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qcow2: Check refcount table size (CVE-2014-0144) 

Limit the in-memory reference count table size to 8 MB, it's enough in
practice. This fixes an unbounded allocation as well as a buffer
overflow in qcow2_refcount_init().

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 13:05:43 +01:00 committed by Stefan Hajnoczi
parent a1b3955c94
commit 5dab2faddc
4 changed files with 29 additions and 1 deletions
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4
block/qcow2-refcount.c
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@ -40,8 +40,10 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
int qcow2_refcount_init(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int ret, refcount_table_size2, i;
unsigned int refcount_table_size2, i;
int ret;
assert(s->refcount_table_size <= INT_MAX / sizeof(uint64_t));
refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
s->refcount_table = g_malloc(refcount_table_size2);
if (s->refcount_table_size > 0) {

9
block/qcow2.c
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@ -577,10 +577,19 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
s->csize_shift = (62 - (s->cluster_bits - 8));
s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
s->refcount_table_offset = header.refcount_table_offset;
s->refcount_table_size =
header.refcount_table_clusters << (s->cluster_bits - 3);
if (header.refcount_table_clusters > (0x800000 >> s->cluster_bits)) {
/* 8 MB refcount table is enough for 2 PB images at 64k cluster size
* (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
error_setg(errp, "Reference count table too large");
ret = -EINVAL;
goto fail;
}
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;

10
tests/qemu-iotests/080
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@ -45,6 +45,7 @@ _supported_os Linux
header_size=104
offset_backing_file_offset=8
offset_refcount_table_clusters=56
offset_header_size=100
offset_ext_magic=$header_size
offset_ext_size=$((header_size + 4))
@ -67,6 +68,15 @@ poke_file "$TEST_IMG" "$offset_ext_size" "\x7f\xff\xff\xff"
poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x00\x00"
{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== Huge refcount table size =="
_make_test_img 64M
poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\xff\xff\xff\xff"
{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\x00\x02\x00\x01"
{ $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/080.out
View File

@ -13,4 +13,11 @@ 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'
== Huge refcount table size ==
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
qemu-io: can't open device TEST_DIR/t.qcow2: Reference count table too large
no file open, try 'help open'
qemu-io: can't open device TEST_DIR/t.qcow2: Reference count table too large
no file open, try 'help open'
*** done