Re: [PATCH v2 1/3] iotests: Specify explicit backing format where sensible
On a Wednesday in 2020, Eric Blake wrote:
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, convert, and amend 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, convert
has -B but no -F, and amend has no shortcuts.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
[...]
Test #225 still uses -b without a format:
./check -vmdk 225
QEMU --
"/home/jtomko/work/qemu/build/tests/qemu-iotests/../../x86_64-softmmu/qemu-system-x86_64"
-nodefaults -display none -accel qtest
QEMU_IMG --
"/home/jtomko/work/qemu/build/tests/qemu-iotests/../../qemu-img"
QEMU_IO -- "/home/jtomko/work/qemu/build/tests/qemu-iotests/../../qemu-io"
--cache writeback --aio threads -f vmdk
QEMU_NBD --
"/home/jtomko/work/qemu/build/tests/qemu-iotests/../../qemu-nbd"
IMGFMT -- vmdk
IMGPROTO -- file
PLATFORM -- Linux/x86_64 lpt 5.4.18-200.fc31.x86_64
TEST_DIR -- /home/jtomko/work/qemu/build/tests/qemu-iotests/scratch
SOCK_DIR -- /tmp/tmp.OQIdhLcITP
SOCKET_SCM_HELPER -- /home/jtomko/work/qemu/build/tests/qemu-iotests/socket_scm_helper
225 fail [10:02:31] [10:02:32] output mismatch (see
225.out.bad)
--- /home/jtomko/work/qemu/tests/qemu-iotests/225.out 2018-09-07 17:21:39.633931691
+0200
+++ /home/jtomko/work/qemu/build/tests/qemu-iotests/225.out.bad 2020-02-27
10:02:32.362755677 +0100
@@ -1,6 +1,7 @@
QA output created by 225
Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1048576
Formatting 'TEST_DIR/t.IMGFMT.not_base', fmt=IMGFMT size=1048576
+qemu-img: warning: Deprecated use of backing file without explicit backing format
(detected format of IMGFMT)
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576
backing_file=TEST_DIR/t.IMGFMT.base
=== Testing fitting VMDK backing image ===
Failures: 225
Failed 1 of 1 iotests
diff --git a/tests/qemu-iotests/030 b/tests/qemu-iotests/030
index aa911d266a13..322e31e2cd93 100755
--- a/tests/qemu-iotests/030
+++ b/tests/qemu-iotests/030
@@ -32,8 +32,12 @@ class TestSingleDrive(iotests.QMPTestCase):
def setUp(self):
iotests.create_image(backing_img, TestSingleDrive.image_len)
- qemu_img('create', '-f', iotests.imgfmt, '-o',
'backing_file=%s' % backing_img, mid_img)
- qemu_img('create', '-f', iotests.imgfmt, '-o',
'backing_file=%s' % mid_img, test_img)
+ qemu_img('create', '-f', iotests.imgfmt,
+ '-o', 'backing_file=%s' % backing_img,
+ '-F', 'raw', mid_img)
+ qemu_img('create', '-f', iotests.imgfmt,
+ '-o', 'backing_file=%s' % mid_img,
+ '-F', iotests.imgfmt, test_img)
Consider not mixing shortcuts with -o options.
qemu_io('-f', 'raw', '-c', 'write
-P 0x1 0 512', backing_img)
qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x1 524288
512', mid_img)
self.vm = iotests.VM().add_drive("blkdebug::" + test_img,
With test #225 fixed:
Reviewed-by: Ján Tomko <jtomko(a)redhat.com>
Jano
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