From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A81FC28CC3 for ; Fri, 31 May 2019 14:58:04 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 672B125173 for ; Fri, 31 May 2019 14:58:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 672B125173 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:44871 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hWiyp-0003pr-Kt for qemu-devel@archiver.kernel.org; Fri, 31 May 2019 10:58:03 -0400 Received: from eggs.gnu.org ([209.51.188.92]:50892) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hWixM-0002iA-Lf for qemu-devel@nongnu.org; Fri, 31 May 2019 10:56:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hWixL-0004aI-El for qemu-devel@nongnu.org; Fri, 31 May 2019 10:56:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60154) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hWixL-0004ZD-8u; Fri, 31 May 2019 10:56:31 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6433530C5846; Fri, 31 May 2019 14:56:20 +0000 (UTC) Received: from t460s.redhat.com (ovpn-116-233.ams2.redhat.com [10.36.116.233]) by smtp.corp.redhat.com (Postfix) with ESMTP id A6EA01759D; Fri, 31 May 2019 14:56:17 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Date: Fri, 31 May 2019 16:56:08 +0200 Message-Id: <20190531145608.28183-3-david@redhat.com> In-Reply-To: <20190531145608.28183-1-david@redhat.com> References: <20190531145608.28183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Fri, 31 May 2019 14:56:25 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v1 2/2] s390x/tcg: Store only the necessary amount of doublewords for STFLE X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Stefan Liebler , Thomas Huth , David Hildenbrand , Andreas Krebbel , Cornelia Huck , qemu-s390x@nongnu.org, Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The PoP (z14, 7-382) says: Doublewords to the right of the doubleword in which the highest-numbered facility bit is assigned for a model may or may not be stored. However, stack protection in certain binaries can't deal with that. "gzip" example code: f1b4: a7 08 00 03 lhi %r0,3 f1b8: b2 b0 f0 a0 stfle 160(%r15) f1bc: e3 20 f0 b2 00 90 llgc %r2,178(%r15) f1c2: c0 2b 00 00 00 01 nilf %r2,1 f1c8: b2 4f 00 10 ear %r1,%a0 f1cc: b9 14 00 22 lgfr %r2,%r2 f1d0: eb 11 00 20 00 0d sllg %r1,%r1,32 f1d6: b2 4f 00 11 ear %r1,%a1 f1da: d5 07 f0 b8 10 28 clc 184(8,%r15),40(%r1) f1e0: a7 74 00 06 jne f1ec f1e4: eb ef f1 30 00 04 lmg %r14,%r15,304(%r15) f1ea: 07 fe br %r14 f1ec: c0 e5 ff ff 9d 6e brasl %r14,2cc8 <__stack_chk_fail@p= lt> In QEMU, we currently have: max_bytes =3D 24 the code asks for (3 + 1) doublewords =3D=3D 32 bytes. If we write 32 bytes instead of only 24, and return "2 + 1" doublewords ("one less than the number of doulewords needed to contain all of the facility bits"), the example code detects a stack corruption. In my opinion, the code is wrong. However, it seems to work fine on real machines. So let's limit storing to the minimum of the requested and the maximum doublewords. Cc: Stefan Liebler Cc: Andreas Krebbel Signed-off-by: David Hildenbrand --- target/s390x/misc_helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c index 34476134a4..b561c5781b 100644 --- a/target/s390x/misc_helper.c +++ b/target/s390x/misc_helper.c @@ -678,7 +678,7 @@ uint32_t HELPER(stfle)(CPUS390XState *env, uint64_t a= ddr) =20 prepare_stfl(); max_bytes =3D ROUND_UP(used_stfl_bytes, 8); - for (i =3D 0; i < count_bytes; ++i) { + for (i =3D 0; i < MIN(count_bytes, max_bytes); ++i) { cpu_stb_data_ra(env, addr + i, stfl_bytes[i], ra); } =20 --=20 2.20.1