[PATCH v3 2/3] MdeModulePkg/UdfDxe: Content check for 'File' in ResolveSymlink()

[Hao Wu <hao.a.wu@intel.com>]

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1279

The content within 'File' is the output data for ResolveSymlink(). This
commit will add checks to ensure the content in 'File' is valid.
Otherwise, possible null pointer dereference issue will occur during the
subsequent usage of the data returned by ResolveSymlink().

Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Paulo Alcantara <palcantara@suse.de>
Reviewed-by: Star Zeng <star.zeng@intel.com>
---
 MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
index c15741a032..2227f10d07 100644
--- a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
+++ b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
@@ -2145,6 +2145,8 @@ ResolveSymlink (
   UINT8               CompressionId;
   UDF_FILE_INFO       PreviousFile;
 
+  ZeroMem ((VOID *)File, sizeof (UDF_FILE_INFO));
+
   //
   // Symlink files on UDF volumes do not contain so much data other than
   // Path Components which resolves to real filenames, so it's OK to read in
@@ -2288,6 +2290,14 @@ ResolveSymlink (
       break;
     }
 
+    //
+    // Check the content in the file info pointed by File.
+    //
+    if ((File->FileEntry == NULL) || (File->FileIdentifierDesc == NULL)) {
+      Status = EFI_VOLUME_CORRUPTED;
+      goto Error_Find_File;
+    }
+
     if (CompareMem ((VOID *)&PreviousFile, (VOID *)Parent,
                     sizeof (UDF_FILE_INFO)) != 0) {
       CleanupFileInformation (&PreviousFile);
@@ -2301,6 +2311,13 @@ ResolveSymlink (
   //
   FreePool (ReadFileInfo.FileData);
 
+  //
+  // Check the content in the resolved file info.
+  //
+  if ((File->FileEntry == NULL) || (File->FileIdentifierDesc == NULL)) {
+    return EFI_VOLUME_CORRUPTED;
+  }
+
   return EFI_SUCCESS;
 
 Error_Find_File:
-- 
2.12.0.windows.1