Like other vectors already patched, this one here allows the root user to load ACPI tables, which enables arbitrary physical address writes, which in turn makes it possible to disable lockdown. This patch prevents this by checking the lockdown status before allowing a new ACPI table to be installed. The link in the trailer shows a PoC of how this might be used.
Link: https://git.zx2c4.com/american-unsigned-language/tree/american-unsigned-lang... Cc: stable@vger.kernel.org Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com --- drivers/acpi/acpi_configfs.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/acpi/acpi_configfs.c b/drivers/acpi/acpi_configfs.c index ece8c1a921cc..88c8af455ea3 100644 --- a/drivers/acpi/acpi_configfs.c +++ b/drivers/acpi/acpi_configfs.c @@ -11,6 +11,7 @@ #include <linux/module.h> #include <linux/configfs.h> #include <linux/acpi.h> +#include <linux/security.h>
#include "acpica/accommon.h" #include "acpica/actables.h" @@ -28,7 +29,10 @@ static ssize_t acpi_table_aml_write(struct config_item *cfg, { const struct acpi_table_header *header = data; struct acpi_table *table; - int ret; + int ret = security_locked_down(LOCKDOWN_ACPI_TABLES); + + if (ret) + return ret;
table = container_of(cfg, struct acpi_table, cfg);