From: Linn Crosetto Date: Wed, 5 Apr 2017 17:40:31 +0100 Subject: [55/61] acpi: Disable ACPI table override if the kernel is locked down Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=2a3b80bfba52f3f71bbb9b20942fb86ca6f491fe From the kernel documentation (initrd_table_override.txt): If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible to override nearly any ACPI table provided by the BIOS with an instrumented, modified one. When securelevel is set, the kernel should disallow any unauthenticated changes to kernel space. ACPI tables contain code invoked by the kernel, so do not allow ACPI tables to be overridden if the kernel is locked down. Signed-off-by: Linn Crosetto Signed-off-by: David Howells --- drivers/acpi/tables.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c index 2604189d6cd1..601096d0d849 100644 --- a/drivers/acpi/tables.c +++ b/drivers/acpi/tables.c @@ -542,6 +542,11 @@ void __init acpi_table_upgrade(void) if (table_nr == 0) return; + if (kernel_is_locked_down()) { + pr_notice("kernel is locked down, ignoring table override\n"); + return; + } + acpi_tables_addr = memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS, all_tables_size, PAGE_SIZE);