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Distinguish ELOOP diagnosis threshold from SYMLOOP_MAX.

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Roland McGrath 2012-08-01 10:33:11 -07:00
parent 0c41943a4d
commit 4f75b7a09a
9 changed files with 159 additions and 23 deletions
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13
ChangeLog
View file

@ -1,3 +1,16 @@
2012-08-03 Roland McGrath <roland@hack.frob.com>
* sysdeps/mach/hurd/sys/param.h (MAXSYMLINKS): Macro removed.
* sysdeps/mach/hurd/bits/local_lim.h (SYMLOOP_MAX): Macro removed.
* sysdeps/mach/hurd/eloop-threshold.h: New file.
* hurd/lookup-retry.c (__hurd_file_name_lookup_retry): Use
__eloop_threshold instead of SYMLOOP_MAX.
* sysdeps/generic/eloop-threshold.h: New file.
* stdlib/canonicalize.c (__realpath): Use __eloop_threshold instead
of MAXSYMLINKS.
* elf/chroot_canon.c (chroot_canon): Likewise.
2012-08-03 Joseph Myers <joseph@codesourcery.com>
[BZ #13717]

7
elf/chroot_canon.c
View file

@ -1,6 +1,5 @@
/* Return the canonical absolute name of a given file inside chroot.
Copyright (C) 1996,1997,1998,1999,2000,2001,2004,2005,2010,2011
Free Software Foundation, Inc.
Copyright (C) 1996-2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
This program is free software; you can redistribute it and/or modify
@ -20,12 +19,12 @@
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <eloop-threshold.h>
#include <ldconfig.h>
#ifndef PATH_MAX
@ -127,7 +126,7 @@ chroot_canon (const char *chroot, const char *name)
char *buf = alloca (PATH_MAX);
size_t len;
if (++num_links > MAXSYMLINKS)
if (++num_links > __eloop_threshold ())
{
__set_errno (ELOOP);
goto error;

5
hurd/lookup-retry.c
View file

@ -24,6 +24,7 @@
#include <fcntl.h>
#include <string.h>
#include <_itoa.h>
#include <eloop-threshold.h>
/* Translate the error from dir_lookup into the error the user sees. */
static inline error_t
@ -103,7 +104,7 @@ __hurd_file_name_lookup_retry (error_t (*use_init_port)
/* Fall through. */
case FS_RETRY_NORMAL:
if (nloops++ >= SYMLOOP_MAX)
if (nloops++ >= __eloop_threshold ())
{
__mach_port_deallocate (__mach_task_self (), *result);
return ELOOP;
@ -180,7 +181,7 @@ __hurd_file_name_lookup_retry (error_t (*use_init_port)
dirport = INIT_PORT_CRDIR;
if (*result != MACH_PORT_NULL)
__mach_port_deallocate (__mach_task_self (), *result);
if (nloops++ >= SYMLOOP_MAX)
if (nloops++ >= __eloop_threshold ())
return ELOOP;
file_name = &retryname[1];
break;

6
stdlib/canonicalize.c
View file

@ -1,5 +1,5 @@
/* Return the canonical absolute name of a given file.
Copyright (C) 1996-2002,2004,2005,2006,2008 Free Software Foundation, Inc.
Copyright (C) 1996-2012 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
@ -21,11 +21,11 @@
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <stddef.h>
#include <eloop-threshold.h>
#include <shlib-compat.h>
/* Return the canonical absolute name of file NAME. A canonical name
@ -166,7 +166,7 @@ __realpath (const char *name, char *resolved)
char *buf = __alloca (path_max);
size_t len;
if (++num_links > MAXSYMLINKS)
if (++num_links > __eloop_threshold ())
{
__set_errno (ELOOP);
goto error;

