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=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,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 3751BC433E1 for ; Wed, 19 Aug 2020 15:22:20 +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 0358F208A9 for ; Wed, 19 Aug 2020 15:22:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="c+eNYZRD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0358F208A9 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]:55384 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8Put-0007Ji-9K for qemu-devel@archiver.kernel.org; Wed, 19 Aug 2020 11:22:19 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34066) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8Pu9-0006qE-4D for qemu-devel@nongnu.org; Wed, 19 Aug 2020 11:21:33 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:50247) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8Pu6-00006C-TS for qemu-devel@nongnu.org; Wed, 19 Aug 2020 11:21:32 -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=ZtRxeBigbG6gmROAcIZ4FEytzipHBrNxijGpWvqaC+8=; b=c+eNYZRDwQLGmAa/SIAagq7OJl uyFnyHrG7GDQkDOmsWqBCCZHOi6Kjyp7hBWJ1+izT5hv4yPyJhOr15KfnIjlRreiEC93oooPXIji/ +8s9bgozeYaYz/6F0pjf9pMlwvf5XR/O5J/Bc9VOF8BUlDaRuPjYFx7RxU8DMfd8nD/fz7TYHoR/m MhjzrUVRZ1FtQ6Yq85yGHKUdhfhh/eGWPLKDxnhdq/TIDTKXQLftryNajq2r5Ck5yajpcNDaRHW58 UIw0SAyCJsH7ItPtim/hm1O4HdWPo2U5gwVf1NGZ9rT09ft+/8zIzr5lmdGz4fDczy/7Vm19OC1V5 IAhWu7ww==; From: Christian Schoenebeck To: qemu-devel@nongnu.org Cc: Geoffrey McRae , kraxel@redhat.com Subject: Re: [PATCH v5 1/1] audio/jack: fix use after free segfault Date: Wed, 19 Aug 2020 17:21:27 +0200 Message-ID: <5029913.bOW1W81TKx@silver> In-Reply-To: <20200819062940.52774-2-geoff@hostfission.com> References: <20200819062940.52774-1-geoff@hostfission.com> <20200819062940.52774-2-geoff@hostfission.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" 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 = 2020/08/19 07:30:08 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 Mittwoch, 19. August 2020 08:29:39 CEST Geoffrey McRae wrote: > This change registers a bottom handler to close the JACK client > connection when a server shutdown signal is recieved. Without this > libjack2 attempts to "clean up" old clients and causes a use after free > segfault. > > Signed-off-by: Geoffrey McRae > --- Looks much better now, but ... > audio/jackaudio.c | 29 ++++++++++++++++++++--------- > 1 file changed, 20 insertions(+), 9 deletions(-) > > diff --git a/audio/jackaudio.c b/audio/jackaudio.c > index 72ed7c4929..b0da5cd00b 100644 > --- a/audio/jackaudio.c > +++ b/audio/jackaudio.c > @@ -25,6 +25,7 @@ > #include "qemu/osdep.h" > #include "qemu/module.h" > #include "qemu/atomic.h" > +#include "qemu/main-loop.h" > #include "qemu-common.h" > #include "audio.h" > > @@ -63,6 +64,7 @@ typedef struct QJackClient { > QJackState state; > jack_client_t *client; > jack_nframes_t freq; > + QEMUBH *shutdown_bh; > > struct QJack *j; > int nchannels; > @@ -306,21 +308,27 @@ static int qjack_xrun(void *arg) > return 0; > } > > +static void qjack_shutdown_bh(void *opaque) > +{ > + QJackClient *c = (QJackClient *)opaque; > + qjack_client_fini(c); > +} > + > static void qjack_shutdown(void *arg) > { > QJackClient *c = (QJackClient *)arg; > - c->state = QJACK_STATE_SHUTDOWN; > + c->state = QJACK_STATE_SHUTDOWN; White space changes are not much embraced on high traffic projects BTW. > + qemu_bh_schedule(c->shutdown_bh); > } > > static void qjack_client_recover(QJackClient *c) > { > - if (c->state == QJACK_STATE_SHUTDOWN) { > - qjack_client_fini(c); > + if (c->state != QJACK_STATE_DISCONNECTED) { > + return; > } > > /* packets is used simply to throttle this */ > - if (c->state == QJACK_STATE_DISCONNECTED && > - c->packets % 100 == 0) { > + if (c->packets % 100 == 0) { > > /* if enabled then attempt to recover */ > if (c->enabled) { > @@ -417,6 +425,10 @@ static int qjack_client_init(QJackClient *c) > options |= JackServerName; > } > > + if (!c->shutdown_bh) { > + c->shutdown_bh = qemu_bh_new(qjack_shutdown_bh, c); > + } > + Where is qemu_bh_delete() ? > c->client = jack_client_open(client_name, options, &status, > c->opt->server_name); > > @@ -489,8 +501,6 @@ static int qjack_init_out(HWVoiceOut *hw, struct > audsettings *as, QJackOut *jo = (QJackOut *)hw; > Audiodev *dev = (Audiodev *)drv_opaque; > > - qjack_client_fini(&jo->c); > - > jo->c.out = true; > jo->c.enabled = false; > jo->c.nchannels = as->nchannels; > @@ -525,8 +535,6 @@ static int qjack_init_in(HWVoiceIn *hw, struct > audsettings *as, QJackIn *ji = (QJackIn *)hw; > Audiodev *dev = (Audiodev *)drv_opaque; > > - qjack_client_fini(&ji->c); > - > ji->c.out = false; > ji->c.enabled = false; > ji->c.nchannels = as->nchannels; > @@ -557,6 +565,8 @@ static int qjack_init_in(HWVoiceIn *hw, struct > audsettings *as, > > static void qjack_client_fini(QJackClient *c) > { > + qemu_bh_cancel(c->shutdown_bh); > + Looks like a potential race. Quote from the API doc of qemu_bh_cancel(): "While cancellation itself is also wait-free and thread-safe, it can of course race with the loop that executes bottom halves unless you are holding the iothread mutex. This makes it mostly useless if you are not holding the mutex." > switch (c->state) { > case QJACK_STATE_RUNNING: > jack_deactivate(c->client); > @@ -564,6 +574,7 @@ static void qjack_client_fini(QJackClient *c) > > case QJACK_STATE_SHUTDOWN: > jack_client_close(c->client); > + c->client = NULL; > /* fallthrough */ > > case QJACK_STATE_DISCONNECTED: Best regards, Christian Schoenebeck