From owner-freebsd-security Sat Dec 1 15:32: 9 2001 Delivered-To: freebsd-security@freebsd.org Received: from mail11.speakeasy.net (mail11.speakeasy.net [216.254.0.211]) by hub.freebsd.org (Postfix) with ESMTP id 02BCC37B417 for ; Sat, 1 Dec 2001 15:32:05 -0800 (PST) Received: (qmail 12319 invoked from network); 1 Dec 2001 23:32:46 -0000 Received: from unknown (HELO laptop.baldwin.cx) ([64.81.54.73]) (envelope-sender ) by mail11.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 1 Dec 2001 23:32:46 -0000 Message-ID: X-Mailer: XFMail 1.4.0 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <3C08E711.A4B08098@bsdprophet.org> Date: Sat, 01 Dec 2001 15:32:04 -0800 (PST) From: John Baldwin To: scott Subject: Re: options USER_LDT Cc: freebsd-security@FreeBSD.ORG, Dave Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On 01-Dec-01 scott wrote: > Dave wrote: >> >> I really have no clue what the kernel option: >> options USER_LDT >> >> means, except this rugged definition I found in LINT (paraphrase): >> "Allow applications running in user space to manipulate the Local >> Descriptor Table (LDT)" >> >> Since it didn't come in the GENERIC (FBSD 4.4 REL), I'm assuming that >> someone, somewhere, thought it would be a good idea to have this disabled >> by default and maybe it was meant to be added in only by people who know >> what they are doing. >> >> Is there a security risk by allowing programs to access the Local >> Descriptor Table? (I'm not sure what the LDT is, but if it was off for a >> reason I wouldn't want to challenge the decisions of those more informed >> than myself. If it wasn't for an efficiency judgement, it could of been >> for a security judgement) > > Yes there is a security risk. > Here read all about it: > http://www.phrack.org/show.php?p=51&a=9 What in the _world_ does this have to do with _LDT_ (aka Local Descriptor Table). This is talking about making a LKM (Loadable Kernel Module) which is an entirely separate issue from LDT. I don't know of any security problems with LDT's, please stop spreading FUD. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message