wifi: wilc1000: validate pairwise and authentication suite offsets

There is no validation of 'offset' which can trigger an out-of-bounds
read when extracting RSN capabilities.
Signed-off-by: Phil Turnbull <philipturnbull@github.com>
Tested-by: Ajay Kathat <ajay.kathat@microchip.com>
Acked-by: Ajay Kathat <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221123153543.8568-2-philipturnbull@github.com

drivers/net/wireless/microchip/wilc1000/hif.c

@@ -482,14 +482,25 @@ void *wilc_parse_join_bss_param(struct cfg80211_bss *bss,
 
 	rsn_ie = cfg80211_find_ie(WLAN_EID_RSN, ies->data, ies->len);
 	if (rsn_ie) {
+		int rsn_ie_len = sizeof(struct element) + rsn_ie[1];
 		int offset = 8;
 
-		param->mode_802_11i = 2;
-		param->rsn_found = true;
 		/* extract RSN capabilities */
-		offset += (rsn_ie[offset] * 4) + 2;
-		offset += (rsn_ie[offset] * 4) + 2;
-		memcpy(param->rsn_cap, &rsn_ie[offset], 2);
+		if (offset < rsn_ie_len) {
+			/* skip over pairwise suites */
+			offset += (rsn_ie[offset] * 4) + 2;
+
+			if (offset < rsn_ie_len) {
+				/* skip over authentication suites */
+				offset += (rsn_ie[offset] * 4) + 2;
+
+				if (offset + 1 < rsn_ie_len) {
+					param->mode_802_11i = 2;
+					param->rsn_found = true;
+					memcpy(param->rsn_cap, &rsn_ie[offset], 2);
+				}
+			}
+		}
 	}
 
 	if (param->rsn_found) {