cfg80211: check S1G beacon compat element length

We need to check the length of this element so that we don't
access data beyond its end. Fix that.

Fixes: 9eaffe5078ca ("cfg80211: convert S1G beacon to scan results")
Link: https://lore.kernel.org/r/20210408142826.f6f4525012de.I9fdeff0afdc683a6024e5ea49d2daa3cd2459d11@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 019952d..758eb7d 100644 (file)
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -2352,14 +2352,16 @@ cfg80211_inform_single_bss_frame_data(struct wiphy *wiphy,
                return NULL;
 
        if (ext) {
-               struct ieee80211_s1g_bcn_compat_ie *compat;
-               u8 *ie;
+               const struct ieee80211_s1g_bcn_compat_ie *compat;
+               const struct element *elem;
 
-               ie = (void *)cfg80211_find_ie(WLAN_EID_S1G_BCN_COMPAT,
-                                             variable, ielen);
-               if (!ie)
+               elem = cfg80211_find_elem(WLAN_EID_S1G_BCN_COMPAT,
+                                         variable, ielen);
+               if (!elem)
+                       return NULL;
+               if (elem->datalen < sizeof(*compat))
                        return NULL;
-               compat = (void *)(ie + 2);
+               compat = (void *)elem->data;
                bssid = ext->u.s1g_beacon.sa;
                capability = le16_to_cpu(compat->compat_info);
                beacon_int = le16_to_cpu(compat->beacon_int);