linux-kernel - Re: [RFC v5 6/7] sprintf: Add [v]sprintf

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202507171644.7FB3379@keescook>
Date: Thu, 17 Jul 2025 16:47:04 -0700
From: Kees Cook <kees@...nel.org>
To: Alejandro Colomar <alx@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	David Laight <david.laight.linux@...il.com>,
	Martin Uecker <ma.uecker@...il.com>, linux-mm@...ck.org,
	linux-hardening@...r.kernel.org,
	Christopher Bazley <chris.bazley.wg14@...il.com>,
	shadow <~hallyn/shadow@...ts.sr.ht>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Marco Elver <elver@...gle.com>, Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Harry Yoo <harry.yoo@...cle.com>,
	Andrew Clayton <andrew@...ital-domain.net>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Michal Hocko <mhocko@...e.com>, Al Viro <viro@...iv.linux.org.uk>,
	Sam James <sam@...too.org>, Andrew Pinski <pinskia@...il.com>
Subject: Re: [RFC v5 6/7] sprintf: Add [v]sprintf_array()

On Tue, Jul 15, 2025 at 09:08:14AM +0200, Alejandro Colomar wrote:
> Hi Kees,
> 
> On Mon, Jul 14, 2025 at 10:19:39PM -0700, Kees Cook wrote:
> > On Fri, Jul 11, 2025 at 10:58:56AM -0700, Linus Torvalds wrote:
> > >         struct seq_buf s;
> > >         seq_buf_init(&s, buf, szie);
> > 
> > And because some folks didn't like this "declaration that requires a
> > function call", we even added:
> > 
> > 	DECLARE_SEQ_BUF(s, 32);
> > 
> > to do it in 1 line. :P
> > 
> > I would love to see more string handling replaced with seq_buf.
> 
> The thing is, it's not as easy as the fixes I'm proposing, and
> sprintf_end() solves a lot of UB in a minimal diff that you can dumbly
> apply.

Note that I'm not arguing against your idea -- I just think it's not
going to be likely to end up in Linux soon given Linus's objections. My
perspective is mainly one of pragmatic damage control: what *can* we do
in Linux that would make things better? Currently, seq_buf is better
than raw C strings...

-- 
Kees Cook