From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59327) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WUuK3-0005nz-Ix for qemu-devel@nongnu.org; Tue, 01 Apr 2014 04:45:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WUuJx-0002o4-16 for qemu-devel@nongnu.org; Tue, 01 Apr 2014 04:45:31 -0400 Date: Tue, 1 Apr 2014 09:45:17 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20140401084516.GA2411@work-vm> References: <1396275242-10810-1-git-send-email-mst@redhat.com> <1396275242-10810-6-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1396275242-10810-6-git-send-email-mst@redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 05/30] virtio-net: out-of-bounds buffer write on load List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-stable@nongnu.org, qemu-devel@nongnu.org, Anthony Liguori , mdroth@linux.vnet.ibm.com * Michael S. Tsirkin (mst@redhat.com) wrote: > CVE-2013-4149 QEMU 1.3.0 out-of-bounds buffer write in > virtio_net_load()@hw/net/virtio-net.c > > > } else if (n->mac_table.in_use) { > > uint8_t *buf = g_malloc0(n->mac_table.in_use); > > We are allocating buffer of size n->mac_table.in_use > > > qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN); > > and read to the n->mac_table.in_use size buffer n->mac_table.in_use * > ETH_ALEN bytes, corrupting memory. > > If adversary controls state then memory written there is controlled > by adversary. > > Reviewed-by: Michael Roth > Signed-off-by: Michael S. Tsirkin > --- > hw/net/virtio-net.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index 439477b..8d037b1 100644 > --- a/hw/net/virtio-net.c > +++ b/hw/net/virtio-net.c > @@ -1363,9 +1363,15 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id) > qemu_get_buffer(f, n->mac_table.macs, > n->mac_table.in_use * ETH_ALEN); > } else if (n->mac_table.in_use) { You can lose that 'else if' test; if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) { qemu_get_buffer(f, n->mac_table.macs, n->mac_table.in_use * ETH_ALEN); } else if (n->mac_table.in_use) { to get to the else in_use > MAC_TABLE_ENTRIES. Dave > - uint8_t *buf = g_malloc0(n->mac_table.in_use); > - qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN); > - g_free(buf); > + int i; > + > + /* Overflow detected - can happen if source has a larger MAC table. > + * We simply set overflow flag so there's no need to maintain the > + * table of addresses, discard them all. > + */ > + for (i = 0; i < n->mac_table.in_use * ETH_ALEN; ++i) { > + qemu_get_byte(f); > + } > n->mac_table.multi_overflow = n->mac_table.uni_overflow = 1; > n->mac_table.in_use = 0; > } > -- > MST > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK