From 30f71c7fc0f6404cb298841a9d2123eaca1877be Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Gardou?= <jerome.gardou@reactos.org>
Date: Fri, 11 Dec 2020 15:29:35 +0100
Subject: [PATCH] [NTOS] Zero data unconditionally after segment end, unless
 section is created with SEC_RESERVE

Use a SEC_RESERVE section in Cc
---
 ntoskrnl/cc/view.c    |  2 +-
 ntoskrnl/mm/section.c | 18 ++++++++++++------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/ntoskrnl/cc/view.c b/ntoskrnl/cc/view.c
index ee0ec497d40..ae6464f2b58 100644
--- a/ntoskrnl/cc/view.c
+++ b/ntoskrnl/cc/view.c
@@ -1286,7 +1286,7 @@ CcRosInitializeFileCache (
             NULL,
             &SharedCacheMap->SectionSize,
             PAGE_READWRITE,
-            0,
+            SEC_RESERVE,
             NULL,
             FileObject);
 
diff --git a/ntoskrnl/mm/section.c b/ntoskrnl/mm/section.c
index d71bc490934..8e9669d9ab9 100644
--- a/ntoskrnl/mm/section.c
+++ b/ntoskrnl/mm/section.c
@@ -1208,7 +1208,8 @@ MiReadPage(PMEMORY_AREA MemoryArea,
         Status = STATUS_SUCCESS;
     }
 
-    if ((MemoryArea->VadNode.u.VadFlags.VadType == VadImageMap) && ((SegOffset + PAGE_SIZE) > MemoryArea->SectionData.Segment->RawLength.QuadPart))
+    if (!MemoryArea->SectionData.Section->u.Flags.Reserve
+        && ((SegOffset + PAGE_SIZE) > MemoryArea->SectionData.Segment->RawLength.QuadPart))
     {
         KIRQL OldIrql;
         PUCHAR PageMap;
@@ -2209,6 +2210,8 @@ MmCreateDataFileSection(PSECTION *SectionObject,
 
     if (AllocationAttributes & SEC_NO_CHANGE)
         Section->u.Flags.NoChange = 1;
+    if (AllocationAttributes & SEC_RESERVE)
+        Section->u.Flags.Reserve = 1;
 
     if (!GotFileHandle)
     {
@@ -4832,13 +4835,16 @@ MmExtendSection(
         PMM_SECTION_SEGMENT Segment = (PMM_SECTION_SEGMENT)Section->Segment;
         Section->SizeOfSection = *NewSize;
 
-        MmLockSectionSegment(Segment);
-        if (Segment->RawLength.QuadPart < NewSize->QuadPart)
+        if (!Section->u.Flags.Reserve)
         {
-            Segment->RawLength = *NewSize;
-            Segment->Length.QuadPart = (NewSize->QuadPart + PAGE_SIZE - 1) & ~((LONGLONG)PAGE_SIZE);
+            MmLockSectionSegment(Segment);
+            if (Segment->RawLength.QuadPart < NewSize->QuadPart)
+            {
+                Segment->RawLength = *NewSize;
+                Segment->Length.QuadPart = (NewSize->QuadPart + PAGE_SIZE - 1) & ~((LONGLONG)PAGE_SIZE);
+            }
+            MmUnlockSectionSegment(Segment);
         }
-        MmUnlockSectionSegment(Segment);
     }
 
     return STATUS_SUCCESS;