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

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Message-ID: <20200811172738.2d632a09@coco.lan>
Date:   Tue, 11 Aug 2020 17:27:38 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     peterz@...radead.org
Cc:     Jessica Yu <jeyu@...nel.org>, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>, keescook@...omium.org,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX

Em Tue, 11 Aug 2020 16:55:24 +0200
peterz@...radead.org escreveu:

> On Tue, Aug 11, 2020 at 04:34:27PM +0200, Mauro Carvalho Chehab wrote:
> >   [33] .plt              PROGBITS         0000000000000340  00035c80
> >        0000000000000001  0000000000000000 WAX       0     0     1
> >   [34] .init.plt         NOBITS           0000000000000341  00035c81
> >        0000000000000001  0000000000000000  WA       0     0     1
> >   [35] .text.ftrace[...] PROGBITS         0000000000000342  00035c81
> >        0000000000000001  0000000000000000 WAX       0     0     1  
> 
> .plt and .text.ftrace_tramplines are buggered.
> 
> arch/arm64/kernel/module.lds even marks then as NOLOAD.

Hmm... Shouldn't the code at module_enforce_rwx_sections() or at
load_module() ignore such sections instead of just rejecting probing
all modules?

I mean, if the existing toolchain is not capable of excluding
those sections, either the STRICT_MODULE_RWX hardening should be
disabled, if a broken toolchain is detected or some runtime code 
should handle such sections on a different way.

Thanks,
Mauro