linux-kernel - Re: [syzbot] [net?] INFO: task hung in new_device

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Message-ID: <6957a38d.050a0220.a1b6.035c.GAE@google.com>
Date: Fri, 02 Jan 2026 02:53:01 -0800
From: syzbot <syzbot+05f9cecd28e356241aba@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, penguin-kernel@...ove.sakura.ne.jp, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] INFO: task hung in new_device_store (5)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in rtnl_lock

INFO: task kworker/0:0:9 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:0     state:D stack:0     pid:9     tgid:9     ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: events reg_todo
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:742 (T)
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1250/0x2a7c kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7017
 __mutex_lock_common+0xd04/0x2678 kernel/locking/mutex.c:692
 __mutex_lock kernel/locking/mutex.c:776 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:828
 rtnl_lock+0x20/0x2c net/core/rtnetlink.c:80
 reg_todo+0x2c/0x98c net/wireless/reg.c:3189
 process_one_work+0x7c0/0x1558 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3421
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
INFO: task kworker/u8:3:42 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:3    state:D stack:0     pid:42    tgid:42    ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: ipv6_addrconf addrconf_dad_work
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:742 (T)
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1250/0x2a7c kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7017
 __mutex_lock_common+0xd04/0x2678 kernel/locking/mutex.c:692
 __mutex_lock kernel/locking/mutex.c:776 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:828
 rtnl_lock+0x20/0x2c net/core/rtnetlink.c:80
 rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 addrconf_dad_work+0x100/0x10cc net/ipv6/addrconf.c:4194
 process_one_work+0x7c0/0x1558 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3421
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Showing all locks held in the system:
1 lock held by kthreadd/2:


Tested on:

commit:         b69053dd wifi: mt76: Remove blank line after mt792x fi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12e1aa9a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8a8594efdc14f07a
dashboard link: https://syzkaller.appspot.com/bug?extid=05f9cecd28e356241aba
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15760a22580000