* [PATCH v2 1/2] block/backup-top: fix failure path
2020-01-21 14:28 [PATCH v2 0/2] backup-top failure path fix Vladimir Sementsov-Ogievskiy
@ 2020-01-21 14:28 ` Vladimir Sementsov-Ogievskiy
2020-01-21 14:28 ` [PATCH v2 2/2] iotests: add test for backup-top failure on permission activation Vladimir Sementsov-Ogievskiy
2020-01-21 16:32 ` [PATCH v2 0/2] backup-top failure path fix Max Reitz
2 siblings, 0 replies; 6+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2020-01-21 14:28 UTC (permalink / raw)
To: qemu-block; +Cc: kwolf, qemu-stable, vsementsov, qemu-devel, mreitz
We can't access top after call bdrv_backup_top_drop, as it is already
freed at this time.
Also, no needs to unref target child by hand, it will be unrefed on
bdrv_close() automatically.
So, just do bdrv_backup_top_drop if append succeed and one bdrv_unref
otherwise.
Note, that in !appended case bdrv_unref(top) moved into drained section
on source. It doesn't really matter, but just for code simplicity.
Fixes: 7df7868b96404
Cc: qemu-stable@nongnu.org # v4.2.0
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
block/backup-top.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/block/backup-top.c b/block/backup-top.c
index b8d863ff08..cdfec782e2 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -190,6 +190,7 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
BlockDriverState *top = bdrv_new_open_driver(&bdrv_backup_top_filter,
filter_node_name,
BDRV_O_RDWR, errp);
+ bool appended = false;
if (!top) {
return NULL;
@@ -212,8 +213,9 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
bdrv_append(top, source, &local_err);
if (local_err) {
error_prepend(&local_err, "Cannot append backup-top filter: ");
- goto append_failed;
+ goto fail;
}
+ appended = true;
/*
* bdrv_append() finished successfully, now we can require permissions
@@ -224,14 +226,14 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
if (local_err) {
error_prepend(&local_err,
"Cannot set permissions for backup-top filter: ");
- goto failed_after_append;
+ goto fail;
}
state->bcs = block_copy_state_new(top->backing, state->target,
cluster_size, write_flags, &local_err);
if (local_err) {
error_prepend(&local_err, "Cannot create block-copy-state: ");
- goto failed_after_append;
+ goto fail;
}
*bcs = state->bcs;
@@ -239,14 +241,15 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
return top;
-failed_after_append:
- state->active = false;
- bdrv_backup_top_drop(top);
+fail:
+ if (appended) {
+ state->active = false;
+ bdrv_backup_top_drop(top);
+ } else {
+ bdrv_unref(top);
+ }
-append_failed:
bdrv_drained_end(source);
- bdrv_unref_child(top, state->target);
- bdrv_unref(top);
error_propagate(errp, local_err);
return NULL;
--
2.21.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 2/2] iotests: add test for backup-top failure on permission activation
2020-01-21 14:28 [PATCH v2 0/2] backup-top failure path fix Vladimir Sementsov-Ogievskiy
2020-01-21 14:28 ` [PATCH v2 1/2] block/backup-top: fix failure path Vladimir Sementsov-Ogievskiy
@ 2020-01-21 14:28 ` Vladimir Sementsov-Ogievskiy
2020-01-21 16:31 ` Max Reitz
2020-01-21 16:32 ` [PATCH v2 0/2] backup-top failure path fix Max Reitz
2 siblings, 1 reply; 6+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2020-01-21 14:28 UTC (permalink / raw)
To: qemu-block; +Cc: kwolf, qemu-stable, vsementsov, qemu-devel, mreitz
This test checks that bug is really fixed by previous commit.
Cc: qemu-stable@nongnu.org # v4.2.0
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
tests/qemu-iotests/283 | 92 ++++++++++++++++++++++++++++++++++++++
tests/qemu-iotests/283.out | 8 ++++
tests/qemu-iotests/group | 1 +
3 files changed, 101 insertions(+)
create mode 100644 tests/qemu-iotests/283
create mode 100644 tests/qemu-iotests/283.out
diff --git a/tests/qemu-iotests/283 b/tests/qemu-iotests/283
new file mode 100644
index 0000000000..293e557bd9
--- /dev/null
+++ b/tests/qemu-iotests/283
@@ -0,0 +1,92 @@
+#!/usr/bin/env python
+#
+# Test for backup-top filter permission activation failure
+#
+# Copyright (c) 2019 Virtuozzo International GmbH.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+import iotests
+
+# The test is unrelated to formats, restrict it to qcow2 to avoid extra runs
+iotests.verify_image_format(supported_fmts=['qcow2'])
+
+size = 1024 * 1024
+
+""" Test description
+
+When performing a backup, all writes on the source subtree must go through the
+backup-top filter so it can copy all data to the target before it is changed.
+backup-top filter is appended above source node, to achieve this thing, so all
+parents of source node are handled. A configuration with side parents of source
+sub-tree with write permission is unsupported (we'd have append several
+backup-top filter like nodes to handle such parents). The test create an
+example of such configuration and checks that a backup is then not allowed
+(blockdev-backup command should fail).
+
+The configuration:
+
+ ┌────────┐ target ┌─────────────┐
+ │ target │ ◀─────── │ backup_top │
+ └────────┘ └─────────────┘
+ │
+ │ backing
+ ▼
+ ┌─────────────┐
+ │ source │
+ └─────────────┘
+ │
+ │ file
+ ▼
+ ┌─────────────┐ write perm ┌───────┐
+ │ base │ ◀──────────── │ other │
+ └─────────────┘ └───────┘
+
+On activation (see .active field of backup-top state in block/backup-top.c),
+backup-top is going to unshare write permission on its source child. Write
+unsharing will be propagated to the "source->base" link and will conflict with
+other node write permission. So permission update will fail and backup job will
+not be started.
+
+Note, that the only thing which prevents backup of running on such
+configuration is default permission propagation scheme. It may be altered by
+different block drivers, so backup will run in invalid configuration. But
+something is better than nothing. Also, before the previous commit (commit
+preceding this test creation), starting backup on such configuration led to
+crash, so current "something" is a lot better, and this test actual goal is
+to check that crash is fixed :)
+"""
+
+vm = iotests.VM()
+vm.launch()
+
+vm.qmp_log('blockdev-add', **{'node-name': 'target', 'driver': 'null-co'})
+
+vm.qmp_log('blockdev-add', **{
+ 'node-name': 'source',
+ 'driver': 'blkdebug',
+ 'image': {'node-name': 'base', 'driver': 'null-co', 'size': size}
+})
+
+vm.qmp_log('blockdev-add', **{
+ 'node-name': 'other',
+ 'driver': 'blkdebug',
+ 'image': 'base',
+ 'take-child-perms': ['write']
+})
+
+vm.qmp_log('blockdev-backup', sync='full', device='source', target='target')
+
+vm.shutdown()
diff --git a/tests/qemu-iotests/283.out b/tests/qemu-iotests/283.out
new file mode 100644
index 0000000000..daaf5828c1
--- /dev/null
+++ b/tests/qemu-iotests/283.out
@@ -0,0 +1,8 @@
+{"execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": "target"}}
+{"return": {}}
+{"execute": "blockdev-add", "arguments": {"driver": "blkdebug", "image": {"driver": "null-co", "node-name": "base", "size": 1048576}, "node-name": "source"}}
+{"return": {}}
+{"execute": "blockdev-add", "arguments": {"driver": "blkdebug", "image": "base", "node-name": "other", "take-child-perms": ["write"]}}
+{"return": {}}
+{"execute": "blockdev-backup", "arguments": {"device": "source", "sync": "full", "target": "target"}}
+{"error": {"class": "GenericError", "desc": "Cannot set permissions for backup-top filter: Conflicts with use by other as 'image', which uses 'write' on base"}}
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 9d30a4b6c4..1904223020 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -289,3 +289,4 @@
279 rw backing quick
280 rw migration quick
281 rw quick
+283 auto quick
--
2.21.0
^ permalink raw reply related [flat|nested] 6+ messages in thread