On Fri, Jun 21, 2019 at 05:03:45PM -0700, Matthew Garrett wrote: > From: Linn Crosetto <[email protected]> > > 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 lockdown is enabled, 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 <[email protected]>
Reviewed-by: Kees Cook <[email protected]> -Kees > Signed-off-by: David Howells <[email protected]> > Signed-off-by: Matthew Garrett <[email protected]> > cc: [email protected] > --- > drivers/acpi/tables.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c > index 8fccbe49612a..41d9ccd0e075 100644 > --- a/drivers/acpi/tables.c > +++ b/drivers/acpi/tables.c > @@ -34,6 +34,7 @@ > #include <linux/memblock.h> > #include <linux/earlycpio.h> > #include <linux/initrd.h> > +#include <linux/security.h> > #include "internal.h" > > #ifdef CONFIG_ACPI_CUSTOM_DSDT > @@ -539,6 +540,11 @@ void __init acpi_table_upgrade(void) > if (table_nr == 0) > return; > > + if (security_locked_down(LOCKDOWN_ACPI_TABLES)) { > + 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); > -- > 2.22.0.410.gd8fdbe21b5-goog > -- Kees Cook
