general protection fault in qfq_reset_qdisc

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e0f8b8a6 Linux 4.14.170
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13fba431e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=633dd9db249084f5
dashboard link: https://syzkaller.appspot.com/bug?extid=a7e0c8be5519cfab2ebf
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a7e0c8...@syzkaller.appspotmail.com

device veth0_macvtap left promiscuous mode
device veth1_vlan left promiscuous mode
device veth0_vlan left promiscuous mode
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 2451 Comm: kworker/u4:4 Not tainted 4.14.170-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
task: ffff8880a1384400 task.stack: ffff8880a1390000
RIP: 0010:qfq_reset_qdisc+0x141/0x2c0 net/sched/sch_qfq.c:1463
RSP: 0018:ffff8880a1397958 EFLAGS: 00010202
RAX: 0000000000000013 RBX: ffff8880a9e1d180 RCX: ffff88805ed9d0c0
RDX: 0000000000000000 RSI: ffff88805ed9d0c0 RDI: 0000000000000098
RBP: ffff8880a13979b0 R08: ffff888081e00590 R09: ffff8880a1384400
R10: dffffc0000000000 R11: ffff8880a1384400 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8880a9e1d1c8 R15: ffff88805ed9d280
FS: 0000000000000000(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001ace0b8 CR3: 000000009fc52000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
qdisc_destroy+0x10e/0x320 net/sched/sch_generic.c:723
dev_shutdown+0x28e/0x44b net/sched/sch_generic.c:1000
rollback_registered_many+0x6fd/0xb60 net/core/dev.c:7199
unregister_netdevice_many.part.0+0x1b/0x1e0 net/core/dev.c:8278
unregister_netdevice_many net/core/dev.c:8277 [inline]
default_device_exit_batch+0x31e/0x3d0 net/core/dev.c:8739
ops_exit_list.isra.0+0xfc/0x150 net/core/net_namespace.c:145
cleanup_net+0x3ba/0x870 net/core/net_namespace.c:484
process_one_work+0x863/0x1600 kernel/workqueue.c:2114
worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code: a5 25 fc 4c 8d 73 48 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 0f 85 15 01 00 00 4c 8b 6b 48 49 8d bd 98 00 00 00 48 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 74 08 3c 03 0f 8e 09 01 00 00 41 8b 85 98
RIP: qfq_reset_qdisc+0x141/0x2c0 net/sched/sch_qfq.c:1463 RSP: ffff8880a1397958
---[ end trace 29bb8e371dea7bde ]---


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.