linux-hardening - RE: [PATCH] exec: Force single empty string when argv is empty

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Date:   Tue, 1 Feb 2022 09:17:47 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Kees Cook' <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Ariadne Conill <ariadne@...eferenced.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Christian Brauner" <brauner@...nel.org>,
        Rich Felker <dalias@...c.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: RE: [PATCH] exec: Force single empty string when argv is empty

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.

	David

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