linux-kernel - Re: [PATCH] proc: avoid leaking eip, esp, or wchan to non-privileged processes (fwd)

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Date:	Sun, 03 May 2009 23:09:24 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	James Morris <jmorris@...ei.org>
Cc:	linux-security-module@...r.kernel.org, Jake Edge <jake@....net>,
	Arjan van de Ven <arjan@...radead.org>,
	Eric Paris <eparis@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Roland McGrath <roland@...hat.com>, mingo@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: avoid leaking eip, esp, or wchan to non-privileged processes (fwd)

James Morris <jmorris@...ei.org> writes:

> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index aa763ab..cd3c0d7 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -319,6 +319,9 @@ static int proc_pid_wchan(struct task_struct *task, char
> *buffer)
>  	unsigned long wchan;
>  	char symname[KSYM_NAME_LEN];
>
> +	if (!ptrace_may_access(task, PTRACE_MODE_READ))
> +		return 0;
> +
>  	wchan = get_wchan(task);
>
>  	if (lookup_symbol_name(wchan, symname) < 0)

If the symbol is in the kernel it should be safe to return it's
name, all that is an information leak of a different sort.
Overall I expect we should return  -EPERM here and not simply
an empty file.

Have you tested these patches against ps top and similar common
tools?

Eric
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