| Message ID | 1396543778-22307-6-git-send-email-mst@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 3 April 2014 17:50, 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 <mdroth@linux.vnet.ibm.com> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > hw/net/virtio-net.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index 439477b..c247529 100644 > --- a/hw/net/virtio-net.c > +++ b/hw/net/virtio-net.c > @@ -1362,10 +1362,16 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id) > 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) { > - 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); > + } else { > + 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); > + } If the incoming data sets the in_use field to INT_MAX then we get integer overflow on the multiply here. That's undefined behaviour in C and we probably shouldn't allow that to happen. thanks -- PMM
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 439477b..c247529 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -1362,10 +1362,16 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id) 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) { - 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); + } else { + 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; }