Re: [PATCH V3 04/11] ACPI: Limit access to custom_method

[James Morris]

On Tue, 3 Sep 2013, Matthew Garrett wrote:

> 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>

Reviewed-by: James Morris <jmorris@xxxxxxxxx>




> ---
>  drivers/acpi/custom_method.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
> index 12b62f2..50647b3 100644
> --- a/drivers/acpi/custom_method.c
> +++ b/drivers/acpi/custom_method.c
> @@ -29,6 +29,9 @@ 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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-- 
James Morris
<jmorris@xxxxxxxxx>
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