On Wed, Nov 30, 2016 at 10:57:02AM +0100, Michal Kubecek wrote:
> Qian Zhang (张谦) reported a potential socket buffer overflow in
> tipc_msg_build() which is also known as CVE-2016-8632: due to
> insufficient checks, a buffer overflow can occur if MTU is too short for
> even tipc headers. As anyone can set device MTU in a user/net namespace,
> this issue can be abused by a regular user.
>
> As agreed in the discussion on Ben Hutchings' original patch, we should
> check the MTU at the moment a bearer is attached rather than for each
> processed packet. We also need to repeat the check when bearer MTU is
> adjusted to new device MTU. UDP case also needs a check to avoid
> overflow when calculating bearer MTU.
>
> Fixes: b97bf3fd8f6a ("[TIPC] Initial merge")
> Signed-off-by: Michal Kubecek <mkube...@suse.cz>
> Reported-by: Qian Zhang (张谦) <zhangqia...@360.cn>
Self-NACK.
Im sorry, while testing this, I overlooked that an attempt to change
MTU of an underlying device to low value issues a warning but it
succeeds anyway.
> @@ -624,6 +626,9 @@ static int tipc_l2_device_event(struct notifier_block
> *nb, unsigned long evt,
> tipc_reset_bearer(net, b);
> break;
> case NETDEV_CHANGEMTU:
> + if (tipc_check_mtu(dev, 0))
> + return -EINVAL;
> + b->mtu = dev->mtu;
> tipc_reset_bearer(net, b);
> break;
> case NETDEV_CHANGEADDR:
This is a notifier so that error value needs to be encoded into notifier
error. I'll send v2 after retesting
Michal Kubecek
