linux-kernel - Re: [PATCH v12 01/11] MODSIGN: Export module signature definitions

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Message-Id: <8736iw9y00.fsf@morokweng.localdomain>
Date:   Tue, 23 Jul 2019 19:39:27 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Philipp Rudo <prudo@...ux.ibm.com>
Cc:     Jessica Yu <jeyu@...nel.org>, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        "James Morris" <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "David Howells" <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        "AKASHI\, Takahiro" <takahiro.akashi@...aro.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v12 01/11] MODSIGN: Export module signature definitions


Hello Philipp,


Philipp Rudo <prudo@...ux.ibm.com> writes:

> Hi Thiago,
>
> On Thu, 04 Jul 2019 15:57:34 -0300
> Thiago Jung Bauermann <bauerman@...ux.ibm.com> wrote:
>
>> Hello Philipp,
>> 
>> Philipp Rudo <prudo@...ux.ibm.com> writes:
>> 
>> > Hi Thiago,
>> >
>> >
>> > On Thu, 04 Jul 2019 03:42:57 -0300
>> > Thiago Jung Bauermann <bauerman@...ux.ibm.com> wrote:
>> >  
>> >> Jessica Yu <jeyu@...nel.org> writes:
>> >>   
>> >> > +++ Thiago Jung Bauermann [27/06/19 23:19 -0300]:    
>> >> >>IMA will use the module_signature format for append signatures, so export
>> >> >>the relevant definitions and factor out the code which verifies that the
>> >> >>appended signature trailer is valid.
>> >> >>
>> >> >>Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
>> >> >>and be able to use mod_check_sig() without having to depend on either
>> >> >>CONFIG_MODULE_SIG or CONFIG_MODULES.
>> >> >>
>> >> >>Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
>> >> >>Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
>> >> >>Cc: Jessica Yu <jeyu@...nel.org>
>> >> >>---
>> >> >> include/linux/module.h           |  3 --
>> >> >> include/linux/module_signature.h | 44 +++++++++++++++++++++++++
>> >> >> init/Kconfig                     |  6 +++-
>> >> >> kernel/Makefile                  |  1 +
>> >> >> kernel/module.c                  |  1 +
>> >> >> kernel/module_signature.c        | 46 ++++++++++++++++++++++++++
>> >> >> kernel/module_signing.c          | 56 +++++---------------------------
>> >> >> scripts/Makefile                 |  2 +-
>> >> >> 8 files changed, 106 insertions(+), 53 deletions(-)
>> >> >>
>> >> >>diff --git a/include/linux/module.h b/include/linux/module.h
>> >> >>index 188998d3dca9..aa56f531cf1e 100644
>> >> >>--- a/include/linux/module.h
>> >> >>+++ b/include/linux/module.h
>> >> >>@@ -25,9 +25,6 @@
>> >> >> #include <linux/percpu.h>
>> >> >> #include <asm/module.h>
>> >> >>
>> >> >>-/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
>> >> >>-#define MODULE_SIG_STRING "~Module signature appended~\n"
>> >> >>-    
>> >> >
>> >> > Hi Thiago, apologies for the delay.    
>> >> 
>> >> Hello Jessica, thanks for reviewing the patch!
>> >>   
>> >> > It looks like arch/s390/kernel/machine_kexec_file.c also relies on
>> >> > MODULE_SIG_STRING being defined, so module_signature.h will need to be
>> >> > included there too, otherwise we'll run into a compilation error.    
>> >> 
>> >> Indeed. Thanks for spotting that. The patch below fixes it. It's
>> >> identical to the previous version except for the changes in 
>> >> arch/s390/kernel/machine_kexec_file.c and their description in the
>> >> commit message. I'm also copying some s390 people in this email.  
>> >
>> > to me the s390 part looks good but for one minor nit.  
>> 
>> Thanks for the prompt review!
>> 
>> > In arch/s390/Kconfig KEXEC_VERIFY_SIG currently depends on
>> > SYSTEM_DATA_VERIFICATION. I'd prefer when you update this to the new
>> > MODULE_SIG_FORMAT. It shouldn't make any difference right now, as we don't
>> > use mod_check_sig in our code path. But it could cause problems in the future,
>> > when more code might be shared.  
>> 
>> Makes sense. Here is the updated patch with the Kconfig change.
>> 
>
> The patch looks good now.

Thanks! Can I add your Reviewed-by?

-- 
Thiago Jung Bauermann
IBM Linux Technology Center