Avoid backtrace from __stack_chk_fail [BZ #12189]

  On Tue, Jul 11, 2017 at 10:49:04AM +0200, Florian Weimer wrote:
> * 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.

Done.

> 
> Could you post an example of the new output?

[hjl@gnu-tools-1 debug]$ ./tst-ssp-1
*** stack smashing detected ***: ./tst-ssp-1 terminated
(gdb) r --direct
Starting program: /export/build/gnu/glibc/build-x86_64-linux/debug/tst-ssp-1 --direct
*** stack smashing detected ***: /export/build/gnu/glibc/build-x86_64-linux/debug/tst-ssp-1 terminated

Program received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
51	}
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007ffff7a5e4e5 in __GI_abort () at abort.c:90
#2  0x00007ffff7a9db98 in __libc_message (action=action@entry=do_abort, 
    fmt=fmt@entry=0x7ffff7b9d0c2 "*** %s ***: %s terminated\n")
    at ../sysdeps/posix/libc_fatal.c:176
#3  0x00007ffff7b29a57 in __GI___fortify_fail_abort (
    do_backtrace=do_backtrace@entry=false, 
    msg=msg@entry=0x7ffff7b9d0aa "stack smashing detected")
    at fortify_fail.c:31
#4  0x00007ffff7b29a12 in __stack_chk_fail () at stack_chk_fail.c:29
#5  0x000000000040138b in do_test () at tst-ssp-1.c:42
#6  0x2a2a2a2a2a2a2a2a in ?? () <<<< Stack is corrupted
#7  0x2a2a2a2a2a2a2a2a in ?? ()
#8  0x2a2a2a2a2a2a2a2a in ?? ()
#9  0x2a2a2a2a2a2a2a2a in ?? ()


Here is the updated patch.  OK for master?


H.J.
---
__stack_chk_fail is called on corrupted stack. Stack backtrace is very
unreliable against corrupted stack.  __libc_message is changed to accept
enum __libc_message_action and call BEFORE_ABORT only if action includes
do_backtrace.  __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: Include <stdbool.h>.
	(_fortify_fail_abort): New function.
	(__fortify_fail): Call _fortify_fail_abort.
	(__fortify_fail_abort): Add a hidden definition.
	* debug/stack_chk_fail.c: Include <stdbool.h>.
	(__stack_chk_fail): Call __fortify_fail_abort, instead of
	__fortify_fail.
	* debug/tst-ssp-1.c: New file.
	* include/stdio.h (__libc_message_action): New enum.
	(__libc_message): Replace int with enum __libc_message_action.
	(__fortify_fail_abort): New hidden prototype.
	* malloc/malloc.c (malloc_printerr): Update __libc_message calls.
	* sysdeps/posix/libc_fatal.c (__libc_message): Replace int
	with enum __libc_message_action.  Call BEFORE_ABORT only if
	action includes do_backtrace.
	(__libc_fatal): Update __libc_message call.
---
 debug/Makefile             |  6 ++++++
 debug/fortify_fail.c       | 15 +++++++++++++--
 debug/stack_chk_fail.c     |  3 ++-
 debug/tst-ssp-1.c          | 45 +++++++++++++++++++++++++++++++++++++++++++++
 include/stdio.h            | 13 ++++++++++++-
 malloc/malloc.c            |  6 ++++--
 sysdeps/posix/libc_fatal.c | 11 ++++++-----
 7 files changed, 88 insertions(+), 11 deletions(-)
 create mode 100644 debug/tst-ssp-1.c
  

