ldconfig: set LC_COLLATE to C [BZ #22505]

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.

3 files changed, 13 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 67d11c9f9a..815e73571d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-12-16  Aurelien Jarno  <aurelien@aurel32.net>
+
+	[BZ #22505]
+	* elf/ldconfig.c (main): Call setlocale to force LC_COLLATE to C.
+
 2017-12-16  Rajalakshmi Srinivasaraghavan  <raji@linux.vnet.ibm.com>
 
 	* sysdeps/s390/fpu/libm-test-ulps: Update.
diff --git a/NEWS b/NEWS
index 61fed654d8..0670585b4c 100644
--- a/NEWS
+++ b/NEWS
@@ -63,6 +63,10 @@ Major new features:
 
 * Optimized memcpy, mempcpy, memmove, and memset for sparc M7.
 
+* The ldconfig utility now processes `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);