kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR

The root->ino_idr is supposed to be protected by kernfs_idr_lock, fix
it.

Fixes: 488dee9 ("kernfs: allow creating kernfs objects with arbitrary uid/gid")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230523024017.24851-1-songmuchun@bytedance.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: songmuchun

fs/kernfs/dir.c

@@ -655,7 +655,9 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	return kn;
 
  err_out3:
+	spin_lock(&kernfs_idr_lock);
 	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
+	spin_unlock(&kernfs_idr_lock);
  err_out2:
 	kmem_cache_free(kernfs_node_cache, kn);
  err_out1: