Re: [syzbot] [net] INFO: task hung in tun_chr_close (5)

syzbot
2026-03-31T17:17:28Z

syzbot has found a reproducer for the following issue on:

HEAD commit: 47ab2c12c87a Merge branch 'correct-bd-length-masks-and-bql..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=153aed02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6754c86e8d9e4c91
dashboard link: https://syzkaller.appspot.com/bug?extid=b0ae8f1abf7d891e0426
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1286e8d2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=106df5da580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/289234295ce6/disk-47ab2c12.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b3f30eb7dc01/vmlinux-47ab2c12.xz
kernel image: https://storage.googleapis.com/syzbot-assets/62a0f5642c08/bzImage-47ab2c12.xz

The issue was bisected to:

commit 5a781ccbd19e4664babcbe4b4ead7aa2b9283d22
Author: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Date: Sat Sep 29 00:59:43 2018 +0000

tc: Add support for configuring the taprio scheduler

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11535418580000
final oops: https://syzkaller.appspot.com/x/report.txt?x=13535418580000
console output: https://syzkaller.appspot.com/x/log.txt?x=15535418580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b0ae8f1abf7d891e0426@syzkaller.appspotmail.com
Fixes: 5a781ccbd19e ("tc: Add support for configuring the taprio scheduler")

INFO: task syz-executor:5978 blocked for more than 143 seconds.
Not tainted syzkaller #0
Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:22400 pid:5978 tgid:5978 ppid:1 task_flags:0x40054c flags:0x00080003
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0x15dd/0x52d0 kernel/sched/core.c:6911
__schedule_loop kernel/sched/core.c:6993 [inline]
schedule+0x164/0x360 kernel/sched/core.c:7008
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7065
__mutex_lock_common kernel/locking/mutex.c:692 [inline]
__mutex_lock+0x7fe/0x1300 kernel/locking/mutex.c:776
tun_detach drivers/net/tun.c:634 [inline]
tun_chr_close+0x3e/0x1c0 drivers/net/tun.c:3436

---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.