syzbot

INFO: task kworker/u4:3:46 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:3    state:D stack:24944 pid:46    ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6697
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x562/0xaf0 kernel/locking/mutex.c:747
 jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
 jfs_write_inode+0x141/0x220 fs/jfs/inode.c:138
 write_inode fs/fs-writeback.c:1470 [inline]
 __writeback_single_inode+0x75b/0x1160 fs/fs-writeback.c:1687
 writeback_sb_inodes+0xb30/0x1850 fs/fs-writeback.c:1913
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:1984
 wb_writeback+0x494/0xd50 fs/fs-writeback.c:2089
 wb_check_background_flush fs/fs-writeback.c:2155 [inline]
 wb_do_writeback fs/fs-writeback.c:2243 [inline]
 wb_workfn+0xc1c/0xee0 fs/fs-writeback.c:2270
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Showing all locks held in the system:
4 locks held by kworker/u4:0/9:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc900000e7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff888073cb00e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88805c35de48 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
4 locks held by kworker/u4:1/11:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000107d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88807870a0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888073584288 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8cb2df30 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8cb2e750 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
 #0: ffffffff8cb2d5a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8cb2d5a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8cb2d5a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
4 locks held by kworker/u4:2/33:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000aa7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88802a5420e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888070a30b08 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
4 locks held by kworker/u4:3/46:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000b77d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88807d20e0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88805c359d88 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
4 locks held by kworker/u4:4/1146:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc900051afd00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff8880740ae0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88805c1426c8 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
2 locks held by getty/4029:
 #0: ffff88814d834098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x429/0x1390 drivers/tty/n_tty.c:2198
3 locks held by kworker/1:22/4432:
 #0: ffff88814d4aed38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003417d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd46ea8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xca/0x14f0 net/ipv6/addrconf.c:4131
4 locks held by syz.0.17/4433:
4 locks held by syz.1.18/4448:
2 locks held by kworker/0:4/4464:
 #0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc900035b7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
3 locks held by kworker/u4:6/4465:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc900035c7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd46ea8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:263
4 locks held by syz.2.19/4470:
4 locks held by kworker/u4:7/4471:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003577d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff88802ed380e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88805c146788 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
4 locks held by syz.3.20/4486:
4 locks held by syz.4.21/4509:
4 locks held by kworker/u4:9/4510:
 #0: ffff888144674938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc900036f7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffff8880553dc0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888059c5b008 (&jfs_ip->commit_mutex){+.+.}-{3:3}, at: jfs_commit_inode+0x1c7/0x520 fs/jfs/inode.c:108
4 locks held by syz.5.22/4538:
4 locks held by syz.6.23/4561:
2 locks held by syz-executor/4564:
 #0: ffffffff8dd46ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8dd46ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x824/0xfc0 net/core/rtnetlink.c:6147
 #1: ffff8880779a13e8 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_open+0x223/0x420 drivers/net/wireguard/device.c:49
2 locks held by dhcpcd/4583:
 #0: ffff8880243dc130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #0: ffff8880243dc130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xce0 net/packet/af_packet.c:3248
 #1: ffffffff8cb33278 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
 #1: ffffffff8cb33278 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2ec/0x890 kernel/rcu/tree_exp.h:962
2 locks held by dhcpcd/4584:
 #0: ffff88807afce130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #0: ffff88807afce130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xce0 net/packet/af_packet.c:3248
 #1: ffffffff8cb33278 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline]
 #1: ffffffff8cb33278 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3c0/0x890 kernel/rcu/tree_exp.h:962
1 lock held by dhcpcd/4585:
 #0: ffff88805bff8130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #0: ffff88805bff8130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xce0 net/packet/af_packet.c:3248
1 lock held by dhcpcd/4586:
 #0: ffff888072bf6130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #0: ffff888072bf6130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xce0 net/packet/af_packet.c:3248
1 lock held by dhcpcd/4587:
 #0: ffff88807329c130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #0: ffff88807329c130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xce0 net/packet/af_packet.c:3248
1 lock held by dhcpcd/4588:
 #0: ffff888073298130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1805 [inline]
 #0: ffff888073298130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xce0 net/packet/af_packet.c:3248

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3e6/0x460 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
 watchdog+0xeee/0xf30 kernel/hung_task.c:377
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4509 Comm: syz.4.21 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:dtSplitRoot+0x700/0x14e0 fs/jfs/jfs_dtree.c:1980
Code: 85 1d 0d 00 00 41 88 2e 4c 0f be f5 49 c1 e6 05 4c 03 34 24 4d 89 f4 49 c1 ec 03 48 b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 <84> c0 75 10 41 0f b6 2e 40 84 ed 78 1b e8 de 94 90 fe eb ca 44 89
RSP: 0018:ffffc900036d7728 EFLAGS: 00000a06
RAX: 0000000000000000 RBX: 0000000000000004 RCX: ffff88801853d940
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 00000000000000ff
RBP: 0000000000000000 R08: ffff8880288e611f R09: 1ffff1100511cc23
R10: dffffc0000000000 R11: ffffed100511cc24 R12: 1ffff1100511cc00
R13: ffff88805c1469f0 R14: ffff8880288e6000 R15: 1ffff1100511cc02
FS:  000055556c3b8500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0d8ee40201 CR3: 000000001ef5e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dtSplitUp fs/jfs/jfs_dtree.c:993 [inline]
 dtInsert+0xe7b/0x5950 fs/jfs/jfs_dtree.c:871
 jfs_mkdir+0x758/0xad0 fs/jfs/namei.c:270
 vfs_mkdir+0x387/0x570 fs/namei.c:4114
 do_mkdirat+0x1d8/0x440 fs/namei.c:4139
 __do_sys_mkdirat fs/namei.c:4154 [inline]
 __se_sys_mkdirat fs/namei.c:4152 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4152
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f466df9b687
Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe4af1fc98 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffe4af1fd20 RCX: 00007f466df9b687
RDX: 00000000000001ff RSI: 0000200000000180 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000200000000240 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000000180
R13: 00007ffe4af1fce0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>