Re: [PATCH v4 2/5] powerpc: Use libfdt functions to fetch IMA buffer properties

Lakshmi Ramasubramanian
2020-08-28T17:46:17Z

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