linux-kernel - RE: [PATCH] fs/exec: require argv[0] presence in do_execveat

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Message-ID: <a33e8f5318e94e01ac4126bc4870b59a@AcuMS.aculab.com>
Date:   Wed, 26 Jan 2022 16:59:53 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Kees Cook' <keescook@...omium.org>,
        Ariadne Conill <ariadne@...eferenced.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "Eric Biederman" <ebiederm@...ssion.com>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: RE: [PATCH] fs/exec: require argv[0] presence in do_execveat_common()

From: Kees Cook
> Sent: 26 January 2022 07:28
...
> >
> >There shouldn't be anything legitimate actually doing this in userspace.
> 
> I spoke too soon.
> 
> Unfortunately, this is not the case:
> https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL&literal=0
> 
> Lots of stuff likes to do:
> execve(path, NULL, NULL);
> 
> Do these things depend on argc==0 would be my next question...

What about ensuring that argv[0] and argv[1] are always present
and both NULL when argc is 0?

Then programs that just scan from argv[1] until they get a NULL
will always be fine.

	David

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