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

Thiago Jung Bauermann
2019-07-23T22:39:55Z

Hello Philipp,

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

> Hi Thiago,
>
> On Thu, 04 Jul 2019 15:57:34 -0300
> Thiago Jung Bauermann <bauerman@linux.ibm.com> wrote:
>
>> Hello Philipp,
>>
>> Philipp Rudo <prudo@linux.ibm.com> writes:
>>
>> > Hi Thiago,
>> >
>> >
>> > On Thu, 04 Jul 2019 03:42:57 -0300
>> > Thiago Jung Bauermann <bauerman@linux.ibm.com> wrote:
>> >
>> >> Jessica Yu <jeyu@kernel.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@linux.ibm.com>
>> >> >>Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
>> >> >>Cc: Jessica Yu <jeyu@kernel.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