linux-kernel - Re: [PATCH 7/7] exec: Implement kernel

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Message-ID: <202007150758.3D1597C6D@keescook>
Date:   Wed, 15 Jul 2020 08:00:16 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Al Viro <viro@...iv.linux.org.uk>,
        Luis Chamberlain <mcgrof@...nel.org>,
        linux-fsdevel@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-security-module@...r.kernel.org,
        "Serge E. Hallyn" <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>,
        Kentaro Takeda <takedakn@...data.co.jp>,
        Casey Schaufler <casey@...aufler-ca.com>,
        John Johansen <john.johansen@...onical.com>
Subject: Re: [PATCH 7/7] exec: Implement kernel_execve

On Wed, Jul 15, 2020 at 07:42:48AM +0100, Christoph Hellwig wrote:
> On Tue, Jul 14, 2020 at 02:49:23PM -0700, Kees Cook wrote:
> > On Tue, Jul 14, 2020 at 08:31:40AM -0500, Eric W. Biederman wrote:
> > > +static int count_strings_kernel(const char *const *argv)
> > > +{
> > > +	int i;
> > > +
> > > +	if (!argv)
> > > +		return 0;
> > > +
> > > +	for (i = 0; argv[i]; ++i) {
> > > +		if (i >= MAX_ARG_STRINGS)
> > > +			return -E2BIG;
> > > +		if (fatal_signal_pending(current))
> > > +			return -ERESTARTNOHAND;
> > > +		cond_resched();
> > > +	}
> > > +	return i;
> > > +}
> > 
> > I notice count() is only ever called with MAX_ARG_STRINGS. Perhaps
> > refactor that too? (And maybe rename it to count_strings_user()?)
> 
> Liks this?
> 
> http://git.infradead.org/users/hch/misc.git/commitdiff/35a3129dab5b712b018c30681d15de42d9509731

Heh, yes please. :) (Which branch is this from? Are yours and Eric's
tree going to collide?)

-- 
Kees Cook