wifi: mac80211: fix mesh id corruption on 32 bit systems

Since the changed field size was increased to u64, mesh_bss_info_changed
pulls invalid bits from the first 3 bytes of the mesh id, clears them, and
passes them on to ieee80211_link_info_change_notify, because
ifmsh->mbss_changed was not updated to match its size.
Fix this by turning into ifmsh->mbss_changed into an unsigned long array with
64 bit size.

Fixes: 15ddba5 ("wifi: mac80211: consistently use u64 for BSS changes")
Reported-by: Thomas Hühn <thomas.huehn@hs-nordhausen.de>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20230913050134.53536-1-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -676,7 +676,7 @@ struct ieee80211_if_mesh {
 	struct timer_list mesh_path_root_timer;
 
 	unsigned long wrkq_flags;
-	unsigned long mbss_changed;
+	unsigned long mbss_changed[64 / BITS_PER_LONG];
 
 	bool userspace_handles_dfs;
 

net/mac80211/mesh.c

@@ -1175,7 +1175,7 @@ void ieee80211_mbss_info_change_notify(struct ieee80211_sub_if_data *sdata,
 
 	/* if we race with running work, worst case this work becomes a noop */
 	for_each_set_bit(bit, &bits, sizeof(changed) * BITS_PER_BYTE)
-		set_bit(bit, &ifmsh->mbss_changed);
+		set_bit(bit, ifmsh->mbss_changed);
 	set_bit(MESH_WORK_MBSS_CHANGED, &ifmsh->wrkq_flags);
 	wiphy_work_queue(sdata->local->hw.wiphy, &sdata->work);
 }
@@ -1257,7 +1257,7 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
 
 	/* clear any mesh work (for next join) we may have accrued */
 	ifmsh->wrkq_flags = 0;
-	ifmsh->mbss_changed = 0;
+	memset(ifmsh->mbss_changed, 0, sizeof(ifmsh->mbss_changed));
 
 	local->fif_other_bss--;
 	atomic_dec(&local->iff_allmultis);
@@ -1724,9 +1724,9 @@ static void mesh_bss_info_changed(struct ieee80211_sub_if_data *sdata)
 	u32 bit;
 	u64 changed = 0;
 
-	for_each_set_bit(bit, &ifmsh->mbss_changed,
+	for_each_set_bit(bit, ifmsh->mbss_changed,
 			 sizeof(changed) * BITS_PER_BYTE) {
-		clear_bit(bit, &ifmsh->mbss_changed);
+		clear_bit(bit, ifmsh->mbss_changed);
 		changed |= BIT(bit);
 	}