linux-kernel - Re: [PATCH] binderfs: rework superblock destruction

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Message-ID: <Yvz0JkdxXwY8uDyT@ZenIV>
Date:   Wed, 17 Aug 2022 14:59:02 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christian Brauner <brauner@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dongliang Mu <mudongliangabcd@...il.com>,
        Dongliang Mu <dzm91@...t.edu.cn>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Carlos Llamas <cmllamas@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        syzkaller <syzkaller@...glegroups.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] binderfs: rework superblock destruction

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);