diff -Naurp util-linux-ng-2.17.1/mount/fstab.c util-linux-ng-2.17.1.oden/mount/fstab.c
--- util-linux-ng-2.17.1/mount/fstab.c	2010-02-16 08:58:57.000000000 +0000
+++ util-linux-ng-2.17.1.oden/mount/fstab.c	2012-05-29 08:30:23.000000000 +0000
@@ -773,7 +773,7 @@ update_mtab (const char *dir, struct my_
 	mntFILE *mfp, *mftmp;
 	const char *fnam = _PATH_MOUNTED;
 	struct mntentchn mtabhead;	/* dummy */
-	struct mntentchn *mc, *mc0, *absent = NULL;
+	struct mntentchn *mc, *mc0 = NULL, *absent = NULL;
 	struct stat sbuf;
 	int fd;
 
@@ -797,10 +797,12 @@ update_mtab (const char *dir, struct my_
 	read_mntentchn(mfp, fnam, mc);
 
 	/* find last occurrence of dir */
-	for (mc = mc0->prev; mc && mc != mc0; mc = mc->prev)
-		if (streq(mc->m.mnt_dir, dir))
-			break;
-	if (mc && mc != mc0) {
+	if (dir) {
+		for (mc = mc0->prev; mc && mc != mc0; mc = mc->prev)
+			if (streq(mc->m.mnt_dir, dir))
+				break;
+	}
+	if (dir && mc && mc != mc0) {
 		if (instead == NULL) {
 			/* An umount - remove entry */
 			if (mc && mc != mc0) {
@@ -846,19 +848,32 @@ update_mtab (const char *dir, struct my_
 		int errsv = errno;
 		error (_("cannot open %s (%s) - mtab not updated"),
 		       _PATH_MOUNTED_TMP, strerror (errsv));
-		discard_mntentchn(mc0);
 		goto leave;
 	}
 
 	for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt) {
 		if (my_addmntent(mftmp, &(mc->m)) == 1) {
 			int errsv = errno;
-			die (EX_FILEIO, _("error writing %s: %s"),
+			error(_("error writing %s: %s"),
 			     _PATH_MOUNTED_TMP, strerror (errsv));
+			goto leave;
 		}
 	}
 
 	discard_mntentchn(mc0);
+	mc0 = NULL;
+
+	/*
+	 * We have to be paranoid with write() to avoid incomplete
+	 * /etc/mtab. Users are able to control writing by RLIMIT_FSIZE.
+	 */
+	if (fflush(mftmp->mntent_fp) != 0) {
+		int errsv = errno;
+		error (_("%s: cannot fflush changes: %s"),
+			_PATH_MOUNTED_TMP, strerror (errsv));
+		goto leave;
+	}
+
 	fd = fileno(mftmp->mntent_fp);
 
 	/*
@@ -900,6 +915,9 @@ update_mtab (const char *dir, struct my_
 	}
 
  leave:
+	if (mc0)
+		discard_mntentchn(mc0);
+	unlink(_PATH_MOUNTED_TMP);
 	unlock_mtab();
 }
 
diff -Naurp util-linux-ng-2.17.1/mount/mount.c util-linux-ng-2.17.1.oden/mount/mount.c
--- util-linux-ng-2.17.1/mount/mount.c	2012-05-29 08:28:47.000000000 +0000
+++ util-linux-ng-2.17.1.oden/mount/mount.c	2012-05-29 08:30:23.000000000 +0000
@@ -1275,6 +1275,7 @@ update_mtab_entry(const char *spec, cons
 			printf(_("mount: no %s found - creating it..\n"),
 			       _PATH_MOUNTED);
 		create_mtab ();
+
 	}
 
 	if (!nomtab && mtab_is_writable()) {
@@ -1282,25 +1283,8 @@ update_mtab_entry(const char *spec, cons
 			update_mtab (mnt.mnt_dir, &mnt);
 		else if (flags & MS_MOVE)
 			update_mtab(mnt.mnt_fsname, &mnt);
-		else {
-			mntFILE *mfp;
-
-			lock_mtab();
-			mfp = my_setmntent(_PATH_MOUNTED, "a+");
-			if (mfp == NULL || mfp->mntent_fp == NULL) {
-				int errsv = errno;
-				error(_("mount: can't open %s: %s"), _PATH_MOUNTED,
-				      strerror (errsv));
-			} else {
-				if ((my_addmntent (mfp, &mnt)) == 1) {
-					int errsv = errno;
-					error(_("mount: error writing %s: %s"),
-					      _PATH_MOUNTED, strerror (errsv));
-				}
-			}
-			my_endmntent(mfp);
-			unlock_mtab();
-		}
+		else
+			update_mtab(NULL, &mnt);
 	}
 	my_free(mnt.mnt_fsname);
 	my_free(mnt.mnt_dir);