cfg80211: don't put kek/kck/replay counter on the stack

There's no need to put the values on the stack, just pass a
pointer to the data in the nl80211 message. This reduces stack
usage and avoids potential issues with putting sensitive data
on the stack.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -1980,14 +1980,12 @@ struct cfg80211_wowlan_wakeup {
 
 /**
  * struct cfg80211_gtk_rekey_data - rekey data
- * @kek: key encryption key
- * @kck: key confirmation key
- * @replay_ctr: replay counter
+ * @kek: key encryption key (NL80211_KEK_LEN bytes)
+ * @kck: key confirmation key (NL80211_KCK_LEN bytes)
+ * @replay_ctr: replay counter (NL80211_REPLAY_CTR_LEN bytes)
  */
 struct cfg80211_gtk_rekey_data {
-	u8 kek[NL80211_KEK_LEN];
-	u8 kck[NL80211_KCK_LEN];
-	u8 replay_ctr[NL80211_REPLAY_CTR_LEN];
+	const u8 *kek, *kck, *replay_ctr;
 };
 
 /**

net/wireless/nl80211.c

@@ -8959,13 +8959,9 @@ static int nl80211_set_rekey_data(struct sk_buff *skb, struct genl_info *info)
 	if (nla_len(tb[NL80211_REKEY_DATA_KCK]) != NL80211_KCK_LEN)
 		return -ERANGE;
 
-	memcpy(rekey_data.kek, nla_data(tb[NL80211_REKEY_DATA_KEK]),
-	       NL80211_KEK_LEN);
-	memcpy(rekey_data.kck, nla_data(tb[NL80211_REKEY_DATA_KCK]),
-	       NL80211_KCK_LEN);
-	memcpy(rekey_data.replay_ctr,
-	       nla_data(tb[NL80211_REKEY_DATA_REPLAY_CTR]),
-	       NL80211_REPLAY_CTR_LEN);
+	rekey_data.kek = nla_data(tb[NL80211_REKEY_DATA_KEK]);
+	rekey_data.kck = nla_data(tb[NL80211_REKEY_DATA_KCK]);
+	rekey_data.replay_ctr = nla_data(tb[NL80211_REKEY_DATA_REPLAY_CTR]);
 
 	wdev_lock(wdev);
 	if (!wdev->current_bss) {