wifi: ath: Silence memcpy run-time false positive warning

The memcpy() in ath_key_config() was attempting to write across
neighboring struct members in struct ath_keyval. Introduce a wrapping
struct_group, kv_values, to be the addressable target of the memcpy
without overflowing an individual member. Silences the false positive
run-time warning:

  memcpy: detected field-spanning write (size 32) of single field "hk.kv_val" at drivers/net/wireless/ath/key.c:506 (size 16)

Link: https://bbs.archlinux.org/viewtopic.php?id=282254
Cc: Kalle Valo <kvalo@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230210054310.never.554-kees@kernel.org

drivers/net/wireless/ath/ath.h

@@ -96,11 +96,13 @@ struct ath_keyval {
 	u8 kv_type;
 	u8 kv_pad;
 	u16 kv_len;
+	struct_group(kv_values,
 		u8 kv_val[16]; /* TK */
 		u8 kv_mic[8]; /* Michael MIC key */
 		u8 kv_txmic[8]; /* Michael MIC TX key (used only if the hardware
 				 * supports both MIC keys in the same key cache entry;
 				 * in that case, kv_mic is the RX key) */
+	);
 };
 
 enum ath_cipher {

drivers/net/wireless/ath/key.c

@@ -503,7 +503,7 @@ int ath_key_config(struct ath_common *common,
 
 	hk.kv_len = key->keylen;
 	if (key->keylen)
-		memcpy(hk.kv_val, key->key, key->keylen);
+		memcpy(&hk.kv_values, key->key, key->keylen);
 
 	if (!(key->flags & IEEE80211_KEY_FLAG_PAIRWISE)) {
 		switch (vif->type) {