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qcow1: Stricter backing file length check

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Like qcow2 since commit 6d33e8e7, error out on invalid lengths instead
of silently truncating them to 1023.

Also don't rely on bdrv_pread() catching integer overflows that make len
negative, but use unsigned variables in the first place.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
This commit is contained in:
Kevin Wolf 2014-05-08 13:35:09 +02:00
parent 46485de0cb
commit d66e5cee00
3 changed files with 23 additions and 2 deletions
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7
block/qcow.c
View File

@ -97,7 +97,8 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVQcowState *s = bs->opaque;
int len, i, shift, ret;
unsigned int len, i, shift;
int ret;
QCowHeader header;
ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
@ -202,7 +203,9 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
if (header.backing_file_offset != 0) {
len = header.backing_file_size;
if (len > 1023) {
len = 1023;
error_setg(errp, "Backing file name too long");
ret = -EINVAL;
goto fail;
}
ret = bdrv_pread(bs->file, header.backing_file_offset,
bs->backing_file, len);

11
tests/qemu-iotests/092
View File

@ -43,6 +43,8 @@ _supported_fmt qcow
_supported_proto generic
_supported_os Linux
offset_backing_file_offset=8
offset_backing_file_size=16
offset_size=24
offset_cluster_bits=32
offset_l2_bits=33
@ -81,6 +83,15 @@ poke_file "$TEST_IMG" "$offset_size" "\xee\xee\xee\xee\xee\xee\xee\xee"
poke_file "$TEST_IMG" "$offset_size" "\x7f\xff\xff\xff\xff\xff\xff\xff"
{ $QEMU_IO -c "write 0 64M" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== Invalid backing file length =="
_make_test_img 64M
poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\xff"
poke_file "$TEST_IMG" "$offset_backing_file_size" "\xff\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_size" "\x7f\xff\xff\xff"
{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
# success, all done
echo "*** done"
rm -f $seq.full

7
tests/qemu-iotests/092.out
View File

@ -28,4 +28,11 @@ qemu-io: can't open device TEST_DIR/t.qcow: Image too large
no file open, try 'help open'
qemu-io: can't open device TEST_DIR/t.qcow: Image too large
no file open, try 'help open'
== Invalid backing file length ==
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
qemu-io: can't open device TEST_DIR/t.qcow: Backing file name too long
no file open, try 'help open'
qemu-io: can't open device TEST_DIR/t.qcow: Backing file name too long
no file open, try 'help open'
*** done