[syzbot] KASAN: use-after-free Read in rxrpc_lookup_local

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+3538a6a72efa8b059c38 at syzkaller.appspotmail.com

Tested on:

commit:         a2220b54 Merge branch 'cn10kb-mac-block-support'
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1589fa4d880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c608c21151db14f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3538a6a72efa8b059c38
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1473515b880000

Note: testing is done by a robot and is best-effort only.