qemu-e2k/tests/qemu-iotests/126
Eric Blake b66ff2c298 iotests: Specify explicit backing format where sensible
There are many existing qcow2 images that specify a backing file but
no format.  This has been the source of CVEs in the past, but has
become more prominent of a problem now that libvirt has switched to
-blockdev.  With older -drive, at least the probing was always done by
qemu (so the only risk of a changed format between successive boots of
a guest was if qemu was upgraded and probed differently).  But with
newer -blockdev, libvirt must specify a format; if libvirt guesses raw
where the image was formatted, this results in data corruption visible
to the guest; conversely, if libvirt guesses qcow2 where qemu was
using raw, this can result in potential security holes, so modern
libvirt instead refuses to use images without explicit backing format.

The change in libvirt to reject images without explicit backing format
has pointed out that a number of tools have been far too reliant on
probing in the past.  It's time to set a better example in our own
iotests of properly setting this parameter.

iotest calls to create, rebase, and convert are all impacted to some
degree.  It's a bit annoying that we are inconsistent on command line
- while all of those accept -o backing_file=...,backing_fmt=..., the
shortcuts are different: create and rebase have -b and -F, while
convert has -B but no -F.  (amend has no shortcuts, but the previous
patch just deprecated the use of amend to change backing chains).

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200706203954.341758-9-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-07-14 15:18:59 +02:00

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#!/usr/bin/env bash
#
# Tests handling of colons in filenames (which may be confused with protocol
# prefixes)
#
# Copyright (C) 2017 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/>.
#
# creator
owner=mreitz@redhat.com
seq="$(basename $0)"
echo "QA output created by $seq"
status=1 # failure is the default!
# get standard environment, filters and checks
. ./common.rc
. ./common.filter
# Needs backing file support
_supported_fmt qcow qcow2 qed vmdk
_unsupported_imgopts "subformat=monolithicFlat" \
"subformat=twoGbMaxExtentFlat"
# This is the default protocol (and we want to test the difference between
# colons which separate a protocol prefix from the rest and colons which are
# just part of the filename, so we cannot test protocols which require a prefix)
_supported_proto file
echo
echo '=== Testing plain files ==='
echo
# A colon after a slash is not a protocol prefix separator
TEST_IMG="$TEST_DIR/a:b.$IMGFMT" _make_test_img 64M
_rm_test_img "$TEST_DIR/a:b.$IMGFMT"
# But if you want to be really sure, you can do this
TEST_IMG="file:$TEST_DIR/a:b.$IMGFMT" _make_test_img 64M
_rm_test_img "$TEST_DIR/a:b.$IMGFMT"
echo
echo '=== Testing relative backing filename resolution ==='
echo
BASE_IMG="$TEST_DIR/image:base.$IMGFMT"
TOP_IMG="$TEST_DIR/image:top.$IMGFMT"
TEST_IMG=$BASE_IMG _make_test_img 64M
TEST_IMG=$TOP_IMG _make_test_img -b ./image:base.$IMGFMT -F $IMGFMT
# (1) The default cluster size depends on the image format
# (2) vmdk only supports vmdk backing files, so it always reports the
# format of its backing file as such (but neither it nor qcow
# support the backing_fmt creation option, so we cannot use that to
# harmonize the output across all image formats this test supports)
TEST_IMG=$TOP_IMG _img_info | grep -ve 'cluster_size' -e 'backing file format'
_rm_test_img "$BASE_IMG"
_rm_test_img "$TOP_IMG"
# Do another test where we access both top and base without any slash in them
echo
pushd "$TEST_DIR" >/dev/null
BASE_IMG="base.$IMGFMT"
TOP_IMG="file:image:top.$IMGFMT"
TEST_IMG=$BASE_IMG _make_test_img 64M
TEST_IMG=$TOP_IMG _make_test_img -b "$BASE_IMG" -F $IMGFMT
TEST_IMG=$TOP_IMG _img_info | grep -ve 'cluster_size' -e 'backing file format'
_rm_test_img "$BASE_IMG"
_rm_test_img "image:top.$IMGFMT"
popd >/dev/null
# Note that we could also do the same test with BASE_IMG=file:image:base.$IMGFMT
# -- but behavior for that case is a bit strange. Protocol-prefixed paths are
# in a sense always absolute paths, so such paths will never be combined with
# the path of the overlay. But since "image:base.$IMGFMT" is actually a
# relative path, it will always be evaluated relative to qemu's CWD (but not
# relative to the overlay!). While this is more or less intended, it is still
# pretty strange and thus not something that is tested here.
# (The root of the issue is the use of a relative path with a protocol prefix.
# This may always give you weird results because in one sense, qemu considers
# such paths absolute, whereas in another, they are still relative.)
# success, all done
echo '*** done'
rm -f $seq.full
status=0