linux-kernel - Re: [PATCH 2/2] exec: increase BINPRM_BUF

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Message-ID: <20181114155413.GC13885@redhat.com>
Date:   Wed, 14 Nov 2018 16:54:14 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Ben Woodard <woodard@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] exec: increase BINPRM_BUF_SIZE to 256

On 11/13, Andrew Morton wrote:
>
> On Tue, 13 Nov 2018 17:55:58 +0100 Oleg Nesterov <oleg@...hat.com> wrote:
>
> > > However it would be basically cost-free to increase
> > > BINPRM_BUF_SIZE up to the point where sizeof(struct linux_binprm) ==
> > > PAGE_SIZE?
> >
> > I don't think we should take sizeof(struct linux_binprm) into account, the
> > new members can come at any time and we can never decrease BINPRM_BUF_SIZE.
>
> My main point is..  why not make BINPRM_BUF_SIZE a lot larger than 256?

Of course we can make it larger. And of course 256 is just another silly/random
value. Currently it seems to work, but if we have another bug report we should
probably rework load_script() to use vmalloc()'ed buffer. Perhaps we should do
this right now and I am just too lazy.

Oleg.