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ACPI: configfs: Disallow loading ACPI tables when locked down

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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+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Jason A. Donenfeld 2020-06-15 04:43:32 -06:00 committed by Rafael J. Wysocki
parent 48778464bb
commit 75b0cea7bf
1 changed files with 5 additions and 1 deletions
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6
drivers/acpi/acpi_configfs.c
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@ -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);