syzbot


INFO: task hung in f2fs_stop_gc_thread

Status: upstream: reported C repro on 2025/11/07 22:55
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+271ecd34c43208563db0@syzkaller.appspotmail.com
First crash: 3d18h, last: 2d15h
Bug presence (2)
Date Name Commit Repro Result
2025/11/08 linux-5.15.y (ToT) cc5ec8769306 C [report] INFO: task hung in f2fs_stop_gc_thread
2025/11/08 upstream (ToT) e811c33b1f13 C Didn't crash
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in f2fs_stop_gc_thread f2fs 1 24 361d 474d 0/29 auto-obsoleted due to no activity on 2025/01/22 18:30

Sample crash report:
INFO: task syz.0.18:4327 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.18        state:D stack:27104 pid: 4327 ppid:  4293 flags:0x00004004
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
 schedule_timeout+0x97/0x280 kernel/time/timer.c:1890
 do_wait_for_common+0x29a/0x440 kernel/sched/completion.c:85
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x48/0x60 kernel/sched/completion.c:138
 kthread_stop+0x16e/0x540 kernel/kthread.c:666
 f2fs_stop_gc_thread+0x61/0xa0 fs/f2fs/gc.c:186
 f2fs_ioc_shutdown fs/f2fs/file.c:2308 [inline]
 __f2fs_ioctl+0x6732/0xc370 fs/f2fs/file.c:4221
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/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: 0033:0x7f66088456c9
RSP: 002b:00007f6607e93038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6608a9c090 RCX: 00007f66088456c9
RDX: 0000200000000080 RSI: 000000008004587d RDI: 0000000000000005
RBP: 00007f66088c7f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6608a9c128 R14: 00007f6608a9c090 R15: 00007ffdcf1829d8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8c11c760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3949:
 #0: ffff88802b8b5098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc900025e62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
1 lock held by syz.0.18/4327:
 #0: ffff88807c7e0460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.1.19/4356:
 #0: ffff88801b944460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.2.21/4392:
 #0: ffff88805c2ae460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.3.22/4419:
 #0: ffff88807a9f6460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.4.25/4467:
 #0: ffff88805022c460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.5.30/4539:
 #0: ffff88805079c460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.6.31/4572:
 #0: ffff88805d4aa460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.7.33/4611:
 #0: ffff88801b5c2460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
1 lock held by syz.8.34/4649:
 #0: ffff8880239f6460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430

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

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 10/02/2025
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: 151 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:match_held_lock+0x77/0xb0 kernel/locking/lockdep.c:5102
Code: 00 48 c7 c1 80 5f 94 8f 48 29 c8 48 c1 f8 06 48 be ab aa aa aa aa aa aa aa 48 0f af f0 b9 01 00 00 00 48 39 d6 74 02 31 c9 5b <89> c8 c3 e8 e1 4d 2e fa 85 c0 74 f1 83 3d 5e 5d c0 03 00 75 e8 48
RSP: 0018:ffffc900018e7ab8 EFLAGS: 00000046
RAX: 000000000000000a RBX: 000000000000000a RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8c11c760 RDI: ffff8880185a8b40
RBP: ffffc900018e7bd0 R08: dffffc0000000000 R09: fffffbfff1ad33a6
R10: fffffbfff1ad33a6 R11: 1ffffffff1ad33a5 R12: ffff8880185a8b40
R13: dffffc0000000000 R14: 0000000000000002 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b50d5c2a38 CR3: 000000002ab26000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 find_held_lock kernel/locking/lockdep.c:5115 [inline]
 __lock_release kernel/locking/lockdep.c:5300 [inline]
 lock_release+0x1f7/0x870 kernel/locking/lockdep.c:5643
 rcu_read_unlock include/linux/rcupdate.h:773 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:416 [inline]
 batadv_nc_worker+0x25b/0x5c0 net/batman-adv/network-coding.c:723
 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>

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/09 02:26 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 23:14 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 20:21 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 17:52 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 15:04 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 08:09 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 05:25 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/08 02:36 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
2025/11/07 22:54 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in f2fs_stop_gc_thread
* Struck through repros no longer work on HEAD.