From: Linn Crosetto Date: Fri, 4 Mar 2016 16:08:24 -0700 Subject: [16/18] acpi: Disable ACPI table override if securelevel is set Origin: https://github.com/mjg59/linux/commit/a4a5ed2835e8ea042868b7401dced3f517cafa76 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 securelevel is set. Signed-off-by: Linn Crosetto [bwh: Forward-ported to 4.7: ACPI override code moved to drivers/acpi/tables.c] --- arch/x86/kernel/setup.c | 12 ++++++------ drivers/acpi/tables.c | 6 ++++++ 2 files changed, 12 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1145,6 +1145,12 @@ void __init setup_arch(char **cmdline_p) /* Allocate bigger log buffer */ setup_log_buf(1); +#ifdef CONFIG_EFI_SECURE_BOOT_SECURELEVEL + if (boot_params.secure_boot) { + set_securelevel(1); + } +#endif + reserve_initrd(); early_initrd_acpi_init(); @@ -1153,12 +1159,6 @@ void __init setup_arch(char **cmdline_p) io_delay_init(); -#ifdef CONFIG_EFI_SECURE_BOOT_SECURELEVEL - if (boot_params.secure_boot) { - set_securelevel(1); - } -#endif - /* * Parse the ACPI tables for possible boot-time SMP configuration. */ --- a/drivers/acpi/tables.c +++ b/drivers/acpi/tables.c @@ -34,6 +34,7 @@ #include #include #include +#include #include "internal.h" #ifdef CONFIG_ACPI_CUSTOM_DSDT @@ -539,6 +540,12 @@ static void __init acpi_table_initrd_ini if (table_nr == 0) return; + if (get_securelevel() > 0) { + pr_notice(PREFIX + "securelevel enabled, ignoring table override\n"); + return; + } + acpi_tables_addr = memblock_find_in_range(0, max_low_pfn_mapped << PAGE_SHIFT, all_tables_size, PAGE_SIZE);