From 8e7ad28a33d02c0dcb782c0312a8c80ca5d46d41 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Fri, 5 Feb 2021 19:46:31 +0100
Subject: [PATCH] AK: Avoid UB in TypedTransfer

Don't be calling __builtin_memfoo() with null pointer arguments.

Found by KUBSAN :^)
---
 AK/TypedTransfer.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/AK/TypedTransfer.h b/AK/TypedTransfer.h
index 0e0de78e63..614b42afa9 100644
--- a/AK/TypedTransfer.h
+++ b/AK/TypedTransfer.h
@@ -35,6 +35,9 @@ class TypedTransfer {
 public:
     static size_t move(T* destination, T* source, size_t count)
     {
+        if (!count)
+            return 0;
+
         if constexpr (Traits<T>::is_trivial()) {
             __builtin_memmove(destination, source, count * sizeof(T));
             return count;
@@ -52,6 +55,9 @@ public:
 
     static size_t copy(T* destination, const T* source, size_t count)
     {
+        if (!count)
+            return 0;
+
         if constexpr (Traits<T>::is_trivial()) {
             __builtin_memmove(destination, source, count * sizeof(T));
             return count;
@@ -69,6 +75,9 @@ public:
 
     static bool compare(const T* a, const T* b, size_t count)
     {
+        if (!count)
+            return true;
+
         if constexpr (Traits<T>::is_trivial())
             return !__builtin_memcmp(a, b, count * sizeof(T));