From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05951C43331 for ; Fri, 6 Sep 2019 19:33:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC8B9208C3 for ; Fri, 6 Sep 2019 19:33:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393349AbfIFTdS convert rfc822-to-8bit (ORCPT ); Fri, 6 Sep 2019 15:33:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29088 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393336AbfIFTdS (ORCPT ); Fri, 6 Sep 2019 15:33:18 -0400 Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 735443CBC3 for ; Fri, 6 Sep 2019 19:33:17 +0000 (UTC) Received: by mail-wr1-f72.google.com with SMTP id w3so42592wrv.10 for ; Fri, 06 Sep 2019 12:33:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=R/U7mUhygsddH+fGB+zy3E9CKa5h+Z8Nm54osdGuOgs=; b=Ok1UA/BNnnkFSIMwNG3YHnNJajaqmFN57GNCCutJjFuIh0L3HBl92V/kYOh2Rw2BzR HhZHO68ZQa71EtIVNOat0j4RGEsNB266POpOA/RFB2ph8O6eiu3c7iYU4vMB9xSV2mau nTmgIpuoWdeaSoO2qXVXqeC9hSiaX1HzSSzQ/teczZrqrBoE8wWMzvpiiIas/kagKezk C/EnGY7NU00bz4dreGsgDO/9EnCM4fHhrBBmGnBx+ST9EvIcNOlyrQcFkPNKUyY00Iut 6K0WlIq5DbXMBgEJya6ksonIZRclLxuGgzlHkLTSWNwuFi55AMTs4F3vYj/ZDZZ3yBcF 0gSg== X-Gm-Message-State: APjAAAVZOuJW1PpGZgdGhY/A/Vf6WHyXLAlfElkPJEBn4ISi2kd7p5cO qfwXN8T6wTawEYJnvSzCZmyxoXcUSDK6d5bTxtE8WdjYjuUhPFXpa7d/A1zXsA27UThVtiwMjqF RbI2yQ71aswxNUmD99bJ7joN+i+T6U4JBen8lZjsCx6MZfftJNFQn X-Received: by 2002:a1c:ca02:: with SMTP id a2mr9252528wmg.127.1567798396044; Fri, 06 Sep 2019 12:33:16 -0700 (PDT) X-Google-Smtp-Source: APXvYqyTIyfiPV/yAsPvflKtcRM07P7nCUNe0sQoeZ2AMSNSLR0dzqdoxrOYrd5Bg/c1ZdH+IG1R0aOFq6s5vYlI0XA= X-Received: by 2002:a1c:ca02:: with SMTP id a2mr9252505wmg.127.1567798395711; Fri, 06 Sep 2019 12:33:15 -0700 (PDT) MIME-Version: 1.0 References: <156763534546.18676.3530557439501101639.stgit@warthog.procyon.org.uk> <17703.1567702907@warthog.procyon.org.uk> In-Reply-To: From: Ray Strode Date: Fri, 6 Sep 2019 15:32:37 -0400 Message-ID: Subject: Re: Why add the general notification queue and its sources To: Linus Torvalds Cc: David Howells , Greg Kroah-Hartman , Steven Whitehouse , Nicolas Dichtel , raven@themaw.net, keyrings@vger.kernel.org, linux-usb@vger.kernel.org, linux-block , Christian Brauner , LSM List , linux-fsdevel , Linux API , Linux List Kernel Mailing , Al Viro , "Ray, Debarshi" , Robbie Harwood Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Hi, On Thu, Sep 5, 2019 at 4:39 PM Linus Torvalds wrote: > That is *way* too specific to make for any kind of generic > notification mechanism. Well from my standpoint, I just don't want to have to poll... I don't have a strong opinion about how it looks architecturally to reach that goal. Ideally, at a higher level, I want the userspace api that gnome uses to be something like: err = krb5_cc_watch (ctx, ccache, (krb5_cc_change_fct) on_cc_change , &watch_fd); then a watch_fd would get handed back and caller could poll on it. if it woke up poll(), caller would do krb5_cc_watch_update (ctx, ccache, watch_fd) or so and it would trigger on_cc_change to get called (or something like that). If under the hood, fd comes from opening /dev/watch_queue, and krb5_cc_watch_update reads from some mmap'ed buffer to decide whether or not to call on_cc_change, that's fine with me. If under the hood, fd comes from a pipe fd returned from some ioctl or syscall, and krb5_cc_watch_update reads messages directly from that fd to decide whether or not to call on_cc_change, that's fine with me. too. it could be an eventfd too, or whatever, too, just as long as its something I can add to poll() and don't have to intermittently poll ... :-) > Also, what is the security model here? Open a special character > device, and you get access to random notifications from random > sources? I guess dhowells answered this... > And why would you do a broken big-key thing in the kernel in the first > place? Why don't you just have a kernel key to indirectly encrypt > using a key and "additional user space data". The kernel should simply > not take care of insane 1MB keys. 🤷 dunno. I assume you're referencing the discussions from comment 0 on that 2013 bug. I wasn't involved in those discussions, I just chimed in after they happened trying to avoid having to add polling :-) I have no idea why a ticket would get that large. I assume it only is in weird edge cases. Anyway, gnome treats the tickets as opaque blobs. it doesn't do anything with them other than tell the user when they need to get refreshed... all the actual key manipulation happens from krb5 libraries. of course, one advantage of having the tickets kernel side is nfs could in theory access them directly, rather than up calling back to userspace... --Ray