linux-kernel - Re: [PATCH v2] module: Harden STRICT_MODULE

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Message-ID: <CAMj1kXEn5o_7OOqgcntOPCqBYmpY74OkGqQ_bUBJvHG6Q9GVLA@mail.gmail.com>
Date:   Thu, 13 Aug 2020 10:36:05 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Jessica Yu <jeyu@...nel.org>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        Will Deacon <will@...nel.org>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Mark Rutland <mark.rutland@....com>, nd <nd@....com>
Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX

On Wed, 12 Aug 2020 at 22:00, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Aug 12, 2020 at 06:37:57PM +0200, Ard Biesheuvel wrote:
> > I know there is little we can do at this point, apart from ignoring
> > the permissions - perhaps we should just defer the w^x check until
> > after calling module_frob_arch_sections()?
>
> My earlier suggestion was to ignore it for 0-sized sections.

Only they are 1 byte sections in this case.

We override the sh_type and sh_flags explicitly for these sections at
module load time, so deferring the check seems like a reasonable
alternative to me.