Commit message: 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>
CVE: CVE-2017-7541
CWE: CWE-119
Vulnerability description: The brcmf_cfg80211_mgmt_tx function in drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c in the Linux kernel before 4.12.3 allows local users to cause a denial of service (buffer overflow and system crash) or possibly gain privileges via a crafted NL80211_CMD_FRAME Netlink packet.

Project: linux
File: cfg80211.c

brcmf_cfg80211_mgmt_tx(struct wiphy *wiphy, struct wireless_dev *wdev,
		       struct cfg80211_mgmt_tx_params *params, u64 *cookie)
{
	struct brcmf_cfg80211_info *cfg = wiphy_to_cfg(wiphy);
	struct ieee80211_channel *chan = params->chan;
	const u8 *buf = params->buf;
	size_t len = params->len;
	const struct ieee80211_mgmt *mgmt;
	struct brcmf_cfg80211_vif *vif;
	s32 err = 0;
	s32 ie_offset;
	s32 ie_len;
	struct brcmf_fil_action_frame_le *action_frame;
	struct brcmf_fil_af_params_le *af_params;
	bool ack;
	s32 chan_nr;
	u32 freq;

	brcmf_dbg(TRACE, "Enter\n");

	*cookie = 0;

	mgmt = (const struct ieee80211_mgmt *)buf;

	if (!ieee80211_is_mgmt(mgmt->frame_control)) {
		brcmf_err("Driver only allows MGMT packet type\n");
		return -EPERM;
	}

	vif = container_of(wdev, struct brcmf_cfg80211_vif, wdev);

	if (ieee80211_is_probe_resp(mgmt->frame_control)) {
		/* Right now the only reason to get a probe response */
		/* is for p2p listen response or for p2p GO from     */
		/* wpa_supplicant. Unfortunately the probe is send   */
		/* on primary ndev, while dongle wants it on the p2p */
		/* vif. Since this is only reason for a probe        */
		/* response to be sent, the vif is taken from cfg.   */
		/* If ever desired to send proberesp for non p2p     */
		/* response then data should be checked for          */
		/* "DIRECT-". Note in future supplicant will take    */
		/* dedicated p2p wdev to do this and then this 'hack'*/
		/* is not needed anymore.                            */
		ie_offset =  DOT11_MGMT_HDR_LEN +
			     DOT11_BCN_PRB_FIXED_LEN;
		ie_len = len - ie_offset;
		if (vif == cfg->p2p.bss_idx[P2PAPI_BSSCFG_PRIMARY].vif)
			vif = cfg->p2p.bss_idx[P2PAPI_BSSCFG_DEVICE].vif;
		err = brcmf_vif_set_mgmt_ie(vif,
					    BRCMF_VNDR_IE_PRBRSP_FLAG,
					    &buf[ie_offset],
					    ie_len);
 		cfg80211_mgmt_tx_status(wdev, *cookie, buf, len, true,
 					GFP_KERNEL);
 	} else if (ieee80211_is_action(mgmt->frame_control)) {
 		af_params = kzalloc(sizeof(*af_params), GFP_KERNEL);
 		if (af_params == NULL) {
 			brcmf_err("unable to allocate frame\n");
			err = -ENOMEM;
			goto exit;
		}
		action_frame = &af_params->action_frame;
		/* Add the packet Id */
		action_frame->packet_id = cpu_to_le32(*cookie);
		/* Add BSSID */
		memcpy(&action_frame->da[0], &mgmt->da[0], ETH_ALEN);
		memcpy(&af_params->bssid[0], &mgmt->bssid[0], ETH_ALEN);
		/* Add the length exepted for 802.11 header  */
		action_frame->len = cpu_to_le16(len - DOT11_MGMT_HDR_LEN);
		/* Add the channel. Use the one specified as parameter if any or
		 * the current one (got from the firmware) otherwise
		 */
		if (chan)
			freq = chan->center_freq;
		else
			brcmf_fil_cmd_int_get(vif->ifp, BRCMF_C_GET_CHANNEL,
					      &freq);
		chan_nr = ieee80211_frequency_to_channel(freq);
		af_params->channel = cpu_to_le32(chan_nr);

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

		brcmf_dbg(TRACE, "Action frame, cookie=%lld, len=%d, freq=%d\n",
			  *cookie, le16_to_cpu(action_frame->len), freq);

		ack = brcmf_p2p_send_action_frame(cfg, cfg_to_ndev(cfg),
						  af_params);

		cfg80211_mgmt_tx_status(wdev, *cookie, buf, len, ack,
					GFP_KERNEL);
		kfree(af_params);
	} else {
		brcmf_dbg(TRACE, "Unhandled, fc=%04x!!\n", mgmt->frame_control);
		brcmf_dbg_hex_dump(true, buf, len, "payload, len=%zu\n", len);
	}

exit:
	return err;
}