brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

User-space can choose to omit NL80211_ATTR_SSID and only provide raw
IE TLV data. When doing so it can provide SSID IE with length exceeding
the allowed size. The driver further processes this IE copying it
into a local variable without checking the length. Hence stack can be
corrupted and used as exploit.

Cc: stable@vger.kernel.org # v4.7
Reported-by: Daxing Guo <freener.gdx@gmail.com>
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
s32 brcmf_vif_set_mgmt_ie(struct brcmf_cfg80211_vif *vif, s32 pktflag,
			  const u8 *vndr_ie_buf, u32 vndr_ie_len)
{
	struct brcmf_if *ifp;
	struct vif_saved_ie *saved_ie;
	s32 err = 0;
	u8  *iovar_ie_buf;
	u8  *curr_ie_buf;
	u8  *mgmt_ie_buf = NULL;
	int mgmt_ie_buf_len;
	u32 *mgmt_ie_len;
	u32 del_add_ie_buf_len = 0;
	u32 total_ie_buf_len = 0;
	u32 parsed_ie_buf_len = 0;
	struct parsed_vndr_ies old_vndr_ies;
	struct parsed_vndr_ies new_vndr_ies;
	struct parsed_vndr_ie_info *vndrie_info;
	s32 i;
	u8 *ptr;
	int remained_buf_len;

	if (!vif)
		return -ENODEV;
	ifp = vif->ifp;
	saved_ie = &vif->saved_ie;

	brcmf_dbg(TRACE, "bsscfgidx %d, pktflag : 0x%02X\n", ifp->bsscfgidx,
		  pktflag);
	iovar_ie_buf = kzalloc(WL_EXTRA_BUF_MAX, GFP_KERNEL);
	if (!iovar_ie_buf)
		return -ENOMEM;
	curr_ie_buf = iovar_ie_buf;
	switch (pktflag) {
	case BRCMF_VNDR_IE_PRBREQ_FLAG:
		mgmt_ie_buf = saved_ie->probe_req_ie;
		mgmt_ie_len = &saved_ie->probe_req_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->probe_req_ie);
		break;
	case BRCMF_VNDR_IE_PRBRSP_FLAG:
		mgmt_ie_buf = saved_ie->probe_res_ie;
		mgmt_ie_len = &saved_ie->probe_res_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->probe_res_ie);
		break;
	case BRCMF_VNDR_IE_BEACON_FLAG:
		mgmt_ie_buf = saved_ie->beacon_ie;
		mgmt_ie_len = &saved_ie->beacon_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->beacon_ie);
		break;
	case BRCMF_VNDR_IE_ASSOCREQ_FLAG:
		mgmt_ie_buf = saved_ie->assoc_req_ie;
		mgmt_ie_len = &saved_ie->assoc_req_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->assoc_req_ie);
		break;
	default:
		err = -EPERM;
		brcmf_err("not suitable type\n");
		goto exit;
	}

	if (vndr_ie_len > mgmt_ie_buf_len) {
		err = -ENOMEM;
		brcmf_err("extra IE size too big\n");
		goto exit;
	}

	/* parse and save new vndr_ie in curr_ie_buff before comparing it */
	if (vndr_ie_buf && vndr_ie_len && curr_ie_buf) {
		ptr = curr_ie_buf;
		brcmf_parse_vndr_ies(vndr_ie_buf, vndr_ie_len, &new_vndr_ies);
		for (i = 0; i < new_vndr_ies.count; i++) {
			vndrie_info = &new_vndr_ies.ie_info[i];
			memcpy(ptr + parsed_ie_buf_len, vndrie_info->ie_ptr,
			       vndrie_info->ie_len);
			parsed_ie_buf_len += vndrie_info->ie_len;
		}
	}

	if (mgmt_ie_buf && *mgmt_ie_len) {
		if (parsed_ie_buf_len && (parsed_ie_buf_len == *mgmt_ie_len) &&
		    (memcmp(mgmt_ie_buf, curr_ie_buf,
			    parsed_ie_buf_len) == 0)) {
			brcmf_dbg(TRACE, "Previous mgmt IE equals to current IE\n");
			goto exit;
		}

		/* parse old vndr_ie */
		brcmf_parse_vndr_ies(mgmt_ie_buf, *mgmt_ie_len, &old_vndr_ies);

