Re: [PATCH v3 4/9] fs/resctrl: Fix deadlock for errors during mount

[Chen, Yu C]

On 5/23/2026 3:15 AM, Reinette Chatre wrote:
> @@ -3085,10 +3105,37 @@ static int rdt_get_tree(struct fs_context *fc)
>   						   RESCTRL_PICK_ANY_CPU);
>   	}
>   
> -	goto out;
> +	/*
> +	 * Ensure root kn remains accessible after mutex is unlocked so that

Maybe a little more accurate to say "Ensure rdt_root remains accessible"?
Here we increase reference for rdtgroup_default.kn, and protect
against UAF of
kernfs_kill_sb(sb) ->
  info = kernfs_info(sb) ->
    kernfs_put(info->root->kn)

where the info->root is UAF rather than the kn.

Other looks good to me.

Reviewed-by: Chen Yu <yu.c.chen@xxxxxxxxx>


thanks,
Chenyu

> +	 * kernfs_kill_sb() can run safely if called by kernfs_get_tree()'s
> +	 * failure path after creating a superblock but before taking reference
> +	 * on root kn.
> +	 */
> +	kernfs_get(rdtgroup_default.kn);