[syzbot] [bridge?] possible deadlock in br_multicast_rcv (3)

[syzbot]

syzbot has bisected this issue to:

commit 0ae3eb7b4611207e140e9772398b9f88b72d6839
Author: Amit Cohen <amcohen at nvidia.com>
Date:   Mon Feb 1 19:47:49 2021 +0000

    netdevsim: fib: Perform the route programming in a non-atomic context

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13afdae6680000
start commit:   2faac9a98f01 Merge tag 'keys-fixes-20230321' of git://git...
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=106fdae6680000
console output: https://syzkaller.appspot.com/x/log.txt?x=17afdae6680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=aaa4b45720ca0519
dashboard link: https://syzkaller.appspot.com/bug?extid=d7b7f1412c02134efa6d
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14aea34ec80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13001e91c80000

Reported-by: syzbot+d7b7f1412c02134efa6d at syzkaller.appspotmail.com
Fixes: 0ae3eb7b4611 ("netdevsim: fib: Perform the route programming in a non-atomic context")

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