* Michael S. Tsirkin (m...@redhat.com) wrote:
> CVE-2013-4532
>
> s->next_packet is read from wire as an index into s->rx[]. If
> s->next_packet exceeds the length of s->rx[], the buffer can be
> subsequently overrun with arbitrary data from the wire.
>
> Fix this by failing migration if s->next_packet we read from
> the wire exceeds this.
>
> Similarly, validate rx_fifo against sizeof(s->rx[].data).
>
> Finally, constrain rx len to a sensibly small positive
> value, to avoid integer overruns when data model
> later uses this value.
>
> Reported-by: Michael Roth <mdr...@linux.vnet.ibm.com>
> Reported-by: Peter Maydell <peter.mayd...@linaro.org>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> hw/net/stellaris_enet.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
> index d04e6a4..182fd3e 100644
> --- a/hw/net/stellaris_enet.c
> +++ b/hw/net/stellaris_enet.c
> @@ -358,7 +358,7 @@ static void stellaris_enet_save(QEMUFile *f, void *opaque)
> static int stellaris_enet_load(QEMUFile *f, void *opaque, int version_id)
> {
> stellaris_enet_state *s = (stellaris_enet_state *)opaque;
> - int i;
> + int i, v;
>
> if (version_id != 1)
> return -EINVAL;
> @@ -381,9 +381,25 @@ static int stellaris_enet_load(QEMUFile *f, void
> *opaque, int version_id)
> qemu_get_buffer(f, s->rx[i].data, sizeof(s->rx[i].data));
>
> }
The loop that's just off the top here is:
for (i = 0; i < 31; i++) {
s->rx[i].len = qemu_get_be32(f);
qemu_get_buffer(f, s->rx[i].data, sizeof(s->rx[i].data));
}
Doesn't that 'len' need validating? I assume it's the size of the
packet in the fixed sized buffer? (??)
> - s->next_packet = qemu_get_be32(f);
> - s->rx_fifo = s->rx[s->next_packet].data + qemu_get_be32(f);
> - s->rx_fifo_len = qemu_get_be32(f);
> + v = qemu_get_be32(f);
> + if (v < 0 || v >= ARRAY_SIZE(s->rx)) {
> + return -EINVAL;
> + }
> + s->next_packet = v;
> + v = qemu_get_be32(f);
> + if (v < 0 || v >= sizeof(s->rx[i].data)) {
> + return -EINVAL;
> + }
> + s->rx_fifo = s->rx[s->next_packet].data + v;
> + v = qemu_get_be32(f);
> + /* Set limit low enough to avoid integer overflow when
> + * we do math on len later, but high enough to avoid
> + * truncating any packets.
> + */
> + if (v < 0 || v >= 0x100000) {
> + return -EINVAL;
> + }
> + s->rx_fifo_len = v;
I don't understand this - isn't the requirement that rx_fifo+rx_fifo_len be
within
the buffer (or I think it might be legal for the sum to point to the byte after
the
buffer)?
My (quick first ever look at this code) reading is that rx_fifo and rx_fifo_len
related to the current packet in-flight; although I've not quite convinced
myself
about what is supposed to happen at the end of the packet (which is why
I say rx_fifo might point just at? the end.
Dave
>
> return 0;
> }
> --
> MST
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
