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Date:   Sat, 23 Oct 2021 23:46:18 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Kees Cook <keescook@chromium.org>
Cc:     Mike Rapoport <rppt@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        syzbot <syzbot+b904a1de3ec43711eba5@syzkaller.appspotmail.com>,
        Jordy Zomer <jordy@pwning.systems>, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] WARNING: refcount bug in sys_memfd_secret
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On Sat, Oct 23, 2021 at 10:03:11AM -0700, Kees Cook wrote:
> On October 23, 2021 8:27:28 AM PDT, Mike Rapoport <rppt@kernel.org> wrote:
> >and my first reaction was to send a revert the untested commit 110860541f44
> >("mm/secretmem: use refcount_t instead of atomic_t"). 

I think you should.  This isn't a real problem.  And it abuses the
refcount_t interface.  Your hack is clever, but it's fundamentally
wrong.