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Date: Mon, 5 Mar 2018 11:15:35 -0800
From: Kees Cook <keescook@...omium.org>
To: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
"Maciej S. Szmigiero" <mail@...iej.szmigiero.name>, Patrick McLean <chutzpah@...too.org>,
Emese Revfy <re.emese@...il.com>, Al Viro <viro@...iv.linux.org.uk>,
Bruce Fields <bfields@...hat.com>, "Darrick J. Wong" <darrick.wong@...cle.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux NFS Mailing List <linux-nfs@...r.kernel.org>, Thorsten Leemhuis <regressions@...mhuis.info>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: RANDSTRUCT structs need linux/compiler_types.h (Was: [nfsd4]
potentially hardware breaking regression in 4.14-rc and 4.13.11)
On Mon, Mar 5, 2018 at 1:27 AM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> Sorry for chiming in late.
>
> I noticed this thread today,
> honestly, the commit made me upset.
>
>
> Can I suggest another way to make it less fragile?
> __attribute((...)) can be placed after 'struct'.
>
>
> So, we can write:
>
>
> struct __randomize_layout path {
> struct vfsmount *mnt;
> struct dentry *dentry;
> };
>
>
> instead of
>
>
> struct path {
> struct vfsmount *mnt;
> struct dentry *dentry;
> } __randomize_layout;
Ugh. I had tried this after the struct _name_, not after "struct"
itself. This does fix it, though it remains fragile, as you mention.
> If we force the former notation,
> the undefined __randomize_layout results in a build error
> instead of silent broken code generation.
>
>
> It is true somebody can still place
> __randomize_layout after the closing brace,
> but can we check this by coccicheck or checkpatch.pl?
> (we can describe it in coding style documentation, of course)
>
>
> IMHO, we should not (ab)use include/linux/kconfig.h
> to bring in misc things.
I'm happy to send a patch that reverts the other changes and relocates
all the markings...
Linus, how would you like this to go?
-Kees
--
Kees Cook
Pixel Security
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