path_openat(): fix double fput()

commit f15133df upstream.

path_openat() jumps to the wrong place after do_tmpfile() - it has
already done path_cleanup() (as part of path_lookupat() called by
do_tmpfile()), so doing that again can lead to double fput().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[ luis: backported to 3.16:
  - adjusted context as 3.16 doesn't have path_cleanup() helper,
    introduced by 893b7775 ("fs/namei.c: new helper (path_cleanup())") ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/namei.c

@@ -3194,7 +3194,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 
 	if (unlikely(file->f_flags & __O_TMPFILE)) {
 		error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
-		goto out;
+		goto out2;
 	}
 
 	error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
@@ -3232,6 +3232,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 		path_put(&nd->root);
 	if (base)
 		fput(base);
+out2:
 	if (!(opened & FILE_OPENED)) {
 		BUG_ON(!error);
 		put_filp(file);