Don't all __access_noerrno with stack protector from __tunables_init [BZ #21744]

  On 19/07/2017 22:11, H.J. Lu wrote:
> On Wed, Jul 19, 2017 at 5:56 PM, Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>> On 19/07/2017 18:53, H.J. Lu wrote:
>>> On Tue, Jul 18, 2017 at 6:52 AM, Adhemerval Zanella
>>> <adhemerval.zanella@linaro.org> wrote:
>>>>
>>>>
>>>> On 18/07/2017 10:44, H.J. Lu wrote:
>>>>> This should work for Linux.
>>>>>
>>>>> Thanks.
>>>>>
>>>>
>>>> Now with a proper patch:
>>>>
>>>> [PATCH] tunables: Use direct syscall for access (BZ#21744)
>>>>
>>>> The function maybe_enable_malloc_check, which is called by
>>>> __tunables_init, calls __access_noerrno.  It isn't problem when
>>>> symbol is is in ld.so, which has a special version of __access_noerrno
>>>> without stack protector.  But when glibc is built with stack protector,
>>>> maybe_enable_malloc_check in libc.a can't call the regular version of
>>>> __access_noerrno with stack protector.
>>>>
>>>> This patch changes how Linux defines the __access_noerrno to be an
>>>> inline call instead and thus preventing defining different build
>>>> rules for ld/static and shared.
>>>>
>>>>         H.J. Lu  <hongjiu.lu@intel.com>
>>>>         Adhemerval Zanella  <adhemerval.zanella@linaro.org>
>>>
>>> Missing [BZ#21744]
>>
>> Ack.
>>
>>>
>>>>         * elf/dl-tunables.c: Include not-errno.h header.
>>>>         * include/unistd.h (__access_noerrno): Remove definition.
>>>>         * sysdeps/unix/sysv/linux/access.c (__access_noerrno): Likewise.
>>>>         * sysdeps/generic/not-errno.h: New file.
>>>>         * sysdeps/unix/sysv/linux/not-errno.h: Likewise.
>>>> ---
>>>>  ChangeLog                           |  9 +++++++++
>>>>  elf/dl-tunables.c                   |  2 ++
>>>>  include/unistd.h                    |  7 -------
>>>>  sysdeps/generic/not-errno.h         | 19 +++++++++++++++++++
>>>>  sysdeps/unix/sysv/linux/access.c    | 15 ---------------
>>>>  sysdeps/unix/sysv/linux/not-errno.h | 30 ++++++++++++++++++++++++++++++
>>>>  6 files changed, 60 insertions(+), 22 deletions(-)
>>>>  create mode 100644 sysdeps/generic/not-errno.h
>>>>  create mode 100644 sysdeps/unix/sysv/linux/not-errno.h
>>>>
>>>> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
>>>> index 44c160c..231fb8c 100644
>>>> --- a/elf/dl-tunables.c
>>>> +++ b/elf/dl-tunables.c
>>>> @@ -29,6 +29,8 @@
>>>>  #define TUNABLES_INTERNAL 1
>>>>  #include "dl-tunables.h"
>>>>
>>>> +#include <not-errno.h>
>>>> +
>>>>  #if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
>>>>  # define GLIBC_TUNABLES "GLIBC_TUNABLES"
>>>>  #endif
>>>> diff --git a/include/unistd.h b/include/unistd.h
>>>> index 5b2a414..7f1c2cc 100644
>>>> --- a/include/unistd.h
>>>> +++ b/include/unistd.h
>>>> @@ -182,12 +182,5 @@ extern int __getlogin_r_loginuid (char *name, size_t namesize)
>>>>  #   include <dl-unistd.h>
>>>>  #  endif
>>>>
>>>> -#  if IS_IN (rtld) || !defined SHARED
>>>> -/* __access variant that does not set errno.  Used in very early initialization
>>>> -   code in libc.a and ld.so.  It follows access return semantics (zero for
>>>> -   sucess otherwise a value different than 0).  */
>>>> -extern __typeof (__access) __access_noerrno attribute_hidden;
>>>> -#  endif
>>>> -
>>>>  # endif
>>>>  #endif
>>>> diff --git a/sysdeps/generic/not-errno.h b/sysdeps/generic/not-errno.h
>>>> new file mode 100644
>>>> index 0000000..2aac095
>>>> --- /dev/null
>>>> +++ b/sysdeps/generic/not-errno.h
>>>> @@ -0,0 +1,19 @@
>>>> +/* Syscall wrapper that do not set errno.  Generic version.
>>>> +   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/>.  */
>>>> +
>>>> +extern __typeof (__access) __access_noerrno attribute_hidden;
>>>> diff --git a/sysdeps/unix/sysv/linux/access.c b/sysdeps/unix/sysv/linux/access.c
>>>> index 67e69bd..366b6b6 100644
>>>> --- a/sysdeps/unix/sysv/linux/access.c
>>>> +++ b/sysdeps/unix/sysv/linux/access.c
>>>> @@ -21,21 +21,6 @@
>>>>  #include <sysdep-cancel.h>
>>>>
>>>>  int
>>>> -__access_noerrno (const char *file, int type)
>>>> -{
>>>> -  int res;
>>>> -  INTERNAL_SYSCALL_DECL (err);
>>>> -#ifdef __NR_access
>>>> -  res = INTERNAL_SYSCALL_CALL (access, err, file, type);
>>>> -#else
>>>> -  res = INTERNAL_SYSCALL_CALL (faccessat, err, AT_FDCWD, file, type);
>>>> -#endif
>>>> -  if (INTERNAL_SYSCALL_ERROR_P (res, err))
>>>> -    return INTERNAL_SYSCALL_ERRNO (res, err);
>>>> -  return 0;
>>>> -}
>>>> -
>>>> -int
>>>>  __access (const char *file, int type)
>>>>  {
>>>>  #ifdef __NR_access
>>>> diff --git a/sysdeps/unix/sysv/linux/not-errno.h b/sysdeps/unix/sysv/linux/not-errno.h
>>>> new file mode 100644
>>>> index 0000000..4957038
>>>> --- /dev/null
>>>> +++ b/sysdeps/unix/sysv/linux/not-errno.h
>>>> @@ -0,0 +1,30 @@
>>>> +/* Syscall wrapper that do not set errno.  Linux version.
>>>> +   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/>.  */
>>>> +
>>>> +/* This function is used on maybe_enable_malloc_check (elf/dl-tunables.c)
>>>> +   and to avoid having to build/use multiple versions if stack protection
>>>> +   in enabled it is defined as inline.  */
>>>> +static inline int
>>>> +__access_noerrno (const char *pathname, int mode)
>>>> +{
>>>> +#ifdef __NR_access
>>>> +  return INTERNAL_SYSCALL_CALL (access, pathname, mode);
>>>> +#else
>>>> +  return INTERNAL_SYSCALL_CALL (faccessat, AT_FDCWD, file, type);
>>>> +#endif
>>>> +}
>>>
>>> These are wrong.  INTERNAL_SYSCALL_CALL needs  a dummy err.
>>> This seems to work:
>>>
>>> diff --git a/sysdeps/unix/sysv/linux/not-errno.h
>>> b/sysdeps/unix/sysv/linux/not-errno.h
>>> index 4957038160..a03c399f95 100644
>>> --- a/sysdeps/unix/sysv/linux/not-errno.h
>>> +++ b/sysdeps/unix/sysv/linux/not-errno.h
>>> @@ -23,8 +23,8 @@ static inline int
>>>  __access_noerrno (const char *pathname, int mode)
>>>  {
>>>  #ifdef __NR_access
>>> -  return INTERNAL_SYSCALL_CALL (access, pathname, mode);
>>> +  return INTERNAL_SYSCALL_CALL (access, err, pathname, mode);
>>>  #else
>>> -  return INTERNAL_SYSCALL_CALL (faccessat, AT_FDCWD, file, type);
>>> +  return INTERNAL_SYSCALL_CALL (faccessat, err, AT_FDCWD, file, type);
>>>  #endif
>>>  }
>>>
>>
>> Right, so we will need the 'INTERNAL_SYSCALL_DECL (err);' before as well.
> 
> It compiles fine without "INTERNAL_SYSCALL_DECL (err);".

It will fail for architectures that actually define 'err' to something other
than empty 'do { } while (0)' (for instance sparc and tile). Below it is an
updated patch:

--

	[BZ #21744]
	* elf/dl-tunables.c: Include not-errno.h header.
	* include/unistd.h (__access_noerrno): Remove definition.
	* sysdeps/unix/sysv/linux/access.c (__access_noerrno): Likewise.
	* sysdeps/generic/not-errno.h: New file.
	* sysdeps/unix/sysv/linux/not-errno.h: Likewise.

---

Don't all __access_noerrno with stack protector from __tunables_init [BZ #21744]

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