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Commit 824d0b62 authored by Jason A. Donenfeld's avatar Jason A. Donenfeld Committed by Sasha Levin
Browse files

ACPI: configfs: Disallow loading ACPI tables when locked down 

commit 75b0cea7bf307f362057cc778efe89af4c615354 upstream.

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: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3c4f9a55

drivers/acpi/acpi_configfs.c

+5 −1
Original line number Diff line number Diff line
@@ -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);