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>

diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
index 0881e1f..a8bd952 100644 (file)
--- a/arch/x86/mm/testmmiotrace.c
+++ b/arch/x86/mm/testmmiotrace.c
@@ -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");

diff --git a/include/linux/security.h b/include/linux/security.h
index 1a3404f..d8db7ea 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -114,6 +114,7 @@ enum lockdown_reason {
        LOCKDOWN_PCMCIA_CIS,
        LOCKDOWN_TIOCSSERIAL,
        LOCKDOWN_MODULE_PARAMETERS,
+       LOCKDOWN_MMIOTRACE,
        LOCKDOWN_INTEGRITY_MAX,
        LOCKDOWN_CONFIDENTIALITY_MAX,
 };

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 0fa4342..2eadbe0 100644 (file)
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -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",
 };