From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53427) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wjrqz-0000z9-HM for qemu-devel@nongnu.org; Mon, 12 May 2014 11:09:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wjrqt-0004V6-6T for qemu-devel@nongnu.org; Mon, 12 May 2014 11:09:21 -0400 Received: from lputeaux-656-01-25-125.w80-12.abo.wanadoo.fr ([80.12.84.125]:47838 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wjrqs-0004UU-SV for qemu-devel@nongnu.org; Mon, 12 May 2014 11:09:15 -0400 Date: Mon, 12 May 2014 17:09:48 +0200 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20140512150948.GF7858@irqsave.net> References: <1399899851-5641-1-git-send-email-kwolf@redhat.com> <1399899851-5641-4-git-send-email-kwolf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1399899851-5641-4-git-send-email-kwolf@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 3/5] qcow1: Validate L2 table size (CVE-2014-0222) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, stefanha@redhat.com, ppandit@redhat.com The Monday 12 May 2014 =E0 15:04:09 (+0200), Kevin Wolf wrote : > Too large L2 table sizes cause unbounded allocations. Images actually > created by qemu-img only have 512 byte or 4k L2 tables. >=20 > To keep things consistent with cluster sizes, allow ranges between 512 > bytes and 64k (in fact, down to 1 entry =3D 8 bytes is technically > working, but L2 table sizes smaller than a cluster don't make a lot of > sense). >=20 > This also means that the number of bytes on the virtual disk that are > described by the same L2 table is limited to at most 8k * 64k or 2^29, > preventively avoiding any integer overflows. >=20 > Signed-off-by: Kevin Wolf > --- > block/qcow.c | 8 ++++++++ > tests/qemu-iotests/092 | 10 ++++++++++ > tests/qemu-iotests/092.out | 7 +++++++ > 3 files changed, 25 insertions(+) >=20 > diff --git a/block/qcow.c b/block/qcow.c > index e60df23..e8038e5 100644 > --- a/block/qcow.c > +++ b/block/qcow.c > @@ -139,6 +139,14 @@ static int qcow_open(BlockDriverState *bs, QDict *= options, int flags, > goto fail; > } > =20 > + /* l2_bits specifies number of entries; storing a uint64_t in each= entry, > + * so bytes =3D num_entries << 3. */ > + if (header.l2_bits < 9 - 3 || header.l2_bits > 16 - 3) { > + error_setg(errp, "L2 table size must be between 512 and 64k"); > + ret =3D -EINVAL; > + goto fail; > + } > + > if (header.crypt_method > QCOW_CRYPT_AES) { > error_setg(errp, "invalid encryption method in qcow header"); > ret =3D -EINVAL; > diff --git a/tests/qemu-iotests/092 b/tests/qemu-iotests/092 > index b0f04e3..2196cce 100755 > --- a/tests/qemu-iotests/092 > +++ b/tests/qemu-iotests/092 > @@ -54,6 +54,16 @@ poke_file "$TEST_IMG" "$offset_cluster_bits" "\xff" > poke_file "$TEST_IMG" "$offset_cluster_bits" "\x1f" > { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filt= er_testdir > =20 > +echo > +echo "=3D=3D Invalid L2 table size =3D=3D" > +_make_test_img 64M I see why $offset_l2_bit was present in the previous patch now. > +poke_file "$TEST_IMG" "$offset_l2_bits" "\xff" > +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filt= er_testdir > + > +# 1 << 0x1b =3D 2^31 / L2_CACHE_SIZE > +poke_file "$TEST_IMG" "$offset_l2_bits" "\x1b" > +{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filt= er_testdir The lower limit is not tested "\x05". Some extra room is present for testing the high limit "\0x0e" > + > # success, all done > echo "*** done" > rm -f $seq.full > diff --git a/tests/qemu-iotests/092.out b/tests/qemu-iotests/092.out > index 9e7367a..45a7ac8 100644 > --- a/tests/qemu-iotests/092.out > +++ b/tests/qemu-iotests/092.out > @@ -6,4 +6,11 @@ qemu-io: can't open device TEST_DIR/t.qcow: Cluster si= ze must be between 512 and > no file open, try 'help open' > qemu-io: can't open device TEST_DIR/t.qcow: Cluster size must be betwe= en 512 and 64k > no file open, try 'help open' > + > +=3D=3D Invalid L2 table size =3D=3D > +Formatting 'TEST_DIR/t.IMGFMT', fmt=3DIMGFMT size=3D67108864=20 > +qemu-io: can't open device TEST_DIR/t.qcow: L2 table size must be betw= een 512 and 64k > +no file open, try 'help open' > +qemu-io: can't open device TEST_DIR/t.qcow: L2 table size must be betw= een 512 and 64k > +no file open, try 'help open' > *** done > --=20 > 1.8.3.1 >=20 >=20