1#!/usr/bin/env python3 2# group: rw 3# 4# Test permissions taken by the mirror-top filter 5# 6# Copyright (C) 2021 Red Hat, Inc. 7# 8# This program is free software; you can redistribute it and/or modify 9# it under the terms of the GNU General Public License as published by 10# the Free Software Foundation; either version 2 of the License, or 11# (at your option) any later version. 12# 13# This program is distributed in the hope that it will be useful, 14# but WITHOUT ANY WARRANTY; without even the implied warranty of 15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16# GNU General Public License for more details. 17# 18# You should have received a copy of the GNU General Public License 19# along with this program. If not, see <http://www.gnu.org/licenses/>. 20# 21 22import os 23 24from qemu.machine import machine 25from qemu.qmp import QMPConnectError 26 27import iotests 28from iotests import change_log_level, qemu_img 29 30 31image_size = 1 * 1024 * 1024 32source = os.path.join(iotests.test_dir, 'source.img') 33 34 35class TestMirrorTopPerms(iotests.QMPTestCase): 36 def setUp(self): 37 qemu_img('create', '-f', iotests.imgfmt, source, str(image_size)) 38 self.vm = iotests.VM() 39 self.vm.add_drive(source) 40 self.vm.add_blockdev(f'null-co,node-name=null,size={image_size}') 41 self.vm.launch() 42 43 # Will be created by the test function itself 44 self.vm_b = None 45 46 def tearDown(self): 47 try: 48 self.vm.shutdown() 49 except machine.AbnormalShutdown: 50 pass 51 52 if self.vm_b is not None: 53 self.vm_b.shutdown() 54 55 os.remove(source) 56 57 def test_cancel(self): 58 """ 59 Before commit 53431b9086b28, mirror-top used to not take any 60 permissions but WRITE and share all permissions. Because it 61 is inserted between the source's original parents and the 62 source, there generally was no parent that would have taken or 63 unshared any permissions on the source, which means that an 64 external process could access the image unhindered by locks. 65 (Unless there was a parent above the protocol node that would 66 take its own locks, e.g. a format driver.) 67 This is bad enough, but if the mirror job is then cancelled, 68 the mirroring VM tries to take back the image, restores the 69 original permissions taken and unshared, and assumes this must 70 just work. But it will not, and so the VM aborts. 71 72 Commit 53431b9086b28 made mirror keep the original permissions 73 and so no other process can "steal" the image. 74 75 (Note that you cannot really do the same with the target image 76 and then completing the job, because the mirror job always 77 took/unshared the correct permissions on the target. For 78 example, it does not share READ_CONSISTENT, which makes it 79 difficult to let some other qemu process open the image.) 80 """ 81 82 result = self.vm.qmp('blockdev-mirror', 83 job_id='mirror', 84 device='drive0', 85 target='null', 86 sync='full') 87 self.assert_qmp(result, 'return', {}) 88 89 self.vm.event_wait('BLOCK_JOB_READY') 90 91 # We want this to fail because the image cannot be locked. 92 # If it does not fail, continue still and see what happens. 93 self.vm_b = iotests.VM(path_suffix='b') 94 # Must use -blockdev -device so we can use share-rw. 95 # (And we need share-rw=on because mirror-top was always 96 # forced to take the WRITE permission so it can write to the 97 # source image.) 98 self.vm_b.add_blockdev(f'file,node-name=drive0,filename={source}') 99 self.vm_b.add_device('virtio-blk,drive=drive0,share-rw=on') 100 try: 101 # Silence AQMP errors temporarily. 102 # TODO: Remove this and just allow the errors to be logged when 103 # AQMP fully replaces QMP. 104 with change_log_level('qemu.aqmp'): 105 self.vm_b.launch() 106 print('ERROR: VM B launched successfully, ' 107 'this should not have happened') 108 except (QMPConnectError, machine.VMLaunchFailure): 109 assert 'Is another process using the image' in self.vm_b.get_log() 110 111 result = self.vm.qmp('block-job-cancel', 112 device='mirror') 113 self.assert_qmp(result, 'return', {}) 114 115 self.vm.event_wait('BLOCK_JOB_COMPLETED') 116 117 118if __name__ == '__main__': 119 # No metadata format driver supported, because they would for 120 # example always unshare the WRITE permission. The raw driver 121 # just passes through the permissions from the guest device, and 122 # those are the permissions that we want to test. 123 iotests.main(supported_fmts=['raw'], 124 supported_protocols=['file']) 125