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/* Test that malloc tcache catches double free.
Copyright (C) 2025 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
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <error.h>
#include <limits.h>
#include <malloc.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/signal.h>
/* Test for a double free where the size information gets overwritten by a
* terminating null byte. */
static int
do_test (void)
{
/* The payload is exactly 0x19 Bytes long:
* 0x18 bytes 'B' and one terminating null byte
*/
const char *payload = "BBBBBBBBBBBBBBBBBBBBBBBB";
char *volatile first_chunk
= malloc (strlen (payload)); // <-- off by one error
char *volatile second_chunk = malloc (0x118);
// free the second chunk the first time now it is in the tcache with tc_idx =
free (second_chunk);
// change the the size of the second_chunk using the terminating null byte if
// the PAYLOAD
strcpy (first_chunk, payload);
// now the second_chunk has a new size
// calling free a second time will not trigger the double free detection
free (second_chunk);
printf ("FAIL: tcache double free not detected\n");
return 1;
}
#define TEST_FUNCTION do_test
#define EXPECTED_SIGNAL SIGABRT
#include <support/test-driver.c>
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