ssl: explicitly call rb_gc_mark() against SSLContext/SSLSocket objects

We store the reverse reference to the Ruby object in the OpenSSL
struct for use from OpenSSL callback functions. To prevent the Ruby
object from being relocated by GC.compact, we must "pin" it by calling
rb_gc_mark().

ext/openssl/ossl_ssl.c

@@ -59,6 +59,13 @@ static int ossl_sslctx_ex_ptr_idx;
 static int ossl_sslctx_ex_store_p;
 #endif
 
+static void
+ossl_sslctx_mark(void *ptr)
+{
+    SSL_CTX *ctx = ptr;
+    rb_gc_mark((VALUE)SSL_CTX_get_ex_data(ctx, ossl_sslctx_ex_ptr_idx));
+}
+
 static void
 ossl_sslctx_free(void *ptr)
 {
@@ -73,7 +80,7 @@ ossl_sslctx_free(void *ptr)
 static const rb_data_type_t ossl_sslctx_type = {
     "OpenSSL/SSL/CTX",
     {
-	0, ossl_sslctx_free,
+        ossl_sslctx_mark, ossl_sslctx_free,
     },
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
 };
@@ -1528,6 +1535,14 @@ ssl_started(SSL *ssl)
     return SSL_get_fd(ssl) >= 0;
 }
 
+static void
+ossl_ssl_mark(void *ptr)
+{
+    SSL *ssl = ptr;
+    rb_gc_mark((VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx));
+    rb_gc_mark((VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_vcb_idx));
+}
+
 static void
 ossl_ssl_free(void *ssl)
 {
@@ -1537,7 +1552,7 @@ ossl_ssl_free(void *ssl)
 const rb_data_type_t ossl_ssl_type = {
     "OpenSSL/SSL",
     {
-	0, ossl_ssl_free,
+        ossl_ssl_mark, ossl_ssl_free,
     },
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
 };