On 5 February 2014 18:04, Leif Lindholm <leif.lindholm@xxxxxxxxxx> wrote:
> From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>
> Loading unauthenticated FDT blobs directly from storage is a security hazard,
> so this should only be allowed when running with UEFI Secure Boot disabled.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx>
> ---
> drivers/firmware/efi/arm-stub.c | 4 +++-
> drivers/firmware/efi/efi-stub-helper.c | 24 ++++++++++++++++++++++++
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/arm-stub.c b/drivers/firmware/efi/arm-stub.c
> index b505fde..c651082 100644
> --- a/drivers/firmware/efi/arm-stub.c
> +++ b/drivers/firmware/efi/arm-stub.c
> @@ -95,7 +95,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
>
> /* Load a device tree from the configuration table, if present. */
> fdt_addr = (uintptr_t)get_fdt(sys_table);
> - if (!fdt_addr) {
> + if (efi_secureboot_enabled(sys_table))
> + pr_efi(sys_table, "UEFI Secure Boot is enabled, ignoring dtb= commandline option.\n");
I am pretty sure my original patch had braces on both branches of the if () :-)
Also, I think the precedence is backward here: dtb= should trump
config table, not the other way around.
--
Ard.
> + else if (!fdt_addr) {
> status = handle_cmdline_files(sys_table, image, cmdline_ptr,
> "dtb=",
> ~0UL, (unsigned long *)&fdt_addr,
> diff --git a/drivers/firmware/efi/efi-stub-helper.c b/drivers/firmware/efi/efi-stub-helper.c
> index 2ee69ea..6221be7 100644
> --- a/drivers/firmware/efi/efi-stub-helper.c
> +++ b/drivers/firmware/efi/efi-stub-helper.c
> @@ -721,3 +721,27 @@ static char *efi_convert_cmdline(efi_system_table_t *sys_table_arg,
> *cmd_line_len = options_bytes;
> return (char *)cmdline_addr;
> }
> +
> +static int __init efi_secureboot_enabled(efi_system_table_t *sys_table_arg)
> +{
> + static efi_guid_t const var_guid __initconst = EFI_GLOBAL_VARIABLE_GUID;
> + static efi_char16_t const var_name[] __initconst = {
> + 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 };
> +
> + efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable;
> + unsigned long size = sizeof(u8);
> + efi_status_t status;
> + u8 val;
> +
> + status = efi_call_phys5(f_getvar, (efi_char16_t *)var_name,
> + (efi_guid_t *)&var_guid, NULL, &size, &val);
> +
> + switch (status) {
> + case EFI_SUCCESS:
> + return val;
> + case EFI_NOT_FOUND:
> + return 0;
> + default:
> + return 1;
> + }
> +}
> --
> 1.7.10.4
>
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