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Tue, 5 Nov 2019 20:53:12 +0000 (GMT) From: Michael Roth To: qemu-devel@nongnu.org Subject: [PATCH 45/55] mirror: Do not dereference invalid pointers Date: Tue, 5 Nov 2019 14:52:33 -0600 Message-Id: <20191105205243.3766-46-mdroth@linux.vnet.ibm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191105205243.3766-1-mdroth@linux.vnet.ibm.com> References: <20191105205243.3766-1-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-11-05_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=782 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1911050170 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 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: qemu-stable@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Max Reitz mirror_exit_common() may be called twice (if it is called from mirror_prepare() and fails, it will be called from mirror_abort() again). In such a case, many of the pointers in the MirrorBlockJob object will already be freed. This can be seen most reliably for s->target, which is set to NULL (and then dereferenced by blk_bs()). Cc: qemu-stable@nongnu.org Fixes: 737efc1eda23b904fbe0e66b37715fb0e5c3e58b Signed-off-by: Max Reitz Reviewed-by: John Snow Reviewed-by: Vladimir Sementsov-Ogievskiy Message-id: 20191014153931.20699-2-mreitz@redhat.com Signed-off-by: Max Reitz (cherry picked from commit f93c3add3a773e0e3f6277e5517583c4ad3a43c2) Signed-off-by: Michael Roth --- block/mirror.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 9f5c59ece1..0e3f7923cf 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -618,11 +618,11 @@ static int mirror_exit_common(Job *job) { MirrorBlockJob *s =3D container_of(job, MirrorBlockJob, common.job); BlockJob *bjob =3D &s->common; - MirrorBDSOpaque *bs_opaque =3D s->mirror_top_bs->opaque; + MirrorBDSOpaque *bs_opaque; AioContext *replace_aio_context =3D NULL; - BlockDriverState *src =3D s->mirror_top_bs->backing->bs; - BlockDriverState *target_bs =3D blk_bs(s->target); - BlockDriverState *mirror_top_bs =3D s->mirror_top_bs; + BlockDriverState *src; + BlockDriverState *target_bs; + BlockDriverState *mirror_top_bs; Error *local_err =3D NULL; bool abort =3D job->ret < 0; int ret =3D 0; @@ -632,6 +632,11 @@ static int mirror_exit_common(Job *job) } s->prepared =3D true; =20 + mirror_top_bs =3D s->mirror_top_bs; + bs_opaque =3D mirror_top_bs->opaque; + src =3D mirror_top_bs->backing->bs; + target_bs =3D blk_bs(s->target); + if (bdrv_chain_contains(src, target_bs)) { bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs); } --=20 2.17.1