[PULL 0/4] Block layer patches (CVE-2024-4467)

[PULL 0/4] Block layer patches (CVE-2024-4467)

[Kevin Wolf]

The following changes since commit c80a339587fe4148292c260716482dd2f86d4476:

  Merge tag 'pull-target-arm-20240701' of https://git.linaro.org/people/pmaydell/qemu-arm into staging (2024-07-01 10:41:45 -0700)

are available in the Git repository at:

  https://repo.or.cz/qemu/kevin.git tags/for-upstream

for you to fetch changes up to 7ead946998610657d38d1a505d5f25300d4ca613:

  block: Parse filenames only when explicitly requested (2024-07-02 18:12:30 +0200)

----------------------------------------------------------------
Block layer patches (CVE-2024-4467)

- Don't open qcow2 data files in 'qemu-img info'
- Disallow protocol prefixes for qcow2 data files, VMDK extent files and
  other child nodes that are neither 'file' nor 'backing'

----------------------------------------------------------------
Kevin Wolf (4):
      qcow2: Don't open data_file with BDRV_O_NO_IO
      iotests/244: Don't store data-file with protocol in image
      iotests/270: Don't store data-file with json: prefix in image
      block: Parse filenames only when explicitly requested

 block.c                    | 90 +++++++++++++++++++++++++++++-----------------
 block/qcow2.c              | 17 ++++++++-
 tests/qemu-iotests/061     |  6 ++--
 tests/qemu-iotests/061.out |  8 +++--
 tests/qemu-iotests/244     | 19 ++++++++--
 tests/qemu-iotests/270     | 14 ++++++--
 6 files changed, 110 insertions(+), 44 deletions(-)

[PULL 1/4] qcow2: Don't open data_file with BDRV_O_NO_IO

[Kevin Wolf]

One use case for 'qemu-img info' is verifying that untrusted images
don't reference an unwanted external file, be it as a backing file or an
external data file. To make sure that calling 'qemu-img info' can't
already have undesired side effects with a malicious image, just don't
open the data file at all with BDRV_O_NO_IO. If nothing ever tries to do
I/O, we don't need to have it open.

This changes the output of iotests case 061, which used 'qemu-img info'
to show that opening an image with an invalid data file fails. After
this patch, it succeeds. Replace this part of the test with a qemu-io
call, but keep the final 'qemu-img info' to show that the invalid data
file is correctly displayed in the output.

Fixes: CVE-2024-4467
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
---
 block/qcow2.c              | 17 ++++++++++++++++-
 tests/qemu-iotests/061     |  6 ++++--
 tests/qemu-iotests/061.out |  8 ++++++--
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 10883a2494..70b19730a3 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1636,7 +1636,22 @@ qcow2_do_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
-    if (open_data_file) {
+    if (open_data_file && (flags & BDRV_O_NO_IO)) {
+        /*
+         * Don't open the data file for 'qemu-img info' so that it can be used
+         * to verify that an untrusted qcow2 image doesn't refer to external
+         * files.
+         *
+         * Note: This still makes has_data_file() return true.
+         */
+        if (s->incompatible_features & QCOW2_INCOMPAT_DATA_FILE) {
+            s->data_file = NULL;
+        } else {
+            s->data_file = bs->file;
+        }
+        qdict_extract_subqdict(options, NULL, "data-file.");
+        qdict_del(options, "data-file");
+    } else if (open_data_file) {
         /* Open external data file */
         bdrv_graph_co_rdunlock();
         s->data_file = bdrv_co_open_child(NULL, options, "data-file", bs,
diff --git a/tests/qemu-iotests/061 b/tests/qemu-iotests/061
index 53c7d428e3..b71ac097d1 100755
--- a/tests/qemu-iotests/061
+++ b/tests/qemu-iotests/061
@@ -326,12 +326,14 @@ $QEMU_IMG amend -o "data_file=foo" "$TEST_IMG"
 echo
 _make_test_img -o "compat=1.1,data_file=$TEST_IMG.data" 64M
 $QEMU_IMG amend -o "data_file=foo" "$TEST_IMG"
-_img_info --format-specific
+$QEMU_IO -c "read 0 4k" "$TEST_IMG" 2>&1 | _filter_testdir | _filter_imgfmt
+$QEMU_IO -c "open -o data-file.filename=$TEST_IMG.data,file.filename=$TEST_IMG" -c "read 0 4k" | _filter_qemu_io
 TEST_IMG="data-file.filename=$TEST_IMG.data,file.filename=$TEST_IMG" _img_info --format-specific --image-opts
 
 echo
 $QEMU_IMG amend -o "data_file=" --image-opts "data-file.filename=$TEST_IMG.data,file.filename=$TEST_IMG"
-_img_info --format-specific
+$QEMU_IO -c "read 0 4k" "$TEST_IMG" 2>&1 | _filter_testdir | _filter_imgfmt
+$QEMU_IO -c "open -o data-file.filename=$TEST_IMG.data,file.filename=$TEST_IMG" -c "read 0 4k" | _filter_qemu_io
 TEST_IMG="data-file.filename=$TEST_IMG.data,file.filename=$TEST_IMG" _img_info --format-specific --image-opts
 
 echo
diff --git a/tests/qemu-iotests/061.out b/tests/qemu-iotests/061.out
index 139fc68177..24c33add7c 100644
--- a/tests/qemu-iotests/061.out
+++ b/tests/qemu-iotests/061.out
@@ -545,7 +545,9 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 qemu-img: data-file can only be set for images that use an external data file
 
