b66ff2c298
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>
84 lines
2.7 KiB
Bash
Executable File
84 lines
2.7 KiB
Bash
Executable File
#!/usr/bin/env bash
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#
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# Test large write to a qcow2 image
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#
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# Copyright (C) 2019 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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seq=$(basename "$0")
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echo "QA output created by $seq"
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status=1 # failure is the default!
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_cleanup()
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{
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_cleanup_test_img
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}
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trap "_cleanup; exit \$status" 0 1 2 3 15
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# get standard environment, filters and checks
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. ./common.rc
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. ./common.filter
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# This is a qcow2 regression test
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_supported_fmt qcow2
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_supported_proto file
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_supported_os Linux
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# We use our own external data file and our own cluster size, and we
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# require v3 images
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_unsupported_imgopts data_file cluster_size 'compat=0.10'
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# We need a backing file so that handle_alloc_space() will not do
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# anything. (If it were to do anything, it would simply fail its
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# write-zeroes request because the request range is too large.)
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TEST_IMG="$TEST_IMG.base" _make_test_img 4G
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$QEMU_IO -c 'write 0 512' "$TEST_IMG.base" | _filter_qemu_io
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# (Use .orig because _cleanup_test_img will remove that file)
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# We need a large cluster size, see below for why (above the $QEMU_IO
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# invocation)
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_make_test_img -o cluster_size=2M,data_file="$TEST_IMG.orig" \
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-b "$TEST_IMG.base" -F $IMGFMT 4G
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# We want a null-co as the data file, because it allows us to quickly
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# "write" 2G of data without using any space.
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# (qemu-img create does not like it, though, because null-co does not
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# support image creation.)
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$QEMU_IMG amend -o data_file="json:{'driver':'null-co',,'size':'4294967296'}" \
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"$TEST_IMG"
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# This gives us a range of:
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# 2^31 - 512 + 768 - 1 = 2^31 + 255 > 2^31
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# until the beginning of the end COW block. (The total allocation
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# size depends on the cluster size, but all that is important is that
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# it exceeds INT_MAX.)
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#
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# 2^31 - 512 is the maximum request size. We want this to result in a
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# single allocation, and because the qcow2 driver splits allocations
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# on L2 boundaries, we need large L2 tables; hence the cluster size of
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# 2 MB. (Anything from 256 kB should work, though, because then one L2
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# table covers 8 GB.)
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$QEMU_IO -c "write 768 $((2 ** 31 - 512))" "$TEST_IMG" | _filter_qemu_io
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_check_test_img
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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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