glibc/stdlib/test-bz22786.c

/* Bug 22786: test for buffer overflow in realpath.
   Copyright (C) 2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

/* This file must be run from within a directory called "stdlib".  */

#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <support/check.h>
#include <support/support.h>
#include <support/temp_file.h>
#include <support/test-driver.h>
#include <libc-diag.h>

static int
do_test (void)
{
  const char *dir = support_create_temp_directory ("bz22786.");
  const char *lnk = xasprintf ("%s/symlink", dir);
  const size_t path_len = (size_t) INT_MAX + strlen (lnk) + 1;

  TEST_VERIFY_EXIT (symlink (".", lnk) == 0);

  DIAG_PUSH_NEEDS_COMMENT;
#if __GNUC_PREREQ (7, 0)
  /* GCC 7 warns about too-large allocations; here we need such
     allocation to succeed for the test to work.  */
  DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
  char *path = xmalloc (path_len);
  DIAG_POP_NEEDS_COMMENT;

  /* Construct very long path = "/tmp/bz22786.XXXX/symlink/aaaa....."  */
  char *p = mempcpy (path, lnk, strlen (lnk));
  *(p++) = '/';
  memset (p, 'a', path_len - (p - path) - 2);
  p[path_len - (p - path) - 1] = '\0';

  /* This call crashes before the fix for bz22786 on 32-bit platforms.  */
  p = realpath (path, NULL);

  if (p != NULL || errno != ENAMETOOLONG)
    {
      printf ("realpath: %s (%m)", p);
      return EXIT_FAILURE;
    }

  /* Cleanup.  */
  unlink (lnk);

  return 0;
}

#define TEST_FUNCTION do_test
#include <support/test-driver.c>