Re: [PATCH 04/10] ACPI: Limit access to custom_method

[Lenny Szubowicz]

----- Original Message -----
> From: "Matthew Garrett" <matthew.garrett@xxxxxxxxxx>
> To: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-efi@xxxxxxxxxxxxxxx, jwboyer@xxxxxxxxxx, keescook@xxxxxxxxxxxx, "Matthew Garrett"
> <matthew.garrett@xxxxxxxxxx>
> Sent: Monday, August 19, 2013 12:10:13 PM
> Subject: [PATCH 04/10] ACPI: Limit access to custom_method
> 
> custom_method effectively allows arbitrary access to system memory, making
> it possible for an attacker to circumvent restrictions on module loading.
> Disable it if any such restrictions have been enabled.
> 
> Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
> ---
>  drivers/acpi/custom_method.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
> index 12b62f2..55a013f 100644
> --- a/drivers/acpi/custom_method.c
> +++ b/drivers/acpi/custom_method.c
> @@ -7,6 +7,7 @@
>  #include <linux/kernel.h>
>  #include <linux/uaccess.h>
>  #include <linux/debugfs.h>
> +#include <linux/module.h>
>  #include <acpi/acpi_drivers.h>
>  
>  #include "internal.h"
> @@ -29,6 +30,9 @@ static ssize_t cm_write(struct file *file, const char
> __user * user_buf,
>  	struct acpi_table_header table;
>  	acpi_status status;
>  
> +	if (secure_modules())
> +		return -EPERM;
> +
>  	if (!(*ppos)) {
>  		/* parse the table header to get the table length */
>  		if (count <= sizeof(struct acpi_table_header))
> --
> 1.8.3.1
> 
> --
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Nit: Don't add a second include of linux/module.h.

                      -Lenny.
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