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From a0f50f0877463e9370ffa411bd826d7c704ab9fe Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Sat, 13 Jun 2015 16:22:30 +0200
Subject: [PATCH 36/42] block: Don't probe for unknown backing file format

Message-id: <1434212556-3927-37-git-send-email-mreitz@redhat.com>
Patchwork-id: 66055
O-Subject: [RHEL-7.2 qemu-kvm PATCH 36/42] block: Don't probe for unknown backing file format
Bugzilla: 1129893
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

From: Kevin Wolf <kwolf@redhat.com>

BZ: 1129893

If a qcow2 image specifies a backing file format that doesn't correspond
to any format driver that qemu knows, we shouldn't fall back to probing,
but simply error out.

Not looking up the backing file driver in bdrv_open_backing_file(), but
just filling in the "driver" option if it isn't there moves us closer to
the goal of having everything in QDict options and gets us the error
handling of bdrv_open(), which correctly refuses unknown drivers.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 1416935562-7760-4-git-send-email-kwolf@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit c5f6e493bb5339d244eae5d3f21c5b6d73996739)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

Conflicts:
	block.c
	tests/qemu-iotests/114.out

Downstream is missing a check whether the driver specified by the
"driver" option is actually valid (if it is not, it will be probed
anyway); this check is introduced upstream by
17b005f1d422d4581f8ce95b75d603deb081f4f3, but that commit has a couple
of dependencies and relies on a code path that is very different from
downstream (e.g. not bdrv_file_open() anymore). So I just introduced the
check in this patch.

Also, the different code paths upstream and downstream result in the
error message missing the "Could not open backing file:" part, which
means that 114.out has to be fixed up.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block.c                    | 12 ++++++---
 tests/qemu-iotests/114     | 61 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/114.out | 13 ++++++++++
 tests/qemu-iotests/group   |  1 +
 4 files changed, 83 insertions(+), 4 deletions(-)
 create mode 100755 tests/qemu-iotests/114
 create mode 100644 tests/qemu-iotests/114.out

diff --git a/block.c b/block.c
index fa6e192..e36fa2f 100644
--- a/block.c
+++ b/block.c
@@ -1010,7 +1010,6 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
 {
     char backing_filename[PATH_MAX];
     int back_flags, ret;
-    BlockDriver *back_drv = NULL;
     Error *local_err = NULL;
 
     if (bs->backing_hd != NULL) {
@@ -1036,8 +1035,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
 
     bs->backing_hd = bdrv_new("", &error_abort);
 
-    if (bs->backing_format[0] != '\0') {
-        back_drv = bdrv_find_format(bs->backing_format);
+    if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
+        qdict_put(options, "driver", qstring_from_str(bs->backing_format));
     }
 
     /* backing files always opened read-only */
@@ -1046,7 +1045,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
 
     ret = bdrv_open(bs->backing_hd,
                     *backing_filename ? backing_filename : NULL, options,
-                    back_flags, back_drv, &local_err);
+                    back_flags, NULL, &local_err);
     if (ret < 0) {
         bdrv_unref(bs->backing_hd);
         bs->backing_hd = NULL;
@@ -1244,6 +1243,11 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
     if (drvname) {
         drv = bdrv_find_format(drvname);
         qdict_del(options, "driver");
+        if (!drv) {
+            error_setg(errp, "Unknown driver '%s'", drvname);
+            ret = -EINVAL;
+            goto unlink_and_fail;
+        }
     }
 
     if (!drv) {
diff --git a/tests/qemu-iotests/114 b/tests/qemu-iotests/114
new file mode 100755
index 0000000..d02e7ff
--- /dev/null
+++ b/tests/qemu-iotests/114
@@ -0,0 +1,61 @@
+#!/bin/bash
+#
+# Test invalid backing file format in qcow2 images
+#
+# Copyright (C) 2014 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow2
+_supported_proto generic
+_supported_os Linux
+
+
+TEST_IMG="$TEST_IMG.base" _make_test_img 64M
+_make_test_img -b "$TEST_IMG.base" 64M
+
+# Set an invalid backing file format
+$PYTHON qcow2.py "$TEST_IMG" add-header-ext 0xE2792ACA "foo"
+_img_info
+
+# Try opening the image. Should fail (and not probe) in the first case, but
+# overriding the backing file format should be possible.
+$QEMU_IO -c "open $TEST_IMG" -c "read 0 4k" 2>&1 | _filter_qemu_io | _filter_testdir
+$QEMU_IO -c "open -o backing.driver=$IMGFMT $TEST_IMG" -c "read 0 4k" | _filter_qemu_io
+
+# success, all done
+echo '*** done'
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/114.out b/tests/qemu-iotests/114.out
new file mode 100644
index 0000000..de8f529
--- /dev/null
+++ b/tests/qemu-iotests/114.out
@@ -0,0 +1,13 @@
+QA output created by 114
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file='TEST_DIR/t.IMGFMT.base' 
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 64M (67108864 bytes)
+cluster_size: 65536
+backing file: TEST_DIR/t.IMGFMT.base
+backing file format: foo
+qemu-io: can't open device TEST_DIR/t.qcow2: Unknown driver 'foo'
+read 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+*** done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 695ab02..5867cf7 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -88,3 +88,4 @@
 105 rw auto quick
 107 rw auto quick
 108 rw auto quick
+114 rw auto quick
-- 
1.8.3.1