StandaloneMmPkg: Support to unregister MMI handler in MMI handlers

This patch fix a use-after-free issue where unregistering an
MMI handler could lead to the deletion of the MMI_HANDLER while it is
still in use by MmiManage(). The fix involves modifying
MmiHandlerUnRegister() to detect whether it is being called from
within the MmiManage() stack. If so, the removal of the MMI_HANDLER
is deferred until MmiManage() has finished executing.
Additionally, due to the possibility of recursive MmiManage() calls,
the unregistration and subsequent removal of the MMI_HANDLER are
ensured to occur only after the outermost MmiManage() invocation has
completed.

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>

1 files changed, 136 insertions, 25 deletions

diff --git a/StandaloneMmPkg/Core/Mmi.c b/StandaloneMmPkg/Core/Mmi.c
index 0de6fd17fc..e035245c87 100644
--- a/StandaloneMmPkg/Core/Mmi.c
+++ b/StandaloneMmPkg/Core/Mmi.c
@@ -34,12 +34,52 @@ typedef struct {
   LIST_ENTRY                    Link;        // Link on MMI_ENTRY.MmiHandlers

   EFI_MM_HANDLER_ENTRY_POINT    Handler;     // The mm handler's entry point

   MMI_ENTRY                     *MmiEntry;

+  BOOLEAN                       ToRemove;    // To remove this MMI_HANDLER later

 } MMI_HANDLER;

 

+//

+// mMmiManageCallingDepth is used to track the depth of recursive calls of MmiManage.

+//

+UINTN  mMmiManageCallingDepth = 0;

+

 LIST_ENTRY  mRootMmiHandlerList = INITIALIZE_LIST_HEAD_VARIABLE (mRootMmiHandlerList);

 LIST_ENTRY  mMmiEntryList       = INITIALIZE_LIST_HEAD_VARIABLE (mMmiEntryList);

 

 /**

+  Remove MmiHandler and free the memory it used.

+  If MmiEntry is empty, remove MmiEntry and free the memory it used.

+

+  @param  MmiHandler  Points to MMI handler.

+  @param  MmiEntry    Points to MMI Entry or NULL for root MMI handlers.

+

+  @retval TRUE        MmiEntry is removed.

+  @retval FALSE       MmiEntry is not removed.

+**/

+BOOLEAN

+RemoveMmiHandler (

+  IN MMI_HANDLER  *MmiHandler,

+  IN MMI_ENTRY    *MmiEntry

+  )

+{

+  ASSERT (MmiHandler->ToRemove);

+  RemoveEntryList (&MmiHandler->Link);

+  FreePool (MmiHandler);

+

+  //

+  // Remove the MMI_ENTRY if all handlers have been removed.

+  //

+  if (MmiEntry != NULL) {

+    if (IsListEmpty (&MmiEntry->MmiHandlers)) {

+      RemoveEntryList (&MmiEntry->AllEntries);

+      FreePool (MmiEntry);

+      return TRUE;

+    }

+  }

+

+  return FALSE;

+}

+

+/**

   Finds the MMI entry for the requested handler type.

 

   @param  HandlerType            The type of the interrupt

@@ -126,13 +166,16 @@ MmiManage (
 {

   LIST_ENTRY   *Link;

   LIST_ENTRY   *Head;

+  LIST_ENTRY   *EntryLink;

   MMI_ENTRY    *MmiEntry;

   MMI_HANDLER  *MmiHandler;

-  BOOLEAN      SuccessReturn;

+  EFI_STATUS   ReturnStatus;

+  BOOLEAN      WillReturn;

   EFI_STATUS   Status;

 

-  Status        = EFI_NOT_FOUND;

-  SuccessReturn = FALSE;

+  mMmiManageCallingDepth++;

+  Status       = EFI_NOT_FOUND;

+  ReturnStatus = Status;

   if (HandlerType == NULL) {

     //

     // Root MMI handler

@@ -171,7 +214,16 @@ MmiManage (
         // no additional handlers will be processed and EFI_INTERRUPT_PENDING will be returned.

         //

         if (HandlerType != NULL) {

-          return EFI_INTERRUPT_PENDING;

+          ReturnStatus = EFI_INTERRUPT_PENDING;

+          WillReturn   = TRUE;

+        } else {

+          //

+          // If any other handler's result sets ReturnStatus as EFI_SUCCESS, the return status

+          // will be EFI_SUCCESS.

+          //

+          if (ReturnStatus != EFI_SUCCESS) {

+            ReturnStatus = Status;

+          }

         }

 

         break;

@@ -183,10 +235,10 @@ MmiManage (
         // additional handlers will be processed.

         //

         if (HandlerType != NULL) {

-          return EFI_SUCCESS;

+          WillReturn = TRUE;

         }

 

-        SuccessReturn = TRUE;

+        ReturnStatus = EFI_SUCCESS;

         break;

 

       case EFI_WARN_INTERRUPT_SOURCE_QUIESCED:

@@ -194,7 +246,7 @@ MmiManage (
         // If at least one of the handlers returns EFI_WARN_INTERRUPT_SOURCE_QUIESCED

         // then the function will return EFI_SUCCESS.

