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![Max Reitz](/assets/img/avatar_default.png)
Without any of HEAD^ or HEAD^^ applied, qemu will most likely crash on the qemu-io invocation, for a variety of immediate reasons. The underlying problem is generally a use-after-free access into backup-top's BlockCopyState. With only HEAD^ applied, qemu-io will run into an EIO (which is not capture by the output, but you can see that the qemu-io invocation will be accepted (i.e., qemu-io will run) in contrast to the reference output, where the node name cannot be found), and qemu will then crash in query-named-block-nodes: bdrv_get_allocated_file_size() detects backup-top to be a filter and passes the request through to its child. However, after bdrv_backup_top_drop(), that child is NULL, so the recursive call crashes. With HEAD^^ applied, this test should pass. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-Id: <20210219153348.41861-4-mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
153 lines
5.2 KiB
Python
Executable file
153 lines
5.2 KiB
Python
Executable file
#!/usr/bin/env python3
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# group: auto quick
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#
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# Test for backup-top filter permission activation failure
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#
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# Copyright (c) 2019 Virtuozzo International GmbH.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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import iotests
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# The test is unrelated to formats, restrict it to qcow2 to avoid extra runs
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iotests.script_initialize(
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supported_fmts=['qcow2'],
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)
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size = 1024 * 1024
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""" Test description
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When performing a backup, all writes on the source subtree must go through the
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backup-top filter so it can copy all data to the target before it is changed.
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backup-top filter is appended above source node, to achieve this thing, so all
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parents of source node are handled. A configuration with side parents of source
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sub-tree with write permission is unsupported (we'd have append several
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backup-top filter like nodes to handle such parents). The test create an
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example of such configuration and checks that a backup is then not allowed
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(blockdev-backup command should fail).
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The configuration:
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┌────────┐ target ┌─────────────┐
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│ target │ ◀─────── │ backup_top │
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└────────┘ └─────────────┘
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│
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│ backing
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▼
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┌─────────────┐
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│ source │
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└─────────────┘
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│
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│ file
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▼
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┌─────────────┐ write perm ┌───────┐
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│ base │ ◀──────────── │ other │
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└─────────────┘ └───────┘
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On activation (see .active field of backup-top state in block/backup-top.c),
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backup-top is going to unshare write permission on its source child. Write
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unsharing will be propagated to the "source->base" link and will conflict with
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other node write permission. So permission update will fail and backup job will
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not be started.
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Note, that the only thing which prevents backup of running on such
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configuration is default permission propagation scheme. It may be altered by
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different block drivers, so backup will run in invalid configuration. But
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something is better than nothing. Also, before the previous commit (commit
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preceding this test creation), starting backup on such configuration led to
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crash, so current "something" is a lot better, and this test actual goal is
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to check that crash is fixed :)
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"""
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vm = iotests.VM()
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vm.launch()
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vm.qmp_log('blockdev-add', **{
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'node-name': 'target',
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'driver': 'null-co',
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'size': size,
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})
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vm.qmp_log('blockdev-add', **{
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'node-name': 'source',
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'driver': 'blkdebug',
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'image': {'node-name': 'base', 'driver': 'null-co', 'size': size}
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})
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vm.qmp_log('blockdev-add', **{
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'node-name': 'other',
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'driver': 'blkdebug',
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'image': 'base',
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'take-child-perms': ['write']
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})
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vm.qmp_log('blockdev-backup', sync='full', device='source', target='target')
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vm.shutdown()
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print('\n=== backup-top should be gone after job-finalize ===\n')
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# Check that the backup-top node is gone after job-finalize.
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#
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# During finalization, the node becomes inactive and can no longer
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# function. If it is still present, new parents might be attached, and
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# there would be no meaningful way to handle their I/O requests.
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vm = iotests.VM()
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vm.launch()
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vm.qmp_log('blockdev-add', **{
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'node-name': 'source',
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'driver': 'null-co',
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})
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vm.qmp_log('blockdev-add', **{
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'node-name': 'target',
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'driver': 'null-co',
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})
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vm.qmp_log('blockdev-backup',
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job_id='backup',
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device='source',
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target='target',
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sync='full',
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filter_node_name='backup-filter',
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auto_finalize=False,
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auto_dismiss=False)
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vm.event_wait('BLOCK_JOB_PENDING', 5.0)
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# The backup-top filter should still be present prior to finalization
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assert vm.node_info('backup-filter') is not None
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vm.qmp_log('job-finalize', id='backup')
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vm.event_wait('BLOCK_JOB_COMPLETED', 5.0)
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# The filter should be gone now. Check that by trying to access it
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# with qemu-io (which will most likely crash qemu if it is still
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# there.).
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vm.qmp_log('human-monitor-command',
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command_line='qemu-io backup-filter "write 0 1M"')
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# (Also, do an explicit check.)
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assert vm.node_info('backup-filter') is None
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vm.qmp_log('job-dismiss', id='backup')
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vm.event_wait('JOB_STATUS_CHANGE', 5.0, {'data': {'status': 'null'}})
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vm.shutdown()
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