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[v2,01/57,B] acpi: Disable ACPI table override if the kernel is locked down

Message ID 20200619161621.644540-2-seth.forshee@canonical.com
State New
Headers show
Series Lockdown updates | expand

Commit Message

Seth Forshee June 19, 2020, 4:15 p.m. UTC 
From: Linn Crosetto <lcrosetto@gmail.com>

BugLink: https://bugs.launchpad.net/bugs/1884159

>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 <lcrosetto@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: linux-acpi@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
(backported from commit 6ea0e815fc5e18597724169caa6e4d46dd8e693d)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
 drivers/acpi/osl.c | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 62a2a564a46e..3b6d3247a4c9 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -675,6 +675,11 @@  void __init acpi_initrd_override(void *data, size_t size)
 	if (table_nr == 0)
 		return;
 
+	if (secure_modules()) {
+		pr_notice("kernel is locked down, ignoring table override\n");
+		return;
+	}
+
 	acpi_tables_addr =
 		memblock_find_in_range(0, max_low_pfn_mapped << PAGE_SHIFT,
 				       all_tables_size, PAGE_SIZE);