--- /dev/null
+/* Test that malloc tcache catches double free.
+ 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/>. */
+
+#include <malloc.h>
+#include <string.h>
+
+/* Prevent GCC from optimizing away any malloc/free pairs. */
+#pragma GCC optimize ("O0")
+
+static int
+do_test (void)
+{
+ /* Do two allocation of any size that fit in tcache, and one that
+ doesn't. */
+ int ** volatile a = malloc (32);
+ int ** volatile b = malloc (32);
+ /* This is just under the mmap threshold. */
+ int ** volatile c = malloc (127 * 1024);
+
+ /* The invalid "tcache bucket" we might dereference will likely end
+ up somewhere within this memory block, so make all the accidental
+ "next" pointers cause segfaults. BZ #23907. */
+ memset (c, 0xff, 127 * 1024);
+
+ free (a); // puts in tcache
+
+ /* A is now free and contains the key we use to detect in-tcache.
+ Copy the key to the other chunks. */
+ memcpy (b, a, 32);
+ memcpy (c, a, 32);
+
+ /* This free tests the "are we in the tcache already" loop with a
+ VALID bin but "coincidental" matching key. */
+ free (b); // should NOT abort
+ /* This free tests the "is it a valid tcache bin" test. */
+ free (c); // should NOT abort
+
+ return 0;
+}
+
+#include <support/test-driver.c>