wifi: cfg80211/mac80211: reject bad MBSSID elements

Per spec, the maximum value for the MaxBSSID ('n') indicator is 8,
and the minimum is 1 since a multiple BSSID set with just one BSSID
doesn't make sense (the # of BSSIDs is limited by 2^n).

Limit this in the parsing in both cfg80211 and mac80211, rejecting
any elements with an invalid value.

This fixes potentially bad shifts in the processing of these inside
the cfg80211_gen_new_bssid() function later.

I found this during the investigation of CVE-2022-41674 fixed by the
previous patch.

Fixes: 0b8fb8235be8 ("cfg80211: Parsing of Multiple BSSID information in scanning")
Fixes: 78ac51f81532 ("mac80211: support multi-bssid")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index bf7461c41beff2cabc6ec0a15417678270e1ec5d..f61289c5fed2484f4bf031404bc0472f97ab1f41 100644 (file)
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1445,6 +1445,8 @@ static size_t ieee802_11_find_bssid_profile(const u8 *start, size_t len,
        for_each_element_id(elem, WLAN_EID_MULTIPLE_BSSID, start, len) {
                if (elem->datalen < 2)
                        continue;
+               if (elem->data[0] < 1 || elem->data[0] > 8)
+                       continue;
 
                for_each_element(sub, elem->data + 1, elem->datalen - 1) {
                        u8 new_bssid[ETH_ALEN];

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 62f8c10412ad30c5dc271dda5eec92d3342df424..5dab33e1f3a819f852bca175ce24e53797f0889d 100644 (file)
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -2143,6 +2143,8 @@ static void cfg80211_parse_mbssid_data(struct wiphy *wiphy,
        for_each_element_id(elem, WLAN_EID_MULTIPLE_BSSID, ie, ielen) {
                if (elem->datalen < 4)
                        continue;
+               if (elem->data[0] < 1 || (int)elem->data[0] > 8)
+                       continue;
                for_each_element(sub, elem->data + 1, elem->datalen - 1) {
                        u8 profile_len;