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=-14.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 B6C3DC433DF for ; Tue, 18 Aug 2020 18:12:31 +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 81937206B5 for ; Tue, 18 Aug 2020 18:12:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="NK90NhIi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81937206B5 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=crudebyte.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33778 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8662-0004pM-Hz for qemu-devel@archiver.kernel.org; Tue, 18 Aug 2020 14:12:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41168) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k864z-00046p-5W for qemu-devel@nongnu.org; Tue, 18 Aug 2020 14:11:25 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:43597) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k864v-0003yc-MQ for qemu-devel@nongnu.org; Tue, 18 Aug 2020 14:11:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=QCJzFVU+GF/ZG0svzDimi/WsrT0ZoCs7k2MDXGSZeGI=; b=NK90NhIiWfoXm4pFndjKZzbJeF kq3h9m9XCbu3e/A2SRZJyji53h6x65paCN+nbY+aA7TfI+78+4Wgse+c06r+1vHn2HyxX6TXpqBV0 vNfzRNtnFpyY0NpfuBSNNlFuUyPaEM4RCTkBN03SGEf7PaV6mqF82WWnROK5RlWBc9QPK5eJurtFd zFvks3Iomi9BG9FW7l00L8+gCG1rXsgYnql77nFMQQ/ck2iiN8uuZBAUSSVcnaUfC3dlayUGbLjy4 aGBNBVhJYUNxESPqQJg3my0miYMXaYaEMaFb1gxxU4MmKKy5IpuQU1IpgG2eLdM+hnKWXyQGq2WO9 fX8CEH2A==; From: Christian Schoenebeck To: qemu-devel@nongnu.org Cc: Geoffrey McRae , kraxel@redhat.com Subject: Re: [PATCH] audio/jack: fix use after free segfault Date: Tue, 18 Aug 2020 20:11:15 +0200 Message-ID: <11253274.hK5Fc7SEp3@silver> In-Reply-To: <20200818131206.BB75F3A0B9F@moya.office.hostfission.com> References: <20200818131206.BB75F3A0B9F@moya.office.hostfission.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Received-SPF: pass client-ip=91.194.90.13; envelope-from=qemu_oss@crudebyte.com; helo=lizzy.crudebyte.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/18 14:11:17 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Dienstag, 18. August 2020 14:40:36 CEST Geoffrey McRae wrote: > Due to a ridiculous commit in the Jack library, the client may have been > freed already by a secondary audio device recovering its session. >=20 > https://github.com/jackaudio/jack2/issues/627 >=20 > Until there is a proper fix for this we can not risk using the pointer > at all if we have been notified of a shutdown as it may have been freed > by the jack library, as such the close call is commented out to prevent > a use after free segfault. >=20 > At this time, this will not cause a memory leak as the recovery routine > will trigger the "cleanup" code in the jack library, however, if this is > ever corrected in the jack library this will need to be revisited. >=20 > Signed-off-by: Geoffrey McRae > --- > audio/jackaudio.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) >=20 > diff --git a/audio/jackaudio.c b/audio/jackaudio.c > index 72ed7c4929..e8faf1bb89 100644 > --- a/audio/jackaudio.c > +++ b/audio/jackaudio.c > @@ -563,7 +563,22 @@ static void qjack_client_fini(QJackClient *c) > /* fallthrough */ >=20 > case QJACK_STATE_SHUTDOWN: > - jack_client_close(c->client); > + /* > + * Due to a rediculous commit in the Jack library, the client may > have + * been freed already. No need to be offending, and especially no need to insult St=E9phane in QEM= U=20 code. Could you please describe in more detail how you ran into this situation wi= th=20 your 2nd audio device? > + * > + * Until there is a proper fix for this we can not risk using the > + * pointer at all if we have been notified of a shutdown, as such > the + * below line is commented out to prevent a use after free > segfault. + * This will not cause a memory leak as the recovery > routine will trigger + * the "cleanup" code in the jack library. > + * > + * > https://github.com/jackaudio/jack2/commit/171a3c4a0ddd18d2afae56f3af6291c= 8e > 96ee3ac + */ > + > + //jack_client_close(c->client); > + c->client =3D NULL; > + > /* fallthrough */ Are you aware that there are two distinct variants of JACK? They are common= ly=20 referred to as JACK1 vs. JACK2 and despite their names, they are in fact=20 completely separate implementations and there are people who prefer one ove= r=20 the other. Your change would affect JACK1 as well. Best regards, Christian Schoenebeck