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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 6727FC433DF for ; Mon, 24 Aug 2020 21:11:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41BB92067C for ; Mon, 24 Aug 2020 21:11:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="i6iAMiwP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727931AbgHXVLV (ORCPT ); Mon, 24 Aug 2020 17:11:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726138AbgHXVLT (ORCPT ); Mon, 24 Aug 2020 17:11:19 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 024CAC061574 for ; Mon, 24 Aug 2020 14:11:18 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id o5so5254286pgb.2 for ; Mon, 24 Aug 2020 14:11:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=dSxggIWYJnAj641M9XzShpvsdRzxcqklORI4hC1bcZg=; b=i6iAMiwPrOKxVhhyDgghkvBK9TwV37/kNIOC4qlpoB/S8v4AIsxbqKamVLeWF2dlDL BLdRVqC16KYABOcDzUY0WK5emHjIHJujKi4nQlt5P8Rt2SuDhcTJmSFZJK4xuncFRo05 POO+2SUBU36E7UIhSLSGLInhl8Ud9ashg/i5HDOjjRap+JlXHD9OQNgphN8VxdQqM+o6 wAlEG6xX+0JM9Agr+Z8VpEEJ+Z2bqr9uvTJSmXWcETwZAc0AggPgFFScJHsyFMMgoqEm g4PNeaJrOVL5DhmorOywOsmHKw60An45LSCT1MdMqipWiqmuuoHw9EWglQsDFK3/sB7y S/kA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=dSxggIWYJnAj641M9XzShpvsdRzxcqklORI4hC1bcZg=; b=I86uOgde4MTEDfWdWJqNskG6uVFoViYD65mjKAf4L74f39bj2qRSMkcK4O5mhcuE+n WheMG+DCkQwGNnD8c9Ulld14RