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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,URIBL_SBL,URIBL_SBL_A 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 C2EF2C433FF for ; Wed, 14 Aug 2019 12:08:20 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 991F2205F4 for ; Wed, 14 Aug 2019 12:08:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 991F2205F4 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 ([::1]:59922 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hxs4h-0004Yl-QG for qemu-devel@archiver.kernel.org; Wed, 14 Aug 2019 08:08:19 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41544) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hxs3y-00048d-8L for qemu-devel@nongnu.org; Wed, 14 Aug 2019 08:07:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hxs3w-0007Rn-VO for qemu-devel@nongnu.org; Wed, 14 Aug 2019 08:07:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60638) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hxs3w-0007RY-OM for qemu-devel@nongnu.org; Wed, 14 Aug 2019 08:07:32 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0F23C7BDA7; Wed, 14 Aug 2019 12:07:32 +0000 (UTC) Received: from localhost.localdomain (unknown [10.74.10.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0ABBB34913; Wed, 14 Aug 2019 12:07:24 +0000 (UTC) From: P J P To: Paolo Bonzini Date: Wed, 14 Aug 2019 17:35:21 +0530 Message-Id: <20190814120521.20907-1-ppandit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Wed, 14 Aug 2019 12:07:32 +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 v4] scsi: lsi: exit infinite loop while executing script (CVE-2019-12068) X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Prasad J Pandit , Marcelo Tosatti , Mark Cave-Ayland , QEMU Developers , Bugs SysSec , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Stefano Garzarella Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Prasad J Pandit When executing script in lsi_execute_script(), the LSI scsi adapter emulator advances 's->dsp' index to read next opcode. This can lead to an infinite loop if the next opcode is empty. Exit such loop after 10k iterations. Reported-by: Bugs SysSec Signed-off-by: Prasad J Pandit --- hw/scsi/lsi53c895a.c | 41 +++++++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 14 deletions(-) Update v4: slightly modify the check and exit -> https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg02304.html diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c index 10468c1ec1..72f7b59ab5 100644 --- a/hw/scsi/lsi53c895a.c +++ b/hw/scsi/lsi53c895a.c @@ -185,6 +185,9 @@ static const char *names[] =3D { /* Flag set if this is a tagged command. */ #define LSI_TAG_VALID (1 << 16) =20 +/* Maximum instructions to process. */ +#define LSI_MAX_INSN 10000 + typedef struct lsi_request { SCSIRequest *req; uint32_t tag; @@ -1132,7 +1135,21 @@ static void lsi_execute_script(LSIState *s) =20 s->istat1 |=3D LSI_ISTAT1_SRUN; again: - insn_processed++; + if (++insn_processed > LSI_MAX_INSN) { + /* Some windows drivers make the device spin waiting for a memor= y + location to change. If we have been executed a lot of code t= hen + assume this is the case and force an unexpected device discon= nect. + This is apparently sufficient to beat the drivers into submis= sion. + */ + if (!(s->sien0 & LSI_SIST0_UDC)) { + qemu_log_mask(LOG_GUEST_ERROR, + "lsi_scsi: inf. loop with UDC masked"); + } + lsi_script_scsi_interrupt(s, LSI_SIST0_UDC, 0); + lsi_disconnect(s); + trace_lsi_execute_script_stop(); + return; + } insn =3D read_dword(s, s->dsp); if (!insn) { /* If we receive an empty opcode increment the DSP by 4 bytes @@ -1569,19 +1586,7 @@ again: } } } - if (insn_processed > 10000 && s->waiting =3D=3D LSI_NOWAIT) { - /* Some windows drivers make the device spin waiting for a memor= y - location to change. If we have been executed a lot of code t= hen - assume this is the case and force an unexpected device discon= nect. - This is apparently sufficient to beat the drivers into submis= sion. - */ - if (!(s->sien0 & LSI_SIST0_UDC)) { - qemu_log_mask(LOG_GUEST_ERROR, - "lsi_scsi: inf. loop with UDC masked"); - } - lsi_script_scsi_interrupt(s, LSI_SIST0_UDC, 0); - lsi_disconnect(s); - } else if (s->istat1 & LSI_ISTAT1_SRUN && s->waiting =3D=3D LSI_NOWA= IT) { + if (s->istat1 & LSI_ISTAT1_SRUN && s->waiting =3D=3D LSI_NOWAIT) { if (s->dcntl & LSI_DCNTL_SSM) { lsi_script_dma_interrupt(s, LSI_DSTAT_SSI); } else { @@ -1969,6 +1974,10 @@ static void lsi_reg_writeb(LSIState *s, int offset= , uint8_t val) case 0x2f: /* DSP[24:31] */ s->dsp &=3D 0x00ffffff; s->dsp |=3D val << 24; + /* + * FIXME: if s->waiting !=3D LSI_NOWAIT, this will only execute = one + * instruction. Is this correct? + */ if ((s->dmode & LSI_DMODE_MAN) =3D=3D 0 && (s->istat1 & LSI_ISTAT1_SRUN) =3D=3D 0) lsi_execute_script(s); @@ -1987,6 +1996,10 @@ static void lsi_reg_writeb(LSIState *s, int offset= , uint8_t val) break; case 0x3b: /* DCNTL */ s->dcntl =3D val & ~(LSI_DCNTL_PFF | LSI_DCNTL_STD); + /* + * FIXME: if s->waiting !=3D LSI_NOWAIT, this will only execute = one + * instruction. Is this correct? + */ if ((val & LSI_DCNTL_STD) && (s->istat1 & LSI_ISTAT1_SRUN) =3D=3D= 0) lsi_execute_script(s); break; --=20 2.21.0