Date: Wed, 19 Jul 2017 15:35:46 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: ebiederm@xmission.com (Eric W. Biederman)
Cc: Elena Reshetova <elena.reshetova@intel.com>,
        linux-kernel@vger.kernel.org, peterz@infradead.org,
        gregkh@linuxfoundation.org, mingo@redhat.com, adobriyan@gmail.com,
        serge@hallyn.com, arozansk@redhat.com, dave@stgolabs.net,
        keescook@chromium.org, Hans Liljestrand <ishkamiel@gmail.com>,
        David Windsor <dwindsor@gmail.com>
Subject: Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to
 refcount_t
Message-Id: <20170719153546.37567fbf77861653172fa263@linux-foundation.org>
In-Reply-To: <87bmottgo4.fsf@xmission.com>
References: <1499417992-3238-1-git-send-email-elena.reshetova@intel.com>
        <1499417992-3238-2-git-send-email-elena.reshetova@intel.com>
        <87bmottgo4.fsf@xmission.com>
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On Sun, 09 Jul 2017 16:59:55 -0500 ebiederm@xmission.com (Eric W. Biederman) wrote:

> Elena Reshetova <elena.reshetova@intel.com> writes:
> 
> > refcount_t type and corresponding API should be
> > used instead of atomic_t when the variable is used as
> > a reference counter. This allows to avoid accidental
> > refcounter overflows that might lead to use-after-free
> > situations.
> 
> In this patch you can see all of the uses of the count.
> What accidental refcount overflows are possible?

I do rather dislike these conversions from the point of view of
performance overhead and general code bloat.  But I seem to have lost
that struggle and I don't think any of these are fastpath(?).