Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933886AbXILXtE (ORCPT ); Wed, 12 Sep 2007 19:49:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932178AbXILXsy (ORCPT ); Wed, 12 Sep 2007 19:48:54 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:41940 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932143AbXILXsx (ORCPT ); Wed, 12 Sep 2007 19:48:53 -0400 Date: Wed, 12 Sep 2007 18:48:52 -0500 (CDT) From: Brent Casavant Reply-To: Brent Casavant To: Al Viro cc: linux-kernel@vger.kernel.org Subject: Re: O_NOLINK for open() In-Reply-To: <20070912180937.Y5573@pkunk.americas.sgi.com> Message-ID: <20070912184601.M37791@pkunk.americas.sgi.com> References: <20070912144128.D5573@pkunk.americas.sgi.com> <20070912172519.N5573@pkunk.americas.sgi.com> <20070912224955.GC8181@ftp.linux.org.uk> <20070912180937.Y5573@pkunk.americas.sgi.com> Organization: Silicon Graphics, Inc. MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1381 Lines: 32 On Wed, 12 Sep 2007, Brent Casavant wrote: > On Wed, 12 Sep 2007, Al Viro wrote: > > > Give me a break. And learn about ptrace(2). This "unlinking" bullshit > > buys you zero additional security, both for /proc/*/mem and for /dev/mem > > (see mknod(2)). > > My (limited) understanding of ptrace is that a parent-child > relationship is needed between the tracing process and the traced > process (at least that's what I gather from the man page). This > does give cause for concern, and I might have to see what can be > done to alleviate this concern. I fully realize that making this > design completely unassilable is a fools errand, but closing off > as many attack vectors as possible seems prudent. Hmm. The solution would appear to be as simple as making the target program set-user-id. As long as as the attacker isn't the superuser (or has CAP_SYS_PTRACE) we should be OK. Thanks for the heads-up, Brent -- Brent Casavant All music is folk music. I ain't bcasavan@sgi.com never heard a horse sing a song. Silicon Graphics, Inc. -- Louis Armstrong - 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/