[PATCH 16/27] acpi: Disable ACPI table override if the kernel is locked down

David Howells dhowells at redhat.com
Thu Oct 19 14:52:34 UTC 2017


From: Linn Crosetto <linn at hpe.com>

>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 <linn at hpe.com>
Signed-off-by: David Howells <dhowells at redhat.com>
cc: linux-acpi at vger.kernel.org
---

 drivers/acpi/tables.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index 80ce2a7d224b..5cc13c42daf9 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -526,6 +526,11 @@ void __init acpi_table_upgrade(void)
 	if (table_nr == 0)
 		return;
 
+	if (kernel_is_locked_down("ACPI table override")) {
+		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);

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