syzbot has bisected this bug to:
commit 58956317c8de52009d1a38a721474c24aef74fe7
Author: David Ahern <dsahern@xxxxxxxxx>
Date: Fri Dec 7 20:24:57 2018 +0000
neighbor: Improve garbage collection
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=124a5985e00000
start commit: d0f41851 net, ip_tunnel: fix namespaces move
git tree: net
final crash: https://syzkaller.appspot.com/x/report.txt?x=114a5985e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=164a5985e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=8ce4113dadc4789fac74
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f99369e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d85601e00000
Reported-by: syzbot+8ce4113dadc4789fac74@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 58956317c8de ("neighbor: Improve garbage collection")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
