malloc/tst-tcfree3.c

   1 /* Test that malloc tcache catches double free.
   2    Copyright (C) 2018-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <malloc.h>
  20 #include <string.h>
  21
  22 static int
  23 do_test (void)
  24 {
  25   /* Do two allocation of any size that fit in tcache, and one that
  26      doesn't.  */
  27   int ** volatile a = malloc (32);
  28   int ** volatile b = malloc (32);
  29   /* This is just under the mmap threshold.  */
  30   int ** volatile c = malloc (127 * 1024);
  31
  32   /* The invalid "tcache bucket" we might dereference will likely end
  33      up somewhere within this memory block, so make all the accidental
  34      "next" pointers cause segfaults.  BZ #23907.  */
  35   memset (c, 0xff, 127 * 1024);
  36
  37   free (a); // puts in tcache
  38
  39   /* A is now free and contains the key we use to detect in-tcache.
  40      Copy the key to the other chunks.  */
  41   memcpy (b, a, 32);
  42   memcpy (c, a, 32);
  43
  44   /* This free tests the "are we in the tcache already" loop with a
  45      VALID bin but "coincidental" matching key.  */
  46   free (b); // should NOT abort
  47   /* This free tests the "is it a valid tcache bin" test.  */
  48   free (c); // should NOT abort
  49
  50   return 0;
  51 }
  52
  53 #include <support/test-driver.c>