File Revert-qemu-img-Require-F-with-b-backing.patch of Package qemu

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File Revert-qemu-img-Require-F-with-b-backing.patch of Package qemu (Revision 1b6b72acc9dd7497b5667399d808e5d8)

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From: "Jose R. Ziviani" <jziviani@suse.de>
Date: Thu, 2 Sep 2021 16:13:08 -0300
Subject: Revert "qemu-img: Require -F with -b backing image"

This reverts commit 497a30dbb065937d67f6c43af6dd78492e1d6f6d.
References: bsc#1190135

Signed-off-by: Jose R Ziviani <jose.ziviani@suse.com>
---
 block.c                         | 37 +++++++++++++++++++++++----------
 docs/about/deprecated.rst       | 20 ++++++++++++++++++
 docs/about/removed-features.rst | 19 -----------------
 qemu-img.c                      |  6 ++----
 tests/qemu-iotests/040          |  4 ++--
 tests/qemu-iotests/041          |  6 ++----
 tests/qemu-iotests/114          | 18 ++++++++--------
 tests/qemu-iotests/114.out      | 11 ++++++----
 tests/qemu-iotests/301          |  4 +++-
 tests/qemu-iotests/301.out      | 16 ++++++++++++--
 10 files changed, 85 insertions(+), 56 deletions(-)

diff --git a/block.c b/block.c
index e97ce0b1c83eb68db8abccfe9086..06f5ff49ee79ab5d423008ecc20e 100644
--- a/block.c
+++ b/block.c
@@ -5119,7 +5119,7 @@ int coroutine_fn bdrv_co_check(BlockDriverState *bs,
  * -ENOTSUP - format driver doesn't support changing the backing file
  */
 int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
-                             const char *backing_fmt, bool require)
+                             const char *backing_fmt, bool warn)
 {
     BlockDriver *drv = bs->drv;
     int ret;
@@ -5133,8 +5133,10 @@ int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
         return -EINVAL;
     }
 
-    if (require && backing_file && !backing_fmt) {
-        return -EINVAL;
+    if (warn && backing_file && !backing_fmt) {
+        warn_report("Deprecated use of backing file without explicit "
+                    "backing format, use of this image requires "
+                    "potentially unsafe format probing");
     }
 
     if (drv->bdrv_change_backing_file != NULL) {
@@ -6647,11 +6649,24 @@ void bdrv_img_create(const char *filename, const char *fmt,
             goto out;
         } else {
             if (!backing_fmt) {
-                error_setg(&local_err,
-                           "Backing file specified without backing format");
-                error_append_hint(&local_err, "Detected format of %s.",
-                                  bs->drv->format_name);
-                goto out;
+                warn_report("Deprecated use of backing file without explicit "
+                            "backing format (detected format of %s)",
+                            bs->drv->format_name);
+                if (bs->drv != &bdrv_raw) {
+                    /*
+                     * A probe of raw deserves the most attention:
+                     * leaving the backing format out of the image
+                     * will ensure bs->probed is set (ensuring we
+                     * don't accidentally commit into the backing
+                     * file), and allow more spots to warn the users
+                     * to fix their toolchain when opening this image
+                     * later.  For other images, we can safely record
+                     * the format that we probed.
+                     */
+                    backing_fmt = bs->drv->format_name;
+                    qemu_opt_set(opts, BLOCK_OPT_BACKING_FMT, backing_fmt,
+                                 NULL);
+                }
             }
             if (size == -1) {
                 /* Opened BS, have no size */
@@ -6668,9 +6683,9 @@ void bdrv_img_create(const char *filename, const char *fmt,
         }
         /* (backing_file && !(flags & BDRV_O_NO_BACKING)) */
     } else if (backing_file && !backing_fmt) {
-        error_setg(&local_err,
-                   "Backing file specified without backing format");
-        goto out;
+        warn_report("Deprecated use of unopened backing file without "
+                    "explicit backing format, use of this image requires "
+                    "potentially unsafe format probing");
     }
 
     if (size == -1) {
diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 6d438f1c8d41e19c4fc976d1c7da..638f1000cbd19a72aa456104446f 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -300,6 +300,26 @@ this CPU is also deprecated.
 Related binaries
 ----------------
 
+qemu-img backing file without format (since 5.1)
+''''''''''''''''''''''''''''''''''''''''''''''''
+
+The use of ``qemu-img create``, ``qemu-img rebase``, or ``qemu-img
+convert`` to create or modify an image that depends on a backing file
+now recommends that an explicit backing format be provided.  This is
+for safety: if QEMU probes a different format than what you thought,
+the data presented to the guest will be corrupt; similarly, presenting
+a raw image to a guest allows a potential security exploit if a future
+probe sees a non-raw image based on guest writes.
+
+To avoid the warning message, or even future refusal to create an
+unsafe image, you must pass ``-o backing_fmt=`` (or the shorthand
+``-F`` during create) to specify the intended backing format.  You may
+use ``qemu-img rebase -u`` to retroactively add a backing format to an
+existing image.  However, be aware that there are already potential
+security risks to blindly using ``qemu-img info`` to probe the format
+of an untrusted backing image, when deciding what format to add into
+an existing image.
+
 Backwards compatibility
 -----------------------
 
diff --git a/docs/about/removed-features.rst b/docs/about/removed-features.rst
index cbfa1a8e31a69200c2bb97ddffb1..afadc8f7e0fc4e2377ee85d6166c 100644
--- a/docs/about/removed-features.rst
+++ b/docs/about/removed-features.rst
@@ -678,25 +678,6 @@ backing chain should be performed with ``qemu-img rebase -u`` either
 before or after the remaining changes being performed by amend, as
 appropriate.
 
