On Tue, Dec 28, 2021, syzbot wrote:

Hello,

syzbot found the following issue on:

HEAD commit:    ea586a076e8a Add linux-next specific files for 20211224
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12418ea5b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a9c4e3dde2c568fb
dashboard link: https://syzkaller.appspot.com/bug?extid=4e697fe80a31aa7efe21
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15724985b00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12d1aedbb00000

The issue was bisected to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 7 01:30:37 2021 +0000

    netlink: add net device refcount tracker to struct ethnl_req_info

Heh, while I'd love to blame someone else, there's zero chance this is the
offending commit.  The WARN repros on kvm/queue, it's likely related to the KVM
memslot changes queued for 5.17.  I'll take a look.