From 40017a54f958093ee6a12cd73412aedbe44f0ea1 Mon Sep 17 00:00:00 2001
From: Pierre Schweitzer <pierre@reactos.org>
Date: Sun, 8 Apr 2018 18:58:15 +0200
Subject: [PATCH] [NTOSKRNL] Use interlocked operations when dealing with map
 count.

CORE-14349
---
 ntoskrnl/cc/view.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/ntoskrnl/cc/view.c b/ntoskrnl/cc/view.c
index 1ec4c35b1fa..cde1c2d6fa0 100644
--- a/ntoskrnl/cc/view.c
+++ b/ntoskrnl/cc/view.c
@@ -344,7 +344,7 @@ retry:
         CcRosVacbIncRefCount(current);
 
         /* Check if it's mapped and not dirty */
-        if (current->MappedCount > 0 && !current->Dirty)
+        if (InterlockedCompareExchange((PLONG)&current->MappedCount, 0, 0) > 0 && !current->Dirty)
         {
             /* We have to break these locks because Cc sucks */
             KeReleaseSpinLock(&current->SharedCacheMap->CacheMapLock, oldIrql);
@@ -448,14 +448,13 @@ CcRosReleaseVacb (
 
     if (Mapped)
     {
-        Vacb->MappedCount++;
-    }
-    Refs = CcRosVacbDecRefCount(Vacb);
-    if (Mapped && (Vacb->MappedCount == 1))
-    {
-        CcRosVacbIncRefCount(Vacb);
+        if (InterlockedIncrement((PLONG)&Vacb->MappedCount) == 1)
+        {
+            CcRosVacbIncRefCount(Vacb);
+        }
     }
 
+    Refs = CcRosVacbDecRefCount(Vacb);
     ASSERT(Refs > 0);
 
     CcRosReleaseVacbLock(Vacb);
@@ -630,9 +629,7 @@ CcRosUnmapVacb (
     }
 
     ASSERT(Vacb->MappedCount != 0);
-    Vacb->MappedCount--;
-
-    if (Vacb->MappedCount == 0)
+    if (InterlockedDecrement((PLONG)&Vacb->MappedCount) == 0)
     {
         CcRosVacbDecRefCount(Vacb);
     }