* [2.28 COMMITTED] malloc: tcache double free check
@ 2018-01-01 0:00 DJ Delorie
2018-01-01 0:00 ` Florian Weimer
0 siblings, 1 reply; 2+ messages in thread
From: DJ Delorie @ 2018-01-01 0:00 UTC (permalink / raw)
To: libc-stable
This adds a test that exists in the non-tcache malloc, hence
technically it fixes a regression - simple double frees were detected
before, tcache bypassed that test, so needs its own test.
(cherry picked from commit bcdaad21d4635931d1bd3b54a7894276925d081d)
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.
diff --git a/dlfcn/dlerror.c b/dlfcn/dlerror.c
index 33574faab6..96bf925333 100644
--- a/dlfcn/dlerror.c
+++ b/dlfcn/dlerror.c
@@ -198,7 +198,10 @@ check_free (struct dl_action_result *rec)
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;
+ }
}
}
diff --git a/malloc/Makefile b/malloc/Makefile
index 7d54bad866..e6dfbfc14c 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -38,6 +38,7 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-malloc_info \
tst-malloc-too-large \
tst-malloc-stats-cancellation \
+ tst-tcfree1 tst-tcfree2 \
tests-static := \
tst-interpose-static-nothread \
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 47795601c8..6be2573868 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2888,6 +2888,8 @@ mremap_chunk (mchunkptr p, size_t new_size)
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
@@ -2911,6 +2913,11 @@ tcache_put (mchunkptr chunk, size_t tc_idx)
{
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]);
@@ -2926,6 +2933,7 @@ tcache_get (size_t tc_idx)
assert (tcache->entries[tc_idx] > 0);
tcache->entries[tc_idx] = e->next;
--(tcache->counts[tc_idx]);
+ e->key = NULL;
return (void *) e;
}
@@ -4166,6 +4174,26 @@ _int_free (mstate av, mchunkptr p, int have_lock)
{
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)
diff --git a/malloc/tst-tcfree1.c b/malloc/tst-tcfree1.c
new file mode 100644
index 0000000000..bc29375ce7
--- /dev/null
+++ b/malloc/tst-tcfree1.c
@@ -0,0 +1,42 @@
+/* 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>
diff --git a/malloc/tst-tcfree2.c b/malloc/tst-tcfree2.c
new file mode 100644
index 0000000000..17f06bacd4
--- /dev/null
+++ b/malloc/tst-tcfree2.c
@@ -0,0 +1,48 @@
+/* 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>
diff --git a/manual/probes.texi b/manual/probes.texi
index ab2a3102bb..0ea560ed78 100644
--- a/manual/probes.texi
+++ b/manual/probes.texi
@@ -243,6 +243,18 @@ This probe is triggered when the
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
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [2.28 COMMITTED] malloc: tcache double free check
2018-01-01 0:00 [2.28 COMMITTED] malloc: tcache double free check DJ Delorie
@ 2018-01-01 0:00 ` Florian Weimer
0 siblings, 0 replies; 2+ messages in thread
From: Florian Weimer @ 2018-01-01 0:00 UTC (permalink / raw)
To: DJ Delorie; +Cc: libc-stable
* DJ Delorie:
> This adds a test that exists in the non-tcache malloc, hence
> technically it fixes a regression - simple double frees were detected
> before, tcache bypassed that test, so needs its own test.
>
> (cherry picked from commit bcdaad21d4635931d1bd3b54a7894276925d081d)
The “cherry picked from” line did not make it into your actual commit.
I have reverted this with the patch below due to bug 23907.
Thanks,
Florian
Subject: Revert "malloc: tcache double free check" [BZ #23907]
This reverts commit 481a6cf0c24f02f251d7cd0b776c12d00e6b144f, the
backport of commit bcdaad21d4635931d1bd3b54a7894276925d081d on the
master branch.
---
ChangeLog | 12 ------------
dlfcn/dlerror.c | 5 +----
malloc/Makefile | 1 -
malloc/malloc.c | 28 ----------------------------
malloc/tst-tcfree1.c | 42 ------------------------------------------
malloc/tst-tcfree2.c | 48 ------------------------------------------------
manual/probes.texi | 12 ------------
7 files changed, 1 insertion(+), 147 deletions(-)
delete mode 100644 malloc/tst-tcfree1.c
delete mode 100644 malloc/tst-tcfree2.c
diff --git a/ChangeLog b/ChangeLog
index 1ef4b4abe0..8c92ee7764 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,15 +1,3 @@
-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.
2018-11-19 Florian Weimer <fweimer@redhat.com>
support: Print timestamps in timeout handler.
diff --git a/dlfcn/dlerror.c b/dlfcn/dlerror.c
index 96bf925333..33574faab6 100644
--- a/dlfcn/dlerror.c
+++ b/dlfcn/dlerror.c
@@ -198,10 +198,7 @@ check_free (struct dl_action_result *rec)
Dl_info info;
if (_dl_addr (check_free, &info, &map, NULL) != 0 && map->l_ns == 0)
#endif
- {
- free ((char *) rec->errstring);
- rec->errstring = NULL;
- }
+ free ((char *) rec->errstring);
}
}
diff --git a/malloc/Makefile b/malloc/Makefile
index e6dfbfc14c..7d54bad866 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -38,7 +38,6 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-malloc_info \
tst-malloc-too-large \
tst-malloc-stats-cancellation \
- tst-tcfree1 tst-tcfree2 \
tests-static := \
tst-interpose-static-nothread \
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 6be2573868..47795601c8 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2888,8 +2888,6 @@ mremap_chunk (mchunkptr p, size_t new_size)
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
@@ -2913,11 +2911,6 @@ tcache_put (mchunkptr chunk, size_t tc_idx)
{
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]);
@@ -2933,7 +2926,6 @@ tcache_get (size_t tc_idx)
assert (tcache->entries[tc_idx] > 0);
tcache->entries[tc_idx] = e->next;
--(tcache->counts[tc_idx]);
- e->key = NULL;
return (void *) e;
}
@@ -4174,26 +4166,6 @@ _int_free (mstate av, mchunkptr p, int have_lock)
{
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)
diff --git a/malloc/tst-tcfree1.c b/malloc/tst-tcfree1.c
deleted file mode 100644
index bc29375ce7..0000000000
--- a/malloc/tst-tcfree1.c
+++ /dev/null
@@ -1,42 +0,0 @@
-/* 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>
diff --git a/malloc/tst-tcfree2.c b/malloc/tst-tcfree2.c
deleted file mode 100644
index 17f06bacd4..0000000000
--- a/malloc/tst-tcfree2.c
+++ /dev/null
@@ -1,48 +0,0 @@
-/* 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>
diff --git a/manual/probes.texi b/manual/probes.texi
index 0ea560ed78..ab2a3102bb 100644
--- a/manual/probes.texi
+++ b/manual/probes.texi
@@ -243,18 +243,6 @@ This probe is triggered when the
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
--
2.14.5
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