diff --git a/reactos/ntoskrnl/mm/cont.c b/reactos/ntoskrnl/mm/cont.c
index ee7c49eb350..339556d643f 100644
--- a/reactos/ntoskrnl/mm/cont.c
+++ b/reactos/ntoskrnl/mm/cont.c
@@ -1,4 +1,4 @@
-/* $Id: cont.c,v 1.24 2002/10/01 19:27:22 chorns Exp $
+/* $Id: cont.c,v 1.25 2002/11/05 20:35:33 hbirr Exp $
  * 
  * COPYRIGHT:       See COPYING in the top level directory
  * PROJECT:         ReactOS kernel
@@ -63,11 +63,13 @@ MmAllocateContiguousAlignedMemory(IN ULONG NumberOfBytes,
 				Alignment);
    if (PBase.QuadPart == 0LL)
      {
+       MmLockAddressSpace(MmGetKernelAddressSpace());
        MmFreeMemoryArea(MmGetKernelAddressSpace(),
 			BaseAddress,
 			0,
 			NULL,
 			NULL);
+       MmUnlockAddressSpace(MmGetKernelAddressSpace());
        return(NULL);
      }
    for (i = 0; i < (PAGE_ROUND_UP(NumberOfBytes) / 4096); i++)
@@ -142,11 +144,13 @@ MmAllocateContiguousMemory (IN ULONG NumberOfBytes,
 VOID STDCALL 
 MmFreeContiguousMemory(IN PVOID BaseAddress)
 {
+   MmLockAddressSpace(MmGetKernelAddressSpace());
    MmFreeMemoryArea(MmGetKernelAddressSpace(),
 		    BaseAddress,
 		    0,
 		    MmFreeContinuousPage,
 		    NULL);
+   MmUnlockAddressSpace(MmGetKernelAddressSpace());
 }
 
 
diff --git a/reactos/ntoskrnl/mm/iospace.c b/reactos/ntoskrnl/mm/iospace.c
index 3fd6c22d228..0ce9fba44a5 100644
--- a/reactos/ntoskrnl/mm/iospace.c
+++ b/reactos/ntoskrnl/mm/iospace.c
@@ -16,7 +16,7 @@
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
-/* $Id: iospace.c,v 1.16 2002/10/01 19:27:22 chorns Exp $
+/* $Id: iospace.c,v 1.17 2002/11/05 20:35:33 hbirr Exp $
  *
  * PROJECT:         ReactOS kernel
  * FILE:            ntoskrnl/mm/iospace.c
@@ -96,7 +96,7 @@ MmMapIoSpace (IN PHYSICAL_ADDRESS PhysicalAddress,
      {
 	Attributes |= (PAGE_NOCACHE | PAGE_WRITETHROUGH);
      }
-   for (i = 0; (i < ((NumberOfBytes + PAGE_SIZE - 1) / PAGE_SIZE)); i++)
+   for (i = 0; (i < (PAGE_ROUND_UP(NumberOfBytes) / PAGE_SIZE)); i++)
      {
 	Status = 
 	  MmCreateVirtualMappingForKernel(Result + (i * PAGE_SIZE),
@@ -141,11 +141,13 @@ VOID STDCALL
 MmUnmapIoSpace (IN PVOID BaseAddress,
 		IN ULONG NumberOfBytes)
 {
-   (VOID)MmFreeMemoryArea(&PsGetCurrentProcess()->AddressSpace,
-			  (PVOID)(((ULONG)BaseAddress / PAGE_SIZE) * PAGE_SIZE),
-			  NumberOfBytes,
-			  NULL,
-			  NULL);
+   MmLockAddressSpace(MmGetKernelAddressSpace());
+   MmFreeMemoryArea(MmGetKernelAddressSpace(),
+		    (PVOID)(((ULONG)BaseAddress / PAGE_SIZE) * PAGE_SIZE),
+		    NumberOfBytes,
+		    NULL,
+		    NULL);
+   MmUnlockAddressSpace(MmGetKernelAddressSpace());
 }
 
 
diff --git a/reactos/ntoskrnl/mm/ncache.c b/reactos/ntoskrnl/mm/ncache.c
index 788ed24786d..d6ceb34db8f 100644
--- a/reactos/ntoskrnl/mm/ncache.c
+++ b/reactos/ntoskrnl/mm/ncache.c
@@ -1,4 +1,4 @@
-/* $Id: ncache.c,v 1.22 2002/10/01 19:27:23 chorns Exp $
+/* $Id: ncache.c,v 1.23 2002/11/05 20:35:33 hbirr Exp $
  *
  * COPYRIGHT:       See COPYING in the top level directory
  * PROJECT:         ReactOS kernel
@@ -71,7 +71,7 @@ MmAllocateNonCachedMemory(IN ULONG NumberOfBytes)
      }
    Attributes = PAGE_READWRITE | PAGE_SYSTEM | PAGE_NOCACHE | 
      PAGE_WRITETHROUGH;
-   for (i = 0; i <= (NumberOfBytes / PAGE_SIZE); i++)
+   for (i = 0; i < (PAGE_ROUND_UP(NumberOfBytes) / PAGE_SIZE); i++)
      {
        PHYSICAL_ADDRESS NPage;
 
@@ -125,11 +125,13 @@ MmFreeNonCachedPage(PVOID Context, MEMORY_AREA* MemoryArea, PVOID Address,
 VOID STDCALL MmFreeNonCachedMemory (IN PVOID BaseAddress,
 				    IN ULONG NumberOfBytes)
 {
+  MmLockAddressSpace(MmGetKernelAddressSpace());
   MmFreeMemoryArea (MmGetKernelAddressSpace(),
 		    BaseAddress,
 		    NumberOfBytes,
 		    MmFreeNonCachedPage,
 		    NULL);
+  MmUnlockAddressSpace(MmGetKernelAddressSpace());
 }