File qcow2-Don-t-open-data_file-with-BDRV_O_N.patch of Package qemu.35260
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 11 Apr 2024 15:06:01 +0200
Subject: qcow2: Don't open data_file with BDRV_O_NO_IO (bsc#1227322,
CVE-2024-4467)
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>
(cherry picked from commit bd385a5298d7062668e804d73944d52aec9549f1)
References: bsc#1227322
References: CVE-2024-4467
Signed-off-by: Dario Faggioli <dfaggioli@suse.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 a934db4cf6ac5e8e8019334eb9ff..fecb882a2cbb8fe8b9896b7767f3 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1611,7 +1611,22 @@ 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 5747beb7ed60cd96f2ce6f836589..cd98f716c6f6e05b7acee40f90ee 100755
--- a/tests/qemu-iotests/061
+++ b/tests/qemu-iotests/061
@@ -318,12 +318,14 @@ $QEMU_IMG amend -o "data_file=foo" "$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 ee30da266514537bd3e6885a5958..8ce296b0a14ad57bdab1ec6f3120 100644
--- a/tests/qemu-iotests/061.out
+++ b/tests/qemu-iotests/061.out
@@ -544,7 +544,9 @@ 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)
@@ -559,7 +561,9 @@ 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)
