This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] Avoid backtrace from __stack_chk_fail [BZ #12189]
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?
> +
> 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?
> {
> /* 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.
> +
> +static int
> +do_test (void)
> +{
> + int i;
> + char foo[30];
> +
> + // smash stack
> + for (i = 0; i <= 400; i++)
> + foo[i] = 42;
> +
> + return 1; /* fail */
> +}
> diff --git a/include/stdio.h b/include/stdio.h
> index f68f633..31dc7a6 100644
> --- a/include/stdio.h
> +++ b/include/stdio.h
> @@ -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);
> diff --git a/sysdeps/posix/libc_fatal.c b/sysdeps/posix/libc_fatal.c
> index b261963..a0cd8b2 100644
> --- a/sysdeps/posix/libc_fatal.c
> +++ b/sysdeps/posix/libc_fatal.c
> @@ -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 ();
> -- 2.9.4
>