Distinguish ELOOP diagnosis threshold from SYMLOOP_MAX.

9 files changed, 159 insertions, 23 deletions

diff --git a/ChangeLog b/ChangeLog
index b31e23f..47f1338 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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]
diff --git a/elf/chroot_canon.c b/elf/chroot_canon.c
index a7a7d9b..397125f 100644
--- a/elf/chroot_canon.c
+++ b/elf/chroot_canon.c
@@ -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;
diff --git a/hurd/lookup-retry.c b/hurd/lookup-retry.c
index 4fa2a21..c95ca0f 100644
--- a/hurd/lookup-retry.c
+++ b/hurd/lookup-retry.c
@@ -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;
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 876b482..aeff804 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -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;
diff --git a/sysdeps/generic/eloop-threshold.h b/sysdeps/generic/eloop-threshold.h
new file mode 100644
index 0000000..2342d29
--- /dev/null
+++ b/sysdeps/generic/eloop-threshold.h
@@ -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 */
diff --git a/sysdeps/mach/hurd/bits/local_lim.h b/sysdeps/mach/hurd/bits/local_lim.h
index 48411d0..c957dad 100644
--- a/sysdeps/mach/hurd/bits/local_lim.h
+++ b/sysdeps/mach/hurd/bits/local_lim.h
@@ -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
diff --git a/sysdeps/mach/hurd/eloop-threshold.h b/sysdeps/mach/hurd/eloop-threshold.h
new file mode 100644
index 0000000..b8fae16
--- /dev/null
+++ b/sysdeps/mach/hurd/eloop-threshold.h
@@ -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 */
diff --git a/sysdeps/mach/hurd/sys/param.h b/sysdeps/mach/hurd/sys/param.h
index 42f4f46..e58d517 100644
--- a/sysdeps/mach/hurd/sys/param.h
+++ b/sysdeps/mach/hurd/sys/param.h
@@ -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
diff --git a/sysdeps/mach/hurd/sysconf.c b/sysdeps/mach/hurd/sysconf.c
new file mode 100644
index 0000000..6d1666d
--- /dev/null
+++ b/sysdeps/mach/hurd/sysconf.c
@@ -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>