syzbot

INFO: task kworker/u4:1:144 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:1    state:D stack:24744 pid:  144 ppid:     2 flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
 f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
 f2fs_write_inode+0x531/0x760 fs/f2fs/inode.c:745
 write_inode fs/fs-writeback.c:1495 [inline]
 __writeback_single_inode+0x6c3/0xda0 fs/fs-writeback.c:1705
 writeback_sb_inodes+0x9fe/0x1610 fs/fs-writeback.c:1930
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:2001
 wb_writeback+0x455/0xb90 fs/fs-writeback.c:2106
 wb_check_background_flush fs/fs-writeback.c:2172 [inline]
 wb_do_writeback fs/fs-writeback.c:2260 [inline]
 wb_workfn+0xb47/0xe60 fs/fs-writeback.c:2288
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/0:0/7:
 #0: ffff88802a928138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90000cc7d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffffffff8d237c88 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x1520 net/ipv6/addrconf.c:4110
4 locks held by kworker/u4:0/9:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90000ce7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff888078ffe0e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff8880222d91b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
2 locks held by kworker/0:1/13:
 #0: ffff888016872138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90000d27d00 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
1 lock held by khungtaskd/27:
 #0: ffffffff8c11c460 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
4 locks held by kworker/u4:1/144:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc900015ffd00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff88802b2900e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff88807559d1b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
4 locks held by kworker/u4:2/154:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90001f17d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff888076c520e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff88807d3b51b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
4 locks held by kworker/u4:3/705:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc900039cfd00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff88802a98c0e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff888075a611b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
4 locks held by kworker/u4:4/1279:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90004e87d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff88805c64c0e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff8880222ad1b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
2 locks held by getty/3953:
 #0: ffff88802c2f3098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
5 locks held by syz.0.17/4356:
4 locks held by syz.1.18/4383:
4 locks held by syz.2.19/4417:
4 locks held by kworker/u4:8/4445:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc9000342fd00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff888019fdc0e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff8880717151b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
5 locks held by syz.3.20/4446:
2 locks held by kworker/u4:9/4477:
 #0: ffff8880b913a318 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475
 #1: ffff8880b9127848 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x4d6/0x810 kernel/sched/psi.c:891
4 locks held by syz.4.21/4478:
7 locks held by syz.5.22/4515:
4 locks held by kworker/u4:11/4538:
 #0: ffff8881427d4938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90004a47d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff888055bc40e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff888052f291b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
4 locks held by syz.6.23/4550:
2 locks held by syz-executor/4556:
 #0: ffffffff8d237c88 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:72 [inline]
 #0: ffffffff8d237c88 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x974/0xe60 net/core/rtnetlink.c:5647
 #1: ffff8880775013e8 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_open+0x223/0x420 drivers/net/wireguard/device.c:49
2 locks held by dhcpcd/4577:
 #0: ffff88806ef55010 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #0: ffff88806ef55010 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:648 [inline]
 #0: ffff88806ef55010 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x90/0x240 net/socket.c:1336
 #1: ffffffff8c120ee8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
 #1: ffffffff8c120ee8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x347/0x6b0 kernel/rcu/tree_exp.h:845
2 locks held by dhcpcd/4578:
 #0: ffff88806ef54a10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #0: ffff88806ef54a10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:648 [inline]
 #0: ffff88806ef54a10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x90/0x240 net/socket.c:1336
 #1: 
ffffffff8c120ee8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline]
ffffffff8c120ee8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x320/0x6b0 kernel/rcu/tree_exp.h:845
1 lock held by dhcpcd/4584:
 #0: ffff88801f4c0120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline]
 #0: ffff88801f4c0120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x35/0xce0 net/packet/af_packet.c:3212
1 lock held by dhcpcd/4585:
 #0: ffff88814cb5a120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline]
 #0: ffff88814cb5a120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x35/0xce0 net/packet/af_packet.c:3212
1 lock held by dhcpcd/4586:
 #0: ffff88804fc12120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline]
 #0: ffff88804fc12120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x35/0xce0 net/packet/af_packet.c:3212

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

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
 watchdog+0xe0f/0xe50 kernel/hung_task.c:369
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4537 Comm: kworker/u4:10 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: phy12 ieee80211_iface_work
RIP: 0010:skb_release_data+0x0/0x850 net/core/skbuff.c:660
Code: 26 a8 f9 48 89 df e8 2f fe ff ff 48 89 df e8 17 00 00 00 48 89 df 5b e9 4e e0 ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <55> 41 57 41 56 41 55 41 54 53 48 83 ec 48 49 89 fd 48 bb 00 00 00
RSP: 0018:ffffc90004a37b98 EFLAGS: 00000293
RAX: ffffffff87cf86f7 RBX: ffff888017987500 RCX: ffff888026b78000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888017987500
RBP: 0000000000000000 R08: dffffc0000000000 R09: fffffbfff1ad31be
R10: fffffbfff1ad31be R11: 1ffffffff1ad31bd R12: dffffc0000000000
R13: 0000000000000080 R14: ffff8880179875c8 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe8394bd68 CR3: 0000000069376000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 skb_release_all net/core/skbuff.c:742 [inline]
 __kfree_skb net/core/skbuff.c:756 [inline]
 kfree_skb_reason+0xaf/0x110 net/core/skbuff.c:776
 kfree_skb include/linux/skbuff.h:1118 [inline]
 ieee80211_iface_work+0x798/0xc60 net/mac80211/iface.c:1515
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>