Merge branch 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fix from Tejun Heo:
 "Fix leak of filesystem context root which is triggered by LTP.

  Not too likely to be a problem in non-testing environments"

* 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup1: fix leaked context root causing sporadic NULL deref in LTP

Author: torvalds

fs/internal.h

@@ -61,7 +61,6 @@ extern void __init chrdev_init(void);
  */
 extern const struct fs_context_operations legacy_fs_context_ops;
 extern int parse_monolithic_mount_data(struct fs_context *, void *);
-extern void fc_drop_locked(struct fs_context *);
 extern void vfs_clean_context(struct fs_context *fc);
 extern int finish_clean_context(struct fs_context *fc);
 

include/linux/fs_context.h

@@ -141,6 +141,7 @@ extern int vfs_get_tree(struct fs_context *fc);
 extern void put_fs_context(struct fs_context *fc);
 extern int vfs_parse_fs_param_source(struct fs_context *fc,
 				     struct fs_parameter *param);
+extern void fc_drop_locked(struct fs_context *fc);
 
 /*
  * sget() wrappers to be called from the ->get_tree() op.

kernel/cgroup/cgroup-v1.c

@@ -1221,9 +1221,7 @@ int cgroup1_get_tree(struct fs_context *fc)
 		ret = cgroup_do_get_tree(fc);
 
 	if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
-		struct super_block *sb = fc->root->d_sb;
-		dput(fc->root);
-		deactivate_locked_super(sb);
+		fc_drop_locked(fc);
 		ret = 1;
 	}