x509store: explicitly call rb_gc_mark() against Store/StoreContext

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_x509store.c

@@ -105,6 +105,12 @@ VALUE cX509Store;
 VALUE cX509StoreContext;
 VALUE eX509StoreError;
 
+static void
+ossl_x509store_mark(void *ptr)
+{
+    rb_gc_mark((VALUE)X509_STORE_get_ex_data(ptr, store_ex_verify_cb_idx));
+}
+
 static void
 ossl_x509store_free(void *ptr)
 {
@@ -114,7 +120,7 @@ ossl_x509store_free(void *ptr)
 static const rb_data_type_t ossl_x509store_type = {
     "OpenSSL/X509/STORE",
     {
-	0, ossl_x509store_free,
+        ossl_x509store_mark, ossl_x509store_free,
     },
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
 };
@@ -456,23 +462,15 @@ ossl_x509store_verify(int argc, VALUE *argv, VALUE self)
     return result;
 }
 
-/*
- * Public Functions
- */
-static void ossl_x509stctx_free(void*);
-
-
-static const rb_data_type_t ossl_x509stctx_type = {
-    "OpenSSL/X509/STORE_CTX",
-    {
-	0, ossl_x509stctx_free,
-    },
-    0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
-};
-
 /*
  * Private functions
  */
+static void
+ossl_x509stctx_mark(void *ptr)
+{
+    rb_gc_mark((VALUE)X509_STORE_CTX_get_ex_data(ptr, stctx_ex_verify_cb_idx));
+}
+
 static void
 ossl_x509stctx_free(void *ptr)
 {
@@ -484,6 +482,14 @@ ossl_x509stctx_free(void *ptr)
     X509_STORE_CTX_free(ctx);
 }
 
+static const rb_data_type_t ossl_x509stctx_type = {
+    "OpenSSL/X509/STORE_CTX",
+    {
+        ossl_x509stctx_mark, ossl_x509stctx_free,
+    },
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
+};
+
 static VALUE
 ossl_x509stctx_alloc(VALUE klass)
 {