Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267195AbUIMOac (ORCPT ); Mon, 13 Sep 2004 10:30:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267457AbUIMOaW (ORCPT ); Mon, 13 Sep 2004 10:30:22 -0400 Received: from holomorphy.com ([207.189.100.168]:63627 "EHLO holomorphy.com") by vger.kernel.org with ESMTP id S267195AbUIMO1z (ORCPT ); Mon, 13 Sep 2004 10:27:55 -0400 Date: Mon, 13 Sep 2004 07:27:52 -0700 From: William Lee Irwin III To: Albert Cahalan Cc: linux-kernel mailing list , cw@f00f.org, mingo@elte.hu, anton@samba.org Subject: Re: /proc/sys/kernel/pid_max issues Message-ID: <20040913142752.GC9106@holomorphy.com> References: <1095045628.1173.637.camel@cube> <20040913074230.GW2660@holomorphy.com> <1095084688.1173.1329.camel@cube> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1095084688.1173.1329.camel@cube> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.6+20040722i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1336 Lines: 30 On Mon, 2004-09-13 at 03:42, William Lee Irwin III wrote: >> The resource tracking and locking implications of this are disturbing. >> Would fully pseudorandom allocation be acceptable? On Mon, Sep 13, 2004 at 10:11:29AM -0400, Albert Cahalan wrote: > There's no point. > LRU reduces accidents that don't involve an attacker. > Strong crypto random can make some attacks a bit harder. > OpenBSD does this. It doesn't work well enough to bother > with if the implementation is problematic; there's not > much you can do while avoiding 64-bit or 128-bit PIDs. > Pseudorandom is 100% useless. > Per-user PID recycling would make it much harder for > an attacker to grab a specific PID. Perhaps the attacker > knows that a sched_setscheduler call is coming, and he > has a way to make the right process restart or crash. > Normally, this lets him get SCHED_FIFO or somesuch. > With per-user PID recycling, it would be difficult for > him to grab the desired PID. I'd suggest pushing for 64-bit+ pid's, then. IIRC most of the work there is in userspace (the in-kernel part is trivial). -- wli - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/