		/* make a command to delete old ie */
		for (i = 0; i < old_vndr_ies.count; i++) {
			vndrie_info = &old_vndr_ies.ie_info[i];

			brcmf_dbg(TRACE, "DEL ID : %d, Len: %d , OUI:%02x:%02x:%02x\n",
				  vndrie_info->vndrie.id,
				  vndrie_info->vndrie.len,
				  vndrie_info->vndrie.oui[0],
				  vndrie_info->vndrie.oui[1],
				  vndrie_info->vndrie.oui[2]);

			del_add_ie_buf_len = brcmf_vndr_ie(curr_ie_buf, pktflag,
							   vndrie_info->ie_ptr,
							   vndrie_info->ie_len,
							   "del");
			curr_ie_buf += del_add_ie_buf_len;
			total_ie_buf_len += del_add_ie_buf_len;
		}
	}

	*mgmt_ie_len = 0;
	/* Add if there is any extra IE */
	if (mgmt_ie_buf && parsed_ie_buf_len) {
		ptr = mgmt_ie_buf;

		remained_buf_len = mgmt_ie_buf_len;

		/* make a command to add new ie */
		for (i = 0; i < new_vndr_ies.count; i++) {
			vndrie_info = &new_vndr_ies.ie_info[i];

			/* verify remained buf size before copy data */
			if (remained_buf_len < (vndrie_info->vndrie.len +
							VNDR_IE_VSIE_OFFSET)) {
				brcmf_err("no space in mgmt_ie_buf: len left %d",
					  remained_buf_len);
				break;
			}
			remained_buf_len -= (vndrie_info->ie_len +
					     VNDR_IE_VSIE_OFFSET);

			brcmf_dbg(TRACE, "ADDED ID : %d, Len: %d, OUI:%02x:%02x:%02x\n",
				  vndrie_info->vndrie.id,
				  vndrie_info->vndrie.len,
				  vndrie_info->vndrie.oui[0],
				  vndrie_info->vndrie.oui[1],
				  vndrie_info->vndrie.oui[2]);

			del_add_ie_buf_len = brcmf_vndr_ie(curr_ie_buf, pktflag,
							   vndrie_info->ie_ptr,
							   vndrie_info->ie_len,
							   "add");

			/* save the parsed IE in wl struct */
			memcpy(ptr + (*mgmt_ie_len), vndrie_info->ie_ptr,
			       vndrie_info->ie_len);
			*mgmt_ie_len += vndrie_info->ie_len;

			curr_ie_buf += del_add_ie_buf_len;
			total_ie_buf_len += del_add_ie_buf_len;
		}
	}
	if (total_ie_buf_len) {
		err  = brcmf_fil_bsscfg_data_set(ifp, "vndr_ie", iovar_ie_buf,
						 total_ie_buf_len);
		if (err)
			brcmf_err("vndr ie set error : %d\n", err);
	}

exit:
	kfree(iovar_ie_buf);
	return err;
}

s32 brcmf_vif_set_mgmt_ie(struct brcmf_cfg80211_vif *vif, s32 pktflag,
			  const u8 *vndr_ie_buf, u32 vndr_ie_len)
{
	struct brcmf_if *ifp;
	struct vif_saved_ie *saved_ie;
	s32 err = 0;
	u8  *iovar_ie_buf;
	u8  *curr_ie_buf;
	u8  *mgmt_ie_buf = NULL;
	int mgmt_ie_buf_len;
	u32 *mgmt_ie_len;
	u32 del_add_ie_buf_len = 0;
	u32 total_ie_buf_len = 0;
	u32 parsed_ie_buf_len = 0;
	struct parsed_vndr_ies old_vndr_ies;
	struct parsed_vndr_ies new_vndr_ies;
	struct parsed_vndr_ie_info *vndrie_info;
	s32 i;
	u8 *ptr;
	int remained_buf_len;

	if (!vif)
		return -ENODEV;
	ifp = vif->ifp;
	saved_ie = &vif->saved_ie;

	brcmf_dbg(TRACE, "bsscfgidx %d, pktflag : 0x%02X\n", ifp->bsscfgidx,
		  pktflag);
	iovar_ie_buf = kzalloc(WL_EXTRA_BUF_MAX, GFP_KERNEL);
	if (!iovar_ie_buf)
		return -ENOMEM;
	curr_ie_buf = iovar_ie_buf;
	switch (pktflag) {
	case BRCMF_VNDR_IE_PRBREQ_FLAG:
		mgmt_ie_buf = saved_ie->probe_req_ie;
		mgmt_ie_len = &saved_ie->probe_req_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->probe_req_ie);
		break;
	case BRCMF_VNDR_IE_PRBRSP_FLAG:
		mgmt_ie_buf = saved_ie->probe_res_ie;
		mgmt_ie_len = &saved_ie->probe_res_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->probe_res_ie);
		break;
	case BRCMF_VNDR_IE_BEACON_FLAG:
		mgmt_ie_buf = saved_ie->beacon_ie;
		mgmt_ie_len = &saved_ie->beacon_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->beacon_ie);
		break;
	case BRCMF_VNDR_IE_ASSOCREQ_FLAG:
		mgmt_ie_buf = saved_ie->assoc_req_ie;
		mgmt_ie_len = &saved_ie->assoc_req_ie_len;
		mgmt_ie_buf_len = sizeof(saved_ie->assoc_req_ie);
		break;
	default:
		err = -EPERM;
		brcmf_err("not suitable type\n");
		goto exit;
	}

	if (vndr_ie_len > mgmt_ie_buf_len) {
		err = -ENOMEM;
		brcmf_err("extra IE size too big\n");
		goto exit;
	}

	/* parse and save new vndr_ie in curr_ie_buff before comparing it */
	if (vndr_ie_buf && vndr_ie_len && curr_ie_buf) {
		ptr = curr_ie_buf;
		brcmf_parse_vndr_ies(vndr_ie_buf, vndr_ie_len, &new_vndr_ies);
		for (i = 0; i < new_vndr_ies.count; i++) {
			vndrie_info = &new_vndr_ies.ie_info[i];
			memcpy(ptr + parsed_ie_buf_len, vndrie_info->ie_ptr,
			       vndrie_info->ie_len);
			parsed_ie_buf_len += vndrie_info->ie_len;
		}
	}

	if (mgmt_ie_buf && *mgmt_ie_len) {
		if (parsed_ie_buf_len && (parsed_ie_buf_len == *mgmt_ie_len) &&
		    (memcmp(mgmt_ie_buf, curr_ie_buf,
			    parsed_ie_buf_len) == 0)) {
			brcmf_dbg(TRACE, "Previous mgmt IE equals to current IE\n");
			goto exit;
		}

		/* parse old vndr_ie */
		brcmf_parse_vndr_ies(mgmt_ie_buf, *mgmt_ie_len, &old_vndr_ies);

		/* make a command to delete old ie */
		for (i = 0; i < old_vndr_ies.count; i++) {
			vndrie_info = &old_vndr_ies.ie_info[i];

			brcmf_dbg(TRACE, "DEL ID : %d, Len: %d , OUI:%02x:%02x:%02x\n",
				  vndrie_info->vndrie.id,
				  vndrie_info->vndrie.len,
				  vndrie_info->vndrie.oui[0],
				  vndrie_info->vndrie.oui[1],
				  vndrie_info->vndrie.oui[2]);

			del_add_ie_buf_len = brcmf_vndr_ie(curr_ie_buf, pktflag,
							   vndrie_info->ie_ptr,
							   vndrie_info->ie_len,
							   "del");
			curr_ie_buf += del_add_ie_buf_len;
			total_ie_buf_len += del_add_ie_buf_len;
		}
	}

	*mgmt_ie_len = 0;
	/* Add if there is any extra IE */
	if (mgmt_ie_buf && parsed_ie_buf_len) {
		ptr = mgmt_ie_buf;

		remained_buf_len = mgmt_ie_buf_len;

		/* make a command to add new ie */
		for (i = 0; i < new_vndr_ies.count; i++) {
			vndrie_info = &new_vndr_ies.ie_info[i];

			/* verify remained buf size before copy data */
			if (remained_buf_len < (vndrie_info->vndrie.len +
							VNDR_IE_VSIE_OFFSET)) {
				brcmf_err("no space in mgmt_ie_buf: len left %d",
					  remained_buf_len);
				break;
			}
			remained_buf_len -= (vndrie_info->ie_len +
					     VNDR_IE_VSIE_OFFSET);

			brcmf_dbg(TRACE, "ADDED ID : %d, Len: %d, OUI:%02x:%02x:%02x\n",
				  vndrie_info->vndrie.id,
				  vndrie_info->vndrie.len,
				  vndrie_info->vndrie.oui[0],
				  vndrie_info->vndrie.oui[1],
				  vndrie_info->vndrie.oui[2]);

			del_add_ie_buf_len = brcmf_vndr_ie(curr_ie_buf, pktflag,
							   vndrie_info->ie_ptr,
							   vndrie_info->ie_len,
							   "add");

			/* save the parsed IE in wl struct */
			memcpy(ptr + (*mgmt_ie_len), vndrie_info->ie_ptr,
			       vndrie_info->ie_len);
			*mgmt_ie_len += vndrie_info->ie_len;

			curr_ie_buf += del_add_ie_buf_len;
			total_ie_buf_len += del_add_ie_buf_len;
		}
	}
	if (total_ie_buf_len) {
		err  = brcmf_fil_bsscfg_data_set(ifp, "vndr_ie", iovar_ie_buf,
						 total_ie_buf_len);
		if (err)
			brcmf_err("vndr ie set error : %d\n", err);
	}

exit:
	kfree(iovar_ie_buf);
	return err;
}
