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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Thu, 13 Aug 2020 10:36:05 +0200
Message-ID: <CAMj1kXEn5o_7OOqgcntOPCqBYmpY74OkGqQ_bUBJvHG6Q9GVLA@mail.gmail.com>
Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Jessica Yu <jeyu@kernel.org>,
        Szabolcs Nagy <szabolcs.nagy@arm.com>,
        Will Deacon <will@kernel.org>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Miroslav Benes <mbenes@suse.cz>,
        Mark Rutland <mark.rutland@arm.com>, nd <nd@arm.com>
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On Wed, 12 Aug 2020 at 22:00, Peter Zijlstra <peterz@infradead.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.