Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751507AbdLMId1 (ORCPT ); Wed, 13 Dec 2017 03:33:27 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:59918 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750737AbdLMIdY (ORCPT ); Wed, 13 Dec 2017 03:33:24 -0500 Date: Wed, 13 Dec 2017 09:33:17 +0100 From: Heiko Carstens To: Michal =?iso-8859-1?Q?Such=E1nek?= Cc: Martin Schwidefsky , Marcelo Henrique Cerri , Greg Kroah-Hartman , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] s390/decompressor: add fortify_panic as x86 has. References: <20171207103727.9461-1-msuchanek@suse.de> <20171207135507.275c5809@mschwideX1> <20171211140904.2f023b3c@kitsune.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20171211140904.2f023b3c@kitsune.suse.cz> X-TM-AS-GCONF: 00 x-cbid: 17121308-0016-0000-0000-0000050C8779 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17121308-0017-0000-0000-000028489C82 Message-Id: <20171213083317.GA6931@osiris> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-12-13_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1712130124 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3864 Lines: 101 On Mon, Dec 11, 2017 at 02:09:04PM +0100, Michal Such?nek wrote: > Hello, > > On Thu, 7 Dec 2017 13:55:07 +0100 > Martin Schwidefsky wrote: > > > On Thu, 7 Dec 2017 11:37:27 +0100 > > Michal Suchanek wrote: > > > > > Fix following error: > > > > > > LD arch/s390/boot/compressed/vmlinux > > > drivers/s390/char/sclp_early_core.o: In function `memcpy': > > > ../include/linux/string.h:340: undefined reference to > > > `fortify_panic' make[4]: *** > > > [../arch/s390/boot/compressed/Makefile:29: > > > arch/s390/boot/compressed/vmlinux] Error 1 > > > > > > Fixes: 79962038dffa ("s390: add support for FORTIFY_SOURCE") > > > Signed-off-by: Michal Suchanek > > > --- > > > arch/s390/boot/compressed/misc.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/arch/s390/boot/compressed/misc.c > > > b/arch/s390/boot/compressed/misc.c index cecf38b9ec82..e79c4499c548 > > > 100644 --- a/arch/s390/boot/compressed/misc.c > > > +++ b/arch/s390/boot/compressed/misc.c > > > @@ -174,3 +174,7 @@ unsigned long decompress_kernel(void) > > > return (unsigned long) output; > > > } > > > > > > +void fortify_panic(const char *name) > > > +{ > > > + error("detected buffer overflow"); > > > +} > > > > Odd, the current linux master tree builds just fine with > > CONFIG_FORTIFY_SOURCE=y. There *is* a reference to fortify_panic in > > drivers/s390/char/sclp_early.o. This object is included in the link > > for the compressed vmlinux, but the function that contains the call > > to fortify_panic is not included in the compressed image. I wonder > > what causes this difference in behavior. > > > > The patch makes sense though and I will add it to the queue. > > > > It probably depends on the config. > > FWIW attaching the config that fails to build for me. Yes, with that configuration it is reproducable. However I disagree with the fix. We have a call to fortify_panic() within sclp_early_core.c which is our console driver. If that would ever trigger the result would be an endless loop (error() would call the console driver again). This would repeat until we hit an addressing exception or code gets overwritten due to the ever increasing stack. At some point we simply have to trust the code. That's also why I disabled FORTIFY_SOURCE for a couple of other files which contain early code. Therefore the simple solution would be to just disable FORTIFY_SOURCE for the early sclp code as well. The patch below will do that: >From 4ec2a3fd66bb5b1da35807bc2e382f9b8d9eebb8 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Wed, 13 Dec 2017 09:21:59 +0100 Subject: [PATCH] s390/sclp: disable FORTIFY_SOURCE for early sclp code Michal Suchanek reported the following compile error with FORTIFY_SOURCE enabled: drivers/s390/char/sclp_early_core.o: In function `memcpy': include/linux/string.h:340: undefined reference to `fortify_panic' To fix this simply disable FORTIFY_SOURCE on the early sclp code as well, which I forgot on the initial commit. Fixes: 79962038dffa ("s390: add support for FORTIFY_SOURCE") Reported-by: Michal Suchanek Signed-off-by: Heiko Carstens --- drivers/s390/char/Makefile | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/s390/char/Makefile b/drivers/s390/char/Makefile index 05ac6ba15a53..614b44e70a28 100644 --- a/drivers/s390/char/Makefile +++ b/drivers/s390/char/Makefile @@ -17,6 +17,8 @@ CFLAGS_REMOVE_sclp_early_core.o += $(CC_FLAGS_MARCH) CFLAGS_sclp_early_core.o += -march=z900 endif +CFLAGS_sclp_early_core.o += -D__NO_FORTIFY + obj-y += ctrlchar.o keyboard.o defkeymap.o sclp.o sclp_rw.o sclp_quiesce.o \ sclp_cmd.o sclp_config.o sclp_cpi_sys.o sclp_ocf.o sclp_ctl.o \ sclp_early.o sclp_early_core.o -- 2.13.5