Commit 951053a9 authored by Alberto Garcia's avatar Alberto Garcia Committed by Max Reitz
Browse files

qcow2: Don't open images with header.refcount_table_clusters == 0 



qcow2_do_open() is checking that header.refcount_table_clusters is not
too large, but it doesn't check that it's greater than zero. Apart
from the fact that an image like that is obviously corrupted, trying
to use it crashes QEMU since we end up with a null s->refcount_table
after qcow2_refcount_init().

These images can however be repaired, so allow opening them if the
BDRV_O_CHECK flag is set.

Signed-off-by: default avatarAlberto Garcia <berto@igalia.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
Message-id: f9750f50c80359babba11062e88f5075a47e8e16.1509718618.git.berto@igalia.com
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent 8aa34834

block/qcow2.c

+6 −0
Original line number Diff line number Diff line
@@ -1280,6 +1280,12 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags, 
        goto fail;

    }



    if (header.refcount_table_clusters == 0 && !(flags & BDRV_O_CHECK)) {

        error_setg(errp, "Image does not contain a reference count table");

        ret = -EINVAL;

        goto fail;

    }



    ret = validate_table_offset(bs, s->refcount_table_offset,

                                s->refcount_table_size, sizeof(uint64_t));

    if (ret < 0) {

tests/qemu-iotests/060

+7 −0
Original line number Diff line number Diff line
@@ -270,6 +270,13 @@ poke_file "$TEST_IMG" "$rb_offset" "\x00\x00\x00\x00\x00\x00\x00\x00" 
# write will try to allocate a compressed data cluster at offset 0.

$QEMU_IO -c "write -c 0k 64k" "$TEST_IMG" | _filter_qemu_io



echo

echo "=== Testing zero refcount table size ==="

echo

_make_test_img 64M

poke_file "$TEST_IMG" "56"                "\x00\x00\x00\x00"

$QEMU_IO -c "write 0 64k" "$TEST_IMG" 2>&1 | _filter_testdir | _filter_imgfmt



# success, all done

echo "*** done"

rm -f $seq.full

tests/qemu-iotests/060.out

+5 −0
Original line number Diff line number Diff line
@@ -203,4 +203,9 @@ wrote 65536/65536 bytes at offset 65536 
64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

qcow2: Marking image as corrupt: Preventing invalid allocation of compressed cluster at offset 0; further corruption events will be suppressed

write failed: Input/output error



=== Testing zero refcount table size ===



Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864

can't open device TEST_DIR/t.IMGFMT: Image does not contain a reference count table

*** done