linux-hardening - Re: [PATCH] niu: Add "overloaded" struct page union member

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Date:   Tue, 10 May 2022 08:50:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Du Cheng <ducheng2@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Vlastimil Babka <vbabka@...e.cz>,
        William Kucharski <william.kucharski@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <nathan@...nel.org>, netdev@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] niu: Add "overloaded" struct page union member

On Tue, May 10, 2022 at 12:27:53AM -0700, Christoph Hellwig wrote:
> On Mon, May 09, 2022 at 03:23:33PM -0700, Kees Cook wrote:
> > The randstruct GCC plugin gets upset when it sees struct addresspace
> > (which is randomized) being assigned to a struct page (which is not
> > randomized):
> 
> Well, the right fix here is to remove this abuse from the driver, not
> to legitimize it as part of a "driver" patch touching a core mm header

Right, I didn't expect anyone to like the new "overloaded" member.
Mainly I'd just like to understand how niu _should_ be fixed. Is using
the "private" member the correct thing here?

> that doesn't even cc the mm list.

Oops, yes, sorry.

-- 
Kees Cook