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 <nramas@xxxxxxxxxxxxxxxxxxx> 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