Re: [PATCH v2 1/3] iotests: Specify explicit backing format where sensible

[Ján Tomko]

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 <address@hidden>
> ---

[...]

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 <address@hidden>

Jano

signature.asc
Description: PGP signature