Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269387AbUINS7L (ORCPT ); Tue, 14 Sep 2004 14:59:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269362AbUINS5e (ORCPT ); Tue, 14 Sep 2004 14:57:34 -0400 Received: from mail2.bluewin.ch ([195.186.4.73]:45242 "EHLO mail2.bluewin.ch") by vger.kernel.org with ESMTP id S269330AbUINS41 (ORCPT ); Tue, 14 Sep 2004 14:56:27 -0400 Date: Tue, 14 Sep 2004 20:55:25 +0200 From: Roger Luethi To: Chris Wright Cc: William Lee Irwin III , Albert Cahalan , Stephen Smalley , Andrew Morton OSDL , lkml , Paul Jackson , James Morris Subject: Re: [1/1][PATCH] nproc v2: netlink access to /proc information Message-ID: <20040914185524.GB2655@k3.hellgate.ch> Mail-Followup-To: Chris Wright , William Lee Irwin III , Albert Cahalan , Stephen Smalley , Andrew Morton OSDL , lkml , Paul Jackson , James Morris References: <1094942212.1174.20.camel@cube> <20040914064403.GB20929@k3.hellgate.ch> <20040914071058.GH9106@holomorphy.com> <20040914075508.GA10880@k3.hellgate.ch> <20040914080132.GJ9106@holomorphy.com> <20040914092748.GA11238@k3.hellgate.ch> <20040914153758.GO9106@holomorphy.com> <20040914160150.GB13978@k3.hellgate.ch> <20040914163712.GT9106@holomorphy.com> <20040914113736.H1924@build.pdx.osdl.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040914113736.H1924@build.pdx.osdl.net> X-Operating-System: Linux 2.6.8 on i686 X-GPG-Fingerprint: 92 F4 DC 20 57 46 7B 95 24 4E 9E E7 5A 54 DC 1B X-GPG: 1024/80E744BD wwwkeys.ch.pgp.net User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1372 Lines: 28 On Tue, 14 Sep 2004 11:37:36 -0700, Chris Wright wrote: > * William Lee Irwin III (wli@holomorphy.com) wrote: > > On Tue, 14 Sep 2004 08:37:58 -0700, William Lee Irwin III wrote: > > >> No, in general races of the form "permissions were altered after I > > >> checked them" can happen. > > > > On Tue, Sep 14, 2004 at 06:01:50PM +0200, Roger Luethi wrote: > > > Can you make an example? Some scenario where this would be important? > > > > Not particularly. It largely means poorly-coded apps may report gibberish. > > Canonical example is access(2) followed by open(2), not really relevant > in this case. However, exec setuid root app...when do you check, and > when to you fill in data to send back to user? For /proc, this type of > check happens often (see things like may_ptrace_attach and > task_dumpable in fs/proc/base.c). For nproc, the procedure looks like this: A tool send(2)s a request, credentials are attached to skb. Based on said credentials, the kernel is free to provide (netlink_unicast to originating socket) or withhold information. In this regard, nproc works like other netlink interfaces. Roger - 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/