From 242b0931c1918c56cd1dc5563fd250a3c39b996d Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Fri, 20 Sep 2019 21:54:18 +0200 Subject: [PATCH] cfg80211: validate SSID/MBSSID element ordering assumption The code copying the data assumes that the SSID element is before the MBSSID element, but since the data is untrusted from the AP, this cannot be guaranteed. Validate that this is indeed the case and ignore the MBSSID otherwise, to avoid having to deal with both cases for the copy of data that should be between them. Cc: stable@vger.kernel.org Fixes: 0b8fb8235be8 ("cfg80211: Parsing of Multiple BSSID information in scanning") Link: https://lore.kernel.org/r/1569009255-I1673911f5eae02964e21bdc11b2bf58e5e207e59@changeid Signed-off-by: Johannes Berg --- net/wireless/scan.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/wireless/scan.c b/net/wireless/scan.c index d313c9befa23..ff1016607f0b 100644 --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -1723,7 +1723,12 @@ cfg80211_update_notlisted_nontrans(struct wiphy *wiphy, return; new_ie_len -= trans_ssid[1]; mbssid = cfg80211_find_ie(WLAN_EID_MULTIPLE_BSSID, ie, ielen); - if (!mbssid) + /* + * It's not valid to have the MBSSID element before SSID + * ignore if that happens - the code below assumes it is + * after (while copying things inbetween). + */ + if (!mbssid || mbssid < trans_ssid) return; new_ie_len -= mbssid[1]; rcu_read_lock();