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Re: [PATCH] Avoid backtrace from __stack_chk_fail [BZ #12189]
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)
>