linux-kernel - Re: [PATCH v2 1/2] procfs: make /proc/*/{stack,syscall,personality} 0400

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Message-ID: <20140402173429.GA31668@redhat.com>
Date:	Wed, 2 Apr 2014 19:34:29 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Djalal Harouni <tixxdz@...ndz.org>, linux-kernel@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Frank Ch. Eigler" <fche@...hat.com>
Subject: Re: [PATCH v2 1/2] procfs: make
	/proc/*/{stack,syscall,personality} 0400

On 03/28, Andrew Morton wrote:
>
> Now for a six-year-late code review:
>
> - How the heck can target==current in task_current_syscall()?
>
> - Less talk, more action:
>
> From: Andrew Morton <akpm@...ux-foundation.org>
> Subject: lib/syscall.c: unexport task_current_syscall()
>
> It is only used by procfs and procfs cannot be a module.
>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
>
>  lib/syscall.c |    1 -
>  1 file changed, 1 deletion(-)
>
> diff -puN lib/syscall.c~a lib/syscall.c
> --- a/lib/syscall.c~a
> +++ a/lib/syscall.c
> @@ -72,4 +72,3 @@ int task_current_syscall(struct task_str
>
>  	return 0;
>  }
> -EXPORT_SYMBOL_GPL(task_current_syscall);

Well, I guess it was added for external tracing modules like systemtap.
And in this case target==current is very likely. And for utrace modules,
but it is dead.

I do not see any usage of task_current_syscall() in
git://sourceware.org/git/systemtap.git, so this change should not upset
systemtap at least.

And if we unexport task_current_syscall(), perhaps we should actually
lib/syscall.c. proc_pid_syscall() can use syscall_get_*() instead.
Or at least we can simplify it, I don't think /proc/ actually needs
wait_task_inactive().

Oleg.

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