linux-kernel - Re: [PATCH v9 6/8] powerpc: Move ima_get_kexec_buffer() and ima_free_kexec

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Message-ID: <19d10383-7059-ff90-37d1-7806585b331d@linux.microsoft.com>
Date:   Tue, 1 Dec 2020 11:05:46 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, bauerman@...ux.ibm.com,
        robh@...nel.org, gregkh@...uxfoundation.org, james.morse@....com,
        catalin.marinas@....com, sashal@...nel.org, will@...nel.org,
        mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        robh+dt@...nel.org, frowand.list@...il.com,
        vincenzo.frascino@....com, mark.rutland@....com,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com,
        pasha.tatashin@...een.com, allison@...utok.net,
        kstewart@...uxfoundation.org, takahiro.akashi@...aro.org,
        tglx@...utronix.de, masahiroy@...nel.org, bhsharma@...hat.com,
        mbrugger@...e.com, hsinyi@...omium.org, tao.li@...o.com,
        christophe.leroy@....fr
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, prsriva@...ux.microsoft.com,
        balajib@...ux.microsoft.com
Subject: Re: [PATCH v9 6/8] powerpc: Move ima_get_kexec_buffer() and
 ima_free_kexec_buffer() to ima

On 12/1/20 3:38 AM, Mimi Zohar wrote:
> Hi Lakshmi,
> 
> On Fri, 2020-11-13 at 11:22 -0800, Lakshmi Ramasubramanian wrote:
>> ima_get_kexec_buffer() retrieves the address and size of the buffer
>> used for carrying forward the IMA measurement logs on kexec from
>> the device tree.
>>
>> ima_free_kexec_buffer() removes the chosen node namely
>> "linux,ima-kexec-buffer" from the device tree, and frees the buffer
>> used for carrying forward the IMA measurement logs on kexec.
>>
>> These functions do not have architecture specific code, but are
>> currently limited to powerpc.
>>
>> Move ima_get_kexec_buffer() and ima_free_kexec_buffer() to ima_kexec.c
>> in IMA so that they are accessible for other architectures as well.
> 
> This sentence flows from the previous line.  No need for separate
> paragraphs here.

Sure - will update Mimi.

>>
>> With the above change the functions in arch/powerpc/kexec/ima.c are
>> defined only when the kernel config CONFIG_IMA_KEXEC is enabled.
>> Update the Makefile to build arch/powerpc/kexec/ima.c only when
>> CONFIG_IMA_KEXEC is enabled and remove "#ifdef CONFIG_IMA_KEXEC"
>> in arch/powerpc/kexec/ima.c.
>>
>> Co-developed-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
>> Signed-off-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
>> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> 
> After making the two changes,
> 
> Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> 
> 
>> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
>> index 121de3e04af2..3f0fa2673dd3 100644
>> --- a/security/integrity/ima/ima_kexec.c
>> +++ b/security/integrity/ima/ima_kexec.c
>> @@ -9,9 +9,60 @@
>>   
>>   #include <linux/seq_file.h>
>>   #include <linux/vmalloc.h>
>> +#include <linux/memblock.h>
>> +#include <linux/of.h>
>>   #include <linux/kexec.h>
>> +#include <linux/ima.h>
>>   #include "ima.h"
>>   
>> +/**
>> + * ima_get_kexec_buffer - get IMA buffer from the previous kernel
>> + * @addr:	On successful return, set to point to the buffer contents.
>> + * @size:	On successful return, set to the buffer size.
>> + *
>> + * Return: 0 on success, negative errno on error.
>> + */
>> +static int ima_get_kexec_buffer(void **addr, size_t *size)
>> +{
>> +	int ret;
>> +	unsigned long tmp_addr;
>> +	size_t tmp_size;
>> +
>> +	ret = get_ima_kexec_buffer(NULL, 0, &tmp_addr, &tmp_size);
>> +	if (ret)
>> +		return ret;
>> +
>> +	*addr = __va(tmp_addr);
>> +	*size = tmp_size;
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * ima_free_kexec_buffer - free memory used by the IMA buffer
>> + */
>> +static int ima_free_kexec_buffer(void)
>> +{
>> +	int ret;
>> +	unsigned long addr;
>> +	size_t size;
>> +	struct property *prop;
>> +
>> +	prop = of_find_property(of_chosen, "linux,ima-kexec-buffer", NULL);
>> +	if (!prop)
>> +		return -ENOENT;
>> +
>> +	ret = get_ima_kexec_buffer(NULL, 0, &addr, &size);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = of_remove_property(of_chosen, prop);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return memblock_free(addr, size);
>> +}
>> +
> 
> Please move these functions, after the ifdef below, before the function
> where they're used.

Will make the above change.

thanks,
  -lakshmi

> 
>>   #ifdef CONFIG_IMA_KEXEC
>>   static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
>>   				     unsigned long segment_size)
>