[PATCH v2] ldconfig: set LC_COLLATE to C [BZ #22505]

[Aurelien Jarno <aurelien at aurel32 dot net>]

ldconfig supports `include' directives and use the glob function to
process them. The glob function sort entries according to the LC_COLLATE
category. When using a standard "include /etc/ld.so.conf.d/*.conf" entry
in /etc/ld.so.conf, the order therefore depends on the locale used to
run ldconfig. A few examples of locale specific order that might be
disturbing in that context compared to the C locale:
- The cs_CZ and sk_SK locales sort the digits after the letters.
- The et_EE locale sorts the 'z' between 's' and 't'.

This patch fixes that by setting LC_COLLATE to C in order to process
files in deterministic order, independently of the locale used to launch
ldconfig.

NOTE: This should NOT be backported to older release branches.

Changelog:
	[BZ #22505]
	* elf/ldconfig.c (main): Call setlocale to force LC_COLLATE to C.
---
 ChangeLog      | 5 +++++
 NEWS           | 4 ++++
 elf/ldconfig.c | 4 ++++
 3 files changed, 13 insertions(+)


It seems the discussion about doing the change in two steps hasn't
really converged, so I have implemented the single step version. I also
noted that it requires a packaging change doc entry on the Wiki. I'll
copy the NEWS entry there once the commit has been applied to master.

diff --git a/ChangeLog b/ChangeLog
index 8c042b8be6..2899c77fda 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-11-30  Aurelien Jarno  <aurelien@aurel32.net>
+
+	[BZ #22505]
+	* elf/ldconfig.c (main): Call setlocale to force LC_COLLATE to C.
+
 2017-11-30  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/m68k/m680x0/fpu/s_llrint.c: Include
diff --git a/NEWS b/NEWS
index f3fdf9aec5..df699c6997 100644
--- a/NEWS
+++ b/NEWS
@@ -43,6 +43,10 @@ Major new features:
 
 * glibc now implements the memfd_create and mlock2 functions on Linux.
 
+* The ldconfig utility now process `include' directives using the C/POSIX
+  collation ordering.  Previous glibc versions used locale-specific
+  ordering, the change might break systems that relied on that.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * On GNU/Linux, the obsolete Linux constant PTRACE_SEIZE_DEVEL is no longer
diff --git a/elf/ldconfig.c b/elf/ldconfig.c
index 89042351f8..2c01ab567b 100644
--- a/elf/ldconfig.c
+++ b/elf/ldconfig.c
@@ -1259,6 +1259,10 @@ main (int argc, char **argv)
   /* Set locale via LC_ALL.  */
   setlocale (LC_ALL, "");
 
+  /* But keep the C collation.  That way `include' directives using
+     globbing patterns are processed in a locale-independent order.  */
+  setlocale (LC_COLLATE, "C");
+
   /* Set the text message domain.  */
   textdomain (_libc_intl_domainname);
 
-- 
2.15.0