syzbot


INFO: task hung in file_start_write (2)

Status: auto-obsoleted due to no activity on 2025/12/26 09:08
Subsystems: kernfs xfs
[Documentation on labels]
First crash: 185d, last: 97d
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in file_start_write f2fs 1 10 494d 520d 0/29 auto-obsoleted due to no activity on 2024/10/15 18:57

Sample crash report:
INFO: task syz.3.57:6272 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.57        state:D stack:24680 pid:6272  tgid:6270  ppid:5839   task_flags:0x400140 flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 percpu_rwsem_wait+0x2e6/0x330 kernel/locking/percpu-rwsem.c:164
 __percpu_down_read+0xfc/0x140 kernel/locking/percpu-rwsem.c:180
 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs.h:1799 [inline]
 sb_start_write include/linux/fs.h:1935 [inline]
 file_start_write+0x202/0x250 include/linux/fs.h:3108
 direct_splice_actor+0x49/0x160 fs/splice.c:1160
 splice_direct_to_actor+0x5b3/0xcd0 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0x187/0x270 fs/splice.c:1230
 do_sendfile+0x4ec/0x7f0 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1417
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff1850aeec9
RSP: 002b:00007ff18330e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007ff185305fa0 RCX: 00007ff1850aeec9
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 0000000000000008
RBP: 00007ff185131f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020fffe82 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff185306038 R14: 00007ff185305fa0 R15: 00007ffcfc197b88
 </TASK>
INFO: task syz.3.57:6307 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.57        state:D stack:26920 pid:6307  tgid:6270  ppid:5839   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 percpu_rwsem_wait+0x2e6/0x330 kernel/locking/percpu-rwsem.c:164
 __percpu_down_read+0xfc/0x140 kernel/locking/percpu-rwsem.c:180
 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs.h:1799 [inline]
 sb_start_write+0x18e/0x1c0 include/linux/fs.h:1935
 file_start_write include/linux/fs.h:3108 [inline]
 vfs_write+0x217/0xb40 fs/read_write.c:682
 ksys_write+0x14b/0x260 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff1850aeec9
RSP: 002b:00007ff182ea9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ff185306270 RCX: 00007ff1850aeec9
RDX: 0000000000000028 RSI: 0000200000000040 RDI: 0000000000000004
RBP: 00007ff185131f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff185306308 R14: 00007ff185306270 R15: 00007ffcfc197b88
 </TASK>

Showing all locks held in the system:
4 locks held by kworker/u8:1/13:
1 lock held by khungtaskd/38:
 #0: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
7 locks held by kworker/u8:4/70:
 #0: ffff88801a6f4138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff88801a6f4138 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc9000152fbc0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc9000152fbc0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffffffff8ecc6960 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x800 net/core/net_namespace.c:658
 #3: ffff88803c0430d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #3: ffff88803c0430d8 (&dev->mutex){....}-{4:4}, at: devl_dev_lock net/devlink/devl_internal.h:108 [inline]
 #3: ffff88803c0430d8 (&dev->mutex){....}-{4:4}, at: devlink_pernet_pre_exit+0x10a/0x3d0 net/devlink/core.c:506
 #4: ffff88803c041300 (&devlink->lock_key#8){+.+.}-{4:4}, at: devl_lock net/devlink/core.c:276 [inline]
 #4: ffff88803c041300 (&devlink->lock_key#8){+.+.}-{4:4}, at: devl_dev_lock net/devlink/devl_internal.h:109 [inline]
 #4: ffff88803c041300 (&devlink->lock_key#8){+.+.}-{4:4}, at: devlink_pernet_pre_exit+0x11c/0x3d0 net/devlink/core.c:506
 #5: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: nsim_destroy+0xe5/0x670 drivers/net/netdevsim/netdev.c:1135
 #6: ffff888059d38e90 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2761 [inline]
 #6: ffff888059d38e90 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0x52f/0x1fe0 net/core/dev.c:12125
3 locks held by kworker/u8:7/1181:
 #0: ffff88814d2a1138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff88814d2a1138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc90005037bc0 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc90005037bc0 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x119/0x15a0 net/ipv6/addrconf.c:4194
3 locks held by kworker/u8:11/4781:
 #0: ffff888019881138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff888019881138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc9000fd1fbc0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc9000fd1fbc0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:303
2 locks held by dhcpcd/5500:
 #0: ffff888060228910 (nlk_cb_mutex-ROUTE){+.+.}-{4:4}, at: __netlink_dump_start+0xfe/0x7e0 net/netlink/af_netlink.c:2406
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_dumpit+0x92/0x200 net/core/rtnetlink.c:6814
2 locks held by getty/5597:
 #0: ffff88823bf3c8a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e762e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x444/0x1410 drivers/tty/n_tty.c:2222
5 locks held by syz-executor/5846:
1 lock held by syz.3.57/6272:
 #0: ffff888021eb2488 (sb_writers#12){++++}-{0:0}, at: direct_splice_actor+0x49/0x160 fs/splice.c:1160
2 locks held by syz.3.57/6307:
 #0: ffff888023277528 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x253/0x320 fs/file.c:1232
 #1: ffff888021eb2488 (sb_writers#12){++++}-{0:0}, at: file_start_write include/linux/fs.h:3108 [inline]
 #1: ffff888021eb2488 (sb_writers#12){++++}-{0:0}, at: vfs_write+0x217/0xb40 fs/read_write.c:682
2 locks held by syz-executor/6341:
1 lock held by syz-executor/7397:
 #0: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #0: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_newaddr+0x3b0/0x18b0 net/ipv4/devinet.c:978
7 locks held by syz-executor/7442:
 #0: ffff888033efc488 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3108 [inline]
 #0: ffff888033efc488 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x217/0xb40 fs/read_write.c:682
 #1: ffff88805dd69478 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
 #2: ffff888026ff9878 (kn->active#52){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff888026ff9878 (kn->active#52){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x232/0x540 fs/kernfs/file.c:344
 #3: ffffffff8e542ef8 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd1/0x360 drivers/net/netdevsim/bus.c:234
 #4: ffff88802381d0d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #4: ffff88802381d0d8 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1096 [inline]
 #4: ffff88802381d0d8 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb6/0x800 drivers/base/dd.c:1294
 #5: ffff88802381e300 (&devlink->lock_key#5){+.+.}-{4:4}, at: nsim_drv_remove+0x50/0x160 drivers/net/netdevsim/dev.c:1721
 #6: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #6: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: unregister_netdevice_notifier_net+0x8d/0x2a0 net/core/dev.c:2111
2 locks held by syz-executor/7445:
 #0: ffffffff8f1d7f30 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8f1d7f30 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8f1d7f30 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8db/0x1c70 net/core/rtnetlink.c:4056
2 locks held by syz-executor/7455:
 #0: ffffffff8f1efb10 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8f1efb10 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8f1efb10 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8db/0x1c70 net/core/rtnetlink.c:4056
2 locks held by syz-executor/7500:
 #0: ffffffff8f1d7be8 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8f1d7be8 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8f1d7be8 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff8ecd3878 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8db/0x1c70 net/core/rtnetlink.c:4056

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:328 [inline]
 watchdog+0xf93/0xfe0 kernel/hung_task.c:491
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6341 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__lock_acquire+0xafc/0xd20 kernel/locking/lockdep.c:-1
Code: 00 8b 83 18 0b 00 00 ff c0 89 83 18 0b 00 00 83 f8 30 0f 83 64 01 00 00 3b 05 38 e9 61 11 0f 87 c9 01 00 00 41 bf 01 00 00 00 <e9> a7 01 00 00 48 89 fb e8 47 a7 03 00 48 c7 c7 f8 df 22 8d e8 2b
RSP: 0018:ffffc90005767770 EFLAGS: 00000097
RAX: 0000000000000003 RBX: ffff888025403b80 RCX: 677d262de6cd6200
RDX: 0000000000000000 RSI: ffff8880254046f0 RDI: ffff888025403b80
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff819b9c86
R10: dffffc0000000000 R11: fffffbfff1e3ac47 R12: 00000000c6b218ca
R13: ffff8880254046a0 R14: ffff8880254046f0 R15: 0000000000000001
FS:  000055557c540500(0000) GS:ffff8881268bc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcdd331520 CR3: 0000000037f9a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
 rwbase_write_unlock kernel/locking/rwbase_rt.c:206 [inline]
 __up_write kernel/locking/rwsem.c:1506 [inline]
 up_write+0x26/0x60 kernel/locking/rwsem.c:1643
 f2fs_up_write fs/f2fs/f2fs.h:2259 [inline]
 f2fs_unlock_all fs/f2fs/f2fs.h:2319 [inline]
 block_operations fs/f2fs/checkpoint.c:1262 [inline]
 f2fs_write_checkpoint+0x9e8/0x1df0 fs/f2fs/checkpoint.c:1638
 kill_f2fs_super+0x2c3/0x6c0 fs/f2fs/super.c:5347
 deactivate_locked_super+0xb9/0x130 fs/super.c:474
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1375
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6214be01f7
Code: a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffdc31247c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f6214c61d7d RCX: 00007f6214be01f7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffdc3124880
RBP: 00007ffdc3124880 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffdc3125910
R13: 00007f6214c61d7d R14: 00000000000381f3 R15: 00007ffdc3125950
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/27 09:06 upstream 083fc6d7fa0d 001c9061 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in file_start_write
2025/07/21 05:31 upstream 89be9a83ccf1 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in file_start_write
2025/07/01 05:36 upstream 66701750d556 6e83b42d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in file_start_write
* Struck through repros no longer work on HEAD.