-qemu-img backing file without format (removed in 6.1)
-'''''''''''''''''''''''''''''''''''''''''''''''''''''
-
-The use of ``qemu-img create``, ``qemu-img rebase``, or ``qemu-img
-convert`` to create or modify an image that depends on a backing file
-now requires that an explicit backing format be provided.  This is
-for safety: if QEMU probes a different format than what you thought,
-the data presented to the guest will be corrupt; similarly, presenting
-a raw image to a guest allows a potential security exploit if a future
-probe sees a non-raw image based on guest writes.
-
-To avoid creating unsafe backing chains, you must pass ``-o
-backing_fmt=`` (or the shorthand ``-F`` during create) to specify the
-intended backing format.  You may use ``qemu-img rebase -u`` to
-retroactively add a backing format to an existing image.  However, be
-aware that there are already potential security risks to blindly using
-``qemu-img info`` to probe the format of an untrusted backing image,
-when deciding what format to add into an existing image.
-
 Block devices
 -------------
 
diff --git a/qemu-img.c b/qemu-img.c
index 3ebd09245290878c24c8f1412146..4da817857f3efccc2bd83297500b 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2549,10 +2549,8 @@ static int img_convert(int argc, char **argv)
 
     if (out_baseimg_param) {
         if (!qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT)) {
-            error_report("Use of backing file requires explicit "
-                         "backing format");
-            ret = -1;
-            goto out;
+            warn_report("Deprecated use of backing file without explicit "
+                        "backing format");
         }
     }
 
diff --git a/tests/qemu-iotests/040 b/tests/qemu-iotests/040
index f3677de9dfde326ad85515ec8bfa..ba7cb34ce8cf95df6fa63f9eb8f0 100755
--- a/tests/qemu-iotests/040
+++ b/tests/qemu-iotests/040
@@ -920,8 +920,8 @@ class TestCommitWithOverriddenBacking(iotests.QMPTestCase):
     def setUp(self):
         qemu_img('create', '-f', iotests.imgfmt, self.img_base_a, '1M')
         qemu_img('create', '-f', iotests.imgfmt, self.img_base_b, '1M')
-        qemu_img('create', '-f', iotests.imgfmt, '-b', self.img_base_a,
-                 '-F', iotests.imgfmt, self.img_top)
+        qemu_img('create', '-f', iotests.imgfmt, '-b', self.img_base_a, \
+                 self.img_top)
 
         self.vm = iotests.VM()
         self.vm.launch()
diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041
index db9f5dc540e84c597d30521d4b6c..5cc02b24fc7a8be3d28e0e9737cb 100755
--- a/tests/qemu-iotests/041
+++ b/tests/qemu-iotests/041
@@ -1295,10 +1295,8 @@ class TestReplaces(iotests.QMPTestCase):
 class TestFilters(iotests.QMPTestCase):
     def setUp(self):
         qemu_img('create', '-f', iotests.imgfmt, backing_img, '1M')
-        qemu_img('create', '-f', iotests.imgfmt, '-b', backing_img,
-                 '-F', iotests.imgfmt, test_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-b', backing_img,
-                 '-F', iotests.imgfmt, target_img)
+        qemu_img('create', '-f', iotests.imgfmt, '-b', backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt, '-b', backing_img, target_img)
 
         qemu_io('-c', 'write -P 1 0 512k', backing_img)
         qemu_io('-c', 'write -P 2 512k 512k', test_img)
diff --git a/tests/qemu-iotests/114 b/tests/qemu-iotests/114
index de6fd327eea9e2ef5d21fc6fbf0b..43cb0bc6c3443a809f4dcd42ecce 100755
--- a/tests/qemu-iotests/114
+++ b/tests/qemu-iotests/114
@@ -44,16 +44,16 @@ _supported_os Linux
 # qcow2.py does not work too well with external data files
 _unsupported_imgopts data_file
 
-# Older qemu-img could set up backing file without backing format; modern
-# qemu can't but we can use qcow2.py to simulate older files.
+# Intentionally specify backing file without backing format; demonstrate
+# the difference in warning messages when backing file could be probed.
+# Note that only a non-raw probe result will affect the resulting image.
 truncate -s $((64 * 1024 * 1024)) "$TEST_IMG.orig"
-_make_test_img -b "$TEST_IMG.orig" -F raw 64M
-$PYTHON qcow2.py "$TEST_IMG" del-header-ext 0xE2792ACA
+_make_test_img -b "$TEST_IMG.orig" 64M
 
 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
 $QEMU_IMG convert -O qcow2 -B "$TEST_IMG.orig" "$TEST_IMG.orig" "$TEST_IMG"
-_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 64M
-_make_test_img -u -b "$TEST_IMG.base" -F $IMGFMT 64M
+_make_test_img -b "$TEST_IMG.base" 64M
+_make_test_img -u -b "$TEST_IMG.base" 64M
 
 # Set an invalid backing file format
 $PYTHON qcow2.py "$TEST_IMG" add-header-ext 0xE2792ACA "foo"
@@ -64,9 +64,9 @@ _img_info
 $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
 
-# Rebase the image, to show that backing format is required.
-($QEMU_IMG rebase -u -b "$TEST_IMG.base" "$TEST_IMG" 2>&1 && echo "unexpected pass") | _filter_testdir
-$QEMU_IMG rebase -u -b "$TEST_IMG.base" -F $IMGFMT "$TEST_IMG"
+# Rebase the image, to show that omitting backing format triggers a warning,
+# but probing now lets us use the backing file.
+$QEMU_IMG rebase -u -b "$TEST_IMG.base" "$TEST_IMG"
 $QEMU_IO -c "open $TEST_IMG" -c "read 0 4k" 2>&1 | _filter_qemu_io | _filter_testdir
 
 # success, all done
diff --git a/tests/qemu-iotests/114.out b/tests/qemu-iotests/114.out
index 6d638da266e495e8bed2fbcf919e..0a37d20c82a95d6d5ea9fc9635e7 100644
--- a/tests/qemu-iotests/114.out
+++ b/tests/qemu-iotests/114.out
@@ -1,9 +1,12 @@
 QA output created by 114
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.orig backing_fmt=raw
+qemu-img: warning: Deprecated use of backing file without explicit backing format (detected format of raw)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.orig
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-qemu-img: Use of backing file requires explicit backing format
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+qemu-img: warning: Deprecated use of backing file without explicit backing format
+qemu-img: warning: Deprecated use of backing file without explicit backing format (detected format of IMGFMT)
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+qemu-img: warning: Deprecated use of unopened backing file without explicit backing format, use of this image requires potentially unsafe format probing
+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: 64 MiB (67108864 bytes)
@@ -14,7 +17,7 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Could not open backing file: Unknow
 no file open, try 'help open'
 read 4096/4096 bytes at offset 0
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-qemu-img: Could not change the backing file to 'TEST_DIR/t.qcow2.base': Invalid argument
+qemu-img: warning: Deprecated use of backing file without explicit backing format, use of this image requires potentially unsafe format probing
 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/301 b/tests/qemu-iotests/301
index 220de1043fa5dcad8f8563a452c1..9f943cadbe24413c7f453101a6a9 100755
--- a/tests/qemu-iotests/301
+++ b/tests/qemu-iotests/301
@@ -3,7 +3,7 @@
 #
 # Test qcow backing file warnings
 #
-# Copyright (C) 2020-2021 Red Hat, Inc.
+# Copyright (C) 2020 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
@@ -46,6 +46,7 @@ echo "== qcow backed by qcow =="
 
 TEST_IMG="$TEST_IMG.base" _make_test_img $size
 _make_test_img -b "$TEST_IMG.base" $size
+_img_info
 _make_test_img -b "$TEST_IMG.base" -F $IMGFMT $size
 _img_info
 
@@ -70,6 +71,7 @@ echo "== qcow backed by raw =="
 rm "$TEST_IMG.base"
 truncate --size=$size "$TEST_IMG.base"
 _make_test_img -b "$TEST_IMG.base" $size
+_img_info
 _make_test_img -b "$TEST_IMG.base" -F raw $size
 _img_info
 
diff --git a/tests/qemu-iotests/301.out b/tests/qemu-iotests/301.out
index e280658191e1eba861b821fafa35..9004dad6392f4a0ec685fb4a80d1 100644
--- a/tests/qemu-iotests/301.out
+++ b/tests/qemu-iotests/301.out
@@ -2,7 +2,13 @@ QA output created by 301
 
 == qcow backed by qcow ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=33554432
-qemu-img: TEST_DIR/t.IMGFMT: Backing file specified without backing format
+qemu-img: warning: Deprecated use of backing file without explicit backing format (detected format of IMGFMT)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 32 MiB (33554432 bytes)
+cluster_size: 512
+backing file: TEST_DIR/t.IMGFMT.base
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 image: TEST_DIR/t.IMGFMT
 file format: IMGFMT
@@ -30,7 +36,13 @@ cluster_size: 512
 backing file: TEST_DIR/t.IMGFMT.base
 
 == qcow backed by raw ==
-qemu-img: TEST_DIR/t.IMGFMT: Backing file specified without backing format
+qemu-img: warning: Deprecated use of backing file without explicit backing format (detected format of raw)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 32 MiB (33554432 bytes)
+cluster_size: 512
+backing file: TEST_DIR/t.IMGFMT.base
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=raw
 image: TEST_DIR/t.IMGFMT
 file format: IMGFMT

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File Revert-qemu-img-Require-F-with-b-backing.patch of Package qemu (Revision 1b6b72acc9dd7497b5667399d808e5d8)

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