staging: rtl8723bs: fix stack buffer overflow in OnAssocReq IE parsing

commit 6ef0e1c10455927867cac8f0ed6b49f328f8cf95 upstream.

The Supported Rates IE length from an incoming Association Request frame
was used directly as the memcpy() length when copying into a fixed-size
16-byte stack buffer (supportRate). A malicious station can advertise an
IE length larger than 16 bytes, causing a stack buffer overflow.

Clamp ie_len to the buffer size before copying the Supported Rates IE,
and correct the bounds check when merging Extended Supported Rates to
prevent a second potential overflow.

This prevents kernel stack corruption triggered by malformed association
requests.

Signed-off-by: Navaneeth K <knavaneeth786@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ulrich Hecht <uli@kernel.org>

Author: cyberkunju

drivers/staging/rtl8723bs/core/rtw_mlme_ext.c

@@ -1296,14 +1296,17 @@ unsigned int OnAssocReq(struct adapter *padapter, union recv_frame *precv_frame)
 		status = _STATS_FAILURE_;
 		goto OnAssocReqFail;
 	} else {
+		if (ie_len > sizeof(supportRate))
+			ie_len = sizeof(supportRate);
+
 		memcpy(supportRate, p+2, ie_len);
 		supportRateNum = ie_len;
 
 		p = rtw_get_ie(pframe + WLAN_HDR_A3_LEN + ie_offset, _EXT_SUPPORTEDRATES_IE_, &ie_len,
 				pkt_len - WLAN_HDR_A3_LEN - ie_offset);
 		if (p !=  NULL) {
 
-			if (supportRateNum <= sizeof(supportRate)) {
+			if (supportRateNum + ie_len <= sizeof(supportRate)) {
 				memcpy(supportRate+supportRateNum, p+2, ie_len);
 				supportRateNum += ie_len;
 			}