diff options
| -rw-r--r-- | ChangeLog | 13 | ||||
| -rw-r--r-- | dlfcn/dlerror.c | 5 | ||||
| -rw-r--r-- | malloc/Makefile | 1 | ||||
| -rw-r--r-- | malloc/malloc.c | 28 | ||||
| -rw-r--r-- | malloc/tst-tcfree1.c | 42 | ||||
| -rw-r--r-- | malloc/tst-tcfree2.c | 48 | ||||
| -rw-r--r-- | manual/probes.texi | 12 |
7 files changed, 148 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog index be2344248f..9cdd3bad36 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,16 @@ +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. 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 6d7a6a8cab..f730d7a2ee 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -2967,6 +2967,8 @@ 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 @@ -2990,6 +2992,11 @@ 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]); @@ -3005,6 +3012,7 @@ 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; } @@ -4218,6 +4226,26 @@ _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 |