linux-kernel - Re: [regression] TCP_MD5SIG on established sockets

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Date:   Tue, 30 Jun 2020 19:39:13 -0700
From:   Joe Perches <joe@...ches.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        David Miller <davem@...emloft.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Jonathan Rajotte-Julien <joraj@...icios.com>
Subject: Re: [regression] TCP_MD5SIG on established sockets

On Tue, 2020-06-30 at 19:30 -0700, Eric Dumazet wrote:
> On Tue, Jun 30, 2020 at 7:23 PM Herbert Xu <herbert@...dor.apana.org.au> wrote:
> > On Tue, Jun 30, 2020 at 07:17:46PM -0700, Eric Dumazet wrote:
> > > The main issue of the prior code was the double read of key->keylen in
> > > tcp_md5_hash_key(), not that few bytes could change under us.
> > > 
> > > I used smp_rmb() to ease backports, since old kernels had no
> > > READ_ONCE()/WRITE_ONCE(), but ACCESS_ONCE() instead.
> > 
> > If it's the double-read that you're protecting against, you should
> > just use barrier() and the comment should say so too.
> 
> I made this clear in the changelog, do we want comments all over the places ?

Having to run git for every line of code isn't great.

Comments in code is better than comments in changelogs.