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

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

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.