122 lines
4.6 KiB
Python
Executable File
122 lines
4.6 KiB
Python
Executable File
#!/usr/bin/env python3
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# group: rw
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#
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# Test permissions taken by the mirror-top filter
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#
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# Copyright (C) 2021 Red Hat, Inc.
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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 os
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from qemu.machine import machine
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import iotests
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from iotests import change_log_level, qemu_img
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image_size = 1 * 1024 * 1024
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source = os.path.join(iotests.test_dir, 'source.img')
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class TestMirrorTopPerms(iotests.QMPTestCase):
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def setUp(self):
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qemu_img('create', '-f', iotests.imgfmt, source, str(image_size))
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self.vm = iotests.VM()
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self.vm.add_drive(source)
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self.vm.add_blockdev(f'null-co,node-name=null,size={image_size}')
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self.vm.launch()
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# Will be created by the test function itself
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self.vm_b = None
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def tearDown(self):
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try:
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self.vm.shutdown()
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except machine.AbnormalShutdown:
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pass
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if self.vm_b is not None:
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self.vm_b.shutdown()
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os.remove(source)
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def test_cancel(self):
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"""
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Before commit 53431b9086b28, mirror-top used to not take any
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permissions but WRITE and share all permissions. Because it
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is inserted between the source's original parents and the
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source, there generally was no parent that would have taken or
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unshared any permissions on the source, which means that an
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external process could access the image unhindered by locks.
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(Unless there was a parent above the protocol node that would
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take its own locks, e.g. a format driver.)
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This is bad enough, but if the mirror job is then cancelled,
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the mirroring VM tries to take back the image, restores the
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original permissions taken and unshared, and assumes this must
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just work. But it will not, and so the VM aborts.
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Commit 53431b9086b28 made mirror keep the original permissions
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and so no other process can "steal" the image.
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(Note that you cannot really do the same with the target image
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and then completing the job, because the mirror job always
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took/unshared the correct permissions on the target. For
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example, it does not share READ_CONSISTENT, which makes it
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difficult to let some other qemu process open the image.)
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"""
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result = self.vm.qmp('blockdev-mirror',
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job_id='mirror',
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device='drive0',
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target='null',
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sync='full')
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self.assert_qmp(result, 'return', {})
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self.vm.event_wait('BLOCK_JOB_READY')
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# We want this to fail because the image cannot be locked.
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# If it does not fail, continue still and see what happens.
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self.vm_b = iotests.VM(path_suffix='b')
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# Must use -blockdev -device so we can use share-rw.
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# (And we need share-rw=on because mirror-top was always
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# forced to take the WRITE permission so it can write to the
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# source image.)
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self.vm_b.add_blockdev(f'file,node-name=drive0,filename={source}')
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self.vm_b.add_device('virtio-blk,drive=drive0,share-rw=on')
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try:
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# Silence QMP logging errors temporarily.
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with change_log_level('qemu.qmp'):
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self.vm_b.launch()
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print('ERROR: VM B launched successfully, '
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'this should not have happened')
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except machine.VMLaunchFailure as exc:
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assert 'Is another process using the image' in exc.output
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result = self.vm.qmp('block-job-cancel',
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device='mirror')
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self.assert_qmp(result, 'return', {})
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self.vm.event_wait('BLOCK_JOB_COMPLETED')
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if __name__ == '__main__':
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# No metadata format driver supported, because they would for
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# example always unshare the WRITE permission. The raw driver
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# just passes through the permissions from the guest device, and
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# those are the permissions that we want to test.
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iotests.main(supported_fmts=['raw'],
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supported_protocols=['file'])
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