On 11/07/2017 10:25, H.J. Lu wrote:
> On Tue, Jul 11, 2017 at 10:49:04AM +0200, Florian Weimer wrote:
>> * 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.
> 
> Done.
> 
>>
>> Could you post an example of the new output?
> 
> [hjl@gnu-tools-1 debug]$ ./tst-ssp-1
> *** stack smashing detected ***: ./tst-ssp-1 terminated
> (gdb) r --direct
> Starting program: /export/build/gnu/glibc/build-x86_64-linux/debug/tst-ssp-1 --direct
> *** stack smashing detected ***: /export/build/gnu/glibc/build-x86_64-linux/debug/tst-ssp-1 terminated
> 
> Program received signal SIGABRT, Aborted.
> __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
> 51	}
> (gdb) bt
> #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
> #1  0x00007ffff7a5e4e5 in __GI_abort () at abort.c:90
> #2  0x00007ffff7a9db98 in __libc_message (action=action@entry=do_abort, 
>     fmt=fmt@entry=0x7ffff7b9d0c2 "*** %s ***: %s terminated\n")
>     at ../sysdeps/posix/libc_fatal.c:176
> #3  0x00007ffff7b29a57 in __GI___fortify_fail_abort (
>     do_backtrace=do_backtrace@entry=false, 
>     msg=msg@entry=0x7ffff7b9d0aa "stack smashing detected")
>     at fortify_fail.c:31
> #4  0x00007ffff7b29a12 in __stack_chk_fail () at stack_chk_fail.c:29
> #5  0x000000000040138b in do_test () at tst-ssp-1.c:42
> #6  0x2a2a2a2a2a2a2a2a in ?? () <<<< Stack is corrupted
> #7  0x2a2a2a2a2a2a2a2a in ?? ()
> #8  0x2a2a2a2a2a2a2a2a in ?? ()
> #9  0x2a2a2a2a2a2a2a2a in ?? ()
> 
> 
> Here is the updated patch.  OK for master?

LGTM.

