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

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Date:   Mon, 6 Jun 2022 12:06:51 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Jonathan McDowell <noodles@...com>, Coiby Xu <coxu@...hat.com>
Cc:     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>
Subject: Re: [PATCH v4] x86/kexec: Carry forward IMA measurement log on kexec

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>

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));