Fix backing file detection in libvirt live snapshot
When doing a live snapshot, the libvirt driver creates an intermediate qcow2 file with the same backing file as the original disk. However, it calls qemu-img info without specifying the input format explicitly. An authenticated user can write data to a raw disk which will cause this code to misinterpret the disk as a qcow2 file with a user-specified backing file on the host, and return an arbitrary host file as the backing file. This bug does not appear to result in a data leak in this case, but this is hard to verify. It certainly results in corrupt output. Closes-Bug: #1524274 Change-Id: I11485f077d28f4e97529a691e55e3e3c0bea8872
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@ -90,11 +90,11 @@ def create_cow_image(backing_file, path):
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pass
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def get_disk_size(path):
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def get_disk_size(path, format=None):
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return 0
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def get_disk_backing_file(path):
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def get_disk_backing_file(path, format=None):
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return disk_backing_files.get(path, None)
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@ -10957,7 +10957,7 @@ Active: 8381604 kB
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mock_backing.return_value = bckfile
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drvr._live_snapshot(self.context, self.test_instance, mock_dom,
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srcfile, dstfile, "qcow2", {})
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srcfile, dstfile, "qcow2", "qcow2", {})
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mock_dom.XMLDesc.assert_called_once_with(
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fakelibvirt.VIR_DOMAIN_XML_INACTIVE |
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@ -10968,8 +10968,9 @@ Active: 8381604 kB
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fakelibvirt.VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT |
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fakelibvirt.VIR_DOMAIN_BLOCK_REBASE_SHALLOW)
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mock_size.assert_called_once_with(srcfile)
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mock_backing.assert_called_once_with(srcfile, basename=False)
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mock_size.assert_called_once_with(srcfile, format="qcow2")
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mock_backing.assert_called_once_with(srcfile, basename=False,
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format="qcow2")
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mock_create_cow.assert_called_once_with(bckfile, dltfile, 1004009)
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mock_chown.assert_called_once_with(dltfile, os.getuid())
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mock_snapshot.assert_called_once_with(dltfile, "qcow2",
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@ -44,7 +44,7 @@ CONF.register_opts(image_opts)
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IMAGE_API = image.API()
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def qemu_img_info(path):
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def qemu_img_info(path, format=None):
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"""Return an object containing the parsed output from qemu-img info."""
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# TODO(mikal): this code should not be referring to a libvirt specific
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# flag.
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@ -56,8 +56,10 @@ def qemu_img_info(path):
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msg = (_("Path does not exist %(path)s") % {'path': path})
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raise exception.InvalidDiskInfo(reason=msg)
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out, err = utils.execute('env', 'LC_ALL=C', 'LANG=C',
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'qemu-img', 'info', path)
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cmd = ('env', 'LC_ALL=C', 'LANG=C', 'qemu-img', 'info', path)
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if format is not None:
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cmd = cmd + ('-f', format)
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out, err = utils.execute(*cmd)
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if not out:
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msg = (_("Failed to run qemu-img info on %(path)s : %(error)s") %
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{'path': path, 'error': err})
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@ -1429,7 +1429,8 @@ class LibvirtDriver(driver.ComputeDriver):
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# NOTE(xqueralt): libvirt needs o+x in the temp directory
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os.chmod(tmpdir, 0o701)
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self._live_snapshot(context, instance, virt_dom, disk_path,
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out_path, image_format, base)
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out_path, source_format, image_format,
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base)
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else:
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snapshot_backend.snapshot_extract(out_path, image_format)
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finally:
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@ -1539,7 +1540,7 @@ class LibvirtDriver(driver.ComputeDriver):
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self._set_quiesced(context, instance, image_meta, False)
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def _live_snapshot(self, context, instance, domain, disk_path, out_path,
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image_format, image_meta):
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source_format, image_format, image_meta):
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"""Snapshot an instance without downtime."""
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# Save a copy of the domain's persistent XML file
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xml = domain.XMLDesc(
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@ -1557,9 +1558,11 @@ class LibvirtDriver(driver.ComputeDriver):
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# in QEMU 1.3. In order to do this, we need to create
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# a destination image with the original backing file
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# and matching size of the instance root disk.
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src_disk_size = libvirt_utils.get_disk_size(disk_path)
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src_disk_size = libvirt_utils.get_disk_size(disk_path,
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format=source_format)
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src_back_path = libvirt_utils.get_disk_backing_file(disk_path,
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basename=False)
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format=source_format,
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basename=False)
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disk_delta = out_path + '.delta'
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libvirt_utils.create_cow_image(src_back_path, disk_delta,
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src_disk_size)
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@ -270,24 +270,25 @@ def pick_disk_driver_name(hypervisor_version, is_block_dev=False):
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return None
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def get_disk_size(path):
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def get_disk_size(path, format=None):
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"""Get the (virtual) size of a disk image
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:param path: Path to the disk image
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:param format: the on-disk format of path
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:returns: Size (in bytes) of the given disk image as it would be seen
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by a virtual machine.
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"""
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size = images.qemu_img_info(path).virtual_size
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size = images.qemu_img_info(path, format).virtual_size
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return int(size)
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def get_disk_backing_file(path, basename=True):
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def get_disk_backing_file(path, basename=True, format=None):
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"""Get the backing file of a disk image
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:param path: Path to the disk image
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:returns: a path to the image's backing store
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"""
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backing_file = images.qemu_img_info(path).backing_file
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backing_file = images.qemu_img_info(path, format).backing_file
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if backing_file and basename:
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backing_file = os.path.basename(backing_file)
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