Re: [Security] [PATCH] proc: avoid information leaks to non-privileged processes

From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: security@kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Eric Paris <eparis@redhat.com>, Jake Edge <jake@lwn.net>,
	linux-security-module@vger.kernel.org, mingo@redhat.com,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Matt Mackall <mpm@selenic.com>, James Morris <jmorris@namei.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roland McGrath <roland@redhat.com>,
	Arjan van de Ven <arjan@infradead.org>
Subject: Re: [Security] [PATCH] proc: avoid information leaks to non-privileged processes
Date: Tue, 5 May 2009 08:35:35 -0700 (PDT)	[thread overview]
Message-ID: <alpine.LFD.2.01.0905050833180.4983@localhost.localdomain> (raw)
In-Reply-To: <alpine.LFD.2.01.0905050755310.4983@localhost.localdomain>

On Tue, 5 May 2009, Linus Torvalds wrote:
> 
> Note: the "pid + jiffies" is just meant to be a tiny tiny bit of noise. It 
> has no real meaning. It could be anything. I just picked the previous 
> seed, it's just that now we keep the state in between calls and that will 
> feed into the next result, and that should make all the difference.

Actually, thinking about it, we could/should probably just remove that 
tiny bit of noise.

After all, we get _real_ noise from the "keyptr->secret" thing. It's not 
updated all the time, but it's certainly updated often enough that nobody 
will ever see anything remotely guessable, I suspect.

Not that the "pid+jiffies" should hurt either, of course. It just doesn't 
really look meaningful, and only exists as a historical oddity that 
relates to the previous implementation of get_random_int().

			Linus