syzbot


INFO: task hung in iterate_supers

Status: upstream: reported on 2025/06/20 00:37
Reported-by: syzbot+739c128b5557abb9f816@syzkaller.appspotmail.com
First crash: 11h36m, last: 11h36m
Similar bugs (12)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-414 INFO: task hung in iterate_supers 1 2425d 2262d 0/1 auto-closed as invalid on 2019/04/28 09:45
linux-4.14 INFO: task hung in iterate_supers 16 1633d 2247d 0/1 auto-closed as invalid on 2021/04/29 12:11
linux-4.19 INFO: task hung in iterate_supers (2) 1 1834d 1834d 0/1 auto-closed as invalid on 2020/10/09 12:15
upstream INFO: task hung in iterate_supers 9p C error 5804 24d 2537d 0/29 upstream: reported C repro on 2018/07/10 10:30
linux-5.15 INFO: task hung in iterate_supers origin:lts-only C 306 2d10h 834d 0/3 upstream: reported C repro on 2023/03/08 18:22
linux-6.1 INFO: task hung in iterate_supers origin:upstream C 295 1d08h 832d 0/3 upstream: reported C repro on 2023/03/10 21:24
linux-4.14 INFO: task hung in iterate_supers (2) 1 846d 846d 0/1 upstream: reported on 2023/02/24 15:59
linux-4.19 INFO: task hung in iterate_supers 7 1967d 2154d 0/1 auto-closed as invalid on 2020/05/29 21:42
linux-4.19 INFO: task hung in iterate_supers (3) vfs reiserfs ntfs syz 378 836d 1643d 0/1 upstream: reported syz repro on 2020/12/20 03:38
android-49 INFO: task hung in iterate_supers 19 2486d 2587d 0/3 auto-closed as invalid on 2019/02/25 14:49
android-414 INFO: task hung in iterate_supers (2) 1 2244d 2243d 0/1 auto-closed as invalid on 2019/10/25 08:49
upstream INFO: task can't die in iterate_supers (2) ceph fs 1 1467d 1463d 0/29 auto-closed as invalid on 2021/08/13 03:51

Sample crash report:
INFO: task syz.4.2517:15107 blocked for more than 144 seconds.
      Not tainted 6.6.94-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.2517      state:D stack:28936 pid:15107 ppid:14447  flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
 rwsem_down_read_slowpath+0x4f8/0x840 kernel/locking/rwsem.c:1086
 __down_read_common kernel/locking/rwsem.c:1250 [inline]
 __down_read kernel/locking/rwsem.c:1263 [inline]
 down_read+0x98/0x2e0 kernel/locking/rwsem.c:1522
 __super_lock fs/super.c:58 [inline]
 super_lock+0x167/0x360 fs/super.c:117
 super_lock_shared fs/super.c:146 [inline]
 iterate_supers+0x80/0x170 fs/super.c:977
 ksys_sync+0x95/0x150 fs/sync.c:102
 __ia32_sys_sync+0xe/0x20 fs/sync.c:113
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8d7138e929
RSP: 002b:00007f8d721c6038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f8d715b5fa0 RCX: 00007f8d7138e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f8d715b5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8d715b5fa0 R15: 00007ffdcee38b48
 </TASK>

Showing all locks held in the system:
5 locks held by kworker/u4:1/12:
1 lock held by khungtaskd/29:
 #0: ffffffff8cd2f760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8cd2f760 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8cd2f760 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by getty/5531:
 #0: ffff88823bde00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000326b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
3 locks held by kworker/1:15/12241:
3 locks held by syz-executor/14118:
 #0: ffff88805faf20e0 (&type->s_umount_key#95){+.+.}-{3:3}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88805faf20e0 (&type->s_umount_key#95){+.+.}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88805faf20e0 (&type->s_umount_key#95){+.+.}-{3:3}, at: deactivate_super+0xa4/0xe0 fs/super.c:513
 #1: ffff8880b8e3c458 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0xad/0x140 kernel/sched/core.c:566
 #2: ffff888018250018 (&pool->lock){-.-.}-{2:2}, at: __queue_work+0x69f/0x1020 kernel/workqueue.c:1764
1 lock held by syz-executor/14123:
 #0: ffff88801efa20e0 (&type->s_umount_key#83){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88801efa20e0 (&type->s_umount_key#83){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88801efa20e0 (&type->s_umount_key#83){++++}-{3:3}, at: deactivate_super+0xa4/0xe0 fs/super.c:513
1 lock held by syz.4.2517/15107:
 #0: ffff88801efa20e0 (&type->s_umount_key#83){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88801efa20e0 (&type->s_umount_key#83){++++}-{3:3}, at: super_lock+0x167/0x360 fs/super.c:117
4 locks held by syz-executor/15321:
1 lock held by syz.2.2798/16427:
3 locks held by dhcpcd-run-hook/16443:
 #0: ffff8880b8e3c458 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0xad/0x140 kernel/sched/core.c:566
 #1: ffff8880b8f288c8 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x39c/0x6d0 kernel/sched/psi.c:998
 #2: ffff88806682a5b8 (ptlock_ptr(ptdesc)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffff88806682a5b8 (ptlock_ptr(ptdesc)#2){+.+.}-{2:2}, at: __pte_offset_map_lock+0x107/0x1e0 mm/pgtable-generic.c:375
1 lock held by syz.9.2804/16448:
 #0: ffffffff8cd35600 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x580 kernel/rcu/tree.c:4085
1 lock held by syz.3.2801/16460:
 #0: ffffffff8cd35738 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
 #0: ffffffff8cd35738 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x448/0x830 kernel/rcu/tree_exp.h:1004
4 locks held by rm/16461:

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

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x39b/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf41/0xf80 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 12431 Comm: kworker/u4:17 Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:check_kcov_mode kernel/kcov.c:193 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x36/0x60 kernel/kcov.c:216
Code: 20 24 7e 7e 65 8b 15 21 24 7e 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 1c 16 00 00 00 74 2c 8b 91 f8 15 00 00 <83> fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 48 8d 7e 01 8b 89 fc
RSP: 0018:ffffc9000db5f560 EFLAGS: 00000246
RAX: ffffffff813ac8f9 RBX: ffffc9000db5f788 RCX: ffff88802bf0da00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffc9000db5f788
RBP: ffffc9000db5f698 R08: ffff88802bf0da00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffc9000db5f648
R13: dffffc0000000000 R14: ffffc9000db5f788 R15: ffffffff8ecffd1a
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6221445000 CR3: 00000000274b2000 CR4: 00000000003526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __read_once_word_nocheck+0x9/0x10 include/asm-generic/rwonce.h:66
 deref_stack_reg arch/x86/kernel/unwind_orc.c:406 [inline]
 unwind_next_frame+0x15f9/0x2970 arch/x86/kernel/unwind_orc.c:585
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb2/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x117/0x260 net/core/skbuff.c:581
 __alloc_skb+0x138/0x2c0 net/core/skbuff.c:650
 alloc_skb include/linux/skbuff.h:1284 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
 nsim_dev_trap_report_work+0x293/0xb00 drivers/net/netdevsim/dev.c:851
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/20 00:37 linux-6.6.y 6282921b6825 ed3e87f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in iterate_supers
* Struck through repros no longer work on HEAD.