Re: [PATCH] Remove debug/stack_chk_fail_local.c [BZ #21740]

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Jul 10, 2017 at 6:14 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Jul 10, 2017 at 11:50:02AM +0100, Nick Alcock wrote:
>> On 9 Jul 2017, H. J. Lu verbalised:
>>
>> > Since
>> >
>> > commit 524a8ef2ad76af8ac049293d993a1856b0d888fb
>> > Author: Nick Alcock <nick.alcock@oracle.com>
>> > Date:   Mon Dec 26 10:08:57 2016 +0100
>> >
>> >     PLT avoidance for __stack_chk_fail [BZ #7065]
>> >
>> >     Add a hidden __stack_chk_fail_local alias to libc.so,
>> >     and make sure that on targets which use __stack_chk_fail,
>> >     this does not introduce a local PLT reference into libc.so.
>> >
>> > added
>> >
>> > strong_alias (__stack_chk_fail, __stack_chk_fail_local)
>> >
>> > to debug/stack_chk_fail.c, debug/stack_chk_fail_local.c should be
>> > removed.
>> >
>> > OK for master?
>>
>> If it passes a test build with --enable-stack-protector=all without
>> pulling junk into ld.so and exploding at ld.so link time, sure. (That's
>> what happened every time I tried to remove this stuff before, but I may
>> have failed to notice that this may not be necessary any more.)
>
> Here is the updated patch.  tst-_dl_addr_inside_object should be
> linked with $(dummy-stack-chk-fail).  Otherwise, __stack_chk_fail is
> undefined.  OK for master branch?
>
>>
>> > -/* On some architectures, this helps needless PIC pointer setup
>> > -   that would be needed just for the __stack_chk_fail call.  */
>>
>> Does anyone know what architectures these might be? Presumably x86-32...
>>
>
> config/i386/i386.c:   __stack_chk_fail_local hidden function instead of calling
> config/powerpcspe/powerpcspe.c:   setup by using __stack_chk_fail_local hidden function instead of
> config/rs6000/rs6000.c:   setup by using __stack_chk_fail_local hidden function instead of
>
>
> H.J.
> --
> From 712e70de9743a61618001b4c6372a0e3d4fc1d90 Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Sun, 9 Jul 2017 08:39:17 -0700
> Subject: [PATCH] Remove debug/stack_chk_fail_local.c [BZ #21740]
>
> Since
>
> commit 524a8ef2ad76af8ac049293d993a1856b0d888fb
> Author: Nick Alcock <nick.alcock@oracle.com>
> Date:   Mon Dec 26 10:08:57 2016 +0100
>
>     PLT avoidance for __stack_chk_fail [BZ #7065]
>
>     Add a hidden __stack_chk_fail_local alias to libc.so,
>     and make sure that on targets which use __stack_chk_fail,
>     this does not introduce a local PLT reference into libc.so.
>
> added
>
> strong_alias (__stack_chk_fail, __stack_chk_fail_local)
>
> to debug/stack_chk_fail.c, debug/stack_chk_fail_local.c should be
> removed.  Since dummy __stack_chk_fail and __stack_chk_fail_local
> symbols are used in ld.so, tst-_dl_addr_inside_object should be
> linked with $(dummy-stack-chk-fail).   Tested on x86-64 with
> --enable-stack-protector=all and got
>
> FAIL: elf/tst-env-setuid
> FAIL: elf/tst-env-setuid-tunables
> FAIL: stdlib/tst-secure-getenv
>
> which are the same as without this patch.
>
>         * [BZ #21740]
>         * debug/Makefile (static-only-routines): Remove
>         stack_chk_fail_local.
>         * debug/stack_chk_fail_local.c: Removed.
>         * elf/Makefile (LDFLAGS-tst-_dl_addr_inside_object): New.
> ---
>  debug/Makefile               |  2 +-
>  debug/stack_chk_fail_local.c | 46 --------------------------------------------
>  elf/Makefile                 |  1 +
>  3 files changed, 2 insertions(+), 47 deletions(-)
>  delete mode 100644 debug/stack_chk_fail_local.c
>
> diff --git a/debug/Makefile b/debug/Makefile
> index cd4975c..136c9a1 100644
> --- a/debug/Makefile
> +++ b/debug/Makefile
> @@ -51,7 +51,7 @@ routines  = backtrace backtracesyms backtracesymsfd noophooks \
>             explicit_bzero_chk \
>             stack_chk_fail fortify_fail \
>             $(static-only-routines)
> -static-only-routines := warning-nop stack_chk_fail_local
> +static-only-routines := warning-nop
>
>  # Building the stack-protector failure routines with stack protection
>  # makes no sense.
> diff --git a/debug/stack_chk_fail_local.c b/debug/stack_chk_fail_local.c
> deleted file mode 100644
> index eb0a759..0000000
> --- a/debug/stack_chk_fail_local.c
> +++ /dev/null
> @@ -1,46 +0,0 @@
> -/* Copyright (C) 2005-2017 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.
> -
> -   In addition to the permissions in the GNU Lesser General Public
> -   License, the Free Software Foundation gives you unlimited
> -   permission to link the compiled version of this file with other
> -   programs, and to distribute those programs without any restriction
> -   coming from the use of this file. (The GNU Lesser General Public
> -   License restrictions do apply in other respects; for example, they
> -   cover modification of the file, and distribution when not linked
> -   into another program.)
> -
> -   Note that people who make modified versions of this file are not
> -   obligated to grant this special exception for their modified
> -   versions; it is their choice whether to do so. The GNU Lesser
> -   General Public License gives permission to release a modified
> -   version without this exception; this exception also makes it
> -   possible to release a modified version which carries forward this
> -   exception.
> -
> -   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/>.  */
> -
> -#include <sys/cdefs.h>
> -
> -extern void __stack_chk_fail (void) __attribute__ ((noreturn));
> -
> -/* On some architectures, this helps needless PIC pointer setup
> -   that would be needed just for the __stack_chk_fail call.  */
> -
> -void __attribute__ ((noreturn)) attribute_hidden
> -__stack_chk_fail_local (void)
> -{
> -  __stack_chk_fail ();
> -}
> diff --git a/elf/Makefile b/elf/Makefile
> index e758a4c..fb2d855 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -369,6 +369,7 @@ tests-internal += tst-_dl_addr_inside_object
>  tests-pie += tst-_dl_addr_inside_object
>  $(objpfx)tst-_dl_addr_inside_object: $(objpfx)dl-addr-obj.os
>  CFLAGS-tst-_dl_addr_inside_object.c += $(PIE-ccflag)
> +LDFLAGS-tst-_dl_addr_inside_object = $(dummy-stack-chk-fail)
>  endif
>
>  # By default tst-linkall-static should try to use crypt routines to test
> --
> 2.9.4
>

This patch is incorrect.  A testcase is missing to catch the error.


-- 
H.J.