brcmfmac: fix possible buffer overflow in brcmf_cfg80211_mgmt_tx()

The lower level nl80211 code in cfg80211 ensures that "len" is between
25 and NL80211_ATTR_FRAME (2304).  We subtract DOT11_MGMT_HDR_LEN (24) from
"len" so thats's max of 2280.  However, the action_frame->data[] buffer is
only BRCMF_FIL_ACTION_FRAME_SIZE (1800) bytes long so this memcpy() can
overflow.

	memcpy(action_frame->data, &buf[DOT11_MGMT_HDR_LEN],
	       le16_to_cpu(action_frame->len));

Cc: stable@vger.kernel.org # 3.9.x
Fixes: 18e2f61db3b70 ("brcmfmac: P2P action frame tx.")
Reported-by: "freenerguo(郭大兴)" <freenerguo@tencent.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int brcmf_cfg80211_set_pmk(struct wiphy *wiphy, struct net_device *dev,
				  const struct cfg80211_pmk_conf *conf)
{
	struct brcmf_if *ifp;

	brcmf_dbg(TRACE, "enter\n");

	/* expect using firmware supplicant for 1X */
	ifp = netdev_priv(dev);
	if (WARN_ON(ifp->vif->profile.use_fwsup != BRCMF_PROFILE_FWSUP_1X))
		return -EINVAL;

	return brcmf_set_pmk(ifp, conf->pmk, conf->pmk_len);
}

static int brcmf_cfg80211_set_pmk(struct wiphy *wiphy, struct net_device *dev,
				  const struct cfg80211_pmk_conf *conf)
{
	struct brcmf_if *ifp;

	brcmf_dbg(TRACE, "enter\n");

	/* expect using firmware supplicant for 1X */
	ifp = netdev_priv(dev);
	if (WARN_ON(ifp->vif->profile.use_fwsup != BRCMF_PROFILE_FWSUP_1X))
		return -EINVAL;

	return brcmf_set_pmk(ifp, conf->pmk, conf->pmk_len);
}