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 data_file=TEST_DIR/t.IMGFMT.data
-qemu-img: Could not open 'TEST_DIR/t.IMGFMT': Could not open 'foo': No such file or directory
+qemu-io: can't open device TEST_DIR/t.IMGFMT: Could not open 'foo': No such file or directory
+read 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 image: TEST_DIR/t.IMGFMT
 file format: IMGFMT
 virtual size: 64 MiB (67108864 bytes)
@@ -560,7 +562,9 @@ Format specific information:
     corrupt: false
     extended l2: false
 
-qemu-img: Could not open 'TEST_DIR/t.IMGFMT': 'data-file' is required for this image
+qemu-io: can't open device TEST_DIR/t.IMGFMT: 'data-file' is required for this image
+read 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 image: TEST_DIR/t.IMGFMT
 file format: IMGFMT
 virtual size: 64 MiB (67108864 bytes)
-- 
2.45.2

[PULL 2/4] iotests/244: Don't store data-file with protocol in image

[Kevin Wolf]

We want to disable filename parsing for data files because it's too easy
to abuse in malicious image files. Make the test ready for the change by
passing the data file explicitly in command line options.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
---
 tests/qemu-iotests/244 | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/tests/qemu-iotests/244 b/tests/qemu-iotests/244
index 3e61fa25bb..bb9cc6512f 100755
--- a/tests/qemu-iotests/244
+++ b/tests/qemu-iotests/244
@@ -215,9 +215,22 @@ $QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n -C "$TEST_IMG.src" "$TEST_IMG"
 $QEMU_IMG compare -f $IMGFMT -F $IMGFMT "$TEST_IMG.src" "$TEST_IMG"
 
 # blkdebug doesn't support copy offloading, so this tests the error path
-$QEMU_IMG amend -f $IMGFMT -o "data_file=blkdebug::$TEST_IMG.data" "$TEST_IMG"
-$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n -C "$TEST_IMG.src" "$TEST_IMG"
-$QEMU_IMG compare -f $IMGFMT -F $IMGFMT "$TEST_IMG.src" "$TEST_IMG"
+test_img_with_blkdebug="json:{
+    'driver': 'qcow2',
+    'file': {
+        'driver': 'file',
+        'filename': '$TEST_IMG'
+    },
+    'data-file': {
+        'driver': 'blkdebug',
+        'image': {
+            'driver': 'file',
+            'filename': '$TEST_IMG.data'
+        }
+    }
+}"
+$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n -C "$TEST_IMG.src" "$test_img_with_blkdebug"
+$QEMU_IMG compare -f $IMGFMT -F $IMGFMT "$TEST_IMG.src" "$test_img_with_blkdebug"
 
 echo
 echo "=== Flushing should flush the data file ==="
-- 
2.45.2

[PULL 3/4] iotests/270: Don't store data-file with json: prefix in image

[Kevin Wolf]

We want to disable filename parsing for data files because it's too easy
to abuse in malicious image files. Make the test ready for the change by
passing the data file explicitly in command line options.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
---
 tests/qemu-iotests/270 | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/tests/qemu-iotests/270 b/tests/qemu-iotests/270
index 74352342db..c37b674aa2 100755
--- a/tests/qemu-iotests/270
+++ b/tests/qemu-iotests/270
@@ -60,8 +60,16 @@ _make_test_img -o cluster_size=2M,data_file="$TEST_IMG.orig" \
 # "write" 2G of data without using any space.
 # (qemu-img create does not like it, though, because null-co does not
 # support image creation.)
-$QEMU_IMG amend -o data_file="json:{'driver':'null-co',,'size':'4294967296'}" \
-    "$TEST_IMG"
+test_img_with_null_data="json:{
+    'driver': '$IMGFMT',
+    'file': {
+        'filename': '$TEST_IMG'
+    },
+    'data-file': {
+        'driver': 'null-co',
+        'size':'4294967296'
+    }
+}"
 
 # This gives us a range of:
 #   2^31 - 512 + 768 - 1 = 2^31 + 255 > 2^31
@@ -74,7 +82,7 @@ $QEMU_IMG amend -o data_file="json:{'driver':'null-co',,'size':'4294967296'}" \
 # on L2 boundaries, we need large L2 tables; hence the cluster size of
 # 2 MB.  (Anything from 256 kB should work, though, because then one L2
 # table covers 8 GB.)
-$QEMU_IO -c "write 768 $((2 ** 31 - 512))" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write 768 $((2 ** 31 - 512))" "$test_img_with_null_data" | _filter_qemu_io
 
 _check_test_img
 
-- 
2.45.2

[PULL 4/4] block: Parse filenames only when explicitly requested

[Kevin Wolf]

When handling image filenames from legacy options such as -drive or from
tools, these filenames are parsed for protocol prefixes, including for
the json:{} pseudo-protocol.

This behaviour is intended for filenames that come directly from the
command line and for backing files, which may come from the image file
itself. Higher level management tools generally take care to verify that
untrusted images don't contain a bad (or any) backing file reference;
'qemu-img info' is a suitable tool for this.

However, for other files that can be referenced in images, such as
qcow2 data files or VMDK extents, the string from the image file is
usually not verified by management tools - and 'qemu-img info' wouldn't
be suitable because in contrast to backing files, it already opens these
other referenced files. So here the string should be interpreted as a
literal local filename. More complex configurations need to be specified
explicitly on the command line or in QMP.

This patch changes bdrv_open_inherit() so that it only parses filenames
if a new parameter parse_filename is true. It is set for the top level
in bdrv_open(), for the file child and for the backing file child. All
other callers pass false and disable filename parsing this way.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
---
 block.c | 90 ++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 57 insertions(+), 33 deletions(-)

diff --git a/block.c b/block.c
index c1cc313d21..c317de9eaa 100644
--- a/block.c
+++ b/block.c
@@ -86,6 +86,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                            BlockDriverState *parent,
                                            const BdrvChildClass *child_class,
                                            BdrvChildRole child_role,
+                                           bool parse_filename,
                                            Error **errp);
 
 static bool bdrv_recurse_has_child(BlockDriverState *bs,
@@ -2055,7 +2056,8 @@ static void parse_json_protocol(QDict *options, const char **pfilename,
  * block driver has been specified explicitly.
  */
 static int bdrv_fill_options(QDict **options, const char *filename,
-                             int *flags, Error **errp)
+                             int *flags, bool allow_parse_filename,
+                             Error **errp)
 {
     const char *drvname;
     bool protocol = *flags & BDRV_O_PROTOCOL;
@@ -2097,7 +2099,7 @@ static int bdrv_fill_options(QDict **options, const char *filename,
     if (protocol && filename) {
         if (!qdict_haskey(*options, "filename")) {
             qdict_put_str(*options, "filename", filename);
-            parse_filename = true;
+            parse_filename = allow_parse_filename;
         } else {
             error_setg(errp, "Can't specify 'file' and 'filename' options at "
                              "the same time");
@@ -3660,7 +3662,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
     }
 
     backing_hd = bdrv_open_inherit(backing_filename, reference, options, 0, bs,
-                                   &child_of_bds, bdrv_backing_role(bs), errp);
+                                   &child_of_bds, bdrv_backing_role(bs), true,
+                                   errp);
     if (!backing_hd) {
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_prepend(errp, "Could not open backing file: ");
@@ -3694,7 +3697,8 @@ free_exit:
 static BlockDriverState *
 bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
                    BlockDriverState *parent, const BdrvChildClass *child_class,
-                   BdrvChildRole child_role, bool allow_none, Error **errp)
+                   BdrvChildRole child_role, bool allow_none,
+                   bool parse_filename, Error **errp)
 {
     BlockDriverState *bs = NULL;
     QDict *image_options;
@@ -3725,7 +3729,8 @@ bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
     }
 
     bs = bdrv_open_inherit(filename, reference, image_options, 0,
-                           parent, child_class, child_role, errp);
+                           parent, child_class, child_role, parse_filename,
+                           errp);
     if (!bs) {
         goto done;
     }
@@ -3735,6 +3740,33 @@ done:
     return bs;
 }
 
+static BdrvChild *bdrv_open_child_common(const char *filename,
+                                         QDict *options, const char *bdref_key,
+                                         BlockDriverState *parent,
+                                         const BdrvChildClass *child_class,
+                                         BdrvChildRole child_role,
+                                         bool allow_none, bool parse_filename,
+                                         Error **errp)
+{
+    BlockDriverState *bs;
+    BdrvChild *child;
+
+    GLOBAL_STATE_CODE();
+
+    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
+                            child_role, allow_none, parse_filename, errp);
+    if (bs == NULL) {
+        return NULL;
+    }
+
+    bdrv_graph_wrlock();
+    child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
+                              errp);
+    bdrv_graph_wrunlock();
+
+    return child;
+}
+
 /*
  * Opens a disk image whose options are given as BlockdevRef in another block
  * device's options.
@@ -3758,27 +3790,15 @@ BdrvChild *bdrv_open_child(const char *filename,
                            BdrvChildRole child_role,
                            bool allow_none, Error **errp)
 {
-    BlockDriverState *bs;
-    BdrvChild *child;
-
-    GLOBAL_STATE_CODE();
-
-    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
-                            child_role, allow_none, errp);
-    if (bs == NULL) {
-        return NULL;
-    }
-
-    bdrv_graph_wrlock();
-    child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
-                              errp);
-    bdrv_graph_wrunlock();
-
-    return child;
+    return bdrv_open_child_common(filename, options, bdref_key, parent,
+                                  child_class, child_role, allow_none, false,
+                                  errp);
 }
 
 /*
- * Wrapper on bdrv_open_child() for most popular case: open primary child of bs.
+ * This does mostly the same as bdrv_open_child(), but for opening the primary
+ * child of a node. A notable difference from bdrv_open_child() is that it
+ * enables filename parsing for protocol names (including json:).
  *
  * @parent can move to a different AioContext in this function.
  */
@@ -3793,8 +3813,8 @@ int bdrv_open_file_child(const char *filename,
     role = parent->drv->is_filter ?
         (BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY) : BDRV_CHILD_IMAGE;
 
