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

[syzbot <syzbot+b0ae8f1abf7d891e0426@syzkaller.appspotmail.com>]

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


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