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Date:   Mon, 31 Jan 2022 14:49:36 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Christian Brauner <brauner@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        kernel test robot <oliver.sang@intel.com>,
        Ariadne Conill <ariadne@dereferenced.org>,
        0day robot <lkp@intel.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Rich Felker <dalias@libc.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        stable@vger.kernel.org
Subject: Re: [fs/exec]  80bd5afdd8: xfstests.generic.633.fail
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On Mon, Jan 31, 2022 at 01:59:40PM -0800, Andrew Morton wrote:
> On Mon, 31 Jan 2022 18:13:44 +0100 Christian Brauner <brauner@kernel.org> wrote:
> 
> > > in other words, the changes that you see CMD_ARGS[0] == NULL for
> > > execveat() seem higher than for path-based exec.
> > > 
> > > To counter that we should probably at least update the execveat()
> > > manpage with a recommendation what CMD_ARGS[0] should be set to if it
> > > isn't allowed to be set to NULL anymore. This is why was asking what
> > > argv[0] is supposed to be if the binary doesn't take any arguments.
> > 
> > Sent a fix to our fstests now replacing the argv[0] as NULL with "".
> 
> As we hit this check so quickly, I'm thinking that Ariadne's patch
> "fs/exec: require argv[0] presence in do_execveat_common()" (which
> added the check) isn't something we'll be able to merge into mainline?

I think the next best would be to mutate an NULL argv into { "", NULL }.
However, I still think we should do the pr_warn().

Thoughts?

-- 
Kees Cook