Add isTensor guard in FreeCall to prevent abort on corrupted PTE

Differential Revision: D99727453

Pull Request resolved: pytorch#18803

Author: abhinaykukkadapu

runtime/executor/method.cpp

@@ -1521,8 +1521,17 @@ Error Method::execute_instruction() {
       // We know that instr_args_as_FreeCall is non-null because it was checked
       // at init time.
       auto free_call = instruction->instr_args_as_FreeCall();
-      auto t = mutable_value(free_call->value_index()).toTensor();
-      internal::reset_data_ptr(t);
+      auto& val = mutable_value(free_call->value_index());
+      if (val.isTensor()) {
+        auto& t = val.toTensor();
+        internal::reset_data_ptr(t);
+      } else {
+        ET_LOG(
+            Error,
+            "FreeCall target at index %u is not a Tensor",
+            static_cast<unsigned int>(free_call->value_index()));
+        err = Error::InvalidProgram;
+      }
     } break;
     default:
       ET_LOG(