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>

1 files changed, 7 insertions, 7 deletions

diff --git a/tests/qemu-iotests/153 b/tests/qemu-iotests/153
index 11e3d28841..34045ea3cf 100755
--- a/tests/qemu-iotests/153
+++ b/tests/qemu-iotests/153
@@ -94,7 +94,7 @@ for opts1 in "" "read-only=on" "read-only=on,force-share=on"; do
 
     echo
     echo "== Creating test image =="
-    _make_test_img -b "${TEST_IMG}.base"
+    _make_test_img -b "${TEST_IMG}.base" -F $IMGFMT
 
     echo
     echo "== Launching QEMU, opts: '$opts1' =="
@@ -125,7 +125,7 @@ for opts1 in "" "read-only=on" "read-only=on,force-share=on"; do
         _run_cmd $QEMU_IMG amend -o "size=$size" $L "${TEST_IMG}"
         _run_cmd $QEMU_IMG commit      $L "${TEST_IMG}"
         _run_cmd $QEMU_IMG resize      $L "${TEST_IMG}" $size
-        _run_cmd $QEMU_IMG rebase      $L "${TEST_IMG}" -b "${TEST_IMG}.base"
+        _run_cmd $QEMU_IMG rebase      $L "${TEST_IMG}" -b "${TEST_IMG}.base" -F $IMGFMT
         _run_cmd $QEMU_IMG snapshot -l $L "${TEST_IMG}"
         _run_cmd $QEMU_IMG convert     $L "${TEST_IMG}" "${TEST_IMG}.convert"
         _run_cmd $QEMU_IMG dd          $L if="${TEST_IMG}" of="${TEST_IMG}.convert" bs=512 count=1
@@ -135,7 +135,7 @@ for opts1 in "" "read-only=on" "read-only=on,force-share=on"; do
         # qemu-img create does not support -U
         if [ -z "$L" ]; then
             _run_cmd $QEMU_IMG create -f $IMGFMT "${TEST_IMG}" \
-                                      -b ${TEST_IMG}.base
+                                      -b ${TEST_IMG}.base -F $IMGFMT
             # Read the file format.  It used to be the case that
             # file-posix simply truncated the file, but the qcow2
             # driver then failed to format it because it was unable
@@ -167,9 +167,9 @@ done
 
 echo
 echo "== Creating ${TEST_IMG}.[abc] ==" | _filter_testdir
-$QEMU_IMG create -f qcow2 "${TEST_IMG}.a" -b "${TEST_IMG}" | _filter_img_create
-$QEMU_IMG create -f qcow2 "${TEST_IMG}.b" -b "${TEST_IMG}" | _filter_img_create
-$QEMU_IMG create -f qcow2 "${TEST_IMG}.c" -b "${TEST_IMG}.b" \
+$QEMU_IMG create -f qcow2 "${TEST_IMG}.a" -b "${TEST_IMG}" -F $IMGFMT | _filter_img_create
+$QEMU_IMG create -f qcow2 "${TEST_IMG}.b" -b "${TEST_IMG}" -F $IMGFMT | _filter_img_create
+$QEMU_IMG create -f qcow2 "${TEST_IMG}.c" -b "${TEST_IMG}.b" -F $IMGFMT \
     | _filter_img_create
 
 echo
@@ -218,7 +218,7 @@ _send_qemu_cmd $QEMU_HANDLE \
 _run_cmd $QEMU_IO "${TEST_IMG}" -c 'write 0 512'
 
 echo "Creating overlay with qemu-img when the guest is running should be allowed"
-_run_cmd $QEMU_IMG create -f $IMGFMT -b "${TEST_IMG}" "${TEST_IMG}.overlay"
+_run_cmd $QEMU_IMG create -f $IMGFMT -b "${TEST_IMG}" -F $IMGFMT "${TEST_IMG}.overlay"
 
 echo "== Closing an image should unlock it =="
 _send_qemu_cmd $QEMU_HANDLE \