[PATCH v7 6/7] staging: rtl8723bs: fix OOB reads in is_ap_in_tkip() IE loop

[Alexandru Hossu]

The loop in is_ap_in_tkip() iterates over IEs without verifying that
enough bytes remain before dereferencing the IE header or its payload:

- pIE->element_id and pIE->length are read without checking that
  i + sizeof(*pIE) <= ie_length, so a truncated IE at the end of the
  buffer causes an OOB read.

- For WLAN_EID_VENDOR_SPECIFIC the code compares pIE->data + 12,
  which requires pIE->length >= 16.  For WLAN_EID_RSN it compares
  pIE->data + 8, requiring pIE->length >= 12.  Neither requirement
  is checked.

Add the missing IE header and payload bounds checks and guard each
data access with an explicit pIE->length minimum, matching the
pattern established in update_beacon_info().

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Alexandru Hossu <hossu.alexandru@xxxxxxxxx>
---
 drivers/staging/rtl8723bs/core/rtw_wlan_util.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
index dd34f229df12..94bbe7ac13ac 100644
--- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
+++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
@@ -1335,15 +1335,23 @@ unsigned int is_ap_in_tkip(struct adapter *padapter)
 		for (i = sizeof(struct ndis_802_11_fix_ie); i < pmlmeinfo->network.ie_length;) {
 			pIE = (struct ndis_80211_var_ie *)(pmlmeinfo->network.ies + i);
 
+			if (i + sizeof(*pIE) > pmlmeinfo->network.ie_length)
+				break;
+			if (i + sizeof(*pIE) + pIE->length > pmlmeinfo->network.ie_length)
+				break;
+
 			switch (pIE->element_id) {
 			case WLAN_EID_VENDOR_SPECIFIC:
-				if ((!memcmp(pIE->data, RTW_WPA_OUI, 4)) && (!memcmp((pIE->data + 12), WPA_TKIP_CIPHER, 4)))
+				if (pIE->length >= 16 &&
+				    !memcmp(pIE->data, RTW_WPA_OUI, 4) &&
+				    !memcmp((pIE->data + 12), WPA_TKIP_CIPHER, 4))
 					return true;
 
 				break;
 
 			case WLAN_EID_RSN:
-				if (!memcmp((pIE->data + 8), RSN_TKIP_CIPHER, 4))
+				if (pIE->length >= 12 &&
+				    !memcmp((pIE->data + 8), RSN_TKIP_CIPHER, 4))
 					return true;
 				break;
 
@@ -1351,7 +1359,7 @@ unsigned int is_ap_in_tkip(struct adapter *padapter)
 				break;
 			}
 
-			i += (pIE->length + 2);
+			i += sizeof(*pIE) + pIE->length;
 		}
 
 		return false;
-- 
2.54.0