From aa1e138422a6bd04a7b0cbd425919cbd834cd395 Mon Sep 17 00:00:00 2001
From: Jeff Mahoney <jeffm@suse.com>
Date: Wed, 21 Sep 2016 08:31:29 -0400
Subject: [PATCH] btrfs: ensure that file descriptor used with subvol ioctls is
 a dir

commit 325c50e3cebb9208009083e841550f98a863bfa0 upstream.

If the subvol/snapshot create/destroy ioctls are passed a regular file
with execute permissions set, we'll eventually Oops while trying to do
inode->i_op->lookup via lookup_one_len.

This patch ensures that the file descriptor refers to a directory.

Fixes: cb8e70901d (Btrfs: Fix subvolume creation locking rules)
Fixes: 76dda93c6a (Btrfs: add snapshot/subvolume destroy ioctl)
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
[bwh: Backported to 3.2:
 - Open-code file_inode()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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