linux-kernel - Re: [PATCH v3] x86/kexec: Carry forward IMA measurement log on kexec

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Message-ID: <11153650a1c4a70bb83ce67724280313120d07d5.camel@linux.ibm.com>
Date:   Wed, 11 May 2022 21:34:03 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Jonathan McDowell <noodles@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v3] x86/kexec: Carry forward IMA measurement log on kexec

On Wed, 2022-05-11 at 13:53 -0400, Mimi Zohar wrote:
> Hi Jonathan,
> 
> On Wed, 2022-05-11 at 09:59 +0000, Jonathan McDowell wrote:
> > On kexec file load Integrity Measurement Architecture (IMA) subsystem
> > may verify the IMA signature of the kernel and initramfs, and measure
> > it. The command line parameters passed to the kernel in the kexec call
> > may also be measured by IMA. A remote attestation service can verify
> > a TPM quote based on the TPM event log, the IMA measurement list, and
> > the TPM PCR data. This can be achieved only if the IMA measurement log
> > is carried over from the current kernel to the next kernel across
> > the kexec call.
> > 
> > powerpc and ARM64 both achieve this using device tree with a
> > "linux,ima-kexec-buffer" node. x86 platforms generally don't make use of
> > device tree, so use the setup_data mechanism to pass the IMA buffer to
> > the new kernel.
> > 
> > Signed-off-by: Jonathan McDowell <noodles@...com>

Thanks, Jonathan.  The measurement list is now properly being restored
independently of CONFIG_IMA_KEXEC being configured.

> > +++ b/include/linux/ima.h
> > @@ -140,6 +140,9 @@ static inline int ima_measure_critical_data(const char *event_label,
> >  
> >  #endif /* CONFIG_IMA */
> > 

#ifdef CONFIG_HAVE_IMA_KEXEC

> > +int ima_free_kexec_buffer(void);
> > +int ima_get_kexec_buffer(void **addr, size_t *size);

#endif
> 
> Wouldn't moving these function definitions here imply they are
> implemented on all architectures or are using the version in
> drivers/of/kexec.c.

Adding the ifdef around these functions should resolve any issues.

thanks,

Mimi