Avoid backtrace from __stack_chk_fail [BZ #12189]

  On Mon, Jul 10, 2017 at 1:45 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Jul 10, 2017 at 1:39 PM, Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>> On 10/07/2017 17:21, H.J. Lu wrote:
>>> On Mon, Jul 10, 2017 at 1:14 PM, Joseph Myers <joseph@codesourcery.com> wrote:
>>>> 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.
>>>>
>>> Here is the updated patch.   OK for master?
>>>
>>>
>>> -- H.J.
>>>
>>>
>>> 0001-Avoid-backtrace-from-__stack_chk_fail-BZ-12189.patch
>>>
>>>
>>> From 63fc15cbda7fcdeb5e8dcc44c416b6a330cbbf70 Mon Sep 17 00:00:00 2001
>>> From: "H.J. Lu" <hjl.tools@gmail.com>
>>> Date: Mon, 10 Jul 2017 12:21:39 -0700
>>> Subject: [PATCH] Avoid backtrace from __stack_chk_fail [BZ #12189]
>>>
>>> __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.
>>>
>>>       [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          | 39 +++++++++++++++++++++++++++++++++++++++
>>>  include/stdio.h            |  3 +++
>>>  sysdeps/posix/libc_fatal.c |  3 ++-
>>>  6 files changed, 63 insertions(+), 4 deletions(-)
>>>  create mode 100644 debug/tst-ssp-1.c
>>>
>>> diff --git a/debug/Makefile b/debug/Makefile
>>> index cd4975c..10f9dea 100644
>>> --- a/debug/Makefile
>>> +++ b/debug/Makefile
>>> @@ -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
>>
>> Why explicit -O0 here?
>
> GCC 6.3 may optimize out __stack_chk_fail:
>
> [hjl@gnu-6 tmp]$ cat ssp-1.c
> int main (void)
> {
>   int i = 0;
>   char foo[30];
>
>   /* Overflow buffer.  */
>   for (i = 0; i < 400; i++)
>     foo[i] = 42;
>
>   return 1; /* fail */
> }
> [hjl@gnu-6 tmp]$ gcc -S -O2 -fstack-protector ssp-1.c
> ssp-1.c: In function ‘main’:
> ssp-1.c:8:12: warning: iteration 30 invokes undefined behavior
> [-Waggressive-loop-optimizations]
>      foo[i] = 42;
>      ~~~~~~~^~~~
> ssp-1.c:7:3: note: within this loop
>    for (i = 0; i < 400; i++)
>    ^~~
> [hjl@gnu-6 tmp]$ cat ssp-1.s
> .file "ssp-1.c"
> .section .text.startup,"ax",@progbits
> .p2align 4,,15
> .globl main
> .type main, @function
> main:
> .LFB0:
> .cfi_startproc
> movl $1, %eax
> ret
> .cfi_endproc
> .LFE0:
> .size main, .-main
> .ident "GCC: (GNU) 6.3.1 20170216 (Red Hat 6.3.1-3)"
> .section .note.GNU-stack,"",@progbits
> [hjl@gnu-6 tmp]$
>
>>> +
>>>  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
>>> diff --git a/debug/fortify_fail.c b/debug/fortify_fail.c
>>> index a31977a..13063bf 100644
>>> --- a/debug/fortify_fail.c
>>> +++ b/debug/fortify_fail.c
>>> @@ -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)
>>
>> Would be better to use bool since it is an internal function?
>
> I thought about it.  I wanted to avoid including <stdbool.h> in
> include/stdio.h.  I can add it if it is desirable.
>
>>>  {
>>>    /* 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)
>>> diff --git a/debug/stack_chk_fail.c b/debug/stack_chk_fail.c
>>> index 120d269..2f39e43 100644
>>> --- a/debug/stack_chk_fail.c
>>> +++ b/debug/stack_chk_fail.c
>>> @@ -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
>>> diff --git a/debug/tst-ssp-1.c b/debug/tst-ssp-1.c
>>> new file mode 100644
>>> index 0000000..789b035
>>> --- /dev/null
>>> +++ b/debug/tst-ssp-1.c
>>> @@ -0,0 +1,39 @@
>>> +/* Verify that __stack_chk_fail won't segfault.
>>> +   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 <signal.h>
>>> +
>>> +static int do_test (void);
>>> +#define TEST_FUNCTION do_test ()
>>> +#define EXPECTED_SIGNAL SIGABRT
>>> +#include "../test-skeleton.c"
>>
>> Use libsupport.
>
> I will take a look.
>

Done.

I am enclosing 2 patches.  The second one uses bool in __fortify_fail_abort.
If both are approved, I will squash them into one before commit.

Thanks.