> 
> 
> H.J.
> ---
> __stack_chk_fail is called on corrupted stack. Stack backtrace is very
> unreliable against corrupted stack.  __libc_message is changed to accept
> enum __libc_message_action and call BEFORE_ABORT only if action includes
> do_backtrace.  __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: Include <stdbool.h>.
> 	(_fortify_fail_abort): New function.
> 	(__fortify_fail): Call _fortify_fail_abort.
> 	(__fortify_fail_abort): Add a hidden definition.
> 	* debug/stack_chk_fail.c: Include <stdbool.h>.
> 	(__stack_chk_fail): Call __fortify_fail_abort, instead of
> 	__fortify_fail.
> 	* debug/tst-ssp-1.c: New file.
> 	* include/stdio.h (__libc_message_action): New enum.
> 	(__libc_message): Replace int with enum __libc_message_action.
> 	(__fortify_fail_abort): New hidden prototype.
> 	* malloc/malloc.c (malloc_printerr): Update __libc_message calls.
> 	* sysdeps/posix/libc_fatal.c (__libc_message): Replace int
> 	with enum __libc_message_action.  Call BEFORE_ABORT only if
> 	action includes do_backtrace.
> 	(__libc_fatal): Update __libc_message call.
> ---
>  debug/Makefile             |  6 ++++++
>  debug/fortify_fail.c       | 15 +++++++++++++--
>  debug/stack_chk_fail.c     |  3 ++-
>  debug/tst-ssp-1.c          | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  include/stdio.h            | 13 ++++++++++++-
>  malloc/malloc.c            |  6 ++++--
>  sysdeps/posix/libc_fatal.c | 11 ++++++-----
>  7 files changed, 88 insertions(+), 11 deletions(-)
>  create mode 100644 debug/tst-ssp-1.c
> 
> diff --git a/debug/Makefile b/debug/Makefile
> index cd4975c..c6d7872 100644
> --- a/debug/Makefile
> +++ b/debug/Makefile
> @@ -139,12 +139,18 @@ LDFLAGS-tst-backtrace4 = -rdynamic
>  LDFLAGS-tst-backtrace5 = -rdynamic
>  LDFLAGS-tst-backtrace6 = -rdynamic
>  
> +CFLAGS-tst-ssp-1.c = -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
> diff --git a/debug/fortify_fail.c b/debug/fortify_fail.c
> index a31977a..c90d384 100644
> --- a/debug/fortify_fail.c
> +++ b/debug/fortify_fail.c
> @@ -17,17 +17,28 @@
>  
>  #include <stdio.h>
>  #include <stdlib.h>
> +#include <stdbool.h>
>  
>  
>  extern char **__libc_argv attribute_hidden;
>  
>  void
>  __attribute__ ((noreturn)) internal_function
> -__fortify_fail (const char *msg)
> +__fortify_fail_abort (_Bool do_backtrace, const char *msg)
>  {
>    /* The loop is added only to keep gcc happy.  */
>    while (1)
> -    __libc_message (2, "*** %s ***: %s terminated\n",
> +    __libc_message (do_backtrace ? (do_abort | do_backtrace) : do_abort,
> +		    "*** %s ***: %s terminated\n",
>  		    msg, __libc_argv[0] ?: "<unknown>");
>  }
> +
> +void
> +__attribute__ ((noreturn)) internal_function
> +__fortify_fail (const char *msg)
> +{
> +  __fortify_fail_abort (true, 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..4b099b5 100644
> --- a/debug/stack_chk_fail.c
> +++ b/debug/stack_chk_fail.c
> @@ -17,6 +17,7 @@
>  
>  #include <stdio.h>
>  #include <stdlib.h>
> +#include <stdbool.h>
>  
>  
>  extern char **__libc_argv attribute_hidden;
> @@ -25,7 +26,7 @@ void
>  __attribute__ ((noreturn))
>  __stack_chk_fail (void)
>  {
> -  __fortify_fail ("stack smashing detected");
> +  __fortify_fail_abort (false, "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..52c67e2
> --- /dev/null
> +++ b/debug/tst-ssp-1.c
> @@ -0,0 +1,45 @@
> +/* 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 void
> +__attribute__ ((noinline, noclone))
> +test (char *foo)
> +{
> +  int i;
> +
> +  /* smash stack */
> +  for (i = 0; i <= 400; i++)
> +    foo[i] = 42;
> +}
> +
> +static int
> +do_test (void)
> +{
> +  char foo[30];
> +
> +  test (foo);
> +
> +  return 1; /* fail */
> +}
> +
> +#define EXPECTED_SIGNAL SIGABRT
> +#include <support/test-driver.c>
> diff --git a/include/stdio.h b/include/stdio.h
> index f68f633..215f919 100644
> --- a/include/stdio.h
> +++ b/include/stdio.h
> @@ -86,13 +86,24 @@ extern int __gen_tempname (char *__tmpl, int __suffixlen, int __flags,
>  #  define __GT_DIR	1	/* create a directory */
