syzbot


INFO: task hung in do_task_dead

Status: premoderation: reported on 2025/08/01 20:46
Reported-by: syzbot+75d4d103150487774ef0@syzkaller.appspotmail.com
First crash: 32d, last: 32d
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in do_task_dead (4) kernel 1 1 895d 895d 0/29 auto-obsoleted due to no activity on 2023/06/20 16:27
upstream INFO: task hung in do_task_dead kernel 1 1 2354d 2354d 0/29 auto-closed as invalid on 2019/09/21 14:08
upstream INFO: task hung in do_task_dead (6) kernel 1 1 131d 131d 0/29 auto-obsoleted due to no activity on 2025/07/24 12:34
upstream INFO: task hung in do_task_dead (3) mtd 1 2 1983d 1984d 0/29 auto-closed as invalid on 2020/06/28 13:10
upstream INFO: task hung in do_task_dead (2) kernel 1 1 2101d 2101d 0/29 auto-closed as invalid on 2020/03/01 19:02
linux-4.14 INFO: task hung in do_task_dead 1 1 1848d 1848d 0/1 auto-closed as invalid on 2020/12/09 18:36
upstream INFO: task hung in do_task_dead (5) kernel 1 2 345d 386d 0/29 auto-obsoleted due to no activity on 2024/12/21 21:23

