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 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 2D804C433E1 for ; Wed, 19 Aug 2020 15:28:27 +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 E8C8F20897 for ; Wed, 19 Aug 2020 15:28:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=hostfission.com header.i=@hostfission.com header.b="Y0GJ5OKL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8C8F20897 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=hostfission.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42782 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8Q0o-0005ZF-89 for qemu-devel@archiver.kernel.org; Wed, 19 Aug 2020 11:28:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35684) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8Pzn-0004ME-9j for qemu-devel@nongnu.org; Wed, 19 Aug 2020 11:27:23 -0400 Received: from mail1.hostfission.com ([139.99.139.48]:41054) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8Pzl-0000w7-7W for qemu-devel@nongnu.org; Wed, 19 Aug 2020 11:27:23 -0400 Received: from www1.hostfission.com (www1.hostfission.com [139.99.139.52]) by mail1.hostfission.com (Postfix) with ESMTP id 1E85242765; Thu, 20 Aug 2020 01:27:13 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hostfission.com; s=mail; t=1597850833; bh=P0mZm/KVZosvcgg1ag6FG1/GlXGcN5ox6DNv+5jjrOE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Y0GJ5OKLwq4PqzW1WymfEyM+qlkC0BV1thx61XXDHXeiEIWmI0uEX1iiIyDGLdAKg 3nVjH2kYaZWA/lVcpv0Vv5jhhxTbwPFJrr/GF8SBnuKFD7L4piP/LRdTqp4HO13dKI pgQ5fgzdLsVH+m9c2UUgs21//S1Omq/WUTEdR2b0= Received: from mail.hostfission.com (www1.hostfission.com [127.0.0.1]) by www1.hostfission.com (Postfix) with ESMTP id 0A25A89DE3; Thu, 20 Aug 2020 01:27:13 +1000 (AEST) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 20 Aug 2020 01:27:13 +1000 From: Geoffrey McRae To: Christian Schoenebeck Cc: qemu-devel@nongnu.org, kraxel@redhat.com Subject: Re: [PATCH v5 1/1] audio/jack: fix use after free segfault In-Reply-To: <5029913.bOW1W81TKx@silver> References: <20200819062940.52774-1-geoff@hostfission.com> <20200819062940.52774-2-geoff@hostfission.com> <5029913.bOW1W81TKx@silver> Message-ID: <7fca183cc66cf07f6ba72eabea8a44cf@hostfission.com> X-Sender: geoff@hostfission.com User-Agent: Roundcube Webmail/1.3.8 Received-SPF: pass client-ip=139.99.139.48; envelope-from=geoff@hostfission.com; helo=mail1.hostfission.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 11:27:14 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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 2020-08-20 01:21, Christian Schoenebeck wrote: > 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. This change is unintentional and was missed in the rollback from the prior patch version. > >> + 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() ? Whoops... I will correct this :) > >> 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." > Noted. How does one go about holding the iothread 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