syzbot

INFO: task kworker/u4:4:1234 blocked for more than 143 seconds.
      Not tainted 5.15.185-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:4    state:D stack:26344 pid: 1234 ppid:     2 flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 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:738
 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:
1 lock held by khungtaskd/27:
 #0: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
4 locks held by kworker/u4:4/1234:
 #0: ffff888018ba8938 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc900048b7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff88814c84c0e0 (&type->s_umount_key#43){.+.+}-{3:3}, at: trylock_super+0x1c/0xf0 fs/super.c:418
 #3: ffff8880796b91b0 (&sbi->gc_lock){+.+.}-{3:3}, at: f2fs_balance_fs+0x47d/0x660 fs/f2fs/segment.c:528
2 locks held by getty/3931:
 #0: ffff88814c914098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc900026462e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
7 locks held by syz-executor332/4167:
2 locks held by dhcpcd/4211:
 #0: ffff8880202f2120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline]
 #0: ffff8880202f2120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x35/0xce0 net/packet/af_packet.c:3213
 #1: ffffffff8c120a28 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
 #1: ffffffff8c120a28 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x347/0x6b0 kernel/rcu/tree_exp.h:845

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4167 Comm: syz-executor332 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:preempt_count_add+0x4/0x190 kernel/sched/core.c:5480
Code: 80 c1 03 38 c1 7c 97 48 8b 3c 24 e8 a6 db 6b 00 eb 8c e9 f5 fe ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 41 56 <53> 49 bf 00 00 00 00 00 fc ff df 48 c7 c0 60 1f 0a 96 48 c1 e8 03
RSP: 0018:ffffc90002daed90 EFLAGS: 00000282
RAX: 2af0802de0649000 RBX: ffff8880256f6450 RCX: 2af0802de0649000
RDX: 0000000000000000 RSI: ffffffff8a0b2460 RDI: 0000000000000001
RBP: ffffc90002daf2b0 R08: dffffc0000000000 R09: fffffbfff1ff3633
R10: fffffbfff1ff3633 R11: 1ffffffff1ff3632 R12: ffff8880796b8168
R13: dffffc0000000000 R14: ffff8880256f6450 R15: 1ffff11003e35944
FS:  0000555566150380(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055726715f038 CR3: 000000001e848000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __down_read_common kernel/locking/rwsem.c:1237 [inline]
 __down_read kernel/locking/rwsem.c:1252 [inline]
 down_read+0x52/0x2e0 kernel/locking/rwsem.c:1500
 check_valid_map fs/f2fs/gc.c:881 [inline]
 gc_data_segment fs/f2fs/gc.c:1451 [inline]
 do_garbage_collect+0x1c4c/0x60a0 fs/f2fs/gc.c:1671
 f2fs_gc+0x8a9/0x1900 fs/f2fs/gc.c:1765
 f2fs_balance_fs+0x491/0x660 fs/f2fs/segment.c:529
 f2fs_map_blocks+0x2976/0x3310 fs/f2fs/data.c:1746
 expand_inode_data+0x4a0/0x6e0 fs/f2fs/file.c:1716
 f2fs_fallocate+0x423/0x8c0 fs/f2fs/file.c:1818
 vfs_fallocate+0x587/0x6f0 fs/open.c:308
 ioctl_preallocate fs/ioctl.c:294 [inline]
 file_ioctl fs/ioctl.c:-1 [inline]
 do_vfs_ioctl+0x1b70/0x1de0 fs/ioctl.c:853
 __do_sys_ioctl fs/ioctl.c:872 [inline]
 __se_sys_ioctl+0x83/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f27c9001c59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcebd04948 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000200000000180 RCX: 00007f27c9001c59
RDX: 0000200000000000 RSI: 0000000040305828 RDI: 0000000000000004
RBP: 00007f27c907a5f0 R08: 00005555661514c0 R09: 00005555661514c0
R10: 00005555661514c0 R11: 0000000000000246 R12: 00007ffcebd04970
R13: 00007ffcebd04b98 R14: 431bde82d7b634db R15: 00007f27c904a03b
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.055 msecs