Re: [PATCH] MdeModulePkg/SmmCore: Fix hang due to already-freed memory deference

["Zeng, Star" <star.zeng@intel.com>]

Reviewed-by: Star Zeng <star.zeng@intel.com>

BTW, do you want to say " the second call may hang " instead of " the second hang may hang " in the commit log?


Thanks,
Star
-----Original Message-----
From: Ni, Ruiyu 
Sent: Thursday, February 1, 2018 6:16 PM
To: edk2-devel@lists.01.org
Cc: Yao, Jiewen <jiewen.yao@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: [PATCH] MdeModulePkg/SmmCore: Fix hang due to already-freed memory deference

SmiHandlerUnRegister() validates the DispatchHandle by checking whether the first 32bit matches to a certain signature (SMI_HANDLER_SIGNATURE).
But if a caller calls *UnRegister() twice and the memory freed by first call still contains the signature, the second hang may hang.

The patch fixes this issue by locating the DispatchHandle in all SMI handlers, instead of checking the signature.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
---
 MdeModulePkg/Core/PiSmmCore/Smi.c | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/MdeModulePkg/Core/PiSmmCore/Smi.c b/MdeModulePkg/Core/PiSmmCore/Smi.c
index ad483a1877..0c09e7fa10 100644
--- a/MdeModulePkg/Core/PiSmmCore/Smi.c
+++ b/MdeModulePkg/Core/PiSmmCore/Smi.c
@@ -1,7 +1,7 @@
 /** @file
   SMI management.
 
-  Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2018, Intel Corporation. All rights 
+ reserved.<BR>
   This program and the accompanying materials are licensed and made available 
   under the terms and conditions of the BSD License which accompanies this 
   distribution.  The full text of the license may be found at        
@@ -276,14 +276,41 @@ SmiHandlerUnRegister (  {
   SMI_HANDLER  *SmiHandler;
   SMI_ENTRY    *SmiEntry;
+  LIST_ENTRY   *EntryLink;
+  LIST_ENTRY   *HandlerLink;
 
-  SmiHandler = (SMI_HANDLER *) DispatchHandle;
-
-  if (SmiHandler == NULL) {
+  if (DispatchHandle == NULL) {
     return EFI_INVALID_PARAMETER;
   }
 
-  if (SmiHandler->Signature != SMI_HANDLER_SIGNATURE) {
+  //
+  // Look for it in root SMI handlers
+  //
+  SmiHandler = NULL;
+  for ( HandlerLink = GetFirstNode (&mRootSmiEntry.SmiHandlers)
+      ; !IsNull (&mRootSmiEntry.SmiHandlers, HandlerLink) && (SmiHandler != DispatchHandle)
+      ; HandlerLink = GetNextNode (&mRootSmiEntry.SmiHandlers, HandlerLink)
+      ) {
+    SmiHandler = CR (HandlerLink, SMI_HANDLER, Link, 
+ SMI_HANDLER_SIGNATURE);  }
+
+  //
+  // Look for it in non-root SMI handlers  //  for ( EntryLink = 
+ GetFirstNode (&mSmiEntryList)
+      ; !IsNull (&mSmiEntryList, EntryLink) && (SmiHandler != DispatchHandle)
+      ; EntryLink = GetNextNode (&mSmiEntryList, EntryLink)
+      ) {
+    SmiEntry = CR (EntryLink, SMI_ENTRY, AllEntries, SMI_ENTRY_SIGNATURE);
+    for ( HandlerLink = GetFirstNode (&SmiEntry->SmiHandlers)
+        ; !IsNull (&SmiEntry->SmiHandlers, HandlerLink) && (SmiHandler != DispatchHandle)
+        ; HandlerLink = GetNextNode (&SmiEntry->SmiHandlers, HandlerLink)
+        ) {
+      SmiHandler = CR (HandlerLink, SMI_HANDLER, Link, SMI_HANDLER_SIGNATURE);
+    }
+  }
+
+  if (SmiHandler != DispatchHandle) {
     return EFI_INVALID_PARAMETER;
   }
 
--
2.15.1.windows.2