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>
brcmf_parse_vndr_ies(const u8 *vndr_ie_buf, u32 vndr_ie_len,
		     struct parsed_vndr_ies *vndr_ies)
{
	struct brcmf_vs_tlv *vndrie;
	struct brcmf_tlv *ie;
	struct parsed_vndr_ie_info *parsed_info;
	s32 remaining_len;

	remaining_len = (s32)vndr_ie_len;
	memset(vndr_ies, 0, sizeof(*vndr_ies));

	ie = (struct brcmf_tlv *)vndr_ie_buf;
	while (ie) {
		if (ie->id != WLAN_EID_VENDOR_SPECIFIC)
			goto next;
		vndrie = (struct brcmf_vs_tlv *)ie;
		/* len should be bigger than OUI length + one */
		if (vndrie->len < (VS_IE_FIXED_HDR_LEN - TLV_HDR_LEN + 1)) {
			brcmf_err("invalid vndr ie. length is too small %d\n",
				  vndrie->len);
			goto next;
		}
		/* if wpa or wme ie, do not add ie */
		if (!memcmp(vndrie->oui, (u8 *)WPA_OUI, TLV_OUI_LEN) &&
		    ((vndrie->oui_type == WPA_OUI_TYPE) ||
		    (vndrie->oui_type == WME_OUI_TYPE))) {
			brcmf_dbg(TRACE, "Found WPA/WME oui. Do not add it\n");
			goto next;
		}

		parsed_info = &vndr_ies->ie_info[vndr_ies->count];

		/* save vndr ie information */
		parsed_info->ie_ptr = (char *)vndrie;
		parsed_info->ie_len = vndrie->len + TLV_HDR_LEN;
		memcpy(&parsed_info->vndrie, vndrie, sizeof(*vndrie));

		vndr_ies->count++;

		brcmf_dbg(TRACE, "** OUI %02x %02x %02x, type 0x%02x\n",
			  parsed_info->vndrie.oui[0],
			  parsed_info->vndrie.oui[1],
			  parsed_info->vndrie.oui[2],
			  parsed_info->vndrie.oui_type);

		if (vndr_ies->count >= VNDR_IE_PARSE_LIMIT)
			break;
next:
		remaining_len -= (ie->len + TLV_HDR_LEN);
		if (remaining_len <= TLV_HDR_LEN)
			ie = NULL;
		else
			ie = (struct brcmf_tlv *)(((u8 *)ie) + ie->len +
				TLV_HDR_LEN);
	}
	return 0;
}

brcmf_parse_vndr_ies(const u8 *vndr_ie_buf, u32 vndr_ie_len,
		     struct parsed_vndr_ies *vndr_ies)
{
	struct brcmf_vs_tlv *vndrie;
	struct brcmf_tlv *ie;
	struct parsed_vndr_ie_info *parsed_info;
	s32 remaining_len;

	remaining_len = (s32)vndr_ie_len;
	memset(vndr_ies, 0, sizeof(*vndr_ies));

	ie = (struct brcmf_tlv *)vndr_ie_buf;
	while (ie) {
		if (ie->id != WLAN_EID_VENDOR_SPECIFIC)
			goto next;
		vndrie = (struct brcmf_vs_tlv *)ie;
		/* len should be bigger than OUI length + one */
		if (vndrie->len < (VS_IE_FIXED_HDR_LEN - TLV_HDR_LEN + 1)) {
			brcmf_err("invalid vndr ie. length is too small %d\n",
				  vndrie->len);
			goto next;
		}
		/* if wpa or wme ie, do not add ie */
		if (!memcmp(vndrie->oui, (u8 *)WPA_OUI, TLV_OUI_LEN) &&
		    ((vndrie->oui_type == WPA_OUI_TYPE) ||
		    (vndrie->oui_type == WME_OUI_TYPE))) {
			brcmf_dbg(TRACE, "Found WPA/WME oui. Do not add it\n");
			goto next;
		}

		parsed_info = &vndr_ies->ie_info[vndr_ies->count];

		/* save vndr ie information */
		parsed_info->ie_ptr = (char *)vndrie;
		parsed_info->ie_len = vndrie->len + TLV_HDR_LEN;
		memcpy(&parsed_info->vndrie, vndrie, sizeof(*vndrie));

		vndr_ies->count++;

		brcmf_dbg(TRACE, "** OUI %02x %02x %02x, type 0x%02x\n",
			  parsed_info->vndrie.oui[0],
			  parsed_info->vndrie.oui[1],
			  parsed_info->vndrie.oui[2],
			  parsed_info->vndrie.oui_type);

		if (vndr_ies->count >= VNDR_IE_PARSE_LIMIT)
			break;
next:
		remaining_len -= (ie->len + TLV_HDR_LEN);
		if (remaining_len <= TLV_HDR_LEN)
			ie = NULL;
		else
			ie = (struct brcmf_tlv *)(((u8 *)ie) + ie->len +
				TLV_HDR_LEN);
	}
	return 0;
}
