From a1b3955c9415b1e767c130a2f59fee6aa28e575b Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 26 Mar 2014 13:05:42 +0100 Subject: [PATCH] qcow2: Check backing_file_offset (CVE-2014-0144) Header, header extension and the backing file name must all be stored in the first cluster. Setting the backing file to a much higher value allowed header extensions to become much bigger than we want them to be (unbounded allocation). Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Signed-off-by: Stefan Hajnoczi --- block/qcow2.c | 6 ++++++ tests/qemu-iotests/080 | 12 ++++++++++++ tests/qemu-iotests/080.out | 7 +++++++ 3 files changed, 25 insertions(+) diff --git a/block/qcow2.c b/block/qcow2.c index 7809f5c..f0411a9 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -511,6 +511,12 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, } } + if (header.backing_file_offset > s->cluster_size) { + error_setg(errp, "Invalid backing file offset"); + ret = -EINVAL; + goto fail; + } + if (header.backing_file_offset) { ext_end = header.backing_file_offset; } else { diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080 index 6512701..6d588dd 100755 --- a/tests/qemu-iotests/080 +++ b/tests/qemu-iotests/080 @@ -43,6 +43,8 @@ _supported_proto generic _supported_os Linux header_size=104 + +offset_backing_file_offset=8 offset_header_size=100 offset_ext_magic=$header_size offset_ext_size=$((header_size + 4)) @@ -55,6 +57,16 @@ poke_file "$TEST_IMG" "$offset_header_size" "\xff\xff\xff\xff" poke_file "$TEST_IMG" "$offset_header_size" "\x7f\xff\xff\xff" { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir +echo +echo "== Huge unknown header extension ==" +_make_test_img 64M +poke_file "$TEST_IMG" "$offset_backing_file_offset" "\xff\xff\xff\xff\xff\xff\xff\xff" +poke_file "$TEST_IMG" "$offset_ext_magic" "\x12\x34\x56\x78" +poke_file "$TEST_IMG" "$offset_ext_size" "\x7f\xff\xff\xff" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir +poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x00\x00" +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir + # success, all done echo "*** done" rm -f $seq.full diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out index 41a166a..48c40aa 100644 --- a/tests/qemu-iotests/080.out +++ b/tests/qemu-iotests/080.out @@ -6,4 +6,11 @@ qemu-io: can't open device TEST_DIR/t.qcow2: qcow2 header exceeds cluster size no file open, try 'help open' qemu-io: can't open device TEST_DIR/t.qcow2: qcow2 header exceeds cluster size no file open, try 'help open' + +== Huge unknown header extension == +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 +qemu-io: can't open device TEST_DIR/t.qcow2: Invalid backing file offset +no file open, try 'help open' +qemu-io: can't open device TEST_DIR/t.qcow2: Header extension too large +no file open, try 'help open' *** done -- 2.7.4