Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757412Ab1DMAVz (ORCPT ); Tue, 12 Apr 2011 20:21:55 -0400 Received: from smtp.outflux.net ([198.145.64.163]:41048 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751847Ab1DMAVy (ORCPT ); Tue, 12 Apr 2011 20:21:54 -0400 Date: Tue, 12 Apr 2011 17:20:59 -0700 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Len Brown , linux-acpi@vger.kernel.org Subject: Re: [PATCH] acpi: create CONFIG item for debugfs custom_method Message-ID: <20110413002059.GN4398@outflux.net> References: <20110222193250.GA23913@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110222193250.GA23913@outflux.net> Organization: Canonical X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2427 Lines: 74 Hi, Any news on this? I think it's a no-brainer to let this be CONFIG-able. Thanks! -Kees On Tue, Feb 22, 2011 at 11:32:50AM -0800, Kees Cook wrote: > Since /sys/kernel/debug/acpi/custom_method can be used to write arbitrary > kernel memory (http://jon.oberheide.org/files/american-sign-language.c), > it should be able to be left out of the kernel for system owners that > want to be as defensive as possible to potential attacks, even from the > root user. See as examples: CONFIG_DEVKMEM, CONFIG_STRICT_DEVMEM, and > /proc/sys/kernel/modules_disabled. > > Signed-off-by: Kees Cook > --- > drivers/acpi/Kconfig | 10 ++++++++++ > drivers/acpi/debugfs.c | 2 ++ > 2 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig > index 2aa042a..726b7ea 100644 > --- a/drivers/acpi/Kconfig > +++ b/drivers/acpi/Kconfig > @@ -381,6 +381,16 @@ config ACPI_HED > which is used to report some hardware errors notified via > SCI, mainly the corrected errors. > > +config ACPI_DEBUG_CUSTOM_METHOD > + bool "Debugging: Custom Method Insertion" > + depends on DEBUG_FS > + default n > + help > + This creates the debugfs interface file "acpi/custom_method" > + used for loading custom ACPI methods. Note that this allows > + arbitrary kernel memory writing by the root user and is not > + recommended for normal systems. > + > source "drivers/acpi/apei/Kconfig" > > endif # ACPI > diff --git a/drivers/acpi/debugfs.c b/drivers/acpi/debugfs.c > index 5df67f1..0240b15 100644 > --- a/drivers/acpi/debugfs.c > +++ b/drivers/acpi/debugfs.c > @@ -20,6 +20,7 @@ module_param_named(aml_debug_output, acpi_gbl_enable_aml_debug_object, > MODULE_PARM_DESC(aml_debug_output, > "To enable/disable the ACPI Debug Object output."); > > +#ifdef CONFIG_ACPI_DEBUG_CUSTOM_METHOD > /* /sys/kernel/debug/acpi/custom_method */ > > static ssize_t cm_write(struct file *file, const char __user * user_buf, > @@ -92,3 +93,4 @@ err: > debugfs_remove(acpi_dir); > return -EINVAL; > } > +#endif > -- > 1.7.2.3 > > -- > Kees Cook > Ubuntu Security Team -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/