From nobody Tue Feb 10 19:47:39 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1491242024314983.3131516604894; Mon, 3 Apr 2017 10:53:44 -0700 (PDT) Received: from localhost ([::1]:60545 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cv6Ag-0003a1-S0 for importer@patchew.org; Mon, 03 Apr 2017 13:53:42 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36168) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cv693-0002YH-2B for qemu-devel@nongnu.org; Mon, 03 Apr 2017 13:52:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cv692-00049d-8M for qemu-devel@nongnu.org; Mon, 03 Apr 2017 13:52:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40096) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cv68z-00048R-SC; Mon, 03 Apr 2017 13:51:58 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C0EA583F45; Mon, 3 Apr 2017 17:51:56 +0000 (UTC) Received: from localhost (ovpn-204-55.brq.redhat.com [10.40.204.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2C06DA0A26; Mon, 3 Apr 2017 17:51:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com C0EA583F45 Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=mreitz@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com C0EA583F45 From: Max Reitz To: qemu-block@nongnu.org Date: Mon, 3 Apr 2017 19:51:49 +0200 Message-Id: <20170403175150.15253-2-mreitz@redhat.com> In-Reply-To: <20170403175150.15253-1-mreitz@redhat.com> References: <20170403175150.15253-1-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 03 Apr 2017 17:51:56 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH for-2.9 1/2] block/mirror: Fix use-after-free X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-devel@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" If @bs does not have any parents, the only reference to @mirror_top_bs will be held by the BlockJob object after the bdrv_unref() following block_job_create(). However, if block_job_create() fails, this reference will not exist and @mirror_top_bs will have been deleted when we goto fail. The issue comes back at all later entries to the fail label: We delete the BlockJob object before rolling back our changes to the node graph. This means that we will delete @mirror_top_bs in the process. All in all, whenever @bs does not have any parents and we go down the fail path we will dereference @mirror_top_bs after it has been deleted. Fix this by invoking bdrv_unref() only when block_job_create() was successful and by bdrv_ref()'ing @mirror_top_bs in the fail path before deleting the BlockJob object. Finally, bdrv_unref() it at the end of the fail path after we actually no longer need it. Signed-off-by: Max Reitz Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- block/mirror.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 9e2fecc15e..46ecd38ef0 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -1150,7 +1150,7 @@ static void mirror_start_job(const char *job_id, Bloc= kDriverState *bs, mirror_top_bs->total_sectors =3D bs->total_sectors; =20 /* bdrv_append takes ownership of the mirror_top_bs reference, need to= keep - * it alive until block_job_create() even if bs has no parent. */ + * it alive until block_job_create() succeeds even if bs has no parent= . */ bdrv_ref(mirror_top_bs); bdrv_drained_begin(bs); bdrv_append(mirror_top_bs, bs, &local_err); @@ -1168,10 +1168,12 @@ static void mirror_start_job(const char *job_id, Bl= ockDriverState *bs, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANG= ED | BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD, speed, creation_flags, cb, opaque, errp); - bdrv_unref(mirror_top_bs); if (!s) { goto fail; } + /* The block job now has a reference to this node */ + bdrv_unref(mirror_top_bs); + s->source =3D bs; s->mirror_top_bs =3D mirror_top_bs; =20 @@ -1242,6 +1244,10 @@ static void mirror_start_job(const char *job_id, Blo= ckDriverState *bs, =20 fail: if (s) { + /* Make sure this BDS does not go away until we have completed the= graph + * changes below */ + bdrv_ref(mirror_top_bs); + g_free(s->replaces); blk_unref(s->target); block_job_unref(&s->common); @@ -1250,6 +1256,8 @@ fail: bdrv_child_try_set_perm(mirror_top_bs->backing, 0, BLK_PERM_ALL, &error_abort); bdrv_replace_node(mirror_top_bs, backing_bs(mirror_top_bs), &error_abo= rt); + + bdrv_unref(mirror_top_bs); } =20 void mirror_start(const char *job_id, BlockDriverState *bs, --=20 2.12.1