-    if (!bdrv_open_child(filename, options, bdref_key, parent,
-                         &child_of_bds, role, false, errp))
+    if (!bdrv_open_child_common(filename, options, bdref_key, parent,
+                                &child_of_bds, role, false, true, errp))
     {
         return -EINVAL;
     }
@@ -3839,7 +3859,8 @@ BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp)
 
     }
 
-    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, errp);
+    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, false,
+                           errp);
     obj = NULL;
     qobject_unref(obj);
     visit_free(v);
@@ -3929,7 +3950,7 @@ static BlockDriverState * no_coroutine_fn
 bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
                   int flags, BlockDriverState *parent,
                   const BdrvChildClass *child_class, BdrvChildRole child_role,
-                  Error **errp)
+                  bool parse_filename, Error **errp)
 {
     int ret;
     BlockBackend *file = NULL;
@@ -3977,9 +3998,11 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
     }
 
     /* json: syntax counts as explicit options, as if in the QDict */
-    parse_json_protocol(options, &filename, &local_err);
-    if (local_err) {
-        goto fail;
+    if (parse_filename) {
+        parse_json_protocol(options, &filename, &local_err);
+        if (local_err) {
+            goto fail;
+        }
     }
 
     bs->explicit_options = qdict_clone_shallow(options);
@@ -4004,7 +4027,8 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
                                      parent->open_flags, parent->options);
     }
 
-    ret = bdrv_fill_options(&options, filename, &flags, &local_err);
+    ret = bdrv_fill_options(&options, filename, &flags, parse_filename,
+                            &local_err);
     if (ret < 0) {
         goto fail;
     }
@@ -4073,7 +4097,7 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
 
         file_bs = bdrv_open_child_bs(filename, options, "file", bs,
                                      &child_of_bds, BDRV_CHILD_IMAGE,
-                                     true, &local_err);
+                                     true, true, &local_err);
         if (local_err) {
             goto fail;
         }
@@ -4222,7 +4246,7 @@ BlockDriverState *bdrv_open(const char *filename, const char *reference,
     GLOBAL_STATE_CODE();
 
     return bdrv_open_inherit(filename, reference, options, flags, NULL,
-                             NULL, 0, errp);
+                             NULL, 0, true, errp);
 }
 
 /* Return true if the NULL-terminated @list contains @str */
-- 
2.45.2

Re: [PULL 0/4] Block layer patches (CVE-2024-4467)

[Richard Henderson]

On 7/2/24 09:39, Kevin Wolf wrote:
> The following changes since commit c80a339587fe4148292c260716482dd2f86d4476:
> 
>    Merge tag 'pull-target-arm-20240701' ofhttps://git.linaro.org/people/pmaydell/qemu-arm  into staging (2024-07-01 10:41:45 -0700)
> 
> are available in the Git repository at:
> 
>    https://repo.or.cz/qemu/kevin.git  tags/for-upstream
> 
> for you to fetch changes up to 7ead946998610657d38d1a505d5f25300d4ca613:
> 
>    block: Parse filenames only when explicitly requested (2024-07-02 18:12:30 +0200)
> 
> ----------------------------------------------------------------
> Block layer patches (CVE-2024-4467)
> 
> - Don't open qcow2 data files in 'qemu-img info'
> - Disallow protocol prefixes for qcow2 data files, VMDK extent files and
>    other child nodes that are neither 'file' nor 'backing'

Applied, thanks.  Please update https://wiki.qemu.org/ChangeLog/9.1 as appropriate.


r~

Re: [PULL 4/4] block: Parse filenames only when explicitly requested

[Michael Tokarev]

[-- Attachment #1: Type: text/plain, Size: 2020 bytes --]

02.07.2024 19:39, Kevin Wolf wrote:
> When handling image filenames from legacy options such as -drive or from
> tools, these filenames are parsed for protocol prefixes, including for
> the json:{} pseudo-protocol.
> 
> This behaviour is intended for filenames that come directly from the
> command line and for backing files, which may come from the image file
> itself. Higher level management tools generally take care to verify that
> untrusted images don't contain a bad (or any) backing file reference;
> 'qemu-img info' is a suitable tool for this.
> 
> However, for other files that can be referenced in images, such as
> qcow2 data files or VMDK extents, the string from the image file is
> usually not verified by management tools - and 'qemu-img info' wouldn't
> be suitable because in contrast to backing files, it already opens these
> other referenced files. So here the string should be interpreted as a
> literal local filename. More complex configurations need to be specified
> explicitly on the command line or in QMP.
> 
> This patch changes bdrv_open_inherit() so that it only parses filenames
> if a new parameter parse_filename is true. It is set for the top level
> in bdrv_open(), for the file child and for the backing file child. All
> other callers pass false and disable filename parsing this way.

I'm attaching backports of this change to 8.2 and 7.2 series.

Please check if the resulting backports are correct, or if they're needed
in the first place.  Note: 7.2 lacks quite some locking in this area, eg
v8.0.0-2069-g8394c35ee148 "block: Fix AioContext locking in bdrv_open_child()"
v8.2.0-rc0-59-g6bc0bcc89f84 "block: Fix deadlocks in bdrv_graph_wrunlock()".

