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x86/mmiotrace: Lock down the testmmiotrace module 

The testmmiotrace module shouldn't be permitted when the kernel is locked
down as it can be used to arbitrarily read and write MMIO space. This is
a runtime check rather than buildtime in order to allow configurations
where the same kernel may be run in both locked down or permissive modes
depending on local policy.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Howells <dhowells@redhat.com
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: Thomas Gleixner <tglx@linutronix.de>
cc: Steven Rostedt <rostedt@goodmis.org>
cc: Ingo Molnar <mingo@kernel.org>
cc: "H. Peter Anvin" <hpa@zytor.com>
cc: x86@kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells 2019-08-19 17:17:56 -07:00 committed by James Morris
parent 20657f66ef
commit 906357f77a
3 changed files with 7 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/x86/mm/testmmiotrace.c
View File

@ -8,6 +8,7 @@
#include <linux/module.h>
#include <linux/io.h>
#include <linux/mmiotrace.h>
#include <linux/security.h>
static unsigned long mmio_address;
module_param_hw(mmio_address, ulong, iomem, 0);
@ -115,6 +116,10 @@ static void do_test_bulk_ioremapping(void)
static int __init init(void)
{
unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
int ret = security_locked_down(LOCKDOWN_MMIOTRACE);
if (ret)
return ret;
if (mmio_address == 0) {
pr_err("you have to use the module argument mmio_address.\n");

1
include/linux/security.h
View File

@ -114,6 +114,7 @@ enum lockdown_reason {
LOCKDOWN_PCMCIA_CIS,
LOCKDOWN_TIOCSSERIAL,
LOCKDOWN_MODULE_PARAMETERS,
LOCKDOWN_MMIOTRACE,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

1
security/lockdown/lockdown.c
View File

@ -29,6 +29,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
[LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage",
[LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO",
[LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters",
[LOCKDOWN_MMIOTRACE] = "unsafe mmio",
[LOCKDOWN_INTEGRITY_MAX] = "integrity",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
};