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Date:   Wed, 17 Aug 2022 14:59:02 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Christian Brauner <brauner@kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dongliang Mu <mudongliangabcd@gmail.com>,
        Dongliang Mu <dzm91@hust.edu.cn>,
        Arve =?iso-8859-1?B?SGr4bm5lduVn?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>,
        Martijn Coenen <maco@android.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Carlos Llamas <cmllamas@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Kees Cook <keescook@chromium.org>,
        syzkaller <syzkaller@googlegroups.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] binderfs: rework superblock destruction
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 <20220817130306.96978-1-brauner@kernel.org>
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On Wed, Aug 17, 2022 at 03:03:06PM +0200, Christian Brauner wrote:

> +static void binderfs_kill_super(struct super_block *sb)
> +{
> +	struct binderfs_info *info = sb->s_fs_info;
> +
> +	if (info && info->ipc_ns)
> +		put_ipc_ns(info->ipc_ns);
> +
> +	kfree(info);
> +	kill_litter_super(sb);
> +}

Other way round, please - shut the superblock down, *then*
free the objects it'd been using.  IOW,

	struct binderfs_info *info = sb->s_fs_info;

	kill_litter_super(sb);

	if (info && info->ipc_ns)
		put_ipc_ns(info->ipc_ns);

	kfree(info);