linux-kernel - Re: [PATCH 0/3] Convert nsproxy, groups, and creds to refcount

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Message-ID: <202007211144.A68C31D@keescook>
Date:   Tue, 21 Jul 2020 11:44:53 -0700
From:   Kees Cook <keescook@...omium.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Xiaoming Ni <nixiaoming@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        David Windsor <dwindsor@...il.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Paul Moore <paul@...l-moore.com>, edumazet@...gle.com,
        paulmck@...nel.org, shakeelb@...gle.com,
        James Morris <jamorris@...ux.microsoft.com>,
        alex.huangjianhui@...wei.com, dylix.dailei@...wei.com,
        chenzefeng2@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Convert nsproxy, groups, and creds to refcount_t

On Tue, Jul 21, 2020 at 11:51:04AM +0100, David Howells wrote:
> Kees Cook <keescook@...omium.org> wrote:
> 
> > > Should mm->mm_users also be replaced by refcount_t?
> > 
> > I'll say "yes". :)
> > https://lore.kernel.org/lkml/1487671124-11188-1-git-send-email-elena.reshetova@intel.com/
> > 
> > > In addition, is it better to change all variables that use
> > > atomic_dec_and_test to control the release process to refconut_t?
> > 
> > For the most part, yes. The following may find a lot of them:
> > scripts/coccinelle/api/atomic_as_refcounter.cocci
> 
> I've been gradually undoing some of the conversions as there's no equivalent
> of atomic_add_return() and atomic_dec_return() that allow me to log the
> altered refcount through a tracepoint.

Please do not _undo_ the changes; just add the API you need.

-- 
Kees Cook