linux-kernel - Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec

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Message-ID: <alpine.LRH.2.00.1102101337100.19432@tundra.namei.org>
Date:	Thu, 10 Feb 2011 13:44:58 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
cc:	Kees Cook <kees.cook@...onical.com>, linux-kernel@...r.kernel.org,
	Al Viro <viro@....linux.org.uk>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	linux-security-module@...r.kernel.org
Subject: Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec

On Tue, 8 Feb 2011, Eric W. Biederman wrote:

> Kees Cook <kees.cook@...onical.com> writes:
> 
> > On Tue, Feb 08, 2011 at 02:43:15PM +1100, James Morris wrote:

> >> > I don't think /proc/$pid/* needs to stay open across execs, does it? Or at
> >> > least the non-0444 files should be handled separately.
> >> 
> >> Actually, this seems like a more general kind of bug in proc rather than a 
> >> leaked fd.  Each child task should only see its own /proc/[pid] data.
> >
> > Right, that's precisely the problem. The unprivileged process can read
> > the setuid process's /proc files.
> 
> If these are things that we actually care about we should sprinkle in a
> few more ptrace_may_access calls into implementations of the relevant
> proc files.

This seems to be papering over a bug.

It is plainly broken to return an access error to a task which is 
legitimately accessing a file.  The task should not receive the wrong 
information from /proc/[pid]/* .


- James
-- 
James Morris
<jmorris@...ei.org>
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