[metadata] Check for GTDs in setup_generic_array_ifaces (mono/mono#18101)

Judging by https://github.com/mono/mono/blob/mono/mono@4cefdcb7ce2d939ee78fb45d1b4913eb3bc064fd/mono/metadata/metadata.c#L3515 the cached_class is sometimes intentionally a GTD, which can get passed all the way down to setup_generic_array_ifaces and cause a crash.

Commit migrated from https://github.com/mono/mono/commit/e19914fe6991a93af3f4c0730f1399d7bb5f1f66

diff --git a/src/mono/mono/metadata/class-init.c b/src/mono/mono/metadata/class-init.c
index 0ee253c..71eaf37 100644 (file)
--- a/src/mono/mono/metadata/class-init.c
+++ b/src/mono/mono/metadata/class-init.c
@@ -767,6 +767,7 @@ check_valid_generic_inst_arguments (MonoGenericInst *inst, MonoError *error)
 /*
  * Create the `MonoClass' for an instantiation of a generic type.
  * We only do this if we actually need it.
+ * This will sometimes return a GTD due to checking the cached_class.
  */
 MonoClass*
 mono_class_create_generic_inst (MonoGenericClass *gclass)
@@ -4140,10 +4141,20 @@ static void
 setup_generic_array_ifaces (MonoClass *klass, MonoClass *iface, MonoMethod **methods, int pos, GHashTable *cache)
 {
        MonoGenericContext tmp_context;
+       MonoGenericClass *gclass;
        int i;
 
+       // The interface can sometimes be a GTD in cases like IList
+       // See: https://github.com/mono/mono/issues/7095#issuecomment-470465597
+       if (mono_class_is_gtd (iface)) {
+               MonoType *ty = mono_class_gtd_get_canonical_inst (iface);
+               g_assert (ty->type == MONO_TYPE_GENERICINST);
+               gclass = ty->data.generic_class;
+       } else
+               gclass = mono_class_get_generic_class (iface);
+
        tmp_context.class_inst = NULL;
-       tmp_context.method_inst = mono_class_get_generic_class (iface)->context.class_inst;
+       tmp_context.method_inst = gclass->context.class_inst;
        //g_print ("setting up array interface: %s\n", mono_type_get_name_full (m_class_get_byval_arg (iface), 0));
 
        for (i = 0; i < generic_array_method_num; i++) {