syzbot


INFO: task hung in fuse_flush (2)

Status: upstream: reported on 2025/06/09 09:24
Reported-by: syzbot+0c6d0788060a382efb32@syzkaller.appspotmail.com
First crash: 1d21h, last: 1d21h
Similar bugs (11)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in fuse_flush (5) fuse 3 92d 97d 0/28 auto-obsoleted due to no activity on 2025/06/08 10:49
linux-4.19 INFO: task hung in fuse_flush 1 1545d 1545d 0/1 auto-closed as invalid on 2021/07/16 16:14
linux-6.1 INFO: task hung in fuse_flush 1 103d 103d 0/3 auto-obsoleted due to no activity on 2025/06/08 05:58
upstream INFO: task hung in fuse_flush (2) fuse 2 869d 878d 0/28 auto-obsoleted due to no activity on 2023/04/24 00:25
upstream INFO: task hung in fuse_flush (4) fuse 6 205d 352d 0/28 auto-obsoleted due to no activity on 2025/02/15 08:56
upstream INFO: task hung in fuse_flush fuse 2 1314d 1402d 0/28 auto-closed as invalid on 2022/02/03 03:15
linux-5.15 INFO: task hung in fuse_flush 1 353d 353d 0/3 auto-obsoleted due to no activity on 2024/09/30 23:08
linux-4.19 INFO: task hung in fuse_flush (2) 1 1354d 1354d 0/1 auto-closed as invalid on 2022/01/24 04:40
linux-4.14 INFO: task hung in fuse_flush C inconclusive 19 910d 1231d 0/1 upstream: reported C repro on 2022/01/26 21:17
linux-4.19 INFO: task hung in fuse_flush (3) 109 868d 1230d 0/1 upstream: reported on 2022/01/27 11:57
upstream INFO: task hung in fuse_flush (3) fuse 1 622d 622d 0/28 auto-obsoleted due to no activity on 2023/12/26 21:09

