[reactos] 02/05: [FASTFAT] Avoid a use after free in VfatCheckForDismount.

[Thomas Faber]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=bc8307205b725b661d34b…

commit bc8307205b725b661d34b9848de8c7411cc3febc
Author:     Thomas Faber <thomas.faber(a)reactos.org>
AuthorDate: Sat Jan 12 16:25:34 2019 +0100
Commit:     Thomas Faber <thomas.faber(a)reactos.org>
CommitDate: Sat Jan 12 16:27:30 2019 +0100

    [FASTFAT] Avoid a use after free in VfatCheckForDismount.
---
 drivers/filesystems/fastfat/misc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/filesystems/fastfat/misc.c b/drivers/filesystems/fastfat/misc.c
index 2068e8b5e4..b0721230cd 100644
--- a/drivers/filesystems/fastfat/misc.c
+++ b/drivers/filesystems/fastfat/misc.c
@@ -539,12 +539,12 @@ VfatCheckForDismount(
         }
         if (DeviceExt->FATFileObject)
         {
-            Fcb = (PVFATFCB)DeviceExt->FATFileObject->FsContext;
+            Fcb = DeviceExt->FATFileObject->FsContext;
             CcUninitializeCacheMap(DeviceExt->FATFileObject,
                                    &Zero,
                                    NULL);
-            ObDereferenceObject(DeviceExt->FATFileObject);
             DeviceExt->FATFileObject->FsContext = NULL;
+            ObDereferenceObject(DeviceExt->FATFileObject);
             DeviceExt->FATFileObject = NULL;
             vfatDestroyFCB(Fcb);
         }