NULL out mdctx to prevent possible double free introduced in version 1.4

Spotted by maestre@, ok tb@

1 files changed, 2 insertions, 1 deletions

diff --git a/src/lib/libssl/tls13_key_schedule.c b/src/lib/libssl/tls13_key_schedule.c
index af273d6d27..8a0b3e8af4 100644
--- a/src/lib/libssl/tls13_key_schedule.c
+++ b/src/lib/libssl/tls13_key_schedule.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_key_schedule.c,v 1.6 2018/11/10 01:34:02 jsing Exp $ */
+/* $OpenBSD: tls13_key_schedule.c,v 1.7 2018/11/13 01:25:13 beck Exp $ */
 /* Copyright (c) 2018, Bob Beck <beck@openbsd.org>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
@@ -151,6 +151,7 @@ tls13_secrets_create(const EVP_MD *digest, int resumption)
         if (!EVP_DigestFinal_ex(mdctx, secrets->empty_hash.data, &mdlen))
                 goto err;
         EVP_MD_CTX_free(mdctx);
+        mdctx = NULL;
 
         if (secrets->empty_hash.len != mdlen)
                 goto err;