[syzbot] [net?] WARNING in dev_index_reserve

[syzbot]

syzbot has bisected this issue to:

commit 956db0a13b47df7f3d6d624394e602e8bf9b057e
Author: Jakub Kicinski <kuba@xxxxxxxxxx>
Date:   Mon Aug 14 20:56:25 2023 +0000

    net: warn about attempts to register negative ifindex

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17f68f03a80000
start commit:   950fe35831af Merge branch 'ipv6-expired-routes'
git tree:       net-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=140e8f03a80000
console output: https://syzkaller.appspot.com/x/log.txt?x=100e8f03a80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fe63ad15dded26b6
dashboard link: https://syzkaller.appspot.com/bug?extid=5ba06978f34abb058571
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11be0117a80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14950727a80000

Reported-by: syzbot+5ba06978f34abb058571@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 956db0a13b47 ("net: warn about attempts to register negative ifindex")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection