linux-kernel - Re: [PATCH 1/7] ima: on soft reboot, restore the measurement list

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Message-ID: <1470784396.2301.2.camel@mendozajonas.com>
Date:	Wed, 10 Aug 2016 09:13:16 +1000
From:	Samuel Mendoza-Jonas <sam@...dozajonas.com>
To:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	Dave Young <dyoung@...hat.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/7] ima: on soft reboot, restore the measurement list

On Tue, 2016-08-09 at 10:19 -0300, Thiago Jung Bauermann wrote:
> Am Dienstag, 09 August 2016, 09:01:13 schrieb Mimi Zohar:
> > 
> > On Tue, 2016-08-09 at 20:59 +1000, Michael Ellerman wrote:
> > > 
> > > Mimi Zohar <zohar@...ux.vnet.ibm.com> writes:
> > > > 
> > > > diff --git a/security/integrity/ima/ima.h
> > > > b/security/integrity/ima/ima.h
> > > > index b5728da..84e8d36 100644
> > > > --- a/security/integrity/ima/ima.h
> > > > +++ b/security/integrity/ima/ima.h
> > > > @@ -102,6 +102,13 @@ struct ima_queue_entry {
> > > > 
> > > >  };
> > > >  extern struct list_head ima_measurements;	/* list of all 
> measurements
> > 
> > > 
> > > > 
> > > >  */
> > > > 
> > > > +/* Some details preceding the binary serialized measurement list */
> > > > +struct ima_kexec_hdr {
> > > > +	unsigned short version;
> > > > +	unsigned long buffer_size;
> > > > +	unsigned long count;
> > > > +} __packed;
> > > > +
> > > 
> > > Am I understanding it correctly that this structure is passed between
> > > kernels?
> > Yes, the header prefixes the measurement list, which is being passed on
> > the same computer to the next kernel.  Could the architecture (eg.
> > LE/BE) change between soft re-boots?
> 
> Yes. I am able to boot a BE kernel from an LE kernel with my patches. 
> Whether we want to support that or not is another question...

The answer to that question is almost certainly yes - on POWER the most
immediate example would be soft-rebooting from a BE host into an LE
Petitboot kernel, or vice versa.