From 660ebacbe6daa3ab44e4417d7b99ef24e6de9c80 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Gardou?= <jerome.gardou@reactos.org>
Date: Mon, 16 Feb 2015 21:12:51 +0000
Subject: [PATCH] [KERNEL32]  Revert r64525 - Always allocate a guard page at
 the bottom of the stack.

svn path=/trunk/; revision=66323
---
 reactos/dll/win32/kernel32/client/utils.c | 43 ++++++++++++++++-------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/reactos/dll/win32/kernel32/client/utils.c b/reactos/dll/win32/kernel32/client/utils.c
index 80f9bab2eac..31134552815 100644
--- a/reactos/dll/win32/kernel32/client/utils.c
+++ b/reactos/dll/win32/kernel32/client/utils.c
@@ -358,6 +358,7 @@ BaseCreateStack(HANDLE hProcess,
     NTSTATUS Status;
     PIMAGE_NT_HEADERS Headers;
     ULONG_PTR Stack;
+    BOOLEAN UseGuard;
     ULONG PageSize, Dummy, AllocationGranularity;
     SIZE_T StackReserveHeader, StackCommitHeader, GuardPageSize, GuaranteedStackCommit;
     DPRINT("BaseCreateStack (hProcess: %p, Max: %lx, Current: %lx)\n",
@@ -425,6 +426,18 @@ BaseCreateStack(HANDLE hProcess,
     /* Update the Stack Position */
     Stack += StackReserve - StackCommit;
 
+    /* Check if we will need a guard page */
+    if (StackReserve > StackCommit)
+    {
+        Stack -= PageSize;
+        StackCommit += PageSize;
+        UseGuard = TRUE;
+    }
+    else
+    {
+        UseGuard = FALSE;
+    }
+
     /* Allocate memory for the stack */
     Status = NtAllocateVirtualMemory(hProcess,
                                      (PVOID*)&Stack,
@@ -444,21 +457,25 @@ BaseCreateStack(HANDLE hProcess,
     InitialTeb->StackLimit = (PVOID)Stack;
 
     /* Create a guard page */
-    GuardPageSize = PageSize;
-    Status = NtProtectVirtualMemory(hProcess,
-                                    (PVOID*)&Stack,
-                                    &GuardPageSize,
-                                    PAGE_GUARD | PAGE_READWRITE,
-                                    &Dummy);
-    if (!NT_SUCCESS(Status))
+    if (UseGuard)
     {
-        DPRINT1("Failure to set guard page\n");
-        return Status;
-    }
+        /* Set the guard page */
+        GuardPageSize = PAGE_SIZE;
+        Status = NtProtectVirtualMemory(hProcess,
+                                        (PVOID*)&Stack,
+                                        &GuardPageSize,
+                                        PAGE_GUARD | PAGE_READWRITE,
+                                        &Dummy);
+        if (!NT_SUCCESS(Status))
+        {
+            DPRINT1("Failure to set guard page\n");
+            return Status;
+        }
 
-    /* Update the Stack Limit keeping in mind the Guard Page */
-    InitialTeb->StackLimit = (PVOID)((ULONG_PTR)InitialTeb->StackLimit +
-                                     GuardPageSize);
+        /* Update the Stack Limit keeping in mind the Guard Page */
+        InitialTeb->StackLimit = (PVOID)((ULONG_PTR)InitialTeb->StackLimit +
+                                         GuardPageSize);
+    }
 
     /* We are done! */
     return STATUS_SUCCESS;