From 1a0eed705ce5348a9528bb1ecc184e921dcbac2b Mon Sep 17 00:00:00 2001
From: Andrew Kaster <andrewdkaster@gmail.com>
Date: Mon, 24 May 2021 08:00:59 -0600
Subject: [PATCH] DHCPClient: Avoid unaligned access when parsing options

Just casting a void* to a T* and dereferencing it is not particularly
safe. Also UBSAN was complaining. Use memcpy into a default constructed
T instead and require that the T be trivially copyable.
---
 Userland/Services/DHCPClient/DHCPv4.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Userland/Services/DHCPClient/DHCPv4.h b/Userland/Services/DHCPClient/DHCPv4.h
index b3165633b4..7e87f84250 100644
--- a/Userland/Services/DHCPClient/DHCPv4.h
+++ b/Userland/Services/DHCPClient/DHCPv4.h
@@ -114,7 +114,7 @@ struct AK::Traits<DHCPOption> : public GenericTraits<DHCPOption> {
 
 struct ParsedDHCPv4Options {
     template<typename T>
-    Optional<const T> get(DHCPOption option_name) const
+    Optional<const T> get(DHCPOption option_name) const requires(IsTriviallyCopyable<T>)
     {
         auto option = options.get(option_name);
         if (!option.has_value()) {
@@ -123,7 +123,9 @@ struct ParsedDHCPv4Options {
         auto& value = option.value();
         if (value.length != sizeof(T))
             return {};
-        return *(const T*)value.value;
+        T t;
+        __builtin_memcpy(&t, value.value, value.length);
+        return t;
     }
 
     template<typename T>