Add a test accompanying commit 53431b9086b2832ca1aeff0c55e186e9ed79bd11
("block/mirror: Fix mirror_top's permissions").

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 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 <http://www.gnu.org/licenses/>.
+#
+
+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
-- 
2.29.2

On 3/31/21 7:28 AM, Max Reitz wrote:
> Add a test accompanying commit 53431b9086b2832ca1aeff0c55e186e9ed79bd11
> ("block/mirror: Fix mirror_top's permissions").
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  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

Safe for -rc2 if you want to get it in.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

31.03.2021 15:28, Max Reitz wrote:
> Add a test accompanying commit 53431b9086b2832ca1aeff0c55e186e9ed79bd11
> ("block/mirror: Fix mirror_top's permissions").
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>   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 <http://www.gnu.org/licenses/>.
> +#
> +
> +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.

This comment is about vm_b.launch(), not about creating vm object. Probably better to move it down

> +        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')

probably iotests.log() is better here.

> +        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
> 

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

-- 
Best regards,
Vladimir

On 01.04.21 10:32, Vladimir Sementsov-Ogievskiy wrote:
> 31.03.2021 15:28, Max Reitz wrote:
>> Add a test accompanying commit 53431b9086b2832ca1aeff0c55e186e9ed79bd11
>> ("block/mirror: Fix mirror_top's permissions").
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   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 <http://www.gnu.org/licenses/>.
>> +#
>> +
>> +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.
> 
> This comment is about vm_b.launch(), not about creating vm object. 
> Probably better to move it down

I kind of meant this as a general comment on what this VM is for.  I 
think I kind of like any comment here, and I don’t see a practical 
advantage in having this comment above the try-except, because the whole 
“launch VM, see it fail” block is kind of one monolithic concept.

>> +        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')
> 
> probably iotests.log() is better here.

No, because logging is disabled, and so it wouldn’t be visible.  I’d 
need to enable logging, which would make the test quite different overall.

Max

>> +        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
>>
> 
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> 

Am 31.03.2021 um 14:28 hat Max Reitz geschrieben:
> Add a test accompanying commit 53431b9086b2832ca1aeff0c55e186e9ed79bd11
> ("block/mirror: Fix mirror_top's permissions").
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>

Thanks, applied to the block branch.

Kevin