INFO: task hung in do_coredump

Status: upstream: reported C repro on 2025/09/17 06:48
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+3ce7863f8fc836a427e7@syzkaller.appspotmail.com
First crash: 383d, last: 280d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[PATCH] net/9p: fix infinite loop in p9_client_rpc on fatal signal 1 (1) 2026/04/15 15:52
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/09/25 linux-6.6.y (ToT) 79643295eba1 C [report] lost connection to test machine
2026/09/24 upstream (ToT) ee9c669f9bf5 C Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in do_coredump fs 1 1 1318d 1318d 0/29 auto-obsoleted due to no activity on 2023/05/26 05:58
upstream INFO: task hung in do_coredump (2) fs 1 1 845d 845d 0/29 auto-obsoleted due to no activity on 2024/09/10 17:47
upstream INFO: task hung in do_coredump (3) prio:high fs 1 syz, C done error 361 272d 718d 0/29 upstream: reported C repro on 2024/10/17 09:02
android-6-12 INFO: task hung in do_coredump origin:upstream 1 syz, C 44 12h59m 460d 0/1 premoderation: reported C repro on 2025/07/02 01:03
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2026/01/28 01:25 0m bisect fix linux-6.6.y error job log
2025/12/28 23:47 1h37m bisect fix linux-6.6.y OK (0) job log log
2025/11/25 22:04 2h13m bisect fix linux-6.6.y OK (0) job log log
2025/10/25 22:20 2h02m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
INFO: task syz.0.17:5946 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:25544 pid:5946  ppid:5899   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x9b/0x280 kernel/time/timer.c:2143
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common+0x3cb/0x6d0 kernel/sched/completion.c:116
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion_state+0x1c/0x40 kernel/sched/completion.c:264
 coredump_wait fs/coredump.c:443 [inline]
 do_coredump+0x85c/0x2480 fs/coredump.c:640
 get_signal+0x1133/0x1400 kernel/signal.c:2888
 arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 irqentry_exit_to_user_mode+0x9/0x40 kernel/entry/common.c:315
 exc_page_fault+0x8f/0x110 arch/x86/mm/fault.c:1524
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f8711a4f927
RSP: 002b:00007fff322b40e0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 000000000000000b RCX: 0000000000019640
RDX: 00007fff322b4100 RSI: 00007fff322b4230 RDI: 000000000000000b
RBP: 00007f8711dd7da0 R08: 0000000000000068 R09: 0000000000745d1e
R10: 000000379366409e R11: 0000000000004b96 R12: 00000000000199f6
R13: 00007f8711dd6090 R14: ffffffffffffffff R15: 00007fff323b2ee0
 </TASK>
INFO: task syz.0.17:5948 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:26856 pid:5948  ppid:5899   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 coredump_task_exit kernel/exit.c:436 [inline]
 do_exit+0x4a0/0x23c0 kernel/exit.c:825
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 get_signal+0x12fc/0x1400 kernel/signal.c:2902
 arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8711b8eba9
RSP: 002b:00007f87129450e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f8711dd6098 RCX: 00007f8711b8eba9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f8711dd6098
RBP: 00007f8711dd6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8711dd6128 R14: 00007fff323b2b80 R15: 00007fff323b2c68
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8cd2fe20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:7/1326:
1 lock held by klogd/5147:
 #0: ffff8880b8f3c458 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:558
2 locks held by getty/5549:
 #0: ffff888030daa0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217

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

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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: 48 Comm: kworker/u4:3 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:217 [inline]
RIP: 0010:unwind_next_frame+0x220/0x2970 arch/x86/kernel/unwind_orc.c:494
Code: 00 00 49 29 df 49 c1 ef 08 8b 05 d3 9b 42 0b 48 89 44 24 28 8d 68 ff 89 ef 44 89 fe e8 e9 ec 4a 00 44 39 fd 0f 86 4f 1d 00 00 <44> 89 f8 4c 8d 2c 85 0c f1 71 8f 4c 89 e8 48 c1 e8 03 48 bb 00 00
RSP: 0018:ffffc90000b8f558 EFLAGS: 00000216
RAX: ffffffff813aa4d7 RBX: ffffffff81000000 RCX: 0000000000000000
RDX: ffff88801a2fbc00 RSI: 00000000000057c6 RDI: 000000000009a000
RBP: 000000000009a000 R08: ffffc90000b8f6f0 R09: 0000000000000006
R10: 0000000000000004 R11: 0000000000000000 R12: ffffc90000b8f628
R13: dffffc0000000000 R14: ffffc90000b8f65d R15: 00000000000057c6
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e0b4410168 CR3: 000000000cb30000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 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_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 kmem_cache_alloc_node+0x150/0x330 mm/slub.c:3540
 __alloc_skb+0x108/0x2c0 net/core/skbuff.c:640
 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 (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/17 23:00 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/17 19:33 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/17 16:47 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/17 13:19 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/17 10:03 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/18 16:08 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/18 12:47 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/18 09:22 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/18 06:00 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/18 02:33 linux-6.6.y 60a9e718726f e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
2025/09/17 06:47 linux-6.6.y 60a9e718726f e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in do_coredump
* Struck through repros no longer work on HEAD.