linux-kernel - Re: [PATCH v4 0/2] let kexec_file_load use platform keyring to verify the kernel image

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Date:   Mon, 21 Jan 2019 17:08:59 +0800
From:   Kairui Song <kasong@...hat.com>
To:     Dave Young <dyoung@...hat.com>, Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        jwboyer@...oraproject.org, keyrings@...r.kernel.org,
        jmorris@...ei.org, serge@...lyn.com, bauerman@...ux.ibm.com,
        Eric Biggers <ebiggers@...gle.com>, nayna@...ux.ibm.com,
        linux-integrity <linux-integrity@...r.kernel.org>,
        kexec@...ts.infradead.org
Subject: Re: [PATCH v4 0/2] let kexec_file_load use platform keyring to verify
 the kernel image

On Fri, Jan 18, 2019 at 10:28 PM Kairui Song <kasong@...hat.com> wrote:
>
> On Fri, Jan 18, 2019 at 9:42 PM Kairui Song <kasong@...hat.com> wrote:
> >
> > On Fri, Jan 18, 2019 at 8:37 PM Dave Young <dyoung@...hat.com> wrote:
> > >
> > > On 01/18/19 at 08:34pm, Dave Young wrote:
> > > > On 01/18/19 at 06:53am, Mimi Zohar wrote:
> > > > > On Fri, 2019-01-18 at 17:17 +0800, Kairui Song wrote:
> > > > > > This patch series adds a .platform_trusted_keys in system_keyring as the
> > > > > > reference to .platform keyring in integrity subsystem, when platform
> > > > > > keyring is being initialized it will be updated. So other component could
> > > > > > use this keyring as well.
> > > > >
> > > > > Kairui, when people review patches, the comments could be specific,
> > > > > but are normally generic.  My review included a couple of generic
> > > > > suggestions - not to use "#ifdef" in C code (eg. is_enabled), use the
> > > > > term "preboot" keys, and remove any references to "other components".
> > > > >
> > > > > After all the wording suggestions I've made, you are still saying, "So
> > > > > other components could use this keyring as well".  Really?!  How the
> > > > > platform keyring will be used in the future, is up to you and others
> > > > > to convince Linus.  At least for now, please limit its usage to
> > > > > verifying the PE signed kernel image.  If this patch set needs to be
> > > > > reposted, please remove all references to "other components".
> > > > >
> > > > > Dave/David, are you ok with Kairui's usage of "#ifdef's"?  Dave, you
> > > > > Acked the original post.  Can I include it?  Can we get some
> > > > > additional Ack's on these patches?
> > > >
> > > > It is better to update patch to use IS_ENABLED in patch 1/2 as well.
> > >
> > > Hmm, not only for patch 1/2, patch 2/2 also need an update
> > >
> > > > Other than that, for kexec part I'm fine with an ack.
> > > >
> > > > Thanks
> > > > Dave
> >
> > Thanks for the review again, will update the patch using IS_ENABLED
> > along with update the cover letter shortly.
> >
> > --
> > Best Regards,
> > Kairui Song
>
> Hi, before I update it again, most part of the new
> platform_trusted_keyring related code is following how
> secondary_trusted_keyring is implemented (surrounded by ifdefs). I
> thought this could reduce unused code when the keyring is not enabled.
> Else, all ifdef could be simply removed, when platform_keyring is not
> enabled, the platform_trusted_keys will always be NULL, and
> verify_pkcs7_signature will simply return NOKEY if anyone try to use
> platform keyring.
>
> Any suggestions? Or I can just remove the ifdef in
> security/integrity/digsig.c and make set_platform_trusted_keys a
> inline empty function in system_keyring.h.
>
> --
> Best Regards,
> Kairui Song

Hi, after a second thought I'll drop the #ifdef in
security/integrity/digsig.c in PATCH 1/2, and make the
set_platform_trusted_keys function a empty inline function when
CONFIG_INTEGRITY_PLATFORM_KEYRING is undefined.
But for other ifdefs in certs/system_keyring.c I think maybe just keep
then untouched. They were used to strip out the
platform_trusted_keyring variable and related function when
CONFIG_INTEGRITY_PLATFORM_KEYRING is not used, this should help reduce
unused code and prevent compile error, also make code style aligns
with existing code in system_keyring.c.

Will sent v5 with above updates and fix a potential problem found by Nayna.


--
Best Regards,
Kairui Song