From 5778284149254d019b3f127dc32475ab7b72a7d6 Mon Sep 17 00:00:00 2001
From: hscham <hscham@chromium.org>
Date: Wed, 24 Nov 2021 15:31:40 +0900
Subject: [PATCH] Crash when dereferencing nullopt for std::optional

TODO(b/192529039): this is a temporary patch to address security
concerns when migrating base:Optional and absl::optional to
std::optional. libcxx upstream is working on decoupling hardening and
debugging asserts and this patch should be replaced by the upstream
patch upon completion.
---
 libcxx/include/optional | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/libcxx/include/optional b/libcxx/include/optional
index d0b9f6d5171f..1b78925156d8 100644
--- a/libcxx/include/optional
+++ b/libcxx/include/optional
@@ -146,6 +146,8 @@ template<class T>
 
 */
 
+#include <stdio.h>
+
 #include <__availability>
 #include <__config>
 #include <__debug>
@@ -874,56 +876,86 @@ public:
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS
     constexpr
     add_pointer_t<value_type const>
     operator->() const
     {
         _LIBCPP_ASSERT(this->has_value(), "optional operator-> called on a disengaged value");
+        if (!this->has_value()) {
+          fprintf(stderr, "optional operator-> called on a disengaged value\n");
+          __builtin_trap();
+        }
         return _VSTD::addressof(this->__get());
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS
     constexpr
     add_pointer_t<value_type>
     operator->()
     {
         _LIBCPP_ASSERT(this->has_value(), "optional operator-> called on a disengaged value");
+        if (!this->has_value()) {
+          fprintf(stderr, "optional operator-> called on a disengaged value\n");
+          __builtin_trap();
+        }
         return _VSTD::addressof(this->__get());
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS
     constexpr
     const value_type&
     operator*() const& noexcept
     {
         _LIBCPP_ASSERT(this->has_value(), "optional operator* called on a disengaged value");
+        if (!this->has_value()) {
+          fprintf(stderr, "optional operator* called on a disengaged value\n");
+          __builtin_trap();
+        }
         return this->__get();
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS
     constexpr
     value_type&
     operator*() & noexcept
     {
         _LIBCPP_ASSERT(this->has_value(), "optional operator* called on a disengaged value");
+        if (!this->has_value()) {
+          fprintf(stderr, "optional operator* called on a disengaged value\n");
+          __builtin_trap();
+        }
         return this->__get();
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS
     constexpr
     value_type&&
     operator*() && noexcept
     {
         _LIBCPP_ASSERT(this->has_value(), "optional operator* called on a disengaged value");
+        if (!this->has_value()) {
+          fprintf(stderr, "optional operator* called on a disengaged value\n");
+          __builtin_trap();
+        }
         return _VSTD::move(this->__get());
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS
     constexpr
     const value_type&&
     operator*() const&& noexcept
     {
         _LIBCPP_ASSERT(this->has_value(), "optional operator* called on a disengaged value");
+        if (!this->has_value()) {
+          fprintf(stderr, "optional operator* called on a disengaged value\n");
+          __builtin_trap();
+        }
         return _VSTD::move(this->__get());
     }
 
-- 
2.34.1.575.g55b058a8bb-goog