[PATCH 2/2] staging: rtl8723bs: fix OOB read in OnAssocRsp() IE loop

[Alexandru Hossu <hossu.alexandru@gmail.com>]

From: Alexandru Hossu <a.hossu@student.tudelft.nl>

The IE parsing loop in OnAssocRsp() advances by (pIE->length + 2) each
iteration but only guards on i < pkt_len.  When a malicious AP sends an
AssocResponse whose last IE has only one byte remaining in the frame (the
element_id byte lands at pkt_len-1), the loop reads pIE->length from
pframe[pkt_len], which is one byte past the allocated receive buffer.

Additionally, even when the header bytes are in bounds, pIE->length itself
can extend the data window beyond pkt_len, silently passing a truncated IE
to the handler functions.

Add two guards at the top of the loop body:
  1. Break if fewer than sizeof(*pIE) bytes remain (can't read the header).
  2. Break if the IE's declared data extends past pkt_len.

Signed-off-by: Alexandru Hossu <a.hossu@student.tudelft.nl>
---
 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
index 5f00fe282..9666226a6 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
@@ -1400,7 +1400,11 @@ unsigned int OnAssocRsp(struct adapter *padapter, union recv_frame *precv_frame)
 	/* to handle HT, WMM, rate adaptive, update MAC reg */
 	/* for not to handle the synchronous IO in the tasklet */
 	for (i = (6 + WLAN_HDR_A3_LEN); i < pkt_len;) {
+		if (i + sizeof(*pIE) > pkt_len)
+			break;
 		pIE = (struct ndis_80211_var_ie *)(pframe + i);
+		if (i + sizeof(*pIE) + pIE->length > pkt_len)
+			break;
 
 		switch (pIE->element_id) {
 		case WLAN_EID_VENDOR_SPECIFIC:
-- 
2.53.0