linux-kernel - Re: [PATCH 1/2] proc: restrict access to /proc/PID/io

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Date:	Tue, 28 Jun 2011 06:43:54 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Rientjes <rientjes@...gle.com>,
	Stephen Wilson <wilsons@...rt.ca>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	security@...nel.org, Eric Paris <eparis@...hat.com>,
	Solar Designer <solar@...nwall.com>
Subject: Re: [PATCH 1/2] proc: restrict access to /proc/PID/io

On Fri, Jun 24, 2011 at 5:38 PM, Vasiliy Kulikov <segoon@...nwall.com> wrote:
> /proc/PID/io may be used for gathering private information.  E.g. for
> openssh and vsftpd daemons wchars/rchars may be used to learn the
> precise password length.  Restrict it to processes being able to ptrace
> the target process.
>

Hmm.. How do I reproduce this, won't they be enough randomness around
rchar/wchar by the time the attacker reads it?

> ptrace_may_access() is needed to prevent keeping open file descriptor of
> "io" file, executing setuid binary and gathering io information of the
> setuid'ed process.

Balbir Singh
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