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From: Kees Cook <keescook@chromium.org>
To: David Laight <David.Laight@aculab.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Ariadne Conill <ariadne@dereferenced.org>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Matthew Wilcox <willy@infradead.org>,
	Christian Brauner <brauner@kernel.org>,
	Rich Felker <dalias@libc.org>,
	Eric Biederman <ebiederm@xmission.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hardening@vger.kernel.org"
	<linux-hardening@vger.kernel.org>
Subject: Re: [PATCH] exec: Force single empty string when argv is empty
Date: Wed, 2 Feb 2022 12:31:48 -0800	[thread overview]
Message-ID: <202202021229.9681AD39B0@keescook> (raw)
In-Reply-To: <78959c88715049a4be00fc75bb333d3a@AcuMS.aculab.com>

On Tue, Feb 01, 2022 at 09:17:47AM +0000, David Laight wrote:
> From: Kees Cook
> > Sent: 01 February 2022 00:10
> ...
> > While the initial code searches[6][7] turned up what appeared to be
> > mostly corner case tests, trying to that just reject argv == NULL
> > (or an immediately terminated pointer list) quickly started tripping[8]
> > existing userspace programs.
> > 
> > The next best approach is forcing a single empty string into argv and
> > adjusting argc to match. The number of programs depending on argc == 0
> > seems a smaller set than those calling execve with a NULL argv.
> 
> Has anyone considered using the pathname for argv[0]?
> So converting:
> 	execl(path, NULL);
> into:
> 	execl(path, path, NULL);
> 
> I've not spotted any such suggestion.

It came up on some IRC discussions at some point. I'm personally not a
fan of this because it creates a bit of "new" ABI that has a lot of
variability (depending on "" is one thing, but depending on a "missing"
argv matching the exec path is very different). I think there were also
concerns about dealing with fd-based exec ("what is the 'right' name"),
etc.

I'd prefer we stay as simple as possible for this change.

-- 
Kees Cook

  reply	other threads:[~2022-02-02 20:31 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-01  0:09 [PATCH] exec: Force single empty string when argv is empty Kees Cook
2022-02-01  1:00 ` Ariadne Conill
2022-02-01  2:00 ` Andy Lutomirski
2022-02-01  9:17 ` David Laight
2022-02-02 20:31   ` Kees Cook [this message]
2022-02-01 13:22 ` Christian Brauner
2022-02-01 14:53 ` Rich Felker
2022-02-02 15:50   ` Kees Cook
2022-02-02 17:12     ` Rich Felker
2022-02-02 19:03       ` Kees Cook

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