From 4b16ac003410d72b517b87ffedae3822e206a752 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 18 Feb 2020 09:54:34 +0100
Subject: [PATCH] Kernel: Purging a page should point it back to the shared
 zero page

Anonymous VM objects should never have null entries in their physical
page list. Instead, "empty" or untouched pages should refer to the
shared zero page.

Fixes #1237.
---
 Kernel/VM/PurgeableVMObject.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Kernel/VM/PurgeableVMObject.cpp b/Kernel/VM/PurgeableVMObject.cpp
index e293db8c2b..152029b0a1 100644
--- a/Kernel/VM/PurgeableVMObject.cpp
+++ b/Kernel/VM/PurgeableVMObject.cpp
@@ -76,7 +76,7 @@ int PurgeableVMObject::purge_impl()
     for (size_t i = 0; i < m_physical_pages.size(); ++i) {
         if (m_physical_pages[i])
             ++purged_page_count;
-        m_physical_pages[i] = nullptr;
+        m_physical_pages[i] = MM.shared_zero_page();
     }
     m_was_purged = true;