From: Kevin Wolf <kw...@redhat.com>
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-sta...@nongnu.org
Signed-off-by: Kevin Wolf <kw...@redhat.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Hanna Czenczek <hre...@redhat.com>
(cherry picked from commit bd385a5298d7062668e804d73944d52aec9549f1)
Signed-off-by: Michael Tokarev <m...@tls.msk.ru>
diff --git a/block/qcow2.c b/block/qcow2.c
index 4d6666d3ff..c810424feb 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1614,7 +1614,22 @@ static int coroutine_fn qcow2_do_open(BlockDriverState
*bs, QDict *options,
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 */
s->data_file = bdrv_open_child(NULL, options, "data-file", bs,
&child_of_bds, BDRV_CHILD_DATA,
diff --git a/tests/qemu-iotests/061 b/tests/qemu-iotests/061
index 509ad247cd..168a5831dd 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)
--
2.39.2
