hardirqs_on_prepare kernel/locking/lockdep.c:4410 [inline]
 lockdep_hardirqs_on_prepare+0xb4/0x1b0 kernel/locking/lockdep.c:4362
 trace_hardirqs_on+0x36/0x40 kernel/trace/trace_preemptirq.c:78
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
 _raw_spin_unlock_irqrestore+0x52/0x80 kernel/locking/spinlock.c:194
 debug_object_deactivate+0x2e4/0x3b0 lib/debugobjects.c:905
 debug_rcu_head_unqueue kernel/rcu/rcu.h:248 [inline]
 rcu_do_batch kernel/rcu/tree.c:2609 [inline]
 rcu_core+0x532/0x10d0 kernel/rcu/tree.c:2869
 handle_softirqs+0x1eb/0x9e0 kernel/softirq.c:622
 do_softirq kernel/softirq.c:523 [inline]
 do_softirq+0xac/0xe0 kernel/softirq.c:510
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xf8/0x120 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 update_defense_level+0x607/0xf50 net/netfilter/ipvs/ip_vs_ctl.c:209
 defense_work_handler+0x26/0xd0 net/netfilter/ipvs/ip_vs_ctl.c:234
 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
 process_scheduled_works kernel/workqueue.c:3358 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>