Sample crash report:
INFO: task syz.0.476:1923 blocked for more than 122 seconds.
      Not tainted 6.12.38-syzkaller-gbf0fb8bb181b #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.476       state:D stack:0     pid:1923  tgid:1923  ppid:288    flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x1322/0x1df0 kernel/sched/core.c:7791
 do_task_dead+0xa1/0xb0 kernel/sched/core.c:7811
 do_exit+0x1b3c/0x2630 kernel/exit.c:996
 do_group_exit+0x22a/0x300 kernel/exit.c:1095
 get_signal+0x139d/0x14f0 kernel/signal.c:2933
 arch_do_signal_or_restart+0x96/0x720 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 irqentry_exit_to_user_mode+0x4e/0xb0 kernel/entry/common.c:231
 irqentry_exit+0x16/0x60 kernel/entry/common.c:334
 exc_page_fault+0x66/0xc0 arch/x86/mm/fault.c:1542
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f118edc13c0
RSP: 002b:00007f118fc73fa8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007f118efb5fa0 RCX: 0000000000000000
RDX: 00007f118fc73fc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f118ee11df1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f118efb5fa0 R15: 00007fff96ba67d8
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted 6.12.38-syzkaller-gbf0fb8bb181b #0 d02c7cfa86e34ad1734bbfdc1f5f1c3ce9be47fc
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x10c/0x190 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2bf/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xd8f/0xed0 kernel/hung_task.c:423
 kthread+0x2ca/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 2458 Comm: syz-executor Not tainted 6.12.38-syzkaller-gbf0fb8bb181b #0 d02c7cfa86e34ad1734bbfdc1f5f1c3ce9be47fc
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:__copy_skb_header+0x81/0x5e0 net/core/skbuff.c:1530
Code: 48 c1 e8 03 80 3c 08 00 74 12 4c 89 ff e8 d7 7c 79 fd 48 b9 00 00 00 00 00 fc ff df 49 89 1f 4d 8d 7e 10 4c 89 f8 48 c1 e8 03 <80> 3c 08 00 74 12 4c 89 ff e8 91 7b 79 fd 48 b9 00 00 00 00 00 fc
RSP: 0018:ffffc90000230590 EFLAGS: 00000a02
RAX: 1ffff11029687af2 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: 0000000000000100 RSI: ffff88814b43d780 RDI: ffff88814b43edc0
RBP: ffffc900002305d8 R08: ffff88814b43edcf R09: 0000000000000000
R10: ffff88814b43edc0 R11: ffffed1029687dba R12: ffff88814b43edc0
R13: ffff88814b43d780 R14: ffff88814b43d780 R15: ffff88814b43d790
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055da1377fb98 CR3: 00000001208c6000 CR4: 00000000003526b0
Call Trace:
 <IRQ>
 __skb_clone+0x64/0x7a0 net/core/skbuff.c:1583
 skb_clone+0x260/0x460 net/core/skbuff.c:2089
 deliver_clone net/bridge/br_forward.c:125 [inline]
 br_flood+0x661/0x730 net/bridge/br_forward.c:245
 br_handle_frame_finish+0x12bb/0x1720 net/bridge/br_input.c:215
 nf_hook_bridge_pre net/bridge/br_input.c:301 [inline]
 br_handle_frame+0x5a6/0xba0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xf48/0x3940 net/core/dev.c:5651
 __netif_receive_skb_one_core net/core/dev.c:5755 [inline]
 __netif_receive_skb net/core/dev.c:5870 [inline]
 process_backlog+0x3e5/0xae0 net/core/dev.c:6206
 __napi_poll+0xd0/0x610 net/core/dev.c:6857
 napi_poll net/core/dev.c:6926 [inline]
 net_rx_action+0x584/0xce0 net/core/dev.c:7048
 handle_softirqs+0x1ab/0x630 kernel/softirq.c:621
 __do_softirq+0xf/0x16 kernel/softirq.c:659
 do_softirq+0xa6/0x100 kernel/softirq.c:503
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x74/0x80 kernel/softirq.c:430
 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline]
 _raw_spin_unlock_bh+0x54/0x60 kernel/locking/spinlock.c:210
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 addrconf_ifdown+0x608/0x1940 net/ipv6/addrconf.c:3956
 addrconf_notify+0x17a/0xea0 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x10b/0x2c0 kernel/notifier.c:93
 raw_notifier_call_chain+0x31/0x40 kernel/notifier.c:461
 call_netdevice_notifiers_info net/core/dev.c:2067 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2105 [inline]
 call_netdevice_notifiers net/core/dev.c:2119 [inline]
 unregister_netdevice_many_notify+0xe32/0x1bd0 net/core/dev.c:11489
 unregister_netdevice_many net/core/dev.c:11551 [inline]
 unregister_netdevice_queue+0x339/0x380 net/core/dev.c:11425
 unregister_netdevice include/linux/netdevice.h:3165 [inline]
 __tun_detach+0xca1/0x1460 drivers/net/tun.c:685
 tun_detach drivers/net/tun.c:701 [inline]
 tun_chr_close+0x93/0x150 drivers/net/tun.c:3517
 __fput+0x1fb/0xa00 fs/file_table.c:429
 ____fput+0x20/0x30 fs/file_table.c:457
 task_work_run+0x1e0/0x250 kernel/task_work.c:240
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x9bc/0x2630 kernel/exit.c:953
 do_group_exit+0x22a/0x300 kernel/exit.c:1095
 get_signal+0x139d/0x14f0 kernel/signal.c:2933
 arch_do_signal_or_restart+0x96/0x720 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x58/0xb0 kernel/entry/common.c:218
 do_syscall_64+0x64/0xf0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f29e83909a3
Code: Unable to access opcode bytes at 0x7f29e8390979.
RSP: 002b:00007ffe66618668 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: 0000000000000020 RBX: 00007f29e90e4620 RCX: 00007f29e83909a3
RDX: 0000000000000020 RSI: 00007f29e90e4670 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007ffe66618684 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f29e90e4670 R15: 0000000000000000
 </TASK>
net_ratelimit: 93506 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:56:14:f7:82:cb:f8, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
net_ratelimit: 115868 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:56:14:f7:82:cb:f8, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:56:14:f7:82:cb:f8, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/01 20:45 android16-6.12 bf0fb8bb181b 40127d41 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in do_task_dead
* Struck through repros no longer work on HEAD.