Add new API IsDevicePathValid() to UefiDevicePathLib.

Signed-off-by: Ruiyu Ni<ruiyu.ni@intel.com>
Reviewed-by: Liming Gao<liming.gao@intel.com>
Reviewed-by: Kinney Michael D<michael.d.kinney@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13737 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Include/Library/DevicePathLib.h

@@ -4,7 +4,7 @@
   This library provides defines, macros, and functions to help create and parse 
   EFI_DEVICE_PATH_PROTOCOL structures.
 
-Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2012, 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 that accompanies this distribution.  
 The full text of the license may be found at
@@ -20,6 +20,28 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 #define END_DEVICE_PATH_LENGTH               (sizeof (EFI_DEVICE_PATH_PROTOCOL))
 
+/**
+  Determine whether a given device path is valid.
+  If DevicePath is NULL, then ASSERT().
+
+  @param  DevicePath  A pointer to a device path data structure.
+  @param  MaxSize     The maximum size of the device path data structure.
+
+  @retval TRUE        DevicePath is valid.
+  @retval FALSE       The length of any node node in the DevicePath is less
+                      than sizeof (EFI_DEVICE_PATH_PROTOCOL).
+  @retval FALSE       If MaxSize is not zero, the size of the DevicePath
+                      exceeds MaxSize.
+  @retval FALSE       If PcdMaximumDevicePathNodeCount is not zero, the node
+                      count of the DevicePath exceeds PcdMaximumDevicePathNodeCount.
+**/
+BOOLEAN
+EFIAPI
+IsDevicePathValid (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL *DevicePath,
+  IN       UINTN                    MaxSize
+  );
+
 /**
   Returns the Type field of a device path node.
 
@@ -123,7 +145,8 @@ IsDevicePathEndType (
   Determines if a device path node is an end node of an entire device path.
 
   Determines if a device path node specified by Node is an end node of an entire device path.
-  If Node represents the end of an entire device path, then TRUE is returned.  Otherwise, FALSE is returned.
+  If Node represents the end of an entire device path, then TRUE is returned.
+  Otherwise, FALSE is returned.
 
   If Node is NULL, then ASSERT().
 
@@ -143,7 +166,8 @@ IsDevicePathEnd (
   Determines if a device path node is an end node of a device path instance.
 
   Determines if a device path node specified by Node is an end node of a device path instance.
-  If Node represents the end of a device path instance, then TRUE is returned.  Otherwise, FALSE is returned.
+  If Node represents the end of a device path instance, then TRUE is returned.
+  Otherwise, FALSE is returned.
 
   If Node is NULL, then ASSERT().
 
@@ -169,6 +193,7 @@ IsDevicePathEndInstance (
 
   If Node is NULL, then ASSERT().
   If NodeLength >= 0x10000, then ASSERT().
+  If NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL), then ASSERT().
 
   @param  Node      A pointer to a device path node data structure.
   @param  Length    The length, in bytes, of the device path node.
@@ -208,13 +233,14 @@ SetDevicePathEndNode (
 /**
   Returns the size of a device path in bytes.
 
-  This function returns the size, in bytes, of the device path data structure specified by
+  This function returns the size, in bytes, of the device path data structure 
-  DevicePath including the end of device path node.  If DevicePath is NULL, then 0 is returned.
+  specified by DevicePath including the end of device path node.
+  If DevicePath is NULL or invalid, then 0 is returned.
 
-  @param  DevicePath                 A pointer to a device path data structure.
+  @param  DevicePath  A pointer to a device path data structure.
-  
+
-  @retval 0       DevicePath is NULL.
+  @retval 0           If DevicePath is NULL or invalid.
-  @retval Others  The size of a device path in bytes.
+  @retval Others      The size of a device path in bytes.
 
 **/
 UINTN
@@ -235,7 +261,7 @@ GetDevicePathSize (
   
   @param  DevicePath                 A pointer to a device path data structure.
 
-  @retval NULL    DevicePath is NULL.
+  @retval NULL    DevicePath is NULL or invalid.
   @retval Others  A pointer to the duplicated device path.
   
