syzbot

INFO: task kworker/u4:4:75 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:4    state:D stack:24744 pid:75    ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
 f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
 f2fs_write_inode+0x531/0x760 fs/f2fs/inode.c:744
 write_inode fs/fs-writeback.c:1460 [inline]
 __writeback_single_inode+0x75b/0x1160 fs/fs-writeback.c:1677
 writeback_sb_inodes+0xad8/0x17d0 fs/fs-writeback.c:1903
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:1974
 wb_writeback+0x47a/0xd00 fs/fs-writeback.c:2079
 wb_check_background_flush fs/fs-writeback.c:2145 [inline]
 wb_do_writeback fs/fs-writeback.c:2233 [inline]
 wb_workfn+0xbdd/0xec0 fs/fs-writeback.c:2260
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 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: ffff888144240138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc900000e7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff888059e580e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888059e611e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 #3: ffff888059e611e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
4 locks held by kworker/u4:1/11:
 #0: ffff888144240138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000107d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff8880571b20e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888054c351e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 #3: ffff888054c351e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8cb2b570 (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: ffffffff8cb2bd90 (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/27:
 #0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
3 locks held by kworker/1:1/41:
 #0: ffff88814ce92d38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000b27d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd422e8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x14d0 net/ipv6/addrconf.c:4131
4 locks held by kworker/u4:4/75:
 #0: ffff888144240138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90001577d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff8880280460e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff88802eead1e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 #3: ffff88802eead1e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
2 locks held by getty/4028:
 #0: ffff88802f935098 (&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+0x41b/0x1380 drivers/tty/n_tty.c:2198
2 locks held by kworker/0:10/4356:
 #0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003207d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
3 locks held by kworker/0:11/4357:
 #0: ffff88814ce92d38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003227d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd422e8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x14d0 net/ipv6/addrconf.c:4131
4 locks held by kworker/u4:5/4384:
 #0: ffff888144240138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003307d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff8880799ec0e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff8880276bd1e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 #3: ffff8880276bd1e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
5 locks held by syz.0.17/4439:
5 locks held by syz.1.18/4470:
4 locks held by kworker/u4:6/4493:
 #0: ffff888144240138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc900035a7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff888056de80e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff888056de11e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 #3: ffff888056de11e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
5 locks held by syz.2.19/4495:
4 locks held by kworker/u4:7/4516:
 #0: ffff888144240138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90003787d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff88801fbd60e0 (&type->s_umount_key#53){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:415
 #3: ffff8880744911e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2177 [inline]
 #3: ffff8880744911e8 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x4a7/0x680 fs/f2fs/segment.c:428
4 locks held by kworker/u4:8/4521:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc900037c7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8dd422e8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:263
 #3: 
ffffffff8cb308b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
ffffffff8cb308b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x455/0x830 kernel/rcu/tree_exp.h:962
5 locks held by syz.3.20/4522:
7 locks held by syz.4.21/4560:
4 locks held by syz.5.22/4593:
5 locks held by syz.6.23/4625:
3 locks held by syz-executor/4638:
 #0: ffffffff8dda20f0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:860
 #1: ffffffff8dda1f08 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
 #1: ffffffff8dda1f08 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x103/0x780 net/netlink/genetlink.c:848
 #2: ffffffff8dd422e8 (rtnl_mutex){+.+.}-{3:3}, at: ieee80211_register_hw+0x2c52/0x38c0 net/mac80211/main.c:1394

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3f4/0x470 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4522 Comm: syz.3.20 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__lock_acquire+0x4ea/0x7c50 kernel/locking/lockdep.c:4997
Code: e5 14 41 09 cd 45 09 fd 41 09 c5 48 8b 44 24 50 42 0f b6 04 00 84 c0 0f 85 22 62 00 00 44 8b 75 28 48 8b 44 24 78 44 89 68 20 <48> 8d 58 24 48 89 d8 48 c1 e8 03 42 0f b6 04 00 84 c0 4c 8b a4 24
RSP: 0018:ffffc900037e6700 EFLAGS: 00000046
RAX: ffff88802ae04700 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000002c RSI: 0000000000000000 RDI: ffff88802ae04710
RBP: ffffc900037e6950 R08: dffffc0000000000 R09: 0000000000000000
R10: fffffbfff1c3eebe R11: 1ffffffff1c3eebd R12: ffff88802ae04700
R13: 000000000002002c R14: 0000000000000000 R15: 000000000000002c
FS:  000055555a44f500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000557c4feca038 CR3: 0000000077f65000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 mapping_get_entry mm/filemap.c:1878 [inline]
 __filemap_get_folio+0x111/0xdd0 mm/filemap.c:1943
 pagecache_get_page+0x26/0x250 mm/folio-compat.c:110
 find_get_page_flags include/linux/pagemap.h:602 [inline]
 f2fs_grab_cache_page+0x2b/0x3b0 fs/f2fs/f2fs.h:2717
 __get_node_page+0x172/0xf10 fs/f2fs/node.c:1443
 is_alive fs/f2fs/gc.c:1120 [inline]
 gc_data_segment fs/f2fs/gc.c:1557 [inline]
 do_garbage_collect+0x1cec/0x6050 fs/f2fs/gc.c:1776
 f2fs_gc+0xdfa/0x26c0 fs/f2fs/gc.c:1875
 f2fs_balance_fs+0x4b2/0x680 fs/f2fs/segment.c:429
 f2fs_map_blocks+0x1c04/0x3840 fs/f2fs/data.c:1705
 expand_inode_data+0x4ab/0x870 fs/f2fs/file.c:1805
 f2fs_fallocate+0x4c3/0x950 fs/f2fs/file.c:1908
 vfs_fallocate+0x584/0x6f0 fs/open.c:323
 ioctl_preallocate fs/ioctl.c:290 [inline]
 file_ioctl fs/ioctl.c:-1 [inline]
 do_vfs_ioctl+0x1a9d/0x1d10 fs/ioctl.c:849
 __do_sys_ioctl fs/ioctl.c:868 [inline]
 __se_sys_ioctl+0x83/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ffbc558ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffca9c155c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffbc57d5fa0 RCX: 00007ffbc558ec29
RDX: 00002000000000c0 RSI: 0000000040305828 RDI: 0000000000000004
RBP: 00007ffbc5611e41 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffbc57d5fa0 R14: 00007ffbc57d5fa0 R15: 0000000000000003
 </TASK>