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qcow2: Check backing_file_offset (CVE-2014-0144)

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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 <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2014-03-26 13:05:42 +01:00 committed by Stefan Hajnoczi
parent 24342f2cae
commit a1b3955c94
3 changed files with 25 additions and 0 deletions
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6
block/qcow2.c
View File

@ -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) { if (header.backing_file_offset) {
ext_end = header.backing_file_offset; ext_end = header.backing_file_offset;
} else { } else {

12
tests/qemu-iotests/080
View File

@ -43,6 +43,8 @@ _supported_proto generic
_supported_os Linux _supported_os Linux
header_size=104 header_size=104
offset_backing_file_offset=8
offset_header_size=100 offset_header_size=100
offset_ext_magic=$header_size offset_ext_magic=$header_size
offset_ext_size=$((header_size + 4)) offset_ext_size=$((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" 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 { $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 # success, all done
echo "*** done" echo "*** done"
rm -f $seq.full rm -f $seq.full

7
tests/qemu-iotests/080.out
View File

@ -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' no file open, try 'help open'
qemu-io: can't open device TEST_DIR/t.qcow2: qcow2 header exceeds cluster size qemu-io: can't open device TEST_DIR/t.qcow2: qcow2 header exceeds cluster size
no file open, try 'help open' 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 *** done