linux-kernel - Re: [PATCH v4] x86/kexec: Carry forward IMA measurement log on kexec

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Message-ID: <YqMUPISvPs3ce1oi@noodles-fedora.dhcp.thefacebook.com>
Date:   Fri, 10 Jun 2022 09:52:01 +0000
From:   Jonathan McDowell <noodles@...com>
To:     Baoquan He <bhe@...hat.com>
CC:     Coiby Xu <coxu@...hat.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>, Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "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>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: Re: [PATCH v4] x86/kexec: Carry forward IMA measurement log on kexec

On Mon, Jun 06, 2022 at 12:06:51PM +0800, Baoquan He wrote:
> On 05/12/22 at 04:25pm, 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.
> 
> The entire looks good to me, other than a minor concern, please see the
> inline comment.
> 
> Reviewed-by: Baoquan He <bhe@...hat.com>

Thanks. Still waiting to see if Eric has any comments before deciding
whether to spin a v5 or not.

> Hi Coiby,
> 
> You can check this patch, see if you can take the same way to solve the
> LUKS-encrypted disk issue by passing the key via setup_data.
> 
> > 
> > Signed-off-by: Jonathan McDowell <noodles@...com>
> > ---
> ......snip...
> 
> > diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> > index 170d0fd68b1f..54bd4ce5f908 100644
> > --- a/arch/x86/kernel/kexec-bzimage64.c
> > +++ b/arch/x86/kernel/kexec-bzimage64.c
> > @@ -186,6 +186,33 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
> >  }
> >  #endif /* CONFIG_EFI */
> >  
> > +static void
> > +setup_ima_state(const struct kimage *image, struct boot_params *params,
> > +		unsigned long params_load_addr,
> > +		unsigned int ima_setup_data_offset)
> > +{
> > +#ifdef CONFIG_IMA_KEXEC
> > +	struct setup_data *sd = (void *)params + ima_setup_data_offset;
> > +	unsigned long setup_data_phys;
> > +	struct ima_setup_data *ima;
> > +
> > +	if (!image->ima_buffer_size)
> > +		return;
> > +
> > +	sd->type = SETUP_IMA;
> > +	sd->len = sizeof(*ima);
> > +
> > +	ima = (void *)sd + sizeof(struct setup_data);
> > +	ima->addr = image->ima_buffer_addr;
> > +	ima->size = image->ima_buffer_size;
> > +
> > +	/* Add setup data */
> > +	setup_data_phys = params_load_addr + ima_setup_data_offset;
> > +	sd->next = params->hdr.setup_data;
> > +	params->hdr.setup_data = setup_data_phys;
> > +#endif /* CONFIG_IMA_KEXEC */
> > +}
> > +
> >  static int
> >  setup_boot_parameters(struct kimage *image, struct boot_params *params,
> >  		      unsigned long params_load_addr,
> > @@ -247,6 +274,13 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
> >  	setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
> >  			efi_setup_data_offset);
> >  #endif
> > +
> > +	/* Setup IMA log buffer state */
> > +	setup_ima_state(image, params, params_load_addr,
> > +			efi_setup_data_offset +
> > +			sizeof(struct setup_data) +
> > +			sizeof(struct efi_setup_data));
> 
> Is it a little better to update efi_setup_data_offset beforehand, or
> define a local variable?
> 
> 	efi_setup_data_offset += sizeof(struct setup_data) + sizeof(struct efi_setup_data));
> 	setup_ima_state(image, params, params_load_addr,
> 			efi_setup_data_offset));
> 
> No strong opinion. If nobody has concern about it.
> 
> > +
> >  	/* Setup EDD info */
> >  	memcpy(params->eddbuf, boot_params.eddbuf,
> >  				EDDMAXNR * sizeof(struct edd_info));
>