72
sysdeps/generic/eloop-threshold.h Normal file
View file

@ -0,0 +1,72 @@
/* Threshold at which to diagnose ELOOP. Generic version.
Copyright (C) 2012 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/>. */
#ifndef _ELOOP_THRESHOLD_H
#define _ELOOP_THRESHOLD_H 1
#include <limits.h>
#include <sys/param.h>
/* POSIX specifies SYMLOOP_MAX as the "Maximum number of symbolic
links that can be reliably traversed in the resolution of a
pathname in the absence of a loop." This makes it a minimum that
we should certainly accept. But it leaves open the possibility
that more might sometimes work--just not "reliably".
For example, Linux implements a complex policy whereby there is a
small limit on the number of direct symlink traversals (a symlink
to a symlink to a symlink), but larger limit on the total number of
symlink traversals overall. Hence the SYMLOOP_MAX number should be
the small one, but the limit library functions enforce on users
should be the larger one.
So, we use the larger of the reported SYMLOOP_MAX (if any) and our
own constant MIN_ELOOP_THRESHOLD, below. This constant should be
large enough that it never rules out a file name and directory tree
that the underlying system (i.e. calls to 'open' et al) would
resolve successfully. It should be small enough that actual loops
are detected without a huge number of iterations. */
#ifndef MIN_ELOOP_THRESHOLD
# define MIN_ELOOP_THRESHOLD 40
#endif
/* Return the maximum number of symlink traversals to permit
before diagnosing ELOOP. */
static inline unsigned int __attribute__ ((const))
__eloop_threshold (void)
{
#ifdef SYMLOOP_MAX
const int symloop_max = SYMLOOP_MAX;
#else
/* The function is marked 'const' even though we use memory and
call a function, because sysconf is required to return the
same value in every call and so it must always be safe to
call __eloop_threshold exactly once and reuse the value. */
static long int sysconf_symloop_max;
if (sysconf_symloop_max == 0)
sysconf_symloop_max = __sysconf (_SC_SYMLOOP_MAX);
const unsigned int symloop_max = (sysconf_symloop_max <= 0
? _POSIX_SYMLOOP_MAX
: sysconf_symloop_max);
#endif
return MAX (symloop_max, MIN_ELOOP_THRESHOLD);
}
#endif /* eloop-threshold.h */

13
sysdeps/mach/hurd/bits/local_lim.h
View file

@ -1,5 +1,5 @@
/* Minimum guaranteed maximum values for system limits. Hurd version.
Copyright (C) 1993,94,96,98,2002 Free Software Foundation, Inc.
Copyright (C) 1993-2012 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
@ -32,14 +32,3 @@
suitable, and `sysconf' will return a number at least as large. */
#define NGROUPS_MAX 256
/* The maximum number of symbolic links that are allowed in a single file
name resolution. When a further link is encountered, the call returns
ELOOP. This name is a GNU extension; POSIX.1 has no such limit, and BSD
calls it MAXSYMLINKS in <sys/param.h>. (We define the name under
_BSD_SOURCE even without _GNU_SOURCE because our <sys/param.h> uses it
to define MAXSYMLINKS.) */
#if defined __USE_GNU || defined __USE_BSD /* 1003.1a defines this */
#define SYMLOOP_MAX 8
#endif

37
sysdeps/mach/hurd/eloop-threshold.h Normal file
View file

@ -0,0 +1,37 @@
/* Threshold at which to diagnose ELOOP. Hurd version.
Copyright (C) 2012 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/>. */
#ifndef _ELOOP_THRESHOLD_H
#define _ELOOP_THRESHOLD_H 1
/* Return the maximum number of symlink traversals to permit
before diagnosing ELOOP.
In the Hurd version, here we are actually setting the only policy
there is on the system. We use a literal number here rather than
defining SYMLOOP_MAX so that programs don't compile in a number
but instead use sysconf and the number can be changed here to
affect sysconf's result. */
static inline unsigned int __attribute__ ((const))
__eloop_threshold (void)
{
return 32;
}
#endif /* eloop-threshold.h */

3
sysdeps/mach/hurd/sys/param.h
View file

@ -1,4 +1,4 @@
/* Copyright (C) 1993,1994,1995,1997,1999,2011 Free Software Foundation, Inc.
/* Copyright (C) 1993-2012 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
@ -83,7 +83,6 @@
#define NBBY CHAR_BIT
#define NGROUPS NGROUPS_MAX
#define MAXSYMLINKS SYMLOOP_MAX
#define CANBSIZ MAX_CANON /* XXX ? */
/* ARG_MAX is unlimited, but we define NCARGS for BSD programs that want to

26
sysdeps/mach/hurd/sysconf.c Normal file
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@ -0,0 +1,26 @@
/* Return values of system parameters. Hurd version.
Copyright (C) 2012 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/>. */
#include <limits.h>
#include <unistd.h>
#include <eloop-threshold.h>
#define SYMLOOP_MAX (__eloop_threshold ())
#include <sysdeps/posix/sysconf.c>