https://bugzilla.redhat.com/show_bug.cgi?id=688980
http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=e1fb097f447a89aa69a926e45e673a52d86a6c57

--- misc/mntent_r.c	2011-11-25 13:33:42.000000000 +0000
+++ misc/mntent_r.c.oden	2011-11-25 13:33:38.000000000 +0000
@@ -263,8 +263,8 @@ __addmntent (FILE *stream, const struct
 		   mntcopy.mnt_type,
 		   mntcopy.mnt_opts,
 		   mntcopy.mnt_freq,
-		   mntcopy.mnt_passno)
-	  < 0 ? 1 : 0);
+		   mntcopy.mnt_passno) < 0
+	  || fflush (stream) != 0);
 }
 weak_alias (__addmntent, addmntent)