From: Ard Biesheuvel <[email protected]> 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 <[email protected]> Signed-off-by: Leif Lindholm <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Matt Fleming <[email protected]> --- drivers/firmware/efi/arm-stub.c | 15 +++++++++++---- drivers/firmware/efi/efi-stub-helper.c | 24 ++++++++++++++++++++++++ 2 files changed, 35 insertions(+), 4 deletions(-) diff --git a/drivers/firmware/efi/arm-stub.c b/drivers/firmware/efi/arm-stub.c index b9b7c00..c8988b2 100644 --- a/drivers/firmware/efi/arm-stub.c +++ b/drivers/firmware/efi/arm-stub.c @@ -145,7 +145,7 @@ unsigned long __init efi_entry(void *handle, efi_system_table_t *sys_table, /* addr/point and size pairs for memory management*/ unsigned long initrd_addr; u64 initrd_size = 0; - unsigned long fdt_addr; /* Original DTB */ + unsigned long fdt_addr = 0; /* Original DTB */ u64 fdt_size = 0; /* We don't get size from configuration table */ char *cmdline_ptr = NULL; int cmdline_size = 0; @@ -197,9 +197,13 @@ unsigned long __init efi_entry(void *handle, efi_system_table_t *sys_table, goto fail_free_image; } - /* Load a device tree from the configuration table, if present. */ - fdt_addr = (uintptr_t)get_fdt(sys_table); - if (!fdt_addr) { + /* + * Unauthenticated device tree data is a security hazard, so + * ignore 'dtb=' unless UEFI Secure Boot is disabled. + */ + if (efi_secureboot_enabled(sys_table)) { + pr_efi(sys_table, "UEFI Secure Boot is enabled.\n"); + } else { status = handle_cmdline_files(sys_table, image, cmdline_ptr, "dtb=", ~0UL, (unsigned long *)&fdt_addr, @@ -210,6 +214,9 @@ unsigned long __init efi_entry(void *handle, efi_system_table_t *sys_table, goto fail_free_cmdline; } } + if (!fdt_addr) + /* Look for a device tree configuration table entry. */ + fdt_addr = (uintptr_t)get_fdt(sys_table); status = handle_cmdline_files(sys_table, image, cmdline_ptr, "initrd=", dram_base + SZ_512M, diff --git a/drivers/firmware/efi/efi-stub-helper.c b/drivers/firmware/efi/efi-stub-helper.c index 998b884..8f8b538 100644 --- a/drivers/firmware/efi/efi-stub-helper.c +++ b/drivers/firmware/efi/efi-stub-helper.c @@ -632,3 +632,27 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
