From f940b0ac6fa67deb9d0b671cf83070f0286c67e1 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Wed, 31 Mar 2021 14:28:15 +0200 Subject: [PATCH] iotests: Test mirror-top filter permissions Add a test accompanying commit 53431b9086b2832ca1aeff0c55e186e9ed79bd11 ("block/mirror: Fix mirror_top's permissions"). Signed-off-by: Max Reitz Message-Id: <20210331122815.51491-1-mreitz@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf --- tests/qemu-iotests/tests/mirror-top-perms | 121 ++++++++++++++++++++++++++ tests/qemu-iotests/tests/mirror-top-perms.out | 5 ++ 2 files changed, 126 insertions(+) create mode 100755 tests/qemu-iotests/tests/mirror-top-perms create mode 100644 tests/qemu-iotests/tests/mirror-top-perms.out diff --git a/tests/qemu-iotests/tests/mirror-top-perms b/tests/qemu-iotests/tests/mirror-top-perms new file mode 100755 index 0000000000..451a0666f8 --- /dev/null +++ b/tests/qemu-iotests/tests/mirror-top-perms @@ -0,0 +1,121 @@ +#!/usr/bin/env python3 +# group: rw +# +# Test permissions taken by the mirror-top filter +# +# Copyright (C) 2021 Red Hat, Inc. +# +# 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 . +# + +import os +import iotests +from iotests import qemu_img + +# Import qemu after iotests.py has amended sys.path +# pylint: disable=wrong-import-order +import qemu + + +image_size = 1 * 1024 * 1024 +source = os.path.join(iotests.test_dir, 'source.img') + + +class TestMirrorTopPerms(iotests.QMPTestCase): + def setUp(self): + assert qemu_img('create', '-f', iotests.imgfmt, source, + str(image_size)) == 0 + self.vm = iotests.VM() + self.vm.add_drive(source) + self.vm.add_blockdev(f'null-co,node-name=null,size={image_size}') + self.vm.launch() + + # Will be created by the test function itself + self.vm_b = None + + def tearDown(self): + try: + self.vm.shutdown() + except qemu.machine.AbnormalShutdown: + pass + + if self.vm_b is not None: + self.vm_b.shutdown() + + os.remove(source) + + def test_cancel(self): + """ + Before commit 53431b9086b28, mirror-top used to not take any + permissions but WRITE and share all permissions. Because it + is inserted between the source's original parents and the + source, there generally was no parent that would have taken or + unshared any permissions on the source, which means that an + external process could access the image unhindered by locks. + (Unless there was a parent above the protocol node that would + take its own locks, e.g. a format driver.) + This is bad enough, but if the mirror job is then cancelled, + the mirroring VM tries to take back the image, restores the + original permissions taken and unshared, and assumes this must + just work. But it will not, and so the VM aborts. + + Commit 53431b9086b28 made mirror keep the original permissions + and so no other process can "steal" the image. + + (Note that you cannot really do the same with the target image + and then completing the job, because the mirror job always + took/unshared the correct permissions on the target. For + example, it does not share READ_CONSISTENT, which makes it + difficult to let some other qemu process open the image.) + """ + + result = self.vm.qmp('blockdev-mirror', + job_id='mirror', + device='drive0', + target='null', + sync='full') + self.assert_qmp(result, 'return', {}) + + self.vm.event_wait('BLOCK_JOB_READY') + + # We want this to fail because the image cannot be locked. + # If it does not fail, continue still and see what happens. + self.vm_b = iotests.VM(path_suffix='b') + # Must use -blockdev -device so we can use share-rw. + # (And we need share-rw=on because mirror-top was always + # forced to take the WRITE permission so it can write to the + # source image.) + self.vm_b.add_blockdev(f'file,node-name=drive0,filename={source}') + self.vm_b.add_device('virtio-blk,drive=drive0,share-rw=on') + try: + self.vm_b.launch() + print('ERROR: VM B launched successfully, this should not have ' + 'happened') + except qemu.qmp.QMPConnectError: + assert 'Is another process using the image' in self.vm_b.get_log() + + result = self.vm.qmp('block-job-cancel', + device='mirror') + self.assert_qmp(result, 'return', {}) + + self.vm.event_wait('BLOCK_JOB_COMPLETED') + + +if __name__ == '__main__': + # No metadata format driver supported, because they would for + # example always unshare the WRITE permission. The raw driver + # just passes through the permissions from the guest device, and + # those are the permissions that we want to test. + iotests.main(supported_fmts=['raw'], + supported_protocols=['file']) diff --git a/tests/qemu-iotests/tests/mirror-top-perms.out b/tests/qemu-iotests/tests/mirror-top-perms.out new file mode 100644 index 0000000000..ae1213e6f8 --- /dev/null +++ b/tests/qemu-iotests/tests/mirror-top-perms.out @@ -0,0 +1,5 @@ +. +---------------------------------------------------------------------- +Ran 1 tests + +OK -- 2.11.4.GIT