From bd385a5298d7062668e804d73944d52aec9549f1 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 11 Apr 2024 15:06:01 +0200 Subject: [PATCH 1/4] qcow2: Don't open data_file with BDRV_O_NO_IO 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 Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek --- 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 10883a249476..70b19730a390 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 53c7d428e385..b71ac097d14b 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 139fc68177de..24c33add7ce6 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) From 2eb42a728d27a43fdcad5f37d3f65706ce6deba5 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 25 Apr 2024 14:49:40 +0200 Subject: [PATCH 2/4] iotests/244: Don't store data-file with protocol in image 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 Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek --- 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 3e61fa25bb60..bb9cc6512f35 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" "$test_img_with_blkdebug" echo echo "=== Flushing should flush the data file ===" From 7e1110664ecbc4826f3c978ccb06b6c1bce823e6 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 25 Apr 2024 14:49:40 +0200 Subject: [PATCH 3/4] iotests/270: Don't store data-file with json: prefix in image We want to disable filename parsing for data files because it's too easy to abuse in malicious image files. Make the test ready for the change by passing the data file explicitly in command line options. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek --- tests/qemu-iotests/270 | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/tests/qemu-iotests/270 b/tests/qemu-iotests/270 index 74352342db58..c37b674aa2e1 100755 --- a/tests/qemu-iotests/270 +++ b/tests/qemu-iotests/270 @@ -60,8 +60,16 @@ _make_test_img -o cluster_size=2M,data_file="$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 From 7ead946998610657d38d1a505d5f25300d4ca613 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 25 Apr 2024 14:56:02 +0200 Subject: [PATCH 4/4] 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 Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek --- block.c | 90 ++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 57 insertions(+), 33 deletions(-) diff --git a/block.c b/block.c index c1cc313d2167..c317de9eaa64 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 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options, 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 @@ bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key, 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 */