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 25 26import iotests 27from iotests import change_log_level, qemu_img 28 29 30image_size = 1 * 1024 * 1024 31source = os.path.join(iotests.test_dir, 'source.img') 32 33 34class TestMirrorTopPerms(iotests.QMPTestCase): 35 def setUp(self): 36 qemu_img('create', '-f', iotests.imgfmt, source, str(image_size)) 37 self.vm = iotests.VM() 38 self.vm.add_drive(source) 39 self.vm.add_blockdev(f'null-co,node-name=null,size={image_size}') 40 self.vm.launch() 41 42 # Will be created by the test function itself 43 self.vm_b = None 44 45 def tearDown(self): 46 try: 47 self.vm.shutdown() 48 except machine.AbnormalShutdown: 49 pass 50 51 if self.vm_b is not None: 52 self.vm_b.shutdown() 53 54 os.remove(source) 55 56 def test_cancel(self): 57 """ 58 Before commit 53431b9086b28, mirror-top used to not take any 59 permissions but WRITE and share all permissions. Because it 60 is inserted between the source's original parents and the 61 source, there generally was no parent that would have taken or 62 unshared any permissions on the source, which means that an 63 external process could access the image unhindered by locks. 64 (Unless there was a parent above the protocol node that would 65 take its own locks, e.g. a format driver.) 66 This is bad enough, but if the mirror job is then cancelled, 67 the mirroring VM tries to take back the image, restores the 68 original permissions taken and unshared, and assumes this must 69 just work. But it will not, and so the VM aborts. 70 71 Commit 53431b9086b28 made mirror keep the original permissions 72 and so no other process can "steal" the image. 73 74 (Note that you cannot really do the same with the target image 75 and then completing the job, because the mirror job always 76 took/unshared the correct permissions on the target. For 77 example, it does not share READ_CONSISTENT, which makes it 78 difficult to let some other qemu process open the image.) 79 """ 80 81 result = self.vm.qmp('blockdev-mirror', 82 job_id='mirror', 83 device='drive0', 84 target='null', 85 sync='full') 86 self.assert_qmp(result, 'return', {}) 87 88 self.vm.event_wait('BLOCK_JOB_READY') 89 90 # We want this to fail because the image cannot be locked. 91 # If it does not fail, continue still and see what happens. 92 self.vm_b = iotests.VM(path_suffix='b') 93 # Must use -blockdev -device so we can use share-rw. 94 # (And we need share-rw=on because mirror-top was always 95 # forced to take the WRITE permission so it can write to the 96 # source image.) 97 self.vm_b.add_blockdev(f'file,node-name=drive0,filename={source}') 98 self.vm_b.add_device('virtio-blk,drive=drive0,share-rw=on') 99 try: 100 # Silence QMP logging errors temporarily. 101 with change_log_level('qemu.qmp'): 102 self.vm_b.launch() 103 print('ERROR: VM B launched successfully, ' 104 'this should not have happened') 105 except machine.VMLaunchFailure as exc: 106 assert 'Is another process using the image' in exc.output 107 108 result = self.vm.qmp('block-job-cancel', 109 device='mirror') 110 self.assert_qmp(result, 'return', {}) 111 112 self.vm.event_wait('BLOCK_JOB_COMPLETED') 113 114 115if __name__ == '__main__': 116 # No metadata format driver supported, because they would for 117 # example always unshare the WRITE permission. The raw driver 118 # just passes through the permissions from the guest device, and 119 # those are the permissions that we want to test. 120 iotests.main(supported_fmts=['raw'], 121 supported_protocols=['file']) 122