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From:   Johannes Berg <johannes@sipsolutions.net>
To:     linux-wireless@vger.kernel.org
Cc:     Johannes Berg <johannes.berg@intel.com>,
        =?UTF-8?q?S=C3=B6nke=20Huster?= <shuster@seemoo.tu-darmstadt.de>
Subject: [PATCH 1/2] wifi: cfg80211: fix buffer overflow in elem comparison
Date:   Fri, 25 Nov 2022 12:36:57 +0100
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From: Johannes Berg <johannes.berg@intel.com>

For vendor elements, the code here assumes that 5 octets
are present without checking. Since the element itself is
already checked to fit, we only need to check the length.

Reported-and-tested-by: Sönke Huster <shuster@seemoo.tu-darmstadt.de>
Fixes: 0b8fb8235be8 ("cfg80211: Parsing of Multiple BSSID information in scanning")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/wireless/scan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index da752b0cc752..4d217798890a 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -330,7 +330,8 @@ static size_t cfg80211_gen_new_ie(const u8 *ie, size_t ielen,
 			 * determine if they are the same ie.
 			 */
 			if (tmp_old[0] == WLAN_EID_VENDOR_SPECIFIC) {
-				if (!memcmp(tmp_old + 2, tmp + 2, 5)) {
+				if (tmp_old[1] >= 5 && tmp[1] >= 5 &&
+				    !memcmp(tmp_old + 2, tmp + 2, 5)) {
 					/* same vendor ie, copy from
 					 * subelement
 					 */
-- 
2.38.1