From patchwork Wed Feb 23 14:37:24 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: wliang@stu.xidian.edu.cn X-Patchwork-Id: 12757131 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 8D7DDC433FE for ; Wed, 23 Feb 2022 15:50:44 +0000 (UTC) Received: from localhost ([::1]:43326 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nMtud-0007aW-8F for qemu-devel@archiver.kernel.org; Wed, 23 Feb 2022 10:50:43 -0500 Received: from eggs.gnu.org ([209.51.188.92]:54746) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nMsm2-00051M-Vu for qemu-devel@nongnu.org; Wed, 23 Feb 2022 09:37:47 -0500 Received: from azure-sdnproxy.icoremail.net ([52.237.72.81]:50601 helo=azure-sdnproxy-1.icoremail.net) by eggs.gnu.org with smtp (Exim 4.90_1) (envelope-from ) id 1nMslr-0006G9-5r for qemu-devel@nongnu.org; Wed, 23 Feb 2022 09:37:46 -0500 Received: by ajax-webmail-sr0414.icoremail.net (Coremail) ; Wed, 23 Feb 2022 22:37:24 +0800 (GMT+08:00) X-Originating-IP: [39.130.79.173] Date: Wed, 23 Feb 2022 22:37:24 +0800 (GMT+08:00) X-CM-HeaderCharset: UTF-8 From: wliang@stu.xidian.edu.cn To: "qemu-devel@nongnu.org" Subject: Fix a potential Use-after-free in test_blockjob_common_drain_node() (v6.2.0). X-Priority: 3 X-Mailer: Coremail Webmail Server Version XT5.0.13 build 20210401(fdb522e2) Copyright (c) 2002-2022 www.mailtech.cn mispb-ac60dc67-ddbe-4478-9127-1d3314495f10-icoremail.net MIME-Version: 1.0 Message-ID: <21fd23f8.25ce.17f2703f0f8.Coremail.wliang@stu.xidian.edu.cn> X-Coremail-Locale: zh_CN X-CM-TRANSID: AQAAfwBXSwKkRhZiLccKAA--.4020W X-CM-SenderInfo: pzolt0vj6v33wo0lvxldqovvfxof0/1tbiAQMMA1wR-vU9jgACs6 X-Coremail-Antispam: 1Ur529EdanIXcx71UUUUU7IcSsGvfJ3iIAIbVAYjsxI4VWxJw CS07vEb4IE77IF4wCS07vE1I0E4x80FVAKz4kxMIAIbVAFxVCaYxvI4VCIwcAKzIAtYxBI daVFxhVjvjDU= Received-SPF: pass client-ip=52.237.72.81; envelope-from=wliang@stu.xidian.edu.cn; helo=azure-sdnproxy-1.icoremail.net X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, HTML_MESSAGE=0.001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Wed, 23 Feb 2022 10:48:08 -0500 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi all, I find a potential Use-after-free in QEMU 6.2.0, which is in test_blockjob_common_drain_node() (./tests/unit/test-bdrv-drain.c). Specifically, at line 880, the variable 'scr' is released by the bdrv_unref(). However, at line 881, it is subsequently used as the 1st parameter of the function bdrv_set_backing_hd(). As a result, an UAF bug may be triggered. 880 bdrv_unref(src); 881 bdrv_set_backing_hd(src, src_backing, &error_abort); I believe that the problem can be fixed by invoking bdrv_unref() after the call of bdrv_set_backing_hd() rather than before it. --- bdrv_unref(src); 881 bdrv_set_backing_hd(src, src_backing, &error_abort); +++bdrv_unref(src); I'm looking forward to your confirmation. Best, Wentao --- ./tests/unit/test-bdrv-drain.c 2022-02-23 15:06:32.384786070 +0800 +++ ./tests/unit/test-bdrv-drain-PATCH.c 2022-02-23 21:16:43.444928992 +0800 @@ -877,8 +877,8 @@ BDRV_O_RDWR, &error_abort); bdrv_set_backing_hd(src_overlay, src, &error_abort); - bdrv_unref(src); bdrv_set_backing_hd(src, src_backing, &error_abort); + bdrv_unref(src); bdrv_unref(src_backing); blk_src = blk_new(qemu_get_aio_context(), BLK_PERM_ALL, BLK_PERM_ALL);