MdePkg UefiDevicePathLib: Validate before touch input buffer.

Current code not validate the input buffer before touch.
it may touch the buffer outside the validate scope. This
patch validate the input size big enough to touch the
first node.

Cc: Ruiyu NI <ruiyu.ni@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Eric Dong <eric.dong@intel.com>

diff --git a/MdePkg/Library/UefiDevicePathLib/DevicePathUtilities.c b/MdePkg/Library/UefiDevicePathLib/DevicePathUtilities.c
index 024dcc271d9705761a03413a52f9a3d63d4fb62f..bb4a56398e3c92c6b249d765d90b3144f72f492c 100644 (file)
--- a/MdePkg/Library/UefiDevicePathLib/DevicePathUtilities.c
+++ b/MdePkg/Library/UefiDevicePathLib/DevicePathUtilities.c
@@ -61,17 +61,33 @@ IsDevicePathValid (
 \r
   ASSERT (DevicePath != NULL);\r
 \r
 \r
   ASSERT (DevicePath != NULL);\r
 \r

+  if (MaxSize == 0) {\r
+    MaxSize = MAX_UINTN;\r
+  }\r
+\r
+  //\r
+  // Validate the input size big enough to touch the first node.\r
+  //\r
+  if (MaxSize < sizeof (EFI_DEVICE_PATH_PROTOCOL)) {\r
+    return FALSE;\r
+  }\r
+\r

   for (Count = 0, Size = 0; !IsDevicePathEnd (DevicePath); DevicePath = NextDevicePathNode (DevicePath)) {\r
     NodeLength = DevicePathNodeLength (DevicePath);\r
     if (NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL)) {\r
       return FALSE;\r
     }\r
 \r
   for (Count = 0, Size = 0; !IsDevicePathEnd (DevicePath); DevicePath = NextDevicePathNode (DevicePath)) {\r
     NodeLength = DevicePathNodeLength (DevicePath);\r
     if (NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL)) {\r
       return FALSE;\r
     }\r
 \r

-    if (MaxSize > 0) {\r
-      Size += NodeLength;\r
-      if (Size + END_DEVICE_PATH_LENGTH > MaxSize) {\r
-        return FALSE;\r
-      }\r
+    if (NodeLength > MAX_UINTN - Size) {\r
+      return FALSE;\r
+    }\r
+    Size += NodeLength;\r
+\r
+    //\r
+    // Validate next node before touch it.\r
+    //\r
+    if (Size > MaxSize - END_DEVICE_PATH_LENGTH ) {\r
+      return FALSE;\r

     }\r
 \r
     if (PcdGet32 (PcdMaximumDevicePathNodeCount) > 0) {\r
     }\r
 \r
     if (PcdGet32 (PcdMaximumDevicePathNodeCount) > 0) {\r