[V36,20/29] x86/mmiotrace: Lock down the testmmiotrace module
diff mbox series

Message ID 20190718194415.108476-21-matthewgarrett@google.com
State New
Headers show
Series
  • security: Add kernel lockdown functionality
Related show

Commit Message

Matthew Garrett July 18, 2019, 7:44 p.m. UTC
From: David Howells <dhowells@redhat.com>

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>
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
---
 arch/x86/mm/testmmiotrace.c  | 5 +++++
 include/linux/security.h     | 1 +
 security/lockdown/lockdown.c | 1 +
 3 files changed, 7 insertions(+)

Comments

Kees Cook July 18, 2019, 9:06 p.m. UTC | #1
On Thu, Jul 18, 2019 at 12:44:06PM -0700, Matthew Garrett wrote:
> From: David Howells <dhowells@redhat.com>
> 
> 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

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> Signed-off-by: Matthew Garrett <mjg59@google.com>
> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.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
> ---
>  arch/x86/mm/testmmiotrace.c  | 5 +++++
>  include/linux/security.h     | 1 +
>  security/lockdown/lockdown.c | 1 +
>  3 files changed, 7 insertions(+)
> 
> diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
> index 0881e1ff1e58..a8bd952e136d 100644
> --- 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 43fa3486522b..3f7b6a4cd65a 100644
> --- 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 5177938cfa0d..37b7d7e50474 100644
> --- 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",
>  };
> -- 
> 2.22.0.510.g264f2c817a-goog
>

Patch
diff mbox series

diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
index 0881e1ff1e58..a8bd952e136d 100644
--- 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 43fa3486522b..3f7b6a4cd65a 100644
--- 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 5177938cfa0d..37b7d7e50474 100644
--- 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",
 };