From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752212AbdLDMIJ (ORCPT ); Mon, 4 Dec 2017 07:08:09 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58680 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750786AbdLDMII (ORCPT ); Mon, 4 Dec 2017 07:08:08 -0500 Date: Mon, 4 Dec 2017 13:08:08 +0100 From: Greg KH To: Alexei Starovoitov Cc: Sandipan Das , akpm@linux-foundation.org, kstewart@linuxfoundation.org, linux-kernel@vger.kernel.org, yhs@fb.com, atish.patra@oracle.com, Brendan Gregg , Daniel Borkmann Subject: Re: [PATCH] compiler, clang: handle randomizable anonymous structs Message-ID: <20171204120808.GB4478@kroah.com> References: <20171109064645.25581-1-sandipan@linux.vnet.ibm.com> <20171202021806.7ilhguxt4llil6cs@ast-mbp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171202021806.7ilhguxt4llil6cs@ast-mbp> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 01, 2017 at 06:18:08PM -0800, Alexei Starovoitov wrote: > On Thu, Nov 09, 2017 at 12:16:45PM +0530, Sandipan Das wrote: > > The GCC randomize layout plugin can randomize the member > > offsets of sensitive kernel data structures. To use this > > feature, certain annotations and members are added to the > > structures which affect the member offsets even if this > > plugin is not used. > > > > All of these structures are completely randomized, except > > for task_struct which leaves out some of its members. All > > the other members are wrapped within an anonymous struct > > with the __randomize_layout attribute. This is done using > > the randomized_struct_fields_start and > > randomized_struct_fields_end defines. When the plugin is > > disabled, the behaviour of this attribute can vary based > > on the GCC version. For GCC 5.1+, this attribute maps to > > __designated_init otherwise it is just an empty define > > but the anonymous structure is still present. For other > > compilers, both randomized_struct_fields_start and > > randomized_struct_fields_end default to empty defines > > meaning the anonymous structure is not introduced at all. > > So, if a module compiled with Clang, such as a BPF program, > > needs to access task_struct fields such as pid and comm, > > the offsets of these members as recognized by Clang are > > different from those recognized by modules compiled with > > GCC. If GCC 4.6+ is used to build the kernel, this can be > > solved by introducing appropriate defines for Clang so > > that the anonymous structure is seen when determining the > > offsets for the members. > > > > Signed-off-by: Sandipan Das > > --- > > include/linux/compiler-clang.h | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > > index 54dfef70a072..780b1242bf24 100644 > > --- a/include/linux/compiler-clang.h > > +++ b/include/linux/compiler-clang.h > > @@ -16,3 +16,6 @@ > > * with any version that can compile the kernel > > */ > > #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) > > + > > +#define randomized_struct_fields_start struct { > > +#define randomized_struct_fields_end }; > > -- > > 2.13.6 > > Andrew or Greg, > could you please pull this patch into 4.13 and 4.14 releases as well ? > Sorry we missed the stable tag when submitting it originally. > It is commit 4ca59b14e588 ("include/linux/compiler-clang.h: handle randomizable anonymous structs") 4.13 is end-of-life, but 4.14 is not, so I've queued it up for that one. thanks, greg k-h