linux-kernel - Re: [PATCH v2 0/2] exec: Avoid pathological argc, envc, and bprm->p values

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Date: Thu, 27 Jun 2024 12:49:57 -0700
From: Kees Cook <kees@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Eric Biederman <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Laurent Vivier <laurent@...ier.eu>,
	Lukas Bulwahn <lukas.bulwahn@...il.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 0/2] exec: Avoid pathological argc, envc, and bprm->p
 values

On Fri, Jun 21, 2024 at 02:44:05PM -0700, Guenter Roeck wrote:
> On 6/21/24 13:50, Kees Cook wrote:
> > Hi,
> > 
> > This pair of patches replaces the last patch in this[1] series.
> > 
> > Perform bprm argument overflow checking but only do argmin checks for MMU
> > systems. To avoid tripping over this again, argmin is explicitly defined
> > only for CONFIG_MMU. Thank you to Guenter Roeck for finding this issue
> > (again)!
> > 
> 
> That does make me wonder: Is anyone but me testing, much less running,
> the nommu code in the kernel ?
> 
> mps2-an385 trips over the same problem, and xtensa:nommu_kc705_defconfig
> doesn't even build in linux-next right now (spoiler alert: I suspect that
> the problem is caused by "kunit: test: Add vm_mmap() allocation resource
> manager", but I did not have time to bisect it).

This has a fixed pending:
https://lore.kernel.org/lkml/202406271005.4E767DAE@keescook/

> I am kind of tired keeping those tests alive, and I would not exactly
> shed tears if nommu support would just be dropped entirely.

I haven't ever used the nommu builds, so I don't have a useful opinion
here. :)

-Kees

-- 
Kees Cook