Thanks,

/mjt

-- 
GPG Key transition (from rsa2048 to rsa4096) since 2024-04-24.
New key: rsa4096/61AD3D98ECDF2C8E  9D8B E14E 3F2A 9DD7 9199  28F1 61AD 3D98 ECDF 2C8E
Old key: rsa2048/457CE0A0804465C5  6EE1 95D1 886E 8FFB 810D  4324 457C E0A0 8044 65C5
Transition statement: http://www.corpit.ru/mjt/gpg-transition-2024.txt

[-- Attachment #2: 7ead946998-7.2.patch --]
[-- Type: text/x-patch, Size: 10046 bytes --]

From 0408443ecb8785a20652b529aa61f020e304112c Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 25 Apr 2024 14:56:02 +0200
Subject: [PATCH] block: Parse filenames only when explicitly requested

When handling image filenames from legacy options such as -drive or from
tools, these filenames are parsed for protocol prefixes, including for
the json:{} pseudo-protocol.

This behaviour is intended for filenames that come directly from the
command line and for backing files, which may come from the image file
itself. Higher level management tools generally take care to verify that
untrusted images don't contain a bad (or any) backing file reference;
'qemu-img info' is a suitable tool for this.

However, for other files that can be referenced in images, such as
qcow2 data files or VMDK extents, the string from the image file is
usually not verified by management tools - and 'qemu-img info' wouldn't
be suitable because in contrast to backing files, it already opens these
other referenced files. So here the string should be interpreted as a
literal local filename. More complex configurations need to be specified
explicitly on the command line or in QMP.

This patch changes bdrv_open_inherit() so that it only parses filenames
if a new parameter parse_filename is true. It is set for the top level
in bdrv_open(), for the file child and for the backing file child. All
other callers pass false and disable filename parsing this way.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
(cherry picked from commit 7ead946998610657d38d1a505d5f25300d4ca613)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: backport patch to 7.2, without:
  v8.0.0-2069-g8394c35ee148 "block: Fix AioContext locking in bdrv_open_child()"
  v8.1.0-801-gafdaeb9ea06e "block: Mark bdrv_attach_child() GRAPH_WRLOCK"
  v8.2.0-rc0-59-g6bc0bcc89f84 "block: Fix deadlocks in bdrv_graph_wrunlock()"
  v8.2.0-132-g6bc30f194985 "graph-lock: remove AioContext locking"
  v8.2.0-133-gb49f4755c7fa "block: remove AioContext locking")
---
 block.c | 76 +++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 49 insertions(+), 27 deletions(-)

diff --git a/block.c b/block.c
index a18f052374..ea369a3fe5 100644
--- a/block.c
+++ b/block.c
@@ -85,6 +85,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                            BlockDriverState *parent,
                                            const BdrvChildClass *child_class,
                                            BdrvChildRole child_role,
+                                           bool parse_filename,
                                            Error **errp);
 
 static bool bdrv_recurse_has_child(BlockDriverState *bs,
@@ -2051,7 +2052,8 @@ static void parse_json_protocol(QDict *options, const char **pfilename,
  * block driver has been specified explicitly.
  */
 static int bdrv_fill_options(QDict **options, const char *filename,
-                             int *flags, Error **errp)
+                             int *flags, bool allow_parse_filename,
+                             Error **errp)
 {
     const char *drvname;
     bool protocol = *flags & BDRV_O_PROTOCOL;
@@ -2093,7 +2095,7 @@ static int bdrv_fill_options(QDict **options, const char *filename,
     if (protocol && filename) {
         if (!qdict_haskey(*options, "filename")) {
             qdict_put_str(*options, "filename", filename);
-            parse_filename = true;
+            parse_filename = allow_parse_filename;
         } else {
             error_setg(errp, "Can't specify 'file' and 'filename' options at "
                              "the same time");
@@ -3516,7 +3518,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
     }
 
     backing_hd = bdrv_open_inherit(backing_filename, reference, options, 0, bs,
-                                   &child_of_bds, bdrv_backing_role(bs), errp);
+                                   &child_of_bds, bdrv_backing_role(bs), true,
+                                   errp);
     if (!backing_hd) {
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_prepend(errp, "Could not open backing file: ");
@@ -3549,7 +3552,8 @@ free_exit:
 static BlockDriverState *
 bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
                    BlockDriverState *parent, const BdrvChildClass *child_class,
-                   BdrvChildRole child_role, bool allow_none, Error **errp)
+                   BdrvChildRole child_role, bool allow_none,
+                   bool parse_filename, Error **errp)
 {
     BlockDriverState *bs = NULL;
     QDict *image_options;
@@ -3580,7 +3584,8 @@ bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
     }
 
     bs = bdrv_open_inherit(filename, reference, image_options, 0,
-                           parent, child_class, child_role, errp);
+                           parent, child_class, child_role, parse_filename,
+                           errp);
     if (!bs) {
         goto done;
     }
@@ -3590,6 +3595,28 @@ done:
     return bs;
 }
 