Sample crash report:
INFO: task syz.6.388:5958 blocked for more than 143 seconds.
      Not tainted 6.1.141-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.388       state:D stack:26240 pid:5958  ppid:5332   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10e9/0x40d0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
 inode_lock include/linux/fs.h:758 [inline]
 fuse_flush+0x28c/0x820 fs/fuse/file.c:499
 filp_close+0xaa/0x150 fs/open.c:1431
 __range_close fs/file.c:705 [inline]
 __close_range+0x539/0x730 fs/file.c:755
 __do_sys_close_range fs/open.c:1476 [inline]
 __se_sys_close_range fs/open.c:1473 [inline]
 __x64_sys_close_range+0x76/0x80 fs/open.c:1473
 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: 0033:0x7f2d1e78e929
RSP: 002b:00007ffffb09c7c8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007f2d1e9b7ba0 RCX: 00007f2d1e78e929
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f2d1e9b7ba0 R08: 0000000000000000 R09: 0000000bfb09cabf
R10: 00007f2d1e9b7ac0 R11: 0000000000000246 R12: 00000000000390e0
R13: 00007ffffb09c8c0 R14: ffffffffffffffff R15: 00007ffffb09c8e0
 </TASK>
INFO: task syz.6.388:5961 blocked for more than 144 seconds.
      Not tainted 6.1.141-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.388       state:D stack:26792 pid:5961  ppid:5332   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10e9/0x40d0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x97/0x280 kernel/time/timer.c:1941
 do_wait_for_common kernel/sched/completion.c:85 [inline]
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x2b9/0x590 kernel/sched/completion.c:138
 fuse_direct_IO+0xa35/0x1270 fs/fuse/file.c:2968
 fuse_direct_write_iter fs/fuse/file.c:1610 [inline]
 fuse_file_write_iter+0x84b/0x1200 fs/fuse/file.c:1658
 call_write_iter include/linux/fs.h:2265 [inline]
 aio_write+0x50e/0x720 fs/aio.c:1615
 __io_submit_one fs/aio.c:-1 [inline]
 io_submit_one+0x6aa/0x1300 fs/aio.c:2034
 __do_sys_io_submit fs/aio.c:2093 [inline]
 __se_sys_io_submit+0x190/0x300 fs/aio.c:2063
 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: 0033:0x7f2d1e78e929
RSP: 002b:00007f2d1f5d0038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 00007f2d1e9b6080 RCX: 00007f2d1e78e929
RDX: 0000200000000780 RSI: 0000000000000001 RDI: 00007f2d1f5a7000
RBP: 00007f2d1e810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f2d1e9b6080 R15: 00007ffffb09c668
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8c92b430 (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: ffffffff8c92bc50 (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: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
3 locks held by kworker/0:2/125:
 #0: ffff888017470938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90002da7d00 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff88807eac7240 (&data->fib_lock){+.+.}-{3:3}, at: nsim_fib_event_work+0x26b/0x32b0 drivers/net/netdevsim/fib.c:1491
2 locks held by getty/4012:
 #0: ffff88814d41b098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000326b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
2 locks held by kworker/0:5/4344:
 #0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc9000483fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
5 locks held by kworker/u4:13/4891:
 #0: ffff8880b8e3aa98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:537
 #1: ffff8880b8e27848 (&per_cpu_ptr(group->pcpu, cpu)->seq
){-.-.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #2: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #2: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 #2: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: batadv_nc_worker+0xce/0x600 net/batman-adv/network-coding.c:719
 #3: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #3: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #3: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:841 [inline]
 #3: ffffffff8c92aaa0 (rcu_read_lock){....}-{1:2}, at: batadv_iv_ogm_schedule+0x826/0xe90 net/batman-adv/bat_iv_ogm.c:868
 #4: ffffffff96c05440 (&obj_hash[i].lock){-.-.}-{2:2}, at: __debug_check_no_obj_freed lib/debugobjects.c:968 [inline]
 #4: ffffffff96c05440 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_check_no_obj_freed+0x136/0x530 lib/debugobjects.c:1009
3 locks held by kworker/0:12/5702:
 #0: ffff8881442b2538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90004f8fd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff888027829190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:837 [inline]
 #2: ffff888027829190 (&dev->mutex){....}-{3:3}, at: hub_event+0x185/0x5210 drivers/usb/core/hub.c:5813
1 lock held by syz.6.388/5958:
 #0: ffff888070498ed0 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #0: ffff888070498ed0 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: fuse_flush+0x28c/0x820 fs/fuse/file.c:499
1 lock held by syz.6.388/5961:
 #0: ffff888070498ed0 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #0: ffff888070498ed0 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: fuse_direct_write_iter fs/fuse/file.c:-1 [inline]
 #0: ffff888070498ed0 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: fuse_file_write_iter+0x5ed/0x1200 fs/fuse/file.c:1658
1 lock held by syz.2.636/7230:
 #0: ffffffff8c930640 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x48/0x600 kernel/rcu/tree.c:4019
3 locks held by kworker/0:14/7257:
 #0: ffff88814d053d38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc900058cfd00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8db34aa8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x14d0 net/ipv6/addrconf.c:4137
3 locks held by syz-executor/7492:
 #0: ffffffff8db34aa8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8db34aa8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6150
 #1: ffff8880773a93e8 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_open+0x223/0x420 drivers/net/wireguard/device.c:49
 #2: ffffffff8c930778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
 #2: ffffffff8c930778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x455/0x830 kernel/rcu/tree_exp.h:962
2 locks held by syz.8.712/7727:
 #0: ffff888074272c10 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #0: ffff888074272c10 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: __sock_release net/socket.c:653 [inline]
 #0: ffff888074272c10 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: sock_close+0x90/0x240 net/socket.c:1400
 #1: ffffffff8c930778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline]
 #1: ffffffff8c930778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x346/0x830 kernel/rcu/tree_exp.h:962

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted 6.1.141-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7257 Comm: kworker/0:14 Not tainted 6.1.141-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events kfree_rcu_work
RIP: 0010:memset_erms+0xb/0x10 arch/x86/lib/memset_64.S:65
Code: 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3 aa <4c> 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 01 01
RSP: 0018:ffffc900058cf6a0 EFLAGS: 00000202
RAX: ffff8880246f0000 RBX: ffffc900058cf708 RCX: 0000000000000000
RDX: 0000000000000060 RSI: 0000000000000000 RDI: ffffc900058cf768
RBP: ffffc900058cf790 R08: dffffc0000000000 R09: ffffc900058cf708
R10: fffff52000b19eed R11: 1ffff92000b19ee1 R12: 0000000000000000
R13: ffff8880246f0000 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fea07128286 CR3: 000000007fb77000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __unwind_start+0x32/0x740 arch/x86/kernel/unwind_orc.c:645
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xda/0x140 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1750
 slab_free mm/slub.c:3661 [inline]
 kmem_cache_free_bulk+0x348/0x460 mm/slub.c:3779
 kfree_bulk include/linux/slab.h:475 [inline]
 kfree_rcu_work+0x33f/0x890 kernel/rcu/tree.c:3087
 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>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/09 09:23 linux-6.1.y 58485ff1a74f 4826c28e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in fuse_flush
* Struck through repros no longer work on HEAD.