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Subject: Re: [PATCH v4 2/5] powerpc: Use libfdt functions to fetch IMA buffer
 properties
To:     Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc:     zohar@linux.ibm.com, robh@kernel.org, gregkh@linuxfoundation.org,
        james.morse@arm.com, catalin.marinas@arm.com, sashal@kernel.org,
        will@kernel.org, mpe@ellerman.id.au, benh@kernel.crashing.org,
        paulus@samba.org, robh+dt@kernel.org, frowand.list@gmail.com,
        vincenzo.frascino@arm.com, mark.rutland@arm.com,
        dmitry.kasatkin@gmail.com, jmorris@namei.org, serge@hallyn.com,
        pasha.tatashin@soleen.com, allison@lohutok.net,
        kstewart@linuxfoundation.org, takahiro.akashi@linaro.org,
        tglx@linutronix.de, masahiroy@kernel.org, bhsharma@redhat.com,
        mbrugger@suse.com, hsinyi@chromium.org, tao.li@vivo.com,
        christophe.leroy@c-s.fr, linux-integrity@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        prsriva@linux.microsoft.com, balajib@linux.microsoft.com
References: <20200819172134.11243-1-nramas@linux.microsoft.com>
 <20200819172134.11243-3-nramas@linux.microsoft.com>
 <8736478x7l.fsf@morokweng.localdomain>
From:   Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Message-ID: <53685243-60b6-b21b-7f48-827bb296aa72@linux.microsoft.com>
Date:   Fri, 28 Aug 2020 10:46:12 -0700
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On 8/27/20 4:50 PM, Thiago Jung Bauermann wrote:
> 
> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:
> 
>> @@ -63,7 +29,22 @@ void remove_ima_buffer(void *fdt, int chosen_node)
>>   	if (!prop)
>>   		return;
>>   
>> -	ret = do_get_kexec_buffer(prop, len, &addr, &size);
>> +	ret = fdt_address_cells(fdt, chosen_node);
> 
> This change was already present in the previous version of the patch but
> it was just today that I noticed a problem: there's no #address-cells
> property in /chosen. This code will still work though because if there's
> no property this function returns 2 which is the correct value for
> ppc64. But it's conceptually wrong. You need to pass the node offset for
> / so that it gets the #address-cells property from there.

Thanks for the info.
Will fix this.

> 
>> +	if (ret < 0)
>> +		return;
>> +	addr_cells = ret;
>> +
>> +	ret = fdt_size_cells(fdt, chosen_node);
> 
> Here we're not so lucky. The default value returned when no #size-cells
> property is present is 1, which is wrong for ppc64 so this change
> introduces a bug. You also need to pass the node offset for / here.

Will fix this.

> 
>> +	if (ret < 0)
>> +		return;
>> +	size_cells = ret;
>> +
>> +	if (len < 4 * (addr_cells + size_cells))
>> +		return;
>> +
>> +	addr = of_read_number(prop, addr_cells);
>> +	size = of_read_number(prop + 4 * addr_cells, size_cells);
>> +
>>   	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
>>   	if (ret)
>>   		return;
>> @@ -129,9 +110,15 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
>>   	if (!image->arch.ima_buffer_size)
>>   		return 0;
>>   
>> -	ret = get_addr_size_cells(&addr_cells, &size_cells);
>> -	if (ret)
>> +	ret = fdt_address_cells(fdt, chosen_node);
>> +	if (ret < 0)
>> +		return ret;
>> +	addr_cells = ret;
>> +
>> +	ret = fdt_size_cells(fdt, chosen_node);
>> +	if (ret < 0)
>>   		return ret;
>> +	size_cells = ret;
>>   
>>   	entry_size = 4 * (addr_cells + size_cells);
> 
> Ditto here.
> 

Will fix this.

thanks,
  -lakshmi