INFO: task can't die in nf_ct_iterate_cleanup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d72e6319 Add linux-next specific files for 20210706
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=175a11fbd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=59e1e3bbc3afca75
dashboard link: https://syzkaller.appspot.com/bug?extid=6fb98e3acfbc001b4a5a
CC: [core...@netfilter.org da...@davemloft.net f...@strlen.de kad...@netfilter.org ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org netfilt...@vger.kernel.org pa...@netfilter.org]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6fb98e...@syzkaller.appspotmail.com

INFO: task syz-executor.4:11205 can't die for more than 143 seconds.
task:syz-executor.4 state:R running task stack:24656 pid:11205 ppid: 8468 flags:0x00004006
Call Trace:
context_switch kernel/sched/core.c:4700 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5957
preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:6117
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
__local_bh_enable_ip+0x109/0x120 kernel/softirq.c:390
local_bh_enable include/linux/bottom_half.h:32 [inline]
get_next_corpse net/netfilter/nf_conntrack_core.c:2233 [inline]
nf_ct_iterate_cleanup+0x15a/0x450 net/netfilter/nf_conntrack_core.c:2256
nf_conntrack_cleanup_net_list+0x14c/0x4f0 net/netfilter/nf_conntrack_core.c:2450
ops_exit_list+0x10d/0x160 net/core/net_namespace.c:178
setup_net+0x639/0xa30 net/core/net_namespace.c:356
copy_net_ns+0x319/0x760 net/core/net_namespace.c:474
create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
copy_namespaces+0x391/0x450 kernel/nsproxy.c:178
copy_process+0x2cfc/0x74d0 kernel/fork.c:2173
kernel_clone+0xe7/0xac0 kernel/fork.c:2560
__do_sys_clone+0xc8/0x110 kernel/fork.c:2677
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665d9
RSP: 002b:00007fc2e0357188 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 9999999999999999 RSI: 0000000000000000 RDI: 00000000e1004d7c
RBP: 00000000004bfcb9 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffc49089f7f R14: 00007fc2e0357300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/1652:
#0: ffffffff8b97ea40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446
1 lock held by systemd-udevd/4872:
1 lock held by in:imklog/8146:
#0: ffff888034264ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
1 lock held by syz-executor.4/11205:
2 locks held by syz-executor.5/18643:
#0: ffff8880b9c51a98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:460 [inline]
#0: ffff8880b9c51a98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock kernel/sched/sched.h:1309 [inline]
#0: ffff8880b9c51a98 (&rq->__lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1612 [inline]
#0: ffff8880b9c51a98 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0x233/0x26f0 kernel/sched/core.c:5871
#1: ffff8880b9c1f988 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x39d/0x480 kernel/sched/psi.c:880
3 locks held by syz-executor.0/18658:

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[syzbot]

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