[FASTFAT] Avoid a use after free in VfatCheckForDismount.

diff --git a/drivers/filesystems/fastfat/misc.c b/drivers/filesystems/fastfat/misc.c
index 2068e8b..b072123 100644 (file)
--- a/drivers/filesystems/fastfat/misc.c
+++ b/drivers/filesystems/fastfat/misc.c
@@ -539,12 +539,12 @@ VfatCheckForDismount(
         }
         if (DeviceExt->FATFileObject)
         {
         }
         if (DeviceExt->FATFileObject)
         {

-            Fcb = (PVFATFCB)DeviceExt->FATFileObject->FsContext;
+            Fcb = DeviceExt->FATFileObject->FsContext;

             CcUninitializeCacheMap(DeviceExt->FATFileObject,
                                    &Zero,
                                    NULL);
             CcUninitializeCacheMap(DeviceExt->FATFileObject,
                                    &Zero,
                                    NULL);

-            ObDereferenceObject(DeviceExt->FATFileObject);

             DeviceExt->FATFileObject->FsContext = NULL;
             DeviceExt->FATFileObject->FsContext = NULL;

+            ObDereferenceObject(DeviceExt->FATFileObject);

             DeviceExt->FATFileObject = NULL;
             vfatDestroyFCB(Fcb);
         }
             DeviceExt->FATFileObject = NULL;
             vfatDestroyFCB(Fcb);
         }