Re: [PATCH] MdeModulePkg/DxeCore: Avoid accessing non-owned memory

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

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

-----Original Message-----
From: Ni, Ruiyu 
Sent: Wednesday, July 5, 2017 6:46 PM
To: edk2-devel@lists.01.org
Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>; Wu, Hao A <hao.a.wu@intel.com>
Subject: [PATCH] MdeModulePkg/DxeCore: Avoid accessing non-owned memory

The patch fixes two kinds of issues in DxeCore that accesses memory which might be freed or owned by other modules.
The existing bugs don't cause functionality issue.

1. CoreValidateHandle() checks whether the handle is valid by
   validating its signature. The proper way is to check whether
   the handle is in the handle database.
2. CoreDisconnectControllersUsingProtocolInterface() and
   CoreOpenProtocol() de-reference Link pointer which is
   already freed. The proper way is to not de-reference the pointer.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Core/Dxe/Hand/Handle.c | 54 ++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 27 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/Hand/Handle.c b/MdeModulePkg/Core/Dxe/Hand/Handle.c
index 59b89148c8..8e2f361805 100644
--- a/MdeModulePkg/Core/Dxe/Hand/Handle.c
+++ b/MdeModulePkg/Core/Dxe/Hand/Handle.c
@@ -72,15 +72,20 @@ CoreValidateHandle (
   )
 {
   IHANDLE             *Handle;
+  LIST_ENTRY          *Link;
 
-  Handle = (IHANDLE *)UserHandle;
-  if (Handle == NULL) {
+  if (UserHandle == NULL) {
     return EFI_INVALID_PARAMETER;
   }
-  if (Handle->Signature != EFI_HANDLE_SIGNATURE) {
-    return EFI_INVALID_PARAMETER;
+
+  for (Link = gHandleList.ForwardLink; Link != &gHandleList; Link = Link->ForwardLink) {
+    Handle = CR (Link, IHANDLE, AllHandles, EFI_HANDLE_SIGNATURE);
+    if (Handle == (IHANDLE *) UserHandle) {
+      return EFI_SUCCESS;
+    }
   }
-  return EFI_SUCCESS;
+
+  return EFI_INVALID_PARAMETER;
 }
 
 
@@ -643,19 +648,16 @@ CoreDisconnectControllersUsingProtocolInterface (
   //
   do {
     ItemFound = FALSE;
-    for ( Link = Prot->OpenList.ForwardLink;
-          (Link != &Prot->OpenList) && !ItemFound;
-          Link = Link->ForwardLink ) {
+    for (Link = Prot->OpenList.ForwardLink; Link != &Prot->OpenList; 
+ Link = Link->ForwardLink) {
       OpenData = CR (Link, OPEN_PROTOCOL_DATA, Link, OPEN_PROTOCOL_DATA_SIGNATURE);
       if ((OpenData->Attributes & EFI_OPEN_PROTOCOL_BY_DRIVER) != 0) {
-        ItemFound = TRUE;
         CoreReleaseProtocolLock ();
         Status = CoreDisconnectController (UserHandle, OpenData->AgentHandle, NULL);
         CoreAcquireProtocolLock ();
-        if (EFI_ERROR (Status)) {
-           ItemFound = FALSE;
-           break;
+        if (!EFI_ERROR (Status)) {
+          ItemFound = TRUE;
         }
+        break;
       }
     }
   } while (ItemFound);
@@ -664,21 +666,17 @@ CoreDisconnectControllersUsingProtocolInterface (
     //
     // Attempt to remove BY_HANDLE_PROTOOCL and GET_PROTOCOL and TEST_PROTOCOL Open List items
     //
-    do {
-      ItemFound = FALSE;
-      for ( Link = Prot->OpenList.ForwardLink;
-            (Link != &Prot->OpenList) && !ItemFound;
-            Link = Link->ForwardLink ) {
-        OpenData = CR (Link, OPEN_PROTOCOL_DATA, Link, OPEN_PROTOCOL_DATA_SIGNATURE);
-        if ((OpenData->Attributes &
-            (EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL | EFI_OPEN_PROTOCOL_GET_PROTOCOL | EFI_OPEN_PROTOCOL_TEST_PROTOCOL)) != 0) {
-          ItemFound = TRUE;
-          RemoveEntryList (&OpenData->Link);
-          Prot->OpenListCount--;
-          CoreFreePool (OpenData);
-        }
+    for (Link = Prot->OpenList.ForwardLink; Link != &Prot->OpenList;) {
+      OpenData = CR (Link, OPEN_PROTOCOL_DATA, Link, OPEN_PROTOCOL_DATA_SIGNATURE);
+      if ((OpenData->Attributes &
+          (EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL | EFI_OPEN_PROTOCOL_GET_PROTOCOL | EFI_OPEN_PROTOCOL_TEST_PROTOCOL)) != 0) {
+        Link = RemoveEntryList (&OpenData->Link);
+        Prot->OpenListCount--;
+        CoreFreePool (OpenData);
+      } else {
+        Link = Link->ForwardLink;
       }
-    } while (ItemFound);
+    }
   }
 
   //
@@ -1132,7 +1130,7 @@ CoreOpenProtocol (
     if (ByDriver) {
       do {
         Disconnect = FALSE;
-        for ( Link = Prot->OpenList.ForwardLink; (Link != &Prot->OpenList) && (!Disconnect); Link = Link->ForwardLink) {
+        for (Link = Prot->OpenList.ForwardLink; Link != 
+ &Prot->OpenList; Link = Link->ForwardLink) {
           OpenData = CR (Link, OPEN_PROTOCOL_DATA, Link, OPEN_PROTOCOL_DATA_SIGNATURE);
           if ((OpenData->Attributes & EFI_OPEN_PROTOCOL_BY_DRIVER) != 0) {
             Disconnect = TRUE;
@@ -1142,6 +1140,8 @@ CoreOpenProtocol (
             if (EFI_ERROR (Status)) {
               Status = EFI_ACCESS_DENIED;
               goto Done;
+            } else {
+              break;
             }
           }
         }
--
2.12.2.windows.2