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Subject: Re: [regression] TCP_MD5SIG on established sockets
From:   Joe Perches <joe@perches.com>
To:     Eric Dumazet <edumazet@google.com>,
        Herbert Xu <herbert@gondor.apana.org.au>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
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        Linus Torvalds <torvalds@linux-foundation.org>,
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        netdev <netdev@vger.kernel.org>,
        Yuchung Cheng <ycheng@google.com>,
        Jonathan Rajotte-Julien <joraj@efficios.com>
Date:   Tue, 30 Jun 2020 19:39:13 -0700
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On Tue, 2020-06-30 at 19:30 -0700, Eric Dumazet wrote:
> On Tue, Jun 30, 2020 at 7:23 PM Herbert Xu <herbert@gondor.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.