linux-kernel - Re: [PATCH v2 8/8] FS: proc, make limits writable

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Message-ID: <20090904142645.GA10535@redhat.com>
Date:	Fri, 4 Sep 2009 16:26:45 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	akpm@...ux-foundation.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 8/8] FS: proc, make limits writable

On 09/03, Jiri Slaby wrote:
>
> Allow writing strings such as
> Max core file size=0:unlimited
> to /proc/<pid>/limits to change limits.

Can't review the parsing in limits_write() because I don't have enough
"C" skills, but otherwise the whole series looks correct to me.

One small nit, just to suggest the further 9/8 cleanup,

> +static const struct file_operations proc_pid_limits_operations = {
> +	.read		= proc_info_read,
> +	.write		= limits_write,
> +};

I think it makes sense to tweak proc_pid_limits() a little bit (and
rename it), so that we can do

	.read = limits_read,
	.write = limits_write

Then,

> @@ -2501,7 +2571,9 @@ static const struct pid_entry tgid_base_stuff[] = {
> +	NOD("limits",	  S_IFREG|S_IRUSR|S_IWUSR, NULL,
> +			&proc_pid_limits_operations,
> +			{ .proc_read = proc_pid_limits }),

We could use

	REG("limits", S_IRUSR|S_IWUSR, &proc_pid_limits_operations),

instead, this looks a bit cleaner to me.

But as I said, we can do this later.

And another minor nit (just in case you will re-submit this series for
some reason). Perhaps the changelog in 6/8 should mention that we do
not do any security checks when tsk != current (without selinux). We
assume that either the caller is sys_setrlimit(), or the caller should
verify it has rights to change the limits: in case of limits_write()
we rely on ->mode = S_IRUSR|S_IWUSR.

Oleg.

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