From patchwork Wed Sep 11 10:03:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Max Reitz X-Patchwork-Id: 11140841 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B2FEF924 for ; Wed, 11 Sep 2019 10:04:53 +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 91DC32075C for ; Wed, 11 Sep 2019 10:04:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91DC32075C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:49176 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7zUa-0000T5-Ox for patchwork-qemu-devel@patchwork.kernel.org; Wed, 11 Sep 2019 06:04:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48659) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7zTG-0007Nn-6y for qemu-devel@nongnu.org; Wed, 11 Sep 2019 06:03:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i7zTF-0004nP-2D for qemu-devel@nongnu.org; Wed, 11 Sep 2019 06:03:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52532) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i7zTA-0004m6-Cb; Wed, 11 Sep 2019 06:03:26 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 740C5315C02D; Wed, 11 Sep 2019 10:03:22 +0000 (UTC) Received: from localhost (ovpn-116-94.ams2.redhat.com [10.36.116.94]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 175656012A; Wed, 11 Sep 2019 10:03:17 +0000 (UTC) From: Max Reitz To: qemu-block@nongnu.org Date: Wed, 11 Sep 2019 12:03:16 +0200 Message-Id: <20190911100316.32282-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 11 Sep 2019 10:03:22 +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 v3] blockjob: update nodes head while removing all bdrv 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: Kevin Wolf , qemu-stable@nongnu.org, qemu-devel@nongnu.org, Sergio Lopez , Max Reitz Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Sergio Lopez block_job_remove_all_bdrv() iterates through job->nodes, calling bdrv_root_unref_child() for each entry. The call to the latter may reach child_job_[can_]set_aio_ctx(), which will also attempt to traverse job->nodes, potentially finding entries that where freed on previous iterations. To avoid this situation, update job->nodes head on each iteration to ensure that already freed entries are no longer linked to the list. RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1746631 Signed-off-by: Sergio Lopez Cc: qemu-stable@nongnu.org Signed-off-by: Max Reitz Reviewed-by: Sergio Lopez --- v3: - Rewrote the loop to make the whole function a bit simpler (Also, remove the node from the job->nodes list before unref'ing it, just to be extra-safe) --- blockjob.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/blockjob.c b/blockjob.c index 2abed0f551..c6e20e2fcd 100644 --- a/blockjob.c +++ b/blockjob.c @@ -175,14 +175,23 @@ static const BdrvChildRole child_job = { void block_job_remove_all_bdrv(BlockJob *job) { - GSList *l; - for (l = job->nodes; l; l = l->next) { + /* + * bdrv_root_unref_child() may reach child_job_[can_]set_aio_ctx(), + * which will also traverse job->nodes, so consume the list one by + * one to make sure that such a concurrent access does not attempt + * to process an already freed BdrvChild. + */ + while (job->nodes) { + GSList *l = job->nodes; BdrvChild *c = l->data; + + job->nodes = l->next; + bdrv_op_unblock_all(c->bs, job->blocker); bdrv_root_unref_child(c); + + g_slist_free_1(l); } - g_slist_free(job->nodes); - job->nodes = NULL; } bool block_job_has_bdrv(BlockJob *job, BlockDriverState *bs)