         //

-        SuccessReturn = TRUE;

+        ReturnStatus = EFI_SUCCESS;

         break;

 

       case EFI_WARN_INTERRUPT_SOURCE_PENDING:

@@ -202,6 +254,10 @@ MmiManage (
         // If all the handlers returned EFI_WARN_INTERRUPT_SOURCE_PENDING

         // then EFI_WARN_INTERRUPT_SOURCE_PENDING will be returned.

         //

+        if (ReturnStatus != EFI_SUCCESS) {

+          ReturnStatus = Status;

+        }

+

         break;

 

       default:

@@ -211,13 +267,76 @@ MmiManage (
         ASSERT_EFI_ERROR (Status);

         break;

     }

+

+    if (WillReturn) {

+      break;

+    }

   }

 

-  if (SuccessReturn) {

-    Status = EFI_SUCCESS;

+  ASSERT (mMmiManageCallingDepth > 0);

+  mMmiManageCallingDepth--;

+

+  //

+  // MmiHandlerUnRegister() calls from MMI handlers are deferred till this point.

+  // Before returned from MmiManage, delete the MmiHandler which is

+  // marked as ToRemove.

+  // Note that MmiManage can be called recursively.

+  //

+  if (mMmiManageCallingDepth == 0) {

+    //

+    // Go through all MmiHandler in root Mmi handlers

+    //

+    for ( Link = GetFirstNode (&mRootMmiHandlerList)

+          ; !IsNull (&mRootMmiHandlerList, Link);

+          )

+    {

+      //

+      // MmiHandler might be removed in below, so cache the next link in Link

+      //

+      MmiHandler = CR (Link, MMI_HANDLER, Link, MMI_HANDLER_SIGNATURE);

+      Link       = GetNextNode (&mRootMmiHandlerList, Link);

+      if (MmiHandler->ToRemove) {

+        //

+        // Remove MmiHandler if the ToRemove is set.

+        //

+        RemoveMmiHandler (MmiHandler, NULL);

+      }

+    }

+

+    //

+    // Go through all MmiHandler in non-root MMI handlers

+    //

+    for ( EntryLink = GetFirstNode (&mMmiEntryList)

+          ; !IsNull (&mMmiEntryList, EntryLink);

+          )

+    {

+      //

+      // MmiEntry might be removed in below, so cache the next link in EntryLink

+      //

+      MmiEntry  = CR (EntryLink, MMI_ENTRY, AllEntries, MMI_ENTRY_SIGNATURE);

+      EntryLink = GetNextNode (&mMmiEntryList, EntryLink);

+      for ( Link = GetFirstNode (&MmiEntry->MmiHandlers)

+            ; !IsNull (&MmiEntry->MmiHandlers, Link);

+            )

+      {

+        //

+        // MmiHandler might be removed in below, so cache the next link in Link

+        //

+        MmiHandler = CR (Link, MMI_HANDLER, Link, MMI_HANDLER_SIGNATURE);

+        Link       = GetNextNode (&MmiEntry->MmiHandlers, Link);

+        if (MmiHandler->ToRemove) {

+          //

+          // Remove MmiHandler if the ToRemove is set.

+          //

+          if (RemoveMmiHandler (MmiHandler, MmiEntry)) {

+            break;

+          }

+        }

+      }

+    }

   }

 

-  return Status;

+  return ReturnStatus;

 }

 

 /**

@@ -254,6 +373,7 @@ MmiHandlerRegister (
 

   MmiHandler->Signature = MMI_HANDLER_SIGNATURE;

   MmiHandler->Handler   = Handler;

+  MmiHandler->ToRemove  = FALSE;

 

   if (HandlerType == NULL) {

     //

@@ -309,26 +429,17 @@ MmiHandlerUnRegister (
     return EFI_INVALID_PARAMETER;

   }

 

-  MmiEntry = MmiHandler->MmiEntry;

-

-  RemoveEntryList (&MmiHandler->Link);

-  FreePool (MmiHandler);

-

-  if (MmiEntry == NULL) {

+  MmiHandler->ToRemove = TRUE;

+  if (mMmiManageCallingDepth > 0) {

     //

-    // This is root MMI handler

+    // This function is called from MmiManage()

+    // Do not delete or remove MmiHandler or MmiEntry now.

     //

     return EFI_SUCCESS;

   }

 

-  if (IsListEmpty (&MmiEntry->MmiHandlers)) {

-    //

-    // No handler registered for this interrupt now, remove the MMI_ENTRY

-    //

-    RemoveEntryList (&MmiEntry->AllEntries);

-

-    FreePool (MmiEntry);

-  }

+  MmiEntry = MmiHandler->MmiEntry;

+  RemoveMmiHandler (MmiHandler, MmiEntry);

 

   return EFI_SUCCESS;

 }