From patchwork Wed Aug 14 12:05:21 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Prasad Pandit X-Patchwork-Id: 11093813 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 757E76C5 for ; Wed, 14 Aug 2019 12:08:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5D8BC204FB for ; Wed, 14 Aug 2019 12:08:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4DD6A27F98; Wed, 14 Aug 2019 12:08:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id A0E87204FB for ; Wed, 14 Aug 2019 12:08:05 +0000 (UTC) Received: from localhost ([::1]:59922 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hxs4S-0004Yl-PB for patchwork-qemu-devel@patchwork.kernel.org; Wed, 14 Aug 2019 08:08:04 -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) 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_Mathieu-Daud=C3=A9?= , Stefano Garzarella Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP 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[] = { /* Flag set if this is a tagged command. */ #define LSI_TAG_VALID (1 << 16) +/* 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) s->istat1 |= LSI_ISTAT1_SRUN; again: - insn_processed++; + if (++insn_processed > LSI_MAX_INSN) { + /* Some windows drivers make the device spin waiting for a memory + location to change. If we have been executed a lot of code then + assume this is the case and force an unexpected device disconnect. + This is apparently sufficient to beat the drivers into submission. + */ + 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 = 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 == LSI_NOWAIT) { - /* Some windows drivers make the device spin waiting for a memory - location to change. If we have been executed a lot of code then - assume this is the case and force an unexpected device disconnect. - This is apparently sufficient to beat the drivers into submission. - */ - 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 == LSI_NOWAIT) { + if (s->istat1 & LSI_ISTAT1_SRUN && s->waiting == 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 &= 0x00ffffff; s->dsp |= val << 24; + /* + * FIXME: if s->waiting != LSI_NOWAIT, this will only execute one + * instruction. Is this correct? + */ if ((s->dmode & LSI_DMODE_MAN) == 0 && (s->istat1 & LSI_ISTAT1_SRUN) == 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 = val & ~(LSI_DCNTL_PFF | LSI_DCNTL_STD); + /* + * FIXME: if s->waiting != LSI_NOWAIT, this will only execute one + * instruction. Is this correct? + */ if ((val & LSI_DCNTL_STD) && (s->istat1 & LSI_ISTAT1_SRUN) == 0) lsi_execute_script(s); break;