>  #  define __GT_NOCREATE	2	/* just find a name not currently in use */
>  
> +enum __libc_message_action
> +{
> +  do_message	= 0,		/* Print message.  */
> +  do_abort	= 1 << 0,	/* Abort.  */
> +  do_backtrace	= 1 << 1	/* Backtrace.  */
> +};
> +
>  /* Print out MESSAGE on the error output and abort.  */
>  extern void __libc_fatal (const char *__message)
>       __attribute__ ((__noreturn__));
> -extern void __libc_message (int do_abort, const char *__fnt, ...);
> +extern void __libc_message (enum __libc_message_action action,
> +			    const char *__fnt, ...);
>  extern void __fortify_fail (const char *msg)
>       __attribute__ ((__noreturn__)) internal_function;
> +extern void __fortify_fail_abort (_Bool, 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);
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 2527e25..54e406b 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -5397,7 +5397,8 @@ malloc_printerr (int action, const char *str, void *ptr, mstate ar_ptr)
>      set_arena_corrupt (ar_ptr);
>  
>    if ((action & 5) == 5)
> -    __libc_message (action & 2, "%s\n", str);
> +    __libc_message ((action & 2) ? (do_abort | do_backtrace) : do_message,
> +		    "%s\n", str);
>    else if (action & 1)
>      {
>        char buf[2 * sizeof (uintptr_t) + 1];
> @@ -5407,7 +5408,8 @@ malloc_printerr (int action, const char *str, void *ptr, mstate ar_ptr)
>        while (cp > buf)
>          *--cp = '0';
>  
> -      __libc_message (action & 2, "*** Error in `%s': %s: 0x%s ***\n",
> +      __libc_message ((action & 2) ? (do_abort | do_backtrace) : do_message,
> +		      "*** Error in `%s': %s: 0x%s ***\n",
>                        __libc_argv[0] ? : "<unknown>", str, cp);
>      }
>    else if (action & 2)
> diff --git a/sysdeps/posix/libc_fatal.c b/sysdeps/posix/libc_fatal.c
> index b261963..25af8bd 100644
> --- a/sysdeps/posix/libc_fatal.c
> +++ b/sysdeps/posix/libc_fatal.c
> @@ -64,7 +64,7 @@ struct str_list
>  
>  /* Abort with an error message.  */
>  void
> -__libc_message (int do_abort, const char *fmt, ...)
> +__libc_message (enum __libc_message_action action, const char *fmt, ...)
>  {
>    va_list ap;
>    int fd = -1;
> @@ -140,7 +140,7 @@ __libc_message (int do_abort, const char *fmt, ...)
>  
>        written = WRITEV_FOR_FATAL (fd, iov, nlist, total);
>  
> -      if (do_abort)
> +      if ((action & do_abort))
>  	{
>  	  total = ((total + 1 + GLRO(dl_pagesize) - 1)
>  		   & ~(GLRO(dl_pagesize) - 1));
> @@ -167,9 +167,10 @@ __libc_message (int do_abort, const char *fmt, ...)
>  
>    va_end (ap);
>  
> -  if (do_abort)
> +  if ((action & do_abort))
>      {
> -      BEFORE_ABORT (do_abort, written, fd);
> +      if ((action & do_backtrace))
> +	BEFORE_ABORT (do_abort, written, fd);
>  
>        /* Kill the application.  */
>        abort ();
> @@ -182,6 +183,6 @@ __libc_fatal (const char *message)
>  {
>    /* The loop is added only to keep gcc happy.  */
>    while (1)
> -    __libc_message (1, "%s", message);
> +    __libc_message (do_abort | do_backtrace, "%s", message);
>  }
>  libc_hidden_def (__libc_fatal)
>
  

* H. J. Lu:

> +CFLAGS-tst-ssp-1.c = -fstack-protector

This should be -fstack-protector-all, in case the the stack protector
heuristics do not instrument a thirty-byte array.
  

On Tue, Jul 11, 2017 at 12:39 PM, Florian Weimer <fw@deneb.enyo.de> wrote:
> * H. J. Lu:
>
>> +CFLAGS-tst-ssp-1.c = -fstack-protector
>
> This should be -fstack-protector-all, in case the the stack protector
> heuristics do not instrument a thirty-byte array.

Does GCC 4.9 support  -fstack-protector-all?
  

* H. J. Lu:

> On Tue, Jul 11, 2017 at 12:39 PM, Florian Weimer <fw@deneb.enyo.de> wrote:
>> * H. J. Lu:
>>
>>> +CFLAGS-tst-ssp-1.c = -fstack-protector
>>
>> This should be -fstack-protector-all, in case the the stack protector
>> heuristics do not instrument a thirty-byte array.
>
> Does GCC 4.9 support  -fstack-protector-all?

It's mentioned in

<https://gcc.gnu.org/onlinedocs/gcc-4.4.2/gcc/Optimize-Options.html>

so I assume it does.  (-fstack-protector-strong is the recent
addition.)