tls: zero the crypto information from tls_context before freeing

This contains key material in crypto_send_aes_gcm_128 and
crypto_recv_aes_gcm_128.

Introduce union tls_crypto_context, and replace the two identical
unions directly embedded in struct tls_context with it. We can then
use this union to clean up the memory in the new tls_ctx_free()
function.

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index f29b7c4..9e91848 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1055,8 +1055,8 @@ static int tls_read_size(struct strparser *strp, struct sk_buff *skb)
 		goto read_failure;
 	}
 
-	if (header[1] != TLS_VERSION_MINOR(tls_ctx->crypto_recv.version) ||
-	    header[2] != TLS_VERSION_MAJOR(tls_ctx->crypto_recv.version)) {
+	if (header[1] != TLS_VERSION_MINOR(tls_ctx->crypto_recv.info.version) ||
+	    header[2] != TLS_VERSION_MAJOR(tls_ctx->crypto_recv.info.version)) {
 		ret = -EINVAL;
 		goto read_failure;
 	}
@@ -1180,12 +1180,12 @@ int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
 
 	if (tx) {
 		crypto_init_wait(&sw_ctx_tx->async_wait);
-		crypto_info = &ctx->crypto_send;
+		crypto_info = &ctx->crypto_send.info;
 		cctx = &ctx->tx;
 		aead = &sw_ctx_tx->aead_send;
 	} else {
 		crypto_init_wait(&sw_ctx_rx->async_wait);
-		crypto_info = &ctx->crypto_recv;
+		crypto_info = &ctx->crypto_recv.info;
 		cctx = &ctx->rx;
 		aead = &sw_ctx_rx->aead_recv;
 	}