+static BdrvChild *bdrv_open_child_common(const char *filename,
+                                         QDict *options, const char *bdref_key,
+                                         BlockDriverState *parent,
+                                         const BdrvChildClass *child_class,
+                                         BdrvChildRole child_role,
+                                         bool allow_none, bool parse_filename,
+                                         Error **errp)
+{
+    BlockDriverState *bs;
+
+    GLOBAL_STATE_CODE();
+
+    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
+                            child_role, allow_none, parse_filename, errp);
+    if (bs == NULL) {
+        return NULL;
+    }
+
+    return bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
+                             errp);
+}
+
 /*
  * Opens a disk image whose options are given as BlockdevRef in another block
  * device's options.
@@ -3611,18 +3638,9 @@ BdrvChild *bdrv_open_child(const char *filename,
                            BdrvChildRole child_role,
                            bool allow_none, Error **errp)
 {
-    BlockDriverState *bs;
-
-    GLOBAL_STATE_CODE();
-
-    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
-                            child_role, allow_none, errp);
-    if (bs == NULL) {
-        return NULL;
-    }
-
-    return bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
-                             errp);
+    return bdrv_open_child_common(filename, options, bdref_key, parent,
+                                  child_class, child_role, allow_none, false,
+                                  errp);
 }
 
 /*
@@ -3639,8 +3657,8 @@ int bdrv_open_file_child(const char *filename,
     role = parent->drv->is_filter ?
         (BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY) : BDRV_CHILD_IMAGE;
 
-    if (!bdrv_open_child(filename, options, bdref_key, parent,
-                         &child_of_bds, role, false, errp))
+    if (!bdrv_open_child_common(filename, options, bdref_key, parent,
+                                &child_of_bds, role, false, true, errp))
     {
         return -EINVAL;
     }
@@ -3685,7 +3703,8 @@ BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp)
 
     }
 
-    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, errp);
+    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, false,
+                           errp);
     obj = NULL;
     qobject_unref(obj);
     visit_free(v);
@@ -3775,7 +3794,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                            BlockDriverState *parent,
                                            const BdrvChildClass *child_class,
                                            BdrvChildRole child_role,
-                                           Error **errp)
+                                           bool parse_filename, Error **errp)
 {
     int ret;
     BlockBackend *file = NULL;
@@ -3819,9 +3838,11 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
     }
 
     /* json: syntax counts as explicit options, as if in the QDict */
-    parse_json_protocol(options, &filename, &local_err);
-    if (local_err) {
-        goto fail;
+    if (parse_filename) {
+        parse_json_protocol(options, &filename, &local_err);
+        if (local_err) {
+            goto fail;
+        }
     }
 
     bs->explicit_options = qdict_clone_shallow(options);
@@ -3846,7 +3867,8 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                      parent->open_flags, parent->options);
     }
 
-    ret = bdrv_fill_options(&options, filename, &flags, &local_err);
+    ret = bdrv_fill_options(&options, filename, &flags, parse_filename,
+                            &local_err);
     if (ret < 0) {
         goto fail;
     }
@@ -3915,7 +3937,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
 
         file_bs = bdrv_open_child_bs(filename, options, "file", bs,
                                      &child_of_bds, BDRV_CHILD_IMAGE,
-                                     true, &local_err);
+                                     true, true, &local_err);
         if (local_err) {
             goto fail;
         }
@@ -4062,7 +4084,7 @@ BlockDriverState *bdrv_open(const char *filename, const char *reference,
     GLOBAL_STATE_CODE();
 
     return bdrv_open_inherit(filename, reference, options, flags, NULL,
-                             NULL, 0, errp);
+                             NULL, 0, true, errp);
 }
 
 /* Return true if the NULL-terminated @list contains @str */
-- 
2.39.2


[-- Attachment #3: 7ead946998-8.2.patch --]
[-- Type: text/x-patch, Size: 10707 bytes --]

From aea89f41799f85ca1ed724d9e5fc2fc6cce25078 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 25 Apr 2024 14:56:02 +0200
Subject: [PATCH] block: Parse filenames only when explicitly requested

When handling image filenames from legacy options such as -drive or from
tools, these filenames are parsed for protocol prefixes, including for
the json:{} pseudo-protocol.

This behaviour is intended for filenames that come directly from the
command line and for backing files, which may come from the image file
itself. Higher level management tools generally take care to verify that
untrusted images don't contain a bad (or any) backing file reference;
'qemu-img info' is a suitable tool for this.

However, for other files that can be referenced in images, such as
qcow2 data files or VMDK extents, the string from the image file is
usually not verified by management tools - and 'qemu-img info' wouldn't
be suitable because in contrast to backing files, it already opens these
other referenced files. So here the string should be interpreted as a
literal local filename. More complex configurations need to be specified
explicitly on the command line or in QMP.

