Re: [PATCH v4 2/5] powerpc: Use libfdt functions to fetch IMA buffer properties
From: Thiago Jung Bauermann <hidden>
Date: 2020-08-27 23:52:03
Also in:
linux-integrity, lkml
Lakshmi Ramasubramanian [off-list ref] writes:
quoted hunk ↗ jump to hunk
@@ -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.
+ 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.
quoted hunk ↗ jump to hunk
+ 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. -- Thiago Jung Bauermann IBM Linux Technology Center