Re: [PATCH V40 14/29] ACPI: Limit access to custom_method when the kernel is locked down

2019-08-20 Thread Rafael J. Wysocki 
On Tuesday, August 20, 2019 2:17:50 AM CEST Matthew Garrett wrote:
> From: Matthew Garrett 
> 
> custom_method effectively allows arbitrary access to system memory, making
> it possible for an attacker to circumvent restrictions on module loading.
> Disable it if the kernel is locked down.
> 
> Signed-off-by: Matthew Garrett 
> Signed-off-by: David Howells 
> Reviewed-by: Kees Cook 
> cc: linux-a...@vger.kernel.org
> Signed-off-by: James Morris 

Acked-by: Rafael J. Wysocki 

> ---
>  drivers/acpi/custom_method.c | 6 ++
>  include/linux/security.h | 1 +
>  security/lockdown/lockdown.c | 1 +
>  3 files changed, 8 insertions(+)
> 
> diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
> index b2ef4c2ec955..7031307becd7 100644
> --- a/drivers/acpi/custom_method.c
> +++ b/drivers/acpi/custom_method.c
> @@ -9,6 +9,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  
>  #include "internal.h"
>  
> @@ -29,6 +30,11 @@ static ssize_t cm_write(struct file *file, const char 
> __user * user_buf,
>  
>   struct acpi_table_header table;
>   acpi_status status;
> + int ret;
> +
> + ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
> + if (ret)
> + return ret;
>  
>   if (!(*ppos)) {
>   /* parse the table header to get the table length */
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 010637a79eac..390e39395112 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -110,6 +110,7 @@ enum lockdown_reason {
>   LOCKDOWN_PCI_ACCESS,
>   LOCKDOWN_IOPORT,
>   LOCKDOWN_MSR,
> + LOCKDOWN_ACPI_TABLES,
>   LOCKDOWN_INTEGRITY_MAX,
>   LOCKDOWN_CONFIDENTIALITY_MAX,
>  };
> diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
> index b1c1c72440d5..6d44db0ddffa 100644
> --- a/security/lockdown/lockdown.c
> +++ b/security/lockdown/lockdown.c
> @@ -25,6 +25,7 @@ static char 
> *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
>   [LOCKDOWN_PCI_ACCESS] = "direct PCI access",
>   [LOCKDOWN_IOPORT] = "raw io port access",
>   [LOCKDOWN_MSR] = "raw MSR access",
> + [LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
>   [LOCKDOWN_INTEGRITY_MAX] = "integrity",
>   [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
>  };
>

[PATCH V40 14/29] ACPI: Limit access to custom_method when the kernel is locked down

2019-08-19 Thread Matthew Garrett 
From: Matthew Garrett 

custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to circumvent restrictions on module loading.
Disable it if the kernel is locked down.

Signed-off-by: Matthew Garrett 
Signed-off-by: David Howells 
Reviewed-by: Kees Cook 
cc: linux-a...@vger.kernel.org
Signed-off-by: James Morris 
---
 drivers/acpi/custom_method.c | 6 ++
 include/linux/security.h | 1 +
 security/lockdown/lockdown.c | 1 +
 3 files changed, 8 insertions(+)

diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index b2ef4c2ec955..7031307becd7 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -9,6 +9,7 @@
 #include 
 #include 
 #include 
+#include 
 
 #include "internal.h"
 
@@ -29,6 +30,11 @@ static ssize_t cm_write(struct file *file, const char __user 
* user_buf,
 
struct acpi_table_header table;
acpi_status status;
+   int ret;
+
+   ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
+   if (ret)
+   return ret;
 
if (!(*ppos)) {
/* parse the table header to get the table length */
diff --git a/include/linux/security.h b/include/linux/security.h
index 010637a79eac..390e39395112 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -110,6 +110,7 @@ enum lockdown_reason {
LOCKDOWN_PCI_ACCESS,
LOCKDOWN_IOPORT,
LOCKDOWN_MSR,
+   LOCKDOWN_ACPI_TABLES,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
 };
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index b1c1c72440d5..6d44db0ddffa 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -25,6 +25,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] 
= {
[LOCKDOWN_PCI_ACCESS] = "direct PCI access",
[LOCKDOWN_IOPORT] = "raw io port access",
[LOCKDOWN_MSR] = "raw MSR access",
+   [LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
[LOCKDOWN_INTEGRITY_MAX] = "integrity",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };
-- 
2.23.0.rc1.153.gdeed80330f-goog