From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755242AbcHBTOi (ORCPT ); Tue, 2 Aug 2016 15:14:38 -0400 Received: from mail-wm0-f52.google.com ([74.125.82.52]:34953 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753794AbcHBTO1 (ORCPT ); Tue, 2 Aug 2016 15:14:27 -0400 MIME-Version: 1.0 In-Reply-To: <87eg67ooe5.fsf@concordia.ellerman.id.au> References: <1465336628-18219-1-git-send-email-keescook@chromium.org> <1465336628-18219-4-git-send-email-keescook@chromium.org> <87h9b4oebf.fsf@concordia.ellerman.id.au> <87eg67ooe5.fsf@concordia.ellerman.id.au> From: Kees Cook Date: Tue, 2 Aug 2016 12:12:33 -0700 X-Google-Sender-Auth: JRMgunz8HPC5lp-VAnsELaD6ohw Message-ID: Subject: Re: [kernel-hardening] Re: Linker segfault on powerpc when CONFIG_LKDTM=y (was Re: [kernel-hardening] [PATCH 3/5] lkdtm: add function for testing .rodata section) To: Michael Ellerman Cc: "kernel-hardening@lists.openwall.com" , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , "David S. Miller" , Mauro Carvalho Chehab , Jiri Slaby , Guenter Roeck , LKML , "linuxppc-dev@lists.ozlabs.org" , Anton Blanchard , Alan Modra Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 1, 2016 at 8:12 PM, Michael Ellerman wrote: > Kees Cook writes: > >> On Mon, Aug 1, 2016 at 5:37 AM, Michael Ellerman wrote: >>> Kees Cook writes: >>> >>>> This adds a function that lives in the .rodata section. The section >>>> flags are corrected using objcopy since there is no way with gcc to >>>> declare section flags in an architecture-agnostic way. >>>> >>>> Signed-off-by: Kees Cook >>>> --- >>>> drivers/misc/Makefile | 7 +++++++ >>>> drivers/misc/lkdtm.h | 6 ++++++ >>>> drivers/misc/lkdtm_core.c | 24 +++++++++++++++++------- >>>> drivers/misc/lkdtm_rodata.c | 10 ++++++++++ >>>> 4 files changed, 40 insertions(+), 7 deletions(-) >>>> create mode 100644 drivers/misc/lkdtm.h >>>> create mode 100644 drivers/misc/lkdtm_rodata.c >>> >>> This is blowing up my linker :( >>> >>> scripts/link-vmlinux.sh: line 52: 36260 Segmentation fault (core dumped) ${LD} ${LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} -T ${lds} ${KBUILD_VMLINUX_INIT} --start-group ${KBUILD_VMLINUX_MAIN} --end-group ${1} >>> >>> Haven't had a chance to debug it further. >> >> Argh. Do you want a quick fix for this now? I can add a PPC CONFIG >> blacklist for the rodata check, maybe? > > Nah that's OK, none of our defconfigs have it enabled so it's not a real > blocker. It also builds OK as a module - though I haven't tested the > result yet. Okay, I'll leave it as is. >> Also, what version of gcc? I'll see if I can reproduce this with a >> cross compiler... > > The original hit was with gcc-5.3 (which is actually a x86->ppc cross): > > http://kisskb.ellerman.id.au/kisskb/buildresult/12762730/ > > But I can also reproduce with 5.4, and 6.1.0. > > Interestingly I *can't* reproduce with the Ubuntu x86->ppc cross > (5.4.0-6ubuntu1~16.04.1). Oh, weird. Well, that does explains my lack of hitting the problem, though: that's the cross compiler I was using. :P > Those toolchains are all using binutils 2.26 AFAIK. I wonder if this is some gold vs bfd issue, or a specific bug that got fixed in the Ubuntu tree but hasn't landed in 6.1 or 5.4 (??) > Going back to a really old toolchain (gcc 4.6.3/binutils 2.22) it does > build but I get these warnings: > > powerpc64-linux-ld: drivers/misc/built-in.o: .opd is not a regular array of opd entries > powerpc64-linux-ld: drivers/built-in.o: .opd is not a regular array of opd entries How strange. I wonder if there's some corner case of the objcopy that is wrong... > So probably don't worry about it and we'll try and work it out on our end. Okay, sounds good. -Kees -- Kees Cook Chrome OS & Brillo Security From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-x22a.google.com (mail-wm0-x22a.google.com [IPv6:2a00:1450:400c:c09::22a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3s3m6t4bb3zDqQn for ; Wed, 3 Aug 2016 05:12:37 +1000 (AEST) Received: by mail-wm0-x22a.google.com with SMTP id i5so304334378wmg.0 for ; Tue, 02 Aug 2016 12:12:37 -0700 (PDT) MIME-Version: 1.0 Sender: keescook@google.com In-Reply-To: <87eg67ooe5.fsf@concordia.ellerman.id.au> References: <1465336628-18219-1-git-send-email-keescook@chromium.org> <1465336628-18219-4-git-send-email-keescook@chromium.org> <87h9b4oebf.fsf@concordia.ellerman.id.au> <87eg67ooe5.fsf@concordia.ellerman.id.au> From: Kees Cook Date: Tue, 2 Aug 2016 12:12:33 -0700 Message-ID: Subject: Re: [kernel-hardening] Re: Linker segfault on powerpc when CONFIG_LKDTM=y (was Re: [kernel-hardening] [PATCH 3/5] lkdtm: add function for testing .rodata section) To: Michael Ellerman Cc: "kernel-hardening@lists.openwall.com" , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , "David S. Miller" , Mauro Carvalho Chehab , Jiri Slaby , Guenter Roeck , LKML , "linuxppc-dev@lists.ozlabs.org" , Anton Blanchard , Alan Modra Content-Type: text/plain; charset=UTF-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Aug 1, 2016 at 8:12 PM, Michael Ellerman wrote: > Kees Cook writes: > >> On Mon, Aug 1, 2016 at 5:37 AM, Michael Ellerman wrote: >>> Kees Cook writes: >>> >>>> This adds a function that lives in the .rodata section. The section >>>> flags are corrected using objcopy since there is no way with gcc to >>>> declare section flags in an architecture-agnostic way. >>>> >>>> Signed-off-by: Kees Cook >>>> --- >>>> drivers/misc/Makefile | 7 +++++++ >>>> drivers/misc/lkdtm.h | 6 ++++++ >>>> drivers/misc/lkdtm_core.c | 24 +++++++++++++++++------- >>>> drivers/misc/lkdtm_rodata.c | 10 ++++++++++ >>>> 4 files changed, 40 insertions(+), 7 deletions(-) >>>> create mode 100644 drivers/misc/lkdtm.h >>>> create mode 100644 drivers/misc/lkdtm_rodata.c >>> >>> This is blowing up my linker :( >>> >>> scripts/link-vmlinux.sh: line 52: 36260 Segmentation fault (core dumped) ${LD} ${LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} -T ${lds} ${KBUILD_VMLINUX_INIT} --start-group ${KBUILD_VMLINUX_MAIN} --end-group ${1} >>> >>> Haven't had a chance to debug it further. >> >> Argh. Do you want a quick fix for this now? I can add a PPC CONFIG >> blacklist for the rodata check, maybe? > > Nah that's OK, none of our defconfigs have it enabled so it's not a real > blocker. It also builds OK as a module - though I haven't tested the > result yet. Okay, I'll leave it as is. >> Also, what version of gcc? I'll see if I can reproduce this with a >> cross compiler... > > The original hit was with gcc-5.3 (which is actually a x86->ppc cross): > > http://kisskb.ellerman.id.au/kisskb/buildresult/12762730/ > > But I can also reproduce with 5.4, and 6.1.0. > > Interestingly I *can't* reproduce with the Ubuntu x86->ppc cross > (5.4.0-6ubuntu1~16.04.1). Oh, weird. Well, that does explains my lack of hitting the problem, though: that's the cross compiler I was using. :P > Those toolchains are all using binutils 2.26 AFAIK. I wonder if this is some gold vs bfd issue, or a specific bug that got fixed in the Ubuntu tree but hasn't landed in 6.1 or 5.4 (??) > Going back to a really old toolchain (gcc 4.6.3/binutils 2.22) it does > build but I get these warnings: > > powerpc64-linux-ld: drivers/misc/built-in.o: .opd is not a regular array of opd entries > powerpc64-linux-ld: drivers/built-in.o: .opd is not a regular array of opd entries How strange. I wonder if there's some corner case of the objcopy that is wrong... > So probably don't worry about it and we'll try and work it out on our end. Okay, sounds good. -Kees -- Kees Cook Chrome OS & Brillo Security