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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200811212908.GB5637@worktop.programming.kicks-ass.net>
Date:   Tue, 11 Aug 2020 23:29:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...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>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX

On Tue, Aug 11, 2020 at 07:59:12PM +0200, peterz@...radead.org wrote:
> On Tue, Aug 11, 2020 at 06:01:35PM +0200, Jessica Yu wrote:
> 
> > > > 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
> 
> > Interesting, my cross-compiled modules do not have the executable flag -
> > 
> >  [38] .plt              NOBITS           0000000000000340  00038fc0
> >       0000000000000001  0000000000000000  WA       0     0     1
> >  [39] .init.plt         NOBITS           0000000000000341  00038fc0
> >       0000000000000001  0000000000000000  WA       0     0     1
> >  [40] .text.ftrace_tram NOBITS           0000000000000342  00038fc0
> >       0000000000000001  0000000000000000  WA       0     0     1
> 
> > I'm a bit confused about what NOLOAD actually implies in this context. From the
> > ld documentation - "The `(NOLOAD)' directive will mark a section to not be
> > loaded at run time." But these sections are marked SHF_ALLOC and are referenced
> > to in the module plt code. Or does it just tell the linker to not initialize it?
> 
> Yeah, that confusion is wide-spread, so much so that bfd-ld and gold,
> both in bintils, had different behaviour at some point.
> 
> Anyway, another clue is that your build has all NOBITS, while Mauro's
> build has PROGBITS for the broken sections.
> 
> Anyway, my gcc-10.1/binutils-2.34 cross tool chain (from k.org)
> generates the same as Jessica's too. I wonder if binutils-2.35 is
> wonky...

When I use the Debian provided cross compiler which uses:

  binutils-aarch64-linux-gnu           2.35-1

I do indeed see the same thing Mauro does, which seems to suggest
there's something really dodgy with that toolchain. Some tools person
should have a look.