Re: [PATCH] MdeModulePkg: Fix use-after-free error in InstallConfigurationTable()

["Gao, Liming" <liming.gao@intel.com>]

Reviewed-by: Liming Gao <liming.gao@intel.com>

>-----Original Message-----
>From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Star
>Zeng
>Sent: Monday, June 19, 2017 6:24 PM
>To: edk2-devel@lists.01.org
>Cc: Yao, Jiewen <jiewen.yao@intel.com>; Zeng, Star <star.zeng@intel.com>;
>Gao, Liming <liming.gao@intel.com>
>Subject: [edk2] [PATCH] MdeModulePkg: Fix use-after-free error in
>InstallConfigurationTable()
>
>From: "Shi, Steven" <steven.shi@intel.com>
>
>When installing configuration table and the original
>gDxeCoreST->ConfigurationTable[] buffer happen to be not big enough to
>add a new table, the CoreInstallConfigurationTable() enter the branch
>of line 113 in InstallConfigurationTable.c to free the old
>gDxeCoreST->ConfigurationTable[] buffer and allocate a new bigger one.
>The problem happens at line 139 CoreFreePool(), which is to free the
>old gDxeCoreST->ConfigurationTable[] buffer. The CoreFreePool()'s
>behavior is to free the buffer firstly, then call the
>InstallMemoryAttributesTableOnMemoryAllocation (PoolType) to update
>the EfiRuntimeServices type memory info, the
>CoreInstallConfigurationTable() will be re-entered by CoreFreePool()
>in its calling stack, then use-after-free read error will happen at
>line 59 of InstallConfigurationTable.c and use-after-free write error
>will happen at line 151 and 152 of InstallConfigurationTable.c.
>
>The patch is to update System table to the new table pointer before
>calling CoreFreePool() to free the old table.
>
>The case above is in DxeCore, but not in PiSmmCore.
>The change in PiSmmCore is to be consistent with DxeCore.
>
>Cc: Jiewen Yao <jiewen.yao@intel.com>
>Cc: Liming Gao <liming.gao@intel.com>
>Contributed-under: TianoCore Contribution Agreement 1.0
>Signed-off-by: Steven Shi <steven.shi@intel.com>
>Signed-off-by: Star Zeng <star.zeng@intel.com>
>---
> .../Core/Dxe/Misc/InstallConfigurationTable.c      | 34 ++++++++++++++++----
>--
> .../Core/PiSmmCore/InstallConfigurationTable.c     | 34 ++++++++++++++++--
>----
> 2 files changed, 50 insertions(+), 18 deletions(-)
> mode change 100644 => 100755
>MdeModulePkg/Core/Dxe/Misc/InstallConfigurationTable.c
>
>diff --git a/MdeModulePkg/Core/Dxe/Misc/InstallConfigurationTable.c
>b/MdeModulePkg/Core/Dxe/Misc/InstallConfigurationTable.c
>old mode 100644
>new mode 100755
>index e4735db7ba45..dcdeb7f45803
>--- a/MdeModulePkg/Core/Dxe/Misc/InstallConfigurationTable.c
>+++ b/MdeModulePkg/Core/Dxe/Misc/InstallConfigurationTable.c
>@@ -1,7 +1,7 @@
> /** @file
>   UEFI Miscellaneous boot Services InstallConfigurationTable service
>
>-Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>
>+Copyright (c) 2006 - 2017, 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
>@@ -42,6 +42,7 @@ CoreInstallConfigurationTable (
> {
>   UINTN                   Index;
>   EFI_CONFIGURATION_TABLE *EfiConfigurationTable;
>+  EFI_CONFIGURATION_TABLE *OldTable;
>
>   //
>   // If Guid is NULL, then this operation cannot be performed
>@@ -68,7 +69,7 @@ CoreInstallConfigurationTable (
>     if (Table != NULL) {
>       //
>       // If Table is not NULL, then this is a modify operation.
>-      // Modify the table enty and return.
>+      // Modify the table entry and return.
>       //
>       gDxeCoreST->ConfigurationTable[Index].VendorTable = Table;
>
>@@ -134,15 +135,30 @@ CoreInstallConfigurationTable (
>           );
>
>         //
>-        // Free Old Table
>+        // Record the old table pointer.
>         //
>-        CoreFreePool (gDxeCoreST->ConfigurationTable);
>-      }
>+        OldTable = gDxeCoreST->ConfigurationTable;
>
>-      //
>-      // Update System Table
>-      //
>-      gDxeCoreST->ConfigurationTable = EfiConfigurationTable;
>+        //
>+        // As the CoreInstallConfigurationTable() may be re-entered by
>CoreFreePool()
>+        // in its calling stack, updating System table to the new table pointer
>must
>+        // be done before calling CoreFreePool() to free the old table.
>+        // It can make sure the gDxeCoreST->ConfigurationTable point to the
>new table
>+        // and avoid the errors of use-after-free to the old table by the reenter
>of
>+        // CoreInstallConfigurationTable() in CoreFreePool()'s calling stack.
>+        //
>+        gDxeCoreST->ConfigurationTable = EfiConfigurationTable;
>+
>+        //
>+        // Free the old table after updating System Table to the new table
>pointer.
>+        //
>+        CoreFreePool (OldTable);
>+      } else {
>+        //
>+        // Update System Table
>+        //
>+        gDxeCoreST->ConfigurationTable = EfiConfigurationTable;
>+      }
>     }
>
>     //
>diff --git a/MdeModulePkg/Core/PiSmmCore/InstallConfigurationTable.c
>b/MdeModulePkg/Core/PiSmmCore/InstallConfigurationTable.c
>index b2f6769c109f..2b6eef9a0e3e 100644
>--- a/MdeModulePkg/Core/PiSmmCore/InstallConfigurationTable.c
>+++ b/MdeModulePkg/Core/PiSmmCore/InstallConfigurationTable.c
>@@ -1,7 +1,7 @@
> /** @file
>   System Management System Table Services SmmInstallConfigurationTable
>service
>
>-  Copyright (c) 2009 - 2010, Intel Corporation. All rights reserved.<BR>
>+  Copyright (c) 2009 - 2017, 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
>@@ -46,6 +46,7 @@ SmmInstallConfigurationTable (
> {
>   UINTN                    Index;
>   EFI_CONFIGURATION_TABLE  *ConfigurationTable;
>+  EFI_CONFIGURATION_TABLE  *OldTable;
>
>   //
>   // If Guid is NULL, then this operation cannot be performed
>@@ -72,7 +73,7 @@ SmmInstallConfigurationTable (
>     if (Table != NULL) {
>       //
>       // If Table is not NULL, then this is a modify operation.
>-      // Modify the table enty and return.
>+      // Modify the table entry and return.
>       //
>       ConfigurationTable[Index].VendorTable = Table;
>       return EFI_SUCCESS;
>@@ -130,15 +131,30 @@ SmmInstallConfigurationTable (
>           );
>
>         //
>-        // Free Old Table
>+        // Record the old table pointer.
>         //
>-        FreePool (gSmmCoreSmst.SmmConfigurationTable);
>-      }
>+        OldTable = gSmmCoreSmst.SmmConfigurationTable;
>
>-      //
>-      // Update System Table
>-      //
>-      gSmmCoreSmst.SmmConfigurationTable = ConfigurationTable;
>+        //
>+        // As the SmmInstallConfigurationTable() may be re-entered by
>FreePool() in
>+        // its calling stack, updating System table to the new table pointer must
>+        // be done before calling FreePool() to free the old table.
>+        // It can make sure the gSmmCoreSmst->SmmConfigurationTable point
>to the new
>+        // table and avoid the errors of use-after-free to the old table by the
>+        // reenter of SmmInstallConfigurationTable() in FreePool()'s calling stack.
>+        //
>+        gSmmCoreSmst.SmmConfigurationTable = ConfigurationTable;
>+
>+        //
>+        // Free the old table after updating System Table to the new table
>pointer.
>+        //
>+        FreePool (OldTable);
>+      } else {
>+        //
>+        // Update System Table
>+        //
>+        gSmmCoreSmst.SmmConfigurationTable = ConfigurationTable;
>+      }
>     }
>
>     //
>--
>2.7.0.windows.1
>
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