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>
struct wireless_dev *brcmf_ap_add_vif(struct wiphy *wiphy, const char *name,
				      struct vif_params *params)
{
	struct brcmf_cfg80211_info *cfg = wiphy_to_cfg(wiphy);
	struct brcmf_if *ifp = netdev_priv(cfg_to_ndev(cfg));
	struct brcmf_cfg80211_vif *vif;
	int err;

	if (brcmf_cfg80211_vif_event_armed(cfg))
		return ERR_PTR(-EBUSY);

	brcmf_dbg(INFO, "Adding vif \"%s\"\n", name);

	vif = brcmf_alloc_vif(cfg, NL80211_IFTYPE_AP);
	if (IS_ERR(vif))
		return (struct wireless_dev *)vif;

	brcmf_cfg80211_arm_vif_event(cfg, vif);

	err = brcmf_cfg80211_request_ap_if(ifp);
	if (err) {
		brcmf_cfg80211_arm_vif_event(cfg, NULL);
		goto fail;
	}

	/* wait for firmware event */
	err = brcmf_cfg80211_wait_vif_event(cfg, BRCMF_E_IF_ADD,
					    BRCMF_VIF_EVENT_TIMEOUT);
	brcmf_cfg80211_arm_vif_event(cfg, NULL);
	if (!err) {
		brcmf_err("timeout occurred\n");
		err = -EIO;
		goto fail;
	}

	/* interface created in firmware */
	ifp = vif->ifp;
	if (!ifp) {
		brcmf_err("no if pointer provided\n");
		err = -ENOENT;
		goto fail;
	}

	strncpy(ifp->ndev->name, name, sizeof(ifp->ndev->name) - 1);
	err = brcmf_net_attach(ifp, true);
	if (err) {
		brcmf_err("Registering netdevice failed\n");
		free_netdev(ifp->ndev);
		goto fail;
	}

	return &ifp->vif->wdev;

fail:
	brcmf_free_vif(vif);
	return ERR_PTR(err);
}

struct wireless_dev *brcmf_ap_add_vif(struct wiphy *wiphy, const char *name,
				      struct vif_params *params)
{
	struct brcmf_cfg80211_info *cfg = wiphy_to_cfg(wiphy);
	struct brcmf_if *ifp = netdev_priv(cfg_to_ndev(cfg));
	struct brcmf_cfg80211_vif *vif;
	int err;

	if (brcmf_cfg80211_vif_event_armed(cfg))
		return ERR_PTR(-EBUSY);

	brcmf_dbg(INFO, "Adding vif \"%s\"\n", name);

	vif = brcmf_alloc_vif(cfg, NL80211_IFTYPE_AP);
	if (IS_ERR(vif))
		return (struct wireless_dev *)vif;

	brcmf_cfg80211_arm_vif_event(cfg, vif);

	err = brcmf_cfg80211_request_ap_if(ifp);
	if (err) {
		brcmf_cfg80211_arm_vif_event(cfg, NULL);
		goto fail;
	}

	/* wait for firmware event */
	err = brcmf_cfg80211_wait_vif_event(cfg, BRCMF_E_IF_ADD,
					    BRCMF_VIF_EVENT_TIMEOUT);
	brcmf_cfg80211_arm_vif_event(cfg, NULL);
	if (!err) {
		brcmf_err("timeout occurred\n");
		err = -EIO;
		goto fail;
	}

	/* interface created in firmware */
	ifp = vif->ifp;
	if (!ifp) {
		brcmf_err("no if pointer provided\n");
		err = -ENOENT;
		goto fail;
	}

	strncpy(ifp->ndev->name, name, sizeof(ifp->ndev->name) - 1);
	err = brcmf_net_attach(ifp, true);
	if (err) {
		brcmf_err("Registering netdevice failed\n");
		free_netdev(ifp->ndev);
		goto fail;
	}

	return &ifp->vif->wdev;

fail:
	brcmf_free_vif(vif);
	return ERR_PTR(err);
}
