* malloc/malloc.c (tcache_entry): Add key field.
(tcache_put): Set it.
(tcache_get): Likewise.
(_int_free): Check for double free in tcache.
* malloc/tst-tcfree1.c: New.
* malloc/tst-tcfree2.c: New.
* malloc/Makefile: Run the new tests.
* manual/probes.texi: Document memory_tcache_double_free probe.
* dlfcn/dlerror.c (check_free): Prevent double frees.
+2018-11-20 DJ Delorie <dj@redhat.com>
+
+ * malloc/malloc.c (tcache_entry): Add key field.
+ (tcache_put): Set it.
+ (tcache_get): Likewise.
+ (_int_free): Check for double free in tcache.
+ * malloc/tst-tcfree1.c: New.
+ * malloc/tst-tcfree2.c: New.
+ * malloc/Makefile: Run the new tests.
+ * manual/probes.texi: Document memory_tcache_double_free probe.
+
+ * dlfcn/dlerror.c (check_free): Prevent double frees.
+
2018-11-20 Wilco Dijkstra <wdijkstr@arm.com>
* sysdeps/aarch64/memset.S (MEMSET): Improve non-zero memset loop.
Dl_info info;
if (_dl_addr (check_free, &info, &map, NULL) != 0 && map->l_ns == 0)
#endif
- free ((char *) rec->errstring);
+ {
+ free ((char *) rec->errstring);
+ rec->errstring = NULL;
+ }
}
}
tst-malloc_info \
tst-malloc-too-large \
tst-malloc-stats-cancellation \
+ tst-tcfree1 tst-tcfree2 \
tests-static := \
tst-interpose-static-nothread \
typedef struct tcache_entry
{
struct tcache_entry *next;
+ /* This field exists to detect double frees. */
+ struct tcache_perthread_struct *key;
} tcache_entry;
/* There is one of these for each thread, which contains the
{
tcache_entry *e = (tcache_entry *) chunk2mem (chunk);
assert (tc_idx < TCACHE_MAX_BINS);
+
+ /* Mark this chunk as "in the tcache" so the test in _int_free will
+ detect a double free. */
+ e->key = tcache;
+
e->next = tcache->entries[tc_idx];
tcache->entries[tc_idx] = e;
++(tcache->counts[tc_idx]);
assert (tcache->entries[tc_idx] > 0);
tcache->entries[tc_idx] = e->next;
--(tcache->counts[tc_idx]);
+ e->key = NULL;
return (void *) e;
}
{
size_t tc_idx = csize2tidx (size);
+ /* Check to see if it's already in the tcache. */
+ tcache_entry *e = (tcache_entry *) chunk2mem (p);
+
+ /* This test succeeds on double free. However, we don't 100%
+ trust it (it also matches random payload data at a 1 in
+ 2^<size_t> chance), so verify it's not an unlikely coincidence
+ before aborting. */
+ if (__glibc_unlikely (e->key == tcache && tcache))
+ {
+ tcache_entry *tmp;
+ LIBC_PROBE (memory_tcache_double_free, 2, e, tc_idx);
+ for (tmp = tcache->entries[tc_idx];
+ tmp;
+ tmp = tmp->next)
+ if (tmp == e)
+ malloc_printerr ("free(): double free detected in tcache 2");
+ /* If we get here, it was a coincidence. We've wasted a few
+ cycles, but don't abort. */
+ }
+
if (tcache
&& tc_idx < mp_.tcache_bins
&& tcache->counts[tc_idx] < mp_.tcache_count)
--- /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 <errno.h>
+#include <error.h>
+#include <limits.h>
+#include <malloc.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/signal.h>
+
+static int
+do_test (void)
+{
+ /* Do one allocation of any size that fits in tcache. */
+ char * volatile x = malloc (32);
+
+ free (x); // puts in tcache
+ free (x); // should abort
+
+ printf("FAIL: tcache double free not detected\n");
+ return 1;
+}
+
+#define TEST_FUNCTION do_test
+#define EXPECTED_SIGNAL SIGABRT
+#include <support/test-driver.c>
--- /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 <errno.h>
+#include <error.h>
+#include <limits.h>
+#include <malloc.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/signal.h>
+
+static int
+do_test (void)
+{
+ char * volatile ptrs[20];
+ int i;
+
+ /* Allocate enough small chunks so that when we free them all, the tcache
+ is full, and the first one we freed is at the end of its linked list. */
+#define COUNT 20
+ for (i=0; i<COUNT; i++)
+ ptrs[i] = malloc (20);
+ for (i=0; i<COUNT; i++)
+ free (ptrs[i]);
+ free (ptrs[0]);
+
+ printf("FAIL: tcache double free\n");
+ return 1;
+}
+
+#define TEST_FUNCTION do_test
+#define EXPECTED_SIGNAL SIGABRT
+#include <support/test-driver.c>
value of this tunable.
@end deftp
+@deftp Probe memory_tcache_double_free (void *@var{$arg1}, int @var{$arg2})
+This probe is triggered when @code{free} determines that the memory
+being freed has probably already been freed, and resides in the
+per-thread cache. Note that there is an extremely unlikely chance
+that this probe will trigger due to random payload data remaining in
+the allocated memory matching the key used to detect double frees.
+This probe actually indicates that an expensive linear search of the
+tcache, looking for a double free, has happened. Argument @var{$arg1}
+is the memory location as passed to @code{free}, Argument @var{$arg2}
+is the tcache bin it resides in.
+@end deftp
+
@node Mathematical Function Probes
@section Mathematical Function Probes
projects / thirdparty / glibc.git / commitdiff
