linux-kernel - Re: [syzbot] WARNING: refcount bug in sys_memfd

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Message-ID: <YXSQuiahbU7YyYrk@casper.infradead.org>
Date:   Sat, 23 Oct 2021 23:46:18 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Mike Rapoport <rppt@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+b904a1de3ec43711eba5@...kaller.appspotmail.com>,
        Jordy Zomer <jordy@...ing.systems>, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING: refcount bug in sys_memfd_secret

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@...nel.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.