From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58747) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WUhyF-0002lZ-2M for qemu-devel@nongnu.org; Mon, 31 Mar 2014 15:34:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WUhy8-0000fs-8z for qemu-devel@nongnu.org; Mon, 31 Mar 2014 15:34:10 -0400 Date: Mon, 31 Mar 2014 22:34:25 +0300 From: "Michael S. Tsirkin" Message-ID: <20140331193425.GI12208@redhat.com> References: <1396275242-10810-1-git-send-email-mst@redhat.com> <1396275242-10810-5-git-send-email-mst@redhat.com> <5339A41A.40202@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5339A41A.40202@redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 04/30] virtio-net: fix buffer overflow on invalid state load List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: mdroth@linux.vnet.ibm.com, qemu-stable@nongnu.org, qemu-devel@nongnu.org, Anthony Liguori , dgilbert@redhat.com, KONRAD Frederic On Mon, Mar 31, 2014 at 07:21:30PM +0200, Laszlo Ersek wrote: > On 03/31/14 16:16, Michael S. Tsirkin wrote: > > CVE-2013-4148 QEMU 1.0 integer conversion in > > virtio_net_load()@hw/net/virtio-net.c > > > > Deals with loading a corrupted savevm image. > > > >> n->mac_table.in_use = qemu_get_be32(f); > > > > in_use is int so it can get negative when assigned 32bit unsigned value. > > > >> /* MAC_TABLE_ENTRIES may be different from the saved image */ > >> if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) { > > > > passing this check ^^^ > > > >> qemu_get_buffer(f, n->mac_table.macs, > >> n->mac_table.in_use * ETH_ALEN); > > > > with good in_use value, "n->mac_table.in_use * ETH_ALEN" can get > > positive and bigger than mac_table.macs. For example 0x81000000 > > satisfies this condition when ETH_ALEN is 6. > > > > A similar problem exists with is_multi. > > ("first_multi") Actually it doesn't even exist: Peter commented on this in v1 and I forgot to fix up the commit log :( I really wanted to fix the commit log to say "make first_multi unsigned for consistency" but forgot. > > > > Fix both by making the value unsigned. > > > > Reviewed-by: Michael Roth > > Signed-off-by: Michael S. Tsirkin > > Edit: "for consistency, change first_multi as well". > > > > Note: all call sites were audited to confirm that > > making them unsigned didn't cause any issues: > > it turns out we actually never do math on them, > > so it's easy to validate because both values are > > always <= MAC_TABLE_ENTRIES. > > --- > > include/hw/virtio/virtio-net.h | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h > > index df60f16..4b32440 100644 > > --- a/include/hw/virtio/virtio-net.h > > +++ b/include/hw/virtio/virtio-net.h > > @@ -176,8 +176,8 @@ typedef struct VirtIONet { > > uint8_t nobcast; > > uint8_t vhost_started; > > struct { > > - int in_use; > > - int first_multi; > > + uint32_t in_use; > > + uint32_t first_multi; > > uint8_t multi_overflow; > > uint8_t uni_overflow; > > uint8_t *macs; > > > > I ran > > git grep -EHn '\<(in_use|first_multi)\>' > > Many hits, hard to audit (esp. because I'm unfamiliar with the code). > Several loops with signed int loop variables. I checked cursorily. > > Reviewed-by: Laszlo Ersek >