Merge pull request #1650 from bettio/check-before-using-tuple

NIFs: `do_spawn`: check if is tuple and arity before accessing it

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Author: bettio

src/libAtomVM/nifs.c

@@ -1222,13 +1222,17 @@ static term do_spawn(Context *ctx, Context *new_ctx, size_t arity, size_t n_free
     term link_term = interop_proplist_get_value(opts_term, LINK_ATOM);
     term monitor_term = interop_proplist_get_value(opts_term, MONITOR_ATOM);
     term heap_growth_strategy = interop_proplist_get_value_default(opts_term, ATOMVM_HEAP_GROWTH_ATOM, BOUNDED_FREE_ATOM);
-    term request_term = interop_proplist_get_value(opts_term, REQUEST_ATOM);
+    term request_term = interop_proplist_get_value_default(opts_term, REQUEST_ATOM, UNDEFINED_ATOM);
     term group_leader;
+    bool valid_request = false;
 
-    if (UNLIKELY(request_term != term_nil())) {
+    if (LIKELY(request_term == UNDEFINED_ATOM)) {
+        group_leader = ctx->group_leader;
+    } else if (term_is_tuple(request_term) && (term_get_tuple_arity(request_term) >= 5)) {
+        valid_request = true;
         group_leader = term_get_tuple_element(request_term, 3);
     } else {
-        group_leader = ctx->group_leader;
+        RAISE_ERROR(BADARG_ATOM);
     }
 
     if (min_heap_size_term != term_nil()) {
@@ -1338,7 +1342,7 @@ static term do_spawn(Context *ctx, Context *new_ctx, size_t arity, size_t n_free
         term_put_tuple_element(pid_ref_tuple, 1, ref);
 
         return pid_ref_tuple;
-    } else if (UNLIKELY(request_term != term_nil())) {
+    } else if (UNLIKELY(valid_request)) {
         // Handling of spawn_request
         // spawn_request requires that the reply is enqueued before
         // any message from the spawned process