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

[Lakshmi Ramasubramanian]

On 8/27/20 4:50 PM, Thiago Jung Bauermann wrote:

Lakshmi Ramasubramanian <nra...@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