cfg80211: update information elements in cached BSS struct

When a cached BSS struct is updated because a new beacon was received,
the code replaces the cached information elements by the IEs from the
new beacon. However it did not update the pub.information_elements
and pub.len_information_elements fields leaving them either pointing
to the old beacon IEs or in an inconsistent state where the data is
replaced by the new beacon IEs but len_information_elements still has
its value from the first beacon.

Fix this by updating the information elements fields if they are
pointing to beacon IEs.

Signed-off-by: Sven Neumann <s.neumann@raumfeld.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/scan.c

@@ -464,6 +464,9 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 		if (res->pub.beacon_ies) {
 			size_t used = dev->wiphy.bss_priv_size + sizeof(*res);
 			size_t ielen = res->pub.len_beacon_ies;
+			bool information_elements_is_beacon_ies =
+				(found->pub.information_elements ==
+				 found->pub.beacon_ies);
 
 			if (found->pub.beacon_ies &&
 			    !found->beacon_ies_allocated &&
@@ -487,6 +490,14 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 					found->pub.len_beacon_ies = ielen;
 				}
 			}
+
+			/* Override IEs if they were from a beacon before */
+			if (information_elements_is_beacon_ies) {
+				found->pub.information_elements =
+					found->pub.beacon_ies;
+				found->pub.len_information_elements =
+					found->pub.len_beacon_ies;
+			}
 		}
 
 		kref_put(&res->ref, bss_release);