From 75b0cea7bf307f362057cc778efe89af4c615354 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 15 Jun 2020 04:43:32 -0600 Subject: [PATCH] ACPI: configfs: Disallow loading ACPI tables when locked down 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. 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-language-2.sh Cc: 5.4+ # 5.4+ Signed-off-by: Jason A. Donenfeld Signed-off-by: Rafael J. Wysocki --- 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 #include #include +#include #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);