This patch changes bdrv_open_inherit() so that it only parses filenames
if a new parameter parse_filename is true. It is set for the top level
in bdrv_open(), for the file child and for the backing file child. All
other callers pass false and disable filename parsing this way.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
(cherry picked from commit 7ead946998610657d38d1a505d5f25300d4ca613)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: backport patch to 8.2, without:
  v8.2.0-132-g6bc30f194985 "graph-lock: remove AioContext locking"
  v8.2.0-133-gb49f4755c7fa "block: remove AioContext locking")
---
 block.c | 98 +++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 61 insertions(+), 37 deletions(-)

diff --git a/block.c b/block.c
index bfb0861ec6..f89bc98e0e 100644
--- a/block.c
+++ b/block.c
@@ -86,6 +86,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
                                            BlockDriverState *parent,
                                            const BdrvChildClass *child_class,
                                            BdrvChildRole child_role,
+                                           bool parse_filename,
                                            Error **errp);
 
 static bool bdrv_recurse_has_child(BlockDriverState *bs,
@@ -2047,7 +2048,8 @@ static void parse_json_protocol(QDict *options, const char **pfilename,
  * block driver has been specified explicitly.
  */
 static int bdrv_fill_options(QDict **options, const char *filename,
-                             int *flags, Error **errp)
+                             int *flags, bool allow_parse_filename,
+                             Error **errp)
 {
     const char *drvname;
     bool protocol = *flags & BDRV_O_PROTOCOL;
@@ -2089,7 +2091,7 @@ static int bdrv_fill_options(QDict **options, const char *filename,
     if (protocol && filename) {
         if (!qdict_haskey(*options, "filename")) {
             qdict_put_str(*options, "filename", filename);
-            parse_filename = true;
+            parse_filename = allow_parse_filename;
         } else {
             error_setg(errp, "Can't specify 'file' and 'filename' options at "
                              "the same time");
@@ -3675,7 +3677,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
     }
 
     backing_hd = bdrv_open_inherit(backing_filename, reference, options, 0, bs,
-                                   &child_of_bds, bdrv_backing_role(bs), errp);
+                                   &child_of_bds, bdrv_backing_role(bs), true,
+                                   errp);
     if (!backing_hd) {
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_prepend(errp, "Could not open backing file: ");
@@ -3712,7 +3715,8 @@ free_exit:
 static BlockDriverState *
 bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
                    BlockDriverState *parent, const BdrvChildClass *child_class,
-                   BdrvChildRole child_role, bool allow_none, Error **errp)
+                   BdrvChildRole child_role, bool allow_none,
+                   bool parse_filename, Error **errp)
 {
     BlockDriverState *bs = NULL;
     QDict *image_options;
@@ -3743,7 +3747,8 @@ bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
     }
 
     bs = bdrv_open_inherit(filename, reference, image_options, 0,
-                           parent, child_class, child_role, errp);
+                           parent, child_class, child_role, parse_filename,
+                           errp);
     if (!bs) {
         goto done;
     }
@@ -3753,6 +3758,37 @@ done:
     return bs;
 }
 
+static BdrvChild *bdrv_open_child_common(const char *filename,
+                                         QDict *options, const char *bdref_key,
+                                         BlockDriverState *parent,
+                                         const BdrvChildClass *child_class,
+                                         BdrvChildRole child_role,
+                                         bool allow_none, bool parse_filename,
+                                         Error **errp)
+{
+    BlockDriverState *bs;
+    BdrvChild *child;
+    AioContext *ctx;
+
+    GLOBAL_STATE_CODE();
+
+    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
+                            child_role, allow_none, parse_filename, errp);
+    if (bs == NULL) {
+        return NULL;
+    }
+
+    bdrv_graph_wrlock(NULL);
+    ctx = bdrv_get_aio_context(bs);
+    aio_context_acquire(ctx);
+    child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
+                              errp);
+    aio_context_release(ctx);
+    bdrv_graph_wrunlock(NULL);
+
+    return child;
+}
+
 /*
  * Opens a disk image whose options are given as BlockdevRef in another block
  * device's options.
@@ -3778,31 +3814,15 @@ BdrvChild *bdrv_open_child(const char *filename,
                            BdrvChildRole child_role,
                            bool allow_none, Error **errp)
 {
-    BlockDriverState *bs;
-    BdrvChild *child;
-    AioContext *ctx;
-
-    GLOBAL_STATE_CODE();
-
-    bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
-                            child_role, allow_none, errp);
-    if (bs == NULL) {
-        return NULL;
-    }
-
-    bdrv_graph_wrlock(NULL);
-    ctx = bdrv_get_aio_context(bs);
-    aio_context_acquire(ctx);
-    child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
-                              errp);
-    aio_context_release(ctx);
-    bdrv_graph_wrunlock(NULL);
-
-    return child;
+    return bdrv_open_child_common(filename, options, bdref_key, parent,
+                                  child_class, child_role, allow_none, false,
+                                  errp);
 }
 
 /*
- * Wrapper on bdrv_open_child() for most popular case: open primary child of bs.
+ * This does mostly the same as bdrv_open_child(), but for opening the primary
+ * child of a node. A notable difference from bdrv_open_child() is that it
+ * enables filename parsing for protocol names (including json:).
  *
  * The caller must hold the lock of the main AioContext and no other AioContext.
  * @parent can move to a different AioContext in this function. Callers must
@@ -3819,8 +3839,8 @@ int bdrv_open_file_child(const char *filename,
     role = parent->drv->is_filter ?
         (BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY) : BDRV_CHILD_IMAGE;
 
-    if (!bdrv_open_child(filename, options, bdref_key, parent,
-                         &child_of_bds, role, false, errp))
+    if (!bdrv_open_child_common(filename, options, bdref_key, parent,
+                                &child_of_bds, role, false, true, errp))
     {
         return -EINVAL;
     }
@@ -3865,7 +3885,8 @@ BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp)
 
     }
 
-    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, errp);
+    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, false,
+                           errp);
     obj = NULL;
     qobject_unref(obj);
     visit_free(v);
@@ -3962,7 +3983,7 @@ static BlockDriverState * no_coroutine_fn
 bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
                   int flags, BlockDriverState *parent,
                   const BdrvChildClass *child_class, BdrvChildRole child_role,
-                  Error **errp)
+                  bool parse_filename, Error **errp)
 {
     int ret;
     BlockBackend *file = NULL;
@@ -4011,9 +4032,11 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
     }
 
     /* json: syntax counts as explicit options, as if in the QDict */
-    parse_json_protocol(options, &filename, &local_err);
-    if (local_err) {
-        goto fail;
+    if (parse_filename) {
+        parse_json_protocol(options, &filename, &local_err);
+        if (local_err) {
+            goto fail;
+        }
     }
 
     bs->explicit_options = qdict_clone_shallow(options);
@@ -4038,7 +4061,8 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
                                      parent->open_flags, parent->options);
     }
 
-    ret = bdrv_fill_options(&options, filename, &flags, &local_err);
+    ret = bdrv_fill_options(&options, filename, &flags, parse_filename,
+                            &local_err);
     if (ret < 0) {
         goto fail;
     }
@@ -4107,7 +4131,7 @@ bdrv_open_inherit(const char *filename, const char *reference, QDict *options,
 
         file_bs = bdrv_open_child_bs(filename, options, "file", bs,
                                      &child_of_bds, BDRV_CHILD_IMAGE,
-                                     true, &local_err);
+                                     true, true, &local_err);
         if (local_err) {
             goto fail;
         }
@@ -4270,7 +4294,7 @@ BlockDriverState *bdrv_open(const char *filename, const char *reference,
     GLOBAL_STATE_CODE();
 
     return bdrv_open_inherit(filename, reference, options, flags, NULL,
-                             NULL, 0, errp);
+                             NULL, 0, true, errp);
 }
 
 /* Return true if the NULL-terminated @list contains @str */
-- 
2.39.2

Re: [PULL 4/4] block: Parse filenames only when explicitly requested

[Kevin Wolf]

Am 03.07.2024 um 23:16 hat Michael Tokarev geschrieben:
> 02.07.2024 19:39, Kevin Wolf wrote:
> > When handling image filenames from legacy options such as -drive or from
> > tools, these filenames are parsed for protocol prefixes, including for
> > the json:{} pseudo-protocol.
> > 
> > This behaviour is intended for filenames that come directly from the
> > command line and for backing files, which may come from the image file
> > itself. Higher level management tools generally take care to verify that
> > untrusted images don't contain a bad (or any) backing file reference;
> > 'qemu-img info' is a suitable tool for this.
> > 
> > However, for other files that can be referenced in images, such as
> > qcow2 data files or VMDK extents, the string from the image file is
> > usually not verified by management tools - and 'qemu-img info' wouldn't
> > be suitable because in contrast to backing files, it already opens these
> > other referenced files. So here the string should be interpreted as a
> > literal local filename. More complex configurations need to be specified
> > explicitly on the command line or in QMP.
> > 
> > This patch changes bdrv_open_inherit() so that it only parses filenames
> > if a new parameter parse_filename is true. It is set for the top level
> > in bdrv_open(), for the file child and for the backing file child. All
> > other callers pass false and disable filename parsing this way.
> 
> I'm attaching backports of this change to 8.2 and 7.2 series.
> 
> Please check if the resulting backports are correct, or if they're needed
> in the first place.  Note: 7.2 lacks quite some locking in this area, eg
> v8.0.0-2069-g8394c35ee148 "block: Fix AioContext locking in bdrv_open_child()"
> v8.2.0-rc0-59-g6bc0bcc89f84 "block: Fix deadlocks in bdrv_graph_wrunlock()".

Apart from minor style differences, your 7.2 backport is a perfect match
of the RHEL 9.2 backport which I already reviewed downstream. The 8.2
patch is a bit different from the RHEL 9.4 one because we backported the
final bits of the multiqueue work, but the differences make sense for
upstream QEMU 8.2.

So both patches look good to me.

Kevin

Re: [PULL 4/4] block: Parse filenames only when explicitly requested

[Michael Tokarev]

04.07.2024 14:29, Kevin Wolf wrote:
> Am 03.07.2024 um 23:16 hat Michael Tokarev geschrieben:

>> I'm attaching backports of this change to 8.2 and 7.2 series.
>>
>> Please check if the resulting backports are correct, or if they're needed
>> in the first place.  Note: 7.2 lacks quite some locking in this area, eg
>> v8.0.0-2069-g8394c35ee148 "block: Fix AioContext locking in bdrv_open_child()"
>> v8.2.0-rc0-59-g6bc0bcc89f84 "block: Fix deadlocks in bdrv_graph_wrunlock()".
> 
> Apart from minor style differences, your 7.2 backport is a perfect match
> of the RHEL 9.2 backport which I already reviewed downstream. The 8.2
> patch is a bit different from the RHEL 9.4 one because we backported the
> final bits of the multiqueue work, but the differences make sense for
> upstream QEMU 8.2.
> 
> So both patches look good to me.

Ok, this makes sense.  Thank you for the review, Kevin!

/mjt

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