output: #fixed code
                                  public OSFileStore[] getFileStores() {
          // Use getfsstat to map filesystem paths to types
          Map<String, String> fstype = new HashMap<>();
          // Query with null to get total # required
          int numfs = SystemB.INSTANCE.getfsstat64(null, 0, 0);
          if (numfs > 0) {
              // Create array to hold results
              Statfs[] fs = new Statfs[numfs];
              // Fill array with results
              numfs = SystemB.INSTANCE.getfsstat64(fs, numfs * (new Statfs()).size(), SystemB.MNT_NOWAIT);
              for (int f = 0; f < numfs; f++) {
                  // Mount to name will match canonical path.
                  // Byte arrays are null-terminated strings
                  fstype.put(new String(fs[f].f_mntonname).trim(), new String(fs[f].f_fstypename).trim());
              }
          }
          // Now list file systems
          List<OSFileStore> fsList = new ArrayList<>();
          FileSystemView fsv = FileSystemView.getFileSystemView();
          // Mac file systems are mounted in /Volumes
          File volumes = new File("/Volumes");
          if (volumes != null && volumes.listFiles() != null) {
              for (File f : volumes.listFiles()) {
                  // Everyone hates DS Store
                  if (f.getName().endsWith(".DS_Store")) {
                      continue;
                  }
                  String name = fsv.getSystemDisplayName(f);
                  String description = "Volume";
                  String type = "unknown";
                  try {
                      String cp = f.getCanonicalPath();
                      if (cp.equals("/"))
                          name = name + " (/)";
                      FileStore fs = Files.getFileStore(f.toPath());
                      if (localDisk.matcher(fs.name()).matches()) {
                          description = "Local Disk";
                      }
                      if (fs.name().startsWith("localhost:") || fs.name().startsWith("//")) {
                          description = "Network Drive";
                      }
                      if (fstype.containsKey(cp)) {
                          type = fstype.get(cp);
                      }
                  } catch (IOException e) {
                      LOG.trace("", e);
                      continue;
                  }
                  fsList.add(new OSFileStore(name, description, type, f.getUsableSpace(), f.getTotalSpace()));
              }
          }
          return fsList.toArray(new OSFileStore[fsList.size()]);
      }
input: #vulnerable code 
                                  public OSFileStore[] getFileStores() {
          // Use getfsstat to map filesystem paths to types
          Map<String, String> fstype = new HashMap<>();
          // Query with null to get total # required
          int numfs = SystemB.INSTANCE.getfsstat64(null, 0, 0);
          if (numfs > 0) {
              // Create array to hold results
              Statfs[] fs = new Statfs[numfs];
              // Fill array with results
              numfs = SystemB.INSTANCE.getfsstat64(fs, numfs * (new Statfs()).size(), SystemB.MNT_NOWAIT);
              for (int f = 0; f < numfs; f++) {
                  // Mount to name will match canonical path.
                  // Byte arrays are null-terminated strings
                  fstype.put(new String(fs[f].f_mntonname).trim(), new String(fs[f].f_fstypename).trim());
              }
          }
          // Now list file systems
          List<OSFileStore> fsList = new ArrayList<>();
          FileSystemView fsv = FileSystemView.getFileSystemView();
          // Mac file systems are mounted in /Volumes
          File volumes = new File("/Volumes");
          if (volumes != null) {
              for (File f : volumes.listFiles()) {
                  // Everyone hates DS Store
                  if (f.getName().endsWith(".DS_Store")) {
                      continue;
                  }
                  String name = fsv.getSystemDisplayName(f);
                  String description = "Volume";
                  String type = "unknown";
                  try {
                      String cp = f.getCanonicalPath();
                      if (cp.equals("/"))
                          name = name + " (/)";
                      FileStore fs = Files.getFileStore(f.toPath());
                      if (localDisk.matcher(fs.name()).matches()) {
                          description = "Local Disk";
                      }
                      if (fs.name().startsWith("localhost:") || fs.name().startsWith("//")) {
                          description = "Network Drive";
                      }
                      if (fstype.containsKey(cp)) {
                          type = fstype.get(cp);
                      }
                  } catch (IOException e) {
                      LOG.trace("", e);
                      continue;
                  }
                  fsList.add(new OSFileStore(name, description, type, f.getUsableSpace(), f.getTotalSpace()));
              }
          }
          return fsList.toArray(new OSFileStore[fsList.size()]);
      } 
                              #location 23 
                              #vulnerability type NULL_DEREFERENCE