d9f059aa6c
Creating an image that requires format probing of the backing image is potentially unsafe (we've had several CVEs over the years based on probes leaking information to the guest on a subsequent boot, although these days tools like libvirt are aware of the issue enough to prevent the worst effects). For example, if our probing algorithm ever changes, or if other tools like libvirt determine a different probe result than we do, then subsequent use of that backing file under a different format will present corrupted data to the guest. Fortunately, the worst effects occur only when the backing image is originally raw, and we at least prevent commit into a probed raw backing file that would change its probed type. Still, it is worth starting a deprecation clock so that future qemu-img can refuse to create backing chains that would rely on probing, to encourage clients to avoid unsafe practices. Most warnings are intentionally emitted from bdrv_img_create() in the block layer, but qemu-img convert uses bdrv_create() which cannot emit its own warning without causing spurious warnings on other code paths. In the end, all command-line image creation or backing file rewriting now performs a check. Furthermore, if we probe a backing file as non-raw, then it is safe to explicitly record that result (rather than relying on future probes); only where we probe a raw image do we care about further warnings to the user when using such an image (for example, commits into a probed-raw backing file are prevented), to help them improve their tooling. But whether or not we make the probe results explicit, we still warn the user to remind them to upgrade their workflow to supply -F always. iotest 114 specifically wants to create an unsafe image for later amendment rather than defaulting to our new default of recording a probed format, so it needs an update. While touching it, expand it to cover all of the various warnings enabled by this patch. iotest 301 also shows a change to qcow messages. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20200706203954.341758-11-eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
76 lines
2.5 KiB
Bash
Executable file
76 lines
2.5 KiB
Bash
Executable file
#!/usr/bin/env bash
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#
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# Test invalid backing file format in qcow2 images
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#
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# Copyright (C) 2014 Red Hat, Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# creator
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owner=kwolf@redhat.com
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seq="$(basename $0)"
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echo "QA output created by $seq"
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status=1 # failure is the default!
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_cleanup()
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{
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_cleanup_test_img
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}
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trap "_cleanup; exit \$status" 0 1 2 3 15
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# get standard environment, filters and checks
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. ./common.rc
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. ./common.filter
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_supported_fmt qcow2
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_supported_proto generic
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_unsupported_proto vxhs
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# At least OpenBSD doesn't seem to have truncate
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_supported_os Linux
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# qcow2.py does not work too well with external data files
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_unsupported_imgopts data_file
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# Intentionally specify backing file without backing format; demonstrate
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# the difference in warning messages when backing file could be probed.
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# Note that only a non-raw probe result will affect the resulting image.
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truncate -s $((64 * 1024 * 1024)) "$TEST_IMG.orig"
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_make_test_img -b "$TEST_IMG.orig" 64M
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TEST_IMG="$TEST_IMG.base" _make_test_img 64M
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$QEMU_IMG convert -O qcow2 -B "$TEST_IMG.orig" "$TEST_IMG.orig" "$TEST_IMG"
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_make_test_img -b "$TEST_IMG.base" 64M
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_make_test_img -u -b "$TEST_IMG.base" 64M
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# Set an invalid backing file format
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$PYTHON qcow2.py "$TEST_IMG" add-header-ext 0xE2792ACA "foo"
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_img_info
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# Try opening the image. Should fail (and not probe) in the first case, but
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# overriding the backing file format should be possible.
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$QEMU_IO -c "open $TEST_IMG" -c "read 0 4k" 2>&1 | _filter_qemu_io | _filter_testdir
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$QEMU_IO -c "open -o backing.driver=$IMGFMT $TEST_IMG" -c "read 0 4k" | _filter_qemu_io
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# Rebase the image, to show that omitting backing format triggers a warning,
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# but probing now lets us use the backing file.
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$QEMU_IMG rebase -u -b "$TEST_IMG.base" "$TEST_IMG"
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$QEMU_IO -c "open $TEST_IMG" -c "read 0 4k" 2>&1 | _filter_qemu_io | _filter_testdir
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# success, all done
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echo '*** done'
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rm -f $seq.full
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status=0
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