cfg80211: regulatory: make initialization more robust

Since my change to split out the regulatory init to occur later,
any issues during earlier cfg80211_init() or errors during the
platform device allocation would lead to crashes later. Make this
more robust by checking that the earlier initialization succeeded.

Fixes: d7be102f2945 ("cfg80211: initialize regulatory keys/database later")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/reg.c

@@ -3829,6 +3829,15 @@ static int __init regulatory_init_db(void)
 {
 	int err;
 
+	/*
+	 * It's possible that - due to other bugs/issues - cfg80211
+	 * never called regulatory_init() below, or that it failed;
+	 * in that case, don't try to do any further work here as
+	 * it's doomed to lead to crashes.
+	 */
+	if (IS_ERR_OR_NULL(reg_pdev))
+		return -EINVAL;
+
 	err = load_builtin_regdb_keys();
 	if (err)
 		return err;