[PATCH] fuse: fix race conditions on fi->nlookup

[yangyun]

Lock on fi->nlookup is missed in fuse_fill_super_submount(). Add lock
on it to prevent race conditions.

Fixes: 1866d779d5d2 ("fuse: Allow fuse_fill_super_common() for submounts")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: yangyun <yangyun50@xxxxxxxxxx>
---
 fs/fuse/inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 99e44ea7d875..2e220f245ceb 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1593,7 +1593,9 @@ static int fuse_fill_super_submount(struct super_block *sb,
 	 * that, though, so undo it here.
 	 */
 	fi = get_fuse_inode(root);
+	spin_lock(&fi->lock);
 	fi->nlookup--;
+	spin_unlock(&fi->lock);
 
 	sb->s_d_op = &fuse_dentry_operations;
 	sb->s_root = d_make_root(root);
-- 
2.33.0