qemu/tests/qemu-iotests/252
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 for rebasing COW images that require zero cluster support
#
# Copyright (C) 2019 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 $seq"
status=1 # failure is the default!
_cleanup()
{
_cleanup_test_img
_rm_test_img "$TEST_IMG.base_new"
}
trap "_cleanup; exit \$status" 0 1 2 3 15
# get standard environment, filters and checks
. ./common.rc
. ./common.filter
. ./common.pattern
# Currently only qcow2 and qed support rebasing, and only qcow2 v3 has
# zero cluster support
_supported_fmt qcow2
_unsupported_imgopts 'compat=0.10'
_supported_proto file
_supported_os Linux
CLUSTER_SIZE=65536
echo
echo "=== Test rebase without input base ==="
echo
# Cluster allocations to be tested:
#
# Backing (new) 11 -- 11 -- 11 --
# COW image 22 22 11 11 -- --
#
# Expected result:
#
# COW image 22 22 11 11 00 --
#
# (Cluster 2 might be "--" after the rebase, too, but rebase just
# compares the new backing file to the old one and disregards the
# overlay. Therefore, it will never discard overlay clusters.)
_make_test_img $((6 * CLUSTER_SIZE))
TEST_IMG="$TEST_IMG.base_new" _make_test_img $((6 * CLUSTER_SIZE))
echo
$QEMU_IO "$TEST_IMG" \
-c "write -P 0x22 $((0 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
-c "write -P 0x11 $((2 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
| _filter_qemu_io
$QEMU_IO "$TEST_IMG.base_new" \
-c "write -P 0x11 $((0 * CLUSTER_SIZE)) $CLUSTER_SIZE" \
-c "write -P 0x11 $((2 * CLUSTER_SIZE)) $CLUSTER_SIZE" \
-c "write -P 0x11 $((4 * CLUSTER_SIZE)) $CLUSTER_SIZE" \
| _filter_qemu_io
echo
# This should be a no-op
$QEMU_IMG rebase -b "" "$TEST_IMG"
# Verify the data is correct
$QEMU_IO "$TEST_IMG" \
-c "read -P 0x22 $((0 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
-c "read -P 0x11 $((2 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
-c "read -P 0x00 $((4 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
| _filter_qemu_io
echo
# Verify the allocation status (first four cluster should be allocated
# in TEST_IMG, clusters 4 and 5 should be unallocated (marked as zero
# clusters here because there is no backing file))
$QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
echo
$QEMU_IMG rebase -b "$TEST_IMG.base_new" -F $IMGFMT "$TEST_IMG"
# Verify the data is correct
$QEMU_IO "$TEST_IMG" \
-c "read -P 0x22 $((0 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
-c "read -P 0x11 $((2 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
-c "read -P 0x00 $((4 * CLUSTER_SIZE)) $((2 * CLUSTER_SIZE))" \
| _filter_qemu_io
echo
# Verify the allocation status (first four cluster should be allocated
# in TEST_IMG, cluster 4 should be zero, and cluster 5 should be
# unallocated (signified by '"depth": 1'))
$QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
# success, all done
echo "*** done"
rm -f $seq.full
status=0