linux-kernel - Re: [PATCH v2] proc: "mount -o lookup=" support

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Message-ID: <Yeg0zoI8d3oyWuzw@localhost.localdomain>
Date:   Wed, 19 Jan 2022 18:57:02 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     stephen.s.brennan@...cle.com
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        stephen.s.brennan@...cle.com, legion@...nel.org,
        viro@...iv.linux.org.uk, ebiederm@...ssion.com,
        akpm@...ux-foundation.org
Subject: Re: [PATCH v2] proc: "mount -o lookup=" support

On Wed, Jan 19, 2022 at 06:48:03PM +0300, Alexey Dobriyan wrote:
> 	# mount -t proc -o lookup=/ proc /proc

> +static int proc_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
> +{
> +	struct proc_fs_context *src = fc->fs_private;
> +	struct proc_fs_context *dst;
> +
> +	dst = kmemdup(src, sizeof(struct proc_fs_context), GFP_KERNEL);
> +	if (!dst) {
> +		return -ENOMEM;
> +	}
> +
> +	dst->lookup_list = kmemdup(dst->lookup_list, dst->lookup_list_len, GFP_KERNEL);
> +	if (!dst->lookup_list) {
> +		kfree(dst);
> +		return -ENOMEM;
> +	}
> +	get_pid_ns(dst->pid_ns);
> +
> +	fc->fs_private = dst;
> +	return 0;
> +}

Stephen, sorry for not replying earlier.

I don't pretend to understand fully what ->dup() is supposed to do.
And the above code was not tested.

In particular

	p->a = kmemdup(p->a, ...)

reads like "MEMORY LEAK" on the first glance but it is not.

Understanding ->dup is the next thing.