netdev - Re: [PATCH] tcp: md5: Fix overlap between vrf and non-vrf keys

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Date:   Thu, 7 Oct 2021 12:27:41 -0600
From:   David Ahern <dsahern@...il.com>
To:     Leonard Crestez <cdleonard@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Yonghong Song <yhs@...com>,
        Alexander Duyck <alexanderduyck@...com>,
        Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp: md5: Fix overlap between vrf and non-vrf keys

On 10/7/21 12:41 AM, Leonard Crestez wrote:
> 
> 
> On 07.10.2021 04:14, David Ahern wrote:
>> On 10/6/21 11:48 AM, Leonard Crestez wrote:
>>> @@ -1103,11 +1116,11 @@ static struct tcp_md5sig_key
>>> *tcp_md5_do_lookup_exact(const struct sock *sk,
>>>   #endif
>>>       hlist_for_each_entry_rcu(key, &md5sig->head, node,
>>>                    lockdep_sock_is_held(sk)) {
>>>           if (key->family != family)
>>>               continue;
>>> -        if (key->l3index && key->l3index != l3index)
>>> +        if (key->l3index != l3index)
>>
>> That seems like the bug fix there. The L3 reference needs to match for
>> new key and existing key. I think the same change is needed in
>> __tcp_md5_do_lookup.
> 
> Current behavior is that keys added without tcpm_ifindex will match
> connections both inside and outside VRFs. Changing this might break real
> applications, is it really OK to claim that this behavior was a bug all
> along?

no.

It's been a few years. I need to refresh on the logic and that is not
going to happen before this weekend.