Index: /trunk/src/VBox/Runtime/r0drv/alloc-ef-r0drv.cpp
===================================================================
--- /trunk/src/VBox/Runtime/r0drv/alloc-ef-r0drv.cpp	(revision 58271)
+++ /trunk/src/VBox/Runtime/r0drv/alloc-ef-r0drv.cpp	(revision 58272)
@@ -451,5 +451,5 @@
     size_t cbBlock = RT_ALIGN_Z(pBlock->cbAligned, PAGE_SIZE) + RTR0MEM_EF_SIZE;
 
-    int rc = RTR0MemObjProtect(pBlock->hMemObj, 0 /*offSub*/, cbBlock, RTMEM_PROT_READ | RTMEM_PROT_WRITE);
+    int rc = RTR0MemObjProtect(pBlock->hMemObj, 0 /*offSub*/, RT_ALIGN_Z(cbBlock, PAGE_SIZE), RTMEM_PROT_READ | RTMEM_PROT_WRITE);
     if (RT_FAILURE(rc))
         rtR0MemComplain(pszOp, "RTR0MemObjProtect([%p], 0, %#x, RTMEM_PROT_READ | RTMEM_PROT_WRITE) -> %Rrc\n",
@@ -506,14 +506,19 @@
     {
         PRTR0MEMEFBLOCK pBlock = g_pBlocksDelayTail;
-        g_pBlocksDelayTail = (PRTR0MEMEFBLOCK)pBlock->Core.pLeft;
-        if (pBlock->Core.pLeft)
-            pBlock->Core.pLeft->pRight = NULL;
+        if (pBlock)
+        {
+            g_pBlocksDelayTail = (PRTR0MEMEFBLOCK)pBlock->Core.pLeft;
+            if (pBlock->Core.pLeft)
+                pBlock->Core.pLeft->pRight = NULL;
+            else
+                g_pBlocksDelayHead = NULL;
+            rtR0MemBlockUnlock(fSavedIntFlags);
+
+            rtR0MemFreeBlock(pBlock, "rtR0MemEfTerm");
+
+            rtR0MemBlockLock();
+        }
         else
-            g_pBlocksDelayHead = NULL;
-        rtR0MemBlockUnlock(fSavedIntFlags);
-
-        rtR0MemFreeBlock(pBlock, "rtR0MemEfTerm");
-
-        rtR0MemBlockLock();
+            break;
     }
     g_cbBlocksDelay = 0;
@@ -696,9 +701,12 @@
          * That means we'll expand the E-fence to cover the entire block.
          */
+        int rc = RTR0MemObjProtect(pBlock->hMemObj,
 # ifdef RTR0MEM_EF_IN_FRONT
-        int rc = RTR0MemObjProtect(pBlock->hMemObj, RTR0MEM_EF_SIZE /*offSub*/, pBlock->cbAligned, RTMEM_PROT_NONE);
+                                   RTR0MEM_EF_SIZE,
 # else
-        int rc = RTR0MemObjProtect(pBlock->hMemObj, 0 /*offSub*/,               pBlock->cbAligned, RTMEM_PROT_NONE);
+                                   0 /*offSub*/,
 # endif
+                                   RT_ALIGN_Z(pBlock->cbAligned, PAGE_SIZE),
+                                   RTMEM_PROT_NONE);
         if (RT_SUCCESS(rc))
         {