locale: don't crash if locale-archive contains all zeros

In case of power failure followed by filesystem issues locale-archive
can end-up containing all zeros. In that case all calls to setlocale()
generate a SIGFPE. This renders a system with a default non-C locale
unbootable.

Avoid this by ignoring the locale instead of generating a SIGFPE.

ChangeLog

@@ -1,3 +1,8 @@
+2013-12-03  Aurelien Jarno  <aurelien@aurel32.net>
+
+	* locale/loadarchive.c (_nl_load_locale_from_archive): Avoid
+	division by 0.
+
 2013-12-03  Siddhesh Poyarekar  <siddhesh@redhat.com>
 
 	[BZ #16195]

locale/loadarchive.c

@@ -274,6 +274,10 @@ _nl_load_locale_from_archive (int category, const char **namep)
   namehashtab = (struct namehashent *) ((char *) head
 					+ head->namehash_offset);
 
+  /* Avoid division by 0 if the file is corrupted.  */
+  if (__glibc_unlikely (head->namehash_size == 0))
+    goto close_and_out;
+
   idx = hval % head->namehash_size;
   incr = 1 + hval % (head->namehash_size - 2);