 **/
@@ -263,6 +289,7 @@ DuplicateDevicePath (
   @param  SecondDevicePath           A pointer to a device path data structure.
   
   @retval NULL      If there is not enough memory for the newly allocated buffer.
+  @retval NULL      If FirstDevicePath or SecondDevicePath is invalid.
   @retval Others    A pointer to the new device path if success.
                     Or a copy an end-of-device-path if both FirstDevicePath and SecondDevicePath are NULL.
 
@@ -316,6 +343,7 @@ AppendDevicePathNode (
   and a new end-of-device-path-instance node is inserted between. 
   If DevicePath is NULL, then a copy if DevicePathInstance is returned.
   If DevicePathInstance is NULL, then NULL is returned.
+  If DevicePath or DevicePathInstance is invalid, then NULL is returned.
   If there is not enough memory to allocate space for the new device path, then NULL is returned.  
   The memory is allocated from EFI boot services memory. It is the responsibility of the caller to
   free the memory allocated.
@@ -341,6 +369,7 @@ AppendDevicePathInstance (
   point to the next device path instance in the device path (or NULL if no more) and updates Size
   to hold the size of the device path instance copy.
   If DevicePath is NULL, then NULL is returned.
+  If DevicePath points to a invalid device path, then NULL is returned.
   If there is not enough memory to allocate space for the new device path, then NULL is returned.  
   The memory is allocated from EFI boot services memory. It is the responsibility of the caller to
   free the memory allocated.
@@ -394,12 +423,13 @@ CreateDeviceNode (
   Determines if a device path is single or multi-instance.
 
   This function returns TRUE if the device path specified by DevicePath is multi-instance.
-  Otherwise, FALSE is returned.  If DevicePath is NULL, then FALSE is returned.
+  Otherwise, FALSE is returned.
+  If DevicePath is NULL or invalid, then FALSE is returned.
 
   @param  DevicePath                 A pointer to a device path data structure.
 
   @retval  TRUE                      DevicePath is multi-instance.
-  @retval  FALSE                     DevicePath is not multi-instance, or DevicePath is NULL.
+  @retval  FALSE                     DevicePath is not multi-instance, or DevicePath is NULL or invalid.
 
 **/
 BOOLEAN

MdePkg/Library/UefiDevicePathLib/UefiDevicePathLib.c

@@ -8,7 +8,7 @@
   environment varibles. Multi-instance device paths should never be placed
   on a Handle.
 
-  Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2012, 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        
@@ -28,6 +28,7 @@
 #include <Library/MemoryAllocationLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/BaseLib.h>
+#include <Library/PcdLib.h>
 
 //
 // Template for an end-of-device path node.
@@ -41,6 +42,61 @@ GLOBAL_REMOVE_IF_UNREFERENCED CONST EFI_DEVICE_PATH_PROTOCOL  mUefiDevicePathLib
   }
 };
 
+/**
+  Determine whether a given device path is valid.
+  If DevicePath is NULL, then ASSERT().
+
+  @param  DevicePath  A pointer to a device path data structure.
+  @param  MaxSize     The maximum size of the device path data structure.
+
+  @retval TRUE        DevicePath is valid.
+  @retval FALSE       The length of any node node in the DevicePath is less
+                      than sizeof (EFI_DEVICE_PATH_PROTOCOL).
+  @retval FALSE       If MaxSize is not zero, the size of the DevicePath
+                      exceeds MaxSize.
+  @retval FALSE       If PcdMaximumDevicePathNodeCount is not zero, the node
+                      count of the DevicePath exceeds PcdMaximumDevicePathNodeCount.
+**/
+BOOLEAN
+EFIAPI
+IsDevicePathValid (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL *DevicePath,
+  IN       UINTN                    MaxSize
+  )
+{
+  UINTN Count;
+  UINTN Size;
+  UINTN NodeLength;
+
+  ASSERT (DevicePath != NULL);
+
+  for (Count = 0, Size = 0; !IsDevicePathEnd (DevicePath); DevicePath = NextDevicePathNode (DevicePath)) {
+    NodeLength = DevicePathNodeLength (DevicePath);
+    if (NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL)) {
+      return FALSE;
+    }
+
+    if (MaxSize > 0) {
+      Size += NodeLength;
+      if (Size + END_DEVICE_PATH_LENGTH > MaxSize) {
+        return FALSE;
+      }
+    }
+
+    if (PcdGet32 (PcdMaximumDevicePathNodeCount) > 0) {
+      Count++;
+      if (Count >= PcdGet32 (PcdMaximumDevicePathNodeCount)) {
+        return FALSE;
+      }
+    }
+  }
+
+  //
+  // Only return TRUE when the End Device Path node is valid.
+  //
+  return (BOOLEAN) (DevicePathNodeLength (DevicePath) == END_DEVICE_PATH_LENGTH);
+}
+
 /**
   Returns the Type field of a device path node.
 
@@ -106,8 +162,12 @@ DevicePathNodeLength (
   IN CONST VOID  *Node
   )
 {
+  UINTN Length;
+
   ASSERT (Node != NULL);
-  return ReadUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0]);
+  Length = ReadUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0]);
+  ASSERT (Length >= sizeof (EFI_DEVICE_PATH_PROTOCOL));
+  return Length;
 }
 
 /**
@@ -227,7 +287,8 @@ IsDevicePathEndInstance (
   be used to set the contents of the Length field.
 
   If Node is NULL, then ASSERT().
-  If NodeLength >= 0x10000, then ASSERT().
+  If NodeLength >= SIZE_64KB, then ASSERT().
+  If NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL), then ASSERT().
 
   @param  Node      A pointer to a device path node data structure.
   @param  Length    The length, in bytes, of the device path node.
@@ -243,7 +304,7 @@ SetDevicePathNodeLength (
   )
 {
   ASSERT (Node != NULL);
-  ASSERT (Length < 0x10000);
+  ASSERT ((Length >= sizeof (EFI_DEVICE_PATH_PROTOCOL)) && (Length < SIZE_64KB));
   return WriteUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0], (UINT16)(Length));
 }
 
@@ -277,12 +338,12 @@ SetDevicePathEndNode (
   Returns the size of a device path in bytes.
 
   This function returns the size, in bytes, of the device path data structure 
-  specified by DevicePath including the end of device path node.  If DevicePath 
+  specified by DevicePath including the end of device path node.
-  is NULL, then 0 is returned.
+  If DevicePath is NULL or invalid, then 0 is returned.
 
   @param  DevicePath  A pointer to a device path data structure.
-  
+
-  @retval 0           If DevicePath is NULL.
+  @retval 0           If DevicePath is NULL or invalid.
   @retval Others      The size of a device path in bytes.
 
 **/
@@ -298,6 +359,10 @@ GetDevicePathSize (
     return 0;
   }
 
+  if (!IsDevicePathValid (DevicePath, 0)) {
+    return 0;
+  }
+
   //
   // Search for the end of the device path structure
   //
@@ -324,7 +389,7 @@ GetDevicePathSize (
   
   @param  DevicePath    A pointer to a device path data structure.
 
-  @retval NULL          If DevicePath is NULL.
+  @retval NULL          DevicePath is NULL or invalid.
   @retval Others        A pointer to the duplicated device path.
   
 **/
@@ -370,6 +435,7 @@ DuplicateDevicePath (
   @param  SecondDevicePath           A pointer to a device path data structure.
   
   @retval NULL      If there is not enough memory for the newly allocated buffer.
+  @retval NULL      If FirstDevicePath or SecondDevicePath is invalid.
   @retval Others    A pointer to the new device path if success.
                     Or a copy an end-of-device-path if both FirstDevicePath and SecondDevicePath are NULL.
 
@@ -398,6 +464,10 @@ AppendDevicePath (
     return DuplicateDevicePath (FirstDevicePath);
   }
 
+  if (!IsDevicePathValid (FirstDevicePath, 0) || !IsDevicePathValid (SecondDevicePath, 0)) {
+    return NULL;
+  }
+
   //
   // Allocate space for the combined device path. It only has one end node of
   // length EFI_DEVICE_PATH_PROTOCOL.
@@ -500,6 +570,7 @@ AppendDevicePathNode (
   path instance and a new end-of-device-path-instance node is inserted between. 
   If DevicePath is NULL, then a copy if DevicePathInstance is returned.
   If DevicePathInstance is NULL, then NULL is returned.
+  If DevicePath or DevicePathInstance is invalid, then NULL is returned.
   If there is not enough memory to allocate space for the new device path, then 
   NULL is returned.  
   The memory is allocated from EFI boot services memory. It is the responsibility 
@@ -531,6 +602,10 @@ AppendDevicePathInstance (
     return NULL;
   }
 
+  if (!IsDevicePathValid (DevicePath, 0) || !IsDevicePathValid (DevicePathInstance, 0)) {
+    return NULL;
+  }
+
   SrcSize       = GetDevicePathSize (DevicePath);
   InstanceSize  = GetDevicePathSize (DevicePathInstance);
 
@@ -559,6 +634,7 @@ AppendDevicePathInstance (
   DevicePath to point to the next device path instance in the device path (or NULL 
   if no more) and updates Size to hold the size of the device path instance copy.
   If DevicePath is NULL, then NULL is returned.
+  If DevicePath points to a invalid device path, then NULL is returned.
   If there is not enough memory to allocate space for the new device path, then 
   NULL is returned.  
   The memory is allocated from EFI boot services memory. It is the responsibility 
@@ -596,6 +672,10 @@ GetNextDevicePathInstance (
     return NULL;
   }
 
+  if (!IsDevicePathValid (*DevicePath, 0)) {
+    return NULL;
+  }
+
   //
   // Find the end of the device path instance
   //
@@ -681,13 +761,14 @@ CreateDeviceNode (
 
   This function returns TRUE if the device path specified by DevicePath is
   multi-instance.
-  Otherwise, FALSE is returned.  If DevicePath is NULL, then FALSE is returned.
+  Otherwise, FALSE is returned.
+  If DevicePath is NULL or invalid, then FALSE is returned.
 
   @param  DevicePath                 A pointer to a device path data structure.
 
   @retval  TRUE                      DevicePath is multi-instance.
-  @retval  FALSE                     DevicePath is not multi-instance or DevicePath 
+  @retval  FALSE                     DevicePath is not multi-instance, or DevicePath 
-                                     is NULL.
+                                     is NULL or invalid.
 
 **/
 BOOLEAN
@@ -702,6 +783,10 @@ IsDevicePathMultiInstance (
     return FALSE;
   }
 
+  if (!IsDevicePathValid (DevicePath, 0)) {
+    return FALSE;
+  }
+
   Node = DevicePath;
   while (!IsDevicePathEnd (Node)) {
     if (IsDevicePathEndInstance (Node)) {
@@ -776,15 +861,14 @@ FileDevicePath (
   IN CONST CHAR16                    *FileName
   )
 {
-  UINT16                    Size;
+  UINTN                     Size;
   FILEPATH_DEVICE_PATH      *FilePath;
   EFI_DEVICE_PATH_PROTOCOL  *DevicePath;
   EFI_DEVICE_PATH_PROTOCOL  *FileDevicePath;
 
   DevicePath = NULL;
 
-  Size = (UINT16) StrSize (FileName);
+  Size = StrSize (FileName);
-  
   FileDevicePath = AllocatePool (Size + SIZE_OF_FILEPATH_DEVICE_PATH + END_DEVICE_PATH_LENGTH);
   if (FileDevicePath != NULL) {
     FilePath = (FILEPATH_DEVICE_PATH *) FileDevicePath;

MdePkg/Library/UefiDevicePathLib/UefiDevicePathLib.inf

@@ -3,7 +3,7 @@
 #
 # Device Path Library that layers on top of the Memory Allocation Library.
 #
-# Copyright (c) 2007 - 2010, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2007 - 2012, 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
@@ -42,8 +42,10 @@
   MemoryAllocationLib
   DebugLib
   BaseMemoryLib
-
+  PcdLib
 
 [Protocols]
   gEfiDevicePathProtocolGuid                    ## CONSUMES
 
+[Pcd]
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumDevicePathNodeCount

MdePkg/Library/UefiDevicePathLibDevicePathProtocol/UefiDevicePathLib.c

@@ -2,7 +2,7 @@
   Library instance that implement UEFI Device Path Library class based on protocol
   gEfiDevicePathUtilitiesProtocolGuid.
 
-  Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2012, 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
@@ -24,6 +24,7 @@
 #include <Library/MemoryAllocationLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/UefiBootServicesTableLib.h>
+#include <Library/PcdLib.h>
 
 EFI_DEVICE_PATH_UTILITIES_PROTOCOL          *mDevicePathUtilities = NULL;
 
@@ -71,6 +72,61 @@ DevicePathLibConstructor (
   return Status;
 }
 
+/**
+  Determine whether a given device path is valid.
+  If DevicePath is NULL, then ASSERT().
+
+  @param  DevicePath  A pointer to a device path data structure.
+  @param  MaxSize     The maximum size of the device path data structure.
+
+  @retval TRUE        DevicePath is valid.
+  @retval FALSE       The length of any node node in the DevicePath is less
+                      than sizeof (EFI_DEVICE_PATH_PROTOCOL).
+  @retval FALSE       If MaxSize is not zero, the size of the DevicePath
+                      exceeds MaxSize.
+  @retval FALSE       If PcdMaximumDevicePathNodeCount is not zero, the node
+                      count of the DevicePath exceeds PcdMaximumDevicePathNodeCount.
+**/
+BOOLEAN
+EFIAPI
+IsDevicePathValid (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL *DevicePath,
+  IN       UINTN                    MaxSize
+  )
+{
+  UINTN Count;
+  UINTN Size;
+  UINTN NodeLength;
+
+  ASSERT (DevicePath != NULL);
+
+  for (Count = 0, Size = 0; !IsDevicePathEnd (DevicePath); DevicePath = NextDevicePathNode (DevicePath)) {
+    NodeLength = DevicePathNodeLength (DevicePath);
+    if (NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL)) {
+      return FALSE;
+    }
+
+    if (MaxSize > 0) {
+      Size += NodeLength;
+      if (Size + END_DEVICE_PATH_LENGTH > MaxSize) {
+        return FALSE;
+      }
+    }
+
+    if (PcdGet32 (PcdMaximumDevicePathNodeCount) > 0) {
+      Count++;
+      if (Count >= PcdGet32 (PcdMaximumDevicePathNodeCount)) {
+        return FALSE;
+      }
+    }
+  }
+
+  //
+  // Only return TRUE when the End Device Path node is valid.
+  //
+  return (BOOLEAN) (DevicePathNodeLength (DevicePath) == END_DEVICE_PATH_LENGTH);
+}
+
 /**
   Returns the Type field of a device path node.
 
@@ -136,8 +192,12 @@ DevicePathNodeLength (
   IN CONST VOID  *Node
   )
 {
+  UINTN Length;
+
   ASSERT (Node != NULL);
-  return ReadUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0]);
+  Length = ReadUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0]);
+  ASSERT (Length >= sizeof (EFI_DEVICE_PATH_PROTOCOL));
+  return Length;
 }
 
 /**
@@ -256,7 +316,8 @@ IsDevicePathEndInstance (
   be used to set the contents of the Length field.
 
   If Node is NULL, then ASSERT().
-  If NodeLength >= 0x10000, then ASSERT().
+  If NodeLength >= SIZE_64KB, then ASSERT().
+  If NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL), then ASSERT().
 
   @param  Node      A pointer to a device path node data structure.
   @param  Length    The length, in bytes, of the device path node.
@@ -272,7 +333,7 @@ SetDevicePathNodeLength (
   )
 {
   ASSERT (Node != NULL);
-  ASSERT (Length < 0x10000);
+  ASSERT ((Length >= sizeof (EFI_DEVICE_PATH_PROTOCOL)) && (Length < SIZE_64KB));
   return WriteUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0], (UINT16)(Length));
 }
 
@@ -305,13 +366,14 @@ SetDevicePathEndNode (
 /**
   Returns the size of a device path in bytes.
 
-  This function returns the size, in bytes, of the device path data structure specified by
+  This function returns the size, in bytes, of the device path data structure 
-  DevicePath including the end of device path node.  If DevicePath is NULL, then 0 is returned.
+  specified by DevicePath including the end of device path node.
+  If DevicePath is NULL or invalid, then 0 is returned.
 
-  @param  DevicePath                 A pointer to a device path data structure.
+  @param  DevicePath  A pointer to a device path data structure.
-  
+
-  @retval 0       If DevicePath is NULL.
+  @retval 0           If DevicePath is NULL or invalid.
-  @retval Others  The size of a device path in bytes.
+  @retval Others      The size of a device path in bytes.
 
 **/
 UINTN
@@ -336,7 +398,7 @@ GetDevicePathSize (
   
   @param  DevicePath                 A pointer to a device path data structure.
 
-  @retval NULL    If DevicePath is NULL.
+  @retval NULL    If DevicePath is NULL or invalid.
   @retval Others  A pointer to the duplicated device path.
   
 **/
@@ -367,6 +429,7 @@ DuplicateDevicePath (
   @param  SecondDevicePath           A pointer to a device path data structure.
   
   @retval NULL      If there is not enough memory for the newly allocated buffer.
+  @retval NULL      If FirstDevicePath or SecondDevicePath is invalid.
   @retval Others    A pointer to the new device path if success.
                     Or a copy an end-of-device-path if both FirstDevicePath and 
                     SecondDevicePath are NULL.
@@ -431,6 +494,7 @@ AppendDevicePathNode (
   path instance and a new end-of-device-path-instance node is inserted between. 
   If DevicePath is NULL, then a copy if DevicePathInstance is returned.
   If DevicePathInstance is NULL, then NULL is returned.
+  If DevicePath or DevicePathInstance is invalid, then NULL is returned.
   If there is not enough memory to allocate space for the new device path, then 
   NULL is returned.   
   The memory is allocated from EFI boot services memory. It is the responsibility 
@@ -524,15 +588,16 @@ CreateDeviceNode (
 /**
   Determines if a device path is single or multi-instance.
 
-  This function returns TRUE if the device path specified by DevicePath is 
+  This function returns TRUE if the device path specified by DevicePath is
   multi-instance.
-  Otherwise, FALSE is returned.  If DevicePath is NULL, then FALSE is returned.
+  Otherwise, FALSE is returned.
+  If DevicePath is NULL or invalid, then FALSE is returned.
 
   @param  DevicePath                 A pointer to a device path data structure.
 
   @retval  TRUE                      DevicePath is multi-instance.
-  @retval  FALSE                     DevicePath is not multi-instance or DevicePath 
+  @retval  FALSE                     DevicePath is not multi-instance, or DevicePath 
-                                     is NULL.
+                                     is NULL or invalid.
 
 **/
 BOOLEAN

MdePkg/Library/UefiDevicePathLibDevicePathProtocol/UefiDevicePathLibDevicePathProtocol.inf

@@ -4,7 +4,7 @@
 #  Device Path Library that layers on top of the UEFI 2.0 Device Path Protocol.
 #  This library is not available for EFI 1.10 modules.
 #
-#  Copyright (c) 2007 - 2011, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) 2007 - 2012, 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
@@ -44,11 +44,14 @@
   MemoryAllocationLib
   BaseLib
   DebugLib
-
+  PcdLib
 
 [Protocols]
   gEfiDevicePathProtocolGuid                    ## CONSUMES
   gEfiDevicePathUtilitiesProtocolGuid           ## CONSUMES
 
+[Pcd]
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumDevicePathNodeCount
+
 [Depex.common.DXE_DRIVER, Depex.common.DXE_RUNTIME_DRIVER, Depex.common.DXE_SAL_DRIVER, Depex.common.DXE_SMM_DRIVER]
   gEfiDevicePathUtilitiesProtocolGuid

MdePkg/MdePkg.dec

@@ -1287,6 +1287,9 @@
   ## Indicates the maximum node number of linked list
   gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength|1000000|UINT32|0x00000003
 
+  ## Indicates the maximum node number of device path
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumDevicePathNodeCount|0|UINT32|0x00000029
+
   ## Indicates the timeout tick of holding spin lock
   gEfiMdePkgTokenSpaceGuid.PcdSpinLockTimeout|10000000|UINT32|0x00000004