From e89cdd504c3df5073f5876d011f7550d83924e79 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Fri, 15 Nov 2019 15:50:13 +0100
Subject: [PATCH] AK: Fix leak in WeakPtr(WeakPtr&&) and
 WeakPtr::operator=(WeakPtr&&)

We were forgetting to adopt the WeakLink, causing a reference leak.
This ended up costing us one allocation per exec(), with this stack:

    kmalloc_impl()
    Inode::set_vmo()
    InodeVMObject::create_with_inode()
    Process::do_exec()
    Process::exec()
    Process::sys$execve()

This was a pain to track down, in the end I caught it by dumping out
every live kmalloc pointer between runs and diffing the sets. Then it
was just a matter of matching the pointer to a call stack and looking
at what went wrong. :^)
---
 AK/WeakPtr.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/AK/WeakPtr.h b/AK/WeakPtr.h
index 1b8297b356..290a12a0b7 100644
--- a/AK/WeakPtr.h
+++ b/AK/WeakPtr.h
@@ -18,14 +18,14 @@ public:
 
     template<typename U>
     WeakPtr(WeakPtr<U>&& other)
-        : m_link(reinterpret_cast<WeakLink<T>*>(other.leak_link()))
+        : m_link(reinterpret_cast<WeakLink<T>*>(other.take_link().ptr()))
     {
     }
 
     template<typename U>
     WeakPtr& operator=(WeakPtr<U>&& other)
     {
-        m_link = reinterpret_cast<WeakLink<T>*>(other.leak_link());
+        m_link = reinterpret_cast<WeakLink<T>*>(other.take_link().ptr());
         return *this;
     }
 
@@ -46,7 +46,7 @@ public:
     bool is_null() const { return !m_link || !m_link->ptr(); }
     void clear() { m_link = nullptr; }
 
-    WeakLink<T>* leak_link() { return m_link.leak_ref(); }
+    RefPtr<WeakLink<T>> take_link() { return move(m_link); }
 
     bool operator==(const OwnPtr<T>& other) const { return ptr() == other.ptr(); }