Avoid backtrace from __stack_chk_fail [BZ #12189]
Commit Message
__stack_chk_fail is called on corrupted stack. __stack_chk_fail should
use as little stack as possible. __libc_message is extended to avoid
calling BEFORE_ABORT when do_abort >= 3 and __fortify_fail_abort is
added to avoid backtrace from __stack_chk_fail.
OK for master?
H.J.
---
[BZ #12189]
* debug/Makefile (CFLAGS-tst-ssp-1.c): New.
(tests): Add tst-ssp-1 if -fstack-protector works.
* debug/fortify_fail.c (_fortify_fail_abort): New function.
(__fortify_fail): Call _fortify_fail_abort.
(__fortify_fail_abort): Add a hidden definition.
* debug/stack_chk_fail.c (__stack_chk_fail): Call
__fortify_fail_abort, instead of __fortify_fail.
* debug/tst-ssp-1.c: New file.
* include/stdio.h (__fortify_fail_abort): New hidden prototype.
* sysdeps/posix/libc_fatal.c (__libc_message): Call BEFORE_ABORT
if do_abort < 3.
---
debug/Makefile | 7 +++++++
debug/fortify_fail.c | 13 +++++++++++--
debug/stack_chk_fail.c | 2 +-
debug/tst-ssp-1.c | 40 ++++++++++++++++++++++++++++++++++++++++
include/stdio.h | 3 +++
sysdeps/posix/libc_fatal.c | 3 ++-
6 files changed, 64 insertions(+), 4 deletions(-)
create mode 100644 debug/tst-ssp-1.c
Comments
On Mon, 10 Jul 2017, H.J. Lu wrote:
> diff --git a/debug/tst-ssp-1.c b/debug/tst-ssp-1.c
> new file mode 100644
> index 0000000..14d8e26
> --- /dev/null
> +++ b/debug/tst-ssp-1.c
> @@ -0,0 +1,40 @@
> +/* Copyright (C) 2017 Free Software Foundation, Inc.
All new files should have a descriptive comment on their first line,
before the copyright notice.
* H. J. Lu:
> __stack_chk_fail is called on corrupted stack. __stack_chk_fail should
> use as little stack as possible. __libc_message is extended to avoid
> calling BEFORE_ABORT when do_abort >= 3 and __fortify_fail_abort is
> added to avoid backtrace from __stack_chk_fail.
>
> OK for master?
I think you should use an enum for do_abort and avoid the magic
numbers.
Could you post an example of the new output?
On Mon, Jul 10, 2017 at 9:00 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> __fortify_fail_abort is
> added to avoid backtrace from __stack_chk_fail.
Note that this is important for other tools as well e.g. Asan. I've
posted patch a while ago to add fail-safe backtracking APIs to libgcc
in https://gcc.gnu.org/ml/gcc-patches/2017-06/msg01869.html (the
latest ping is https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00447.html)
but it didn't get too much attention to date. Would be great if
someone could take a look.
-Y
@@ -139,12 +139,19 @@ LDFLAGS-tst-backtrace4 = -rdynamic
LDFLAGS-tst-backtrace5 = -rdynamic
LDFLAGS-tst-backtrace6 = -rdynamic
+CFLAGS-tst-ssp-1.c = -Wno-format -Wno-deprecated-declarations -Wno-error \
+ -O0 -fstack-protector
+
tests = backtrace-tst tst-longjmp_chk tst-chk1 tst-chk2 tst-chk3 \
tst-lfschk1 tst-lfschk2 tst-lfschk3 test-strcpy_chk test-stpcpy_chk \
tst-chk4 tst-chk5 tst-chk6 tst-lfschk4 tst-lfschk5 tst-lfschk6 \
tst-longjmp_chk2 tst-backtrace2 tst-backtrace3 tst-backtrace4 \
tst-backtrace5 tst-backtrace6
+ifeq ($(have-ssp),yes)
+tests += tst-ssp-1
+endif
+
ifeq (,$(CXX))
tests-unsupported = tst-chk4 tst-chk5 tst-chk6 \
tst-lfschk4 tst-lfschk5 tst-lfschk6
@@ -23,11 +23,20 @@ extern char **__libc_argv attribute_hidden;
void
__attribute__ ((noreturn)) internal_function
-__fortify_fail (const char *msg)
+__fortify_fail_abort (int no_backtrace, const char *msg)
{
/* The loop is added only to keep gcc happy. */
while (1)
- __libc_message (2, "*** %s ***: %s terminated\n",
+ __libc_message (no_backtrace ? 3 : 2, "*** %s ***: %s terminated\n",
msg, __libc_argv[0] ?: "<unknown>");
}
+
+void
+__attribute__ ((noreturn)) internal_function
+__fortify_fail (const char *msg)
+{
+ __fortify_fail_abort (0, msg);
+}
+
libc_hidden_def (__fortify_fail)
+libc_hidden_def (__fortify_fail_abort)
@@ -25,7 +25,7 @@ void
__attribute__ ((noreturn))
__stack_chk_fail (void)
{
- __fortify_fail ("stack smashing detected");
+ __fortify_fail_abort (1, "stack smashing detected");
}
#ifdef SHARED
new file mode 100644
@@ -0,0 +1,40 @@
+/* Copyright (C) 2017 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/>. */
+
+/* Based on gcc.dg/ssp-1.c from GCC testsuite. */
+
+#include <unistd.h>
+#include <signal.h>
+#include <abort-instr.h>
+
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#define EXPECTED_SIGNAL SIGABRT
+#include "../test-skeleton.c"
+
+static int
+do_test (void)
+{
+ int i;
+ char foo[30];
+
+ // smash stack
+ for (i = 0; i <= 400; i++)
+ foo[i] = 42;
+
+ return 1; /* fail */
+}
@@ -92,7 +92,10 @@ extern void __libc_fatal (const char *__message)
extern void __libc_message (int do_abort, const char *__fnt, ...);
extern void __fortify_fail (const char *msg)
__attribute__ ((__noreturn__)) internal_function;
+extern void __fortify_fail_abort (int, const char *msg)
+ __attribute__ ((__noreturn__)) internal_function;
libc_hidden_proto (__fortify_fail)
+libc_hidden_proto (__fortify_fail_abort)
/* Acquire ownership of STREAM. */
extern void __flockfile (FILE *__stream);
@@ -169,7 +169,8 @@ __libc_message (int do_abort, const char *fmt, ...)
if (do_abort)
{
- BEFORE_ABORT (do_abort, written, fd);
+ if (do_abort < 3)
+ BEFORE_ABORT (do_abort, written, fd);
/* Kill the application. */
abort ();