net: tls: Pass union tls_crypto_context pointer to memzero_explicit

Pass union tls_crypto_context pointer, rather than struct
tls_crypto_info pointer, to memzero_explicit().

The address of the pointer is the same before and after.
But the new construct means that the size of the dereferenced pointer type
matches the size being zeroed. Which aids static analysis.

As reported by Smatch:

  .../tls_main.c:842 do_tls_setsockopt_conf() error: memzero_explicit() 'crypto_info' too small (4 vs 56)

No functional change intended.
Compile tested only.
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240708-tls-memzero-v2-1-9694eaf31b79@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/tls/tls_main.c

@@ -616,6 +616,7 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 	struct tls_crypto_info *alt_crypto_info;
 	struct tls_context *ctx = tls_get_ctx(sk);
 	const struct tls_cipher_desc *cipher_desc;
+	union tls_crypto_context *crypto_ctx;
 	int rc = 0;
 	int conf;
 
@@ -623,13 +624,15 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 		return -EINVAL;
 
 	if (tx) {
-		crypto_info = &ctx->crypto_send.info;
+		crypto_ctx = &ctx->crypto_send;
 		alt_crypto_info = &ctx->crypto_recv.info;
 	} else {
-		crypto_info = &ctx->crypto_recv.info;
+		crypto_ctx = &ctx->crypto_recv;
 		alt_crypto_info = &ctx->crypto_send.info;
 	}
 
+	crypto_info = &crypto_ctx->info;
+
 	/* Currently we don't support set crypto info more than one time */
 	if (TLS_CRYPTO_INFO_READY(crypto_info))
 		return -EBUSY;
@@ -710,7 +713,7 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 	return 0;
 
 err_crypto_info:
-	memzero_explicit(crypto_info, sizeof(union tls_crypto_context));
+	memzero_explicit(crypto_ctx, sizeof(*crypto_ctx));
 	return rc;
 }