[edk2-devel] [PATCH v2 2/4] MdeModulePkg/SMM: Disallow unregister SMI handler in other SMI handler

[Zhiguang Liu]

In last patch, we add code support to unregister SMI handler inside
itself. However, the code doesn't support unregister SMI handler
insider other SMI handler. While this is not a must-have usage.
So add check to disallow unregister SMI handler in other SMI handler.

Cc: Liming Gao <gaolim...@byosoft.com.cn>
Cc: Jiaxin Wu <jiaxin...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Cc: Laszlo Ersek <ler...@redhat.com>
Signed-off-by: Zhiguang Liu <zhiguang....@intel.com>
---
 MdeModulePkg/Core/PiSmmCore/Smi.c | 32 +++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/MdeModulePkg/Core/PiSmmCore/Smi.c 
b/MdeModulePkg/Core/PiSmmCore/Smi.c
index 3489c130fd..1bfbc635fc 100644
--- a/MdeModulePkg/Core/PiSmmCore/Smi.c
+++ b/MdeModulePkg/Core/PiSmmCore/Smi.c
@@ -8,7 +8,8 @@
 
 #include "PiSmmCore.h"
 
-LIST_ENTRY  mSmiEntryList = INITIALIZE_LIST_HEAD_VARIABLE (mSmiEntryList);
+SMI_HANDLER  *gCurrentSmiHandler = NULL;
+LIST_ENTRY   mSmiEntryList       = INITIALIZE_LIST_HEAD_VARIABLE 
(mSmiEntryList);
 
 SMI_ENTRY  mRootSmiEntry = {
   SMI_ENTRY_SIGNATURE,
@@ -142,13 +143,18 @@ SmiManage (
     // Link points to may be freed if unregister SMI handler.
     //
     Link = Link->ForwardLink;
-
-    Status = SmiHandler->Handler (
-                           (EFI_HANDLE)SmiHandler,
-                           Context,
-                           CommBuffer,
-                           CommBufferSize
-                           );
+    //
+    // Assign gCurrentSmiHandle before calling the SMI handler and
+    // set to NULL when it returns.
+    //
+    gCurrentSmiHandler = SmiHandler;
+    Status             = SmiHandler->Handler (
+                                       (EFI_HANDLE)SmiHandler,
+                                       Context,
+                                       CommBuffer,
+                                       CommBufferSize
+                                       );
+    gCurrentSmiHandler = NULL;
 
     switch (Status) {
       case EFI_INTERRUPT_PENDING:
@@ -328,6 +334,16 @@ SmiHandlerUnRegister (
     return EFI_INVALID_PARAMETER;
   }
 
+  //
+  // Check if unregister SMI handler inside a SMI Handler
+  //
+  if (gCurrentSmiHandler != NULL) {
+    //
+    // Only allow to unregister SMI Handler inside itself.
+    //
+    ASSERT (gCurrentSmiHandler == SmiHandler);
+  }
+
   SmiEntry = SmiHandler->SmiEntry;
 
   RemoveEntryList (&SmiHandler->Link);
-- 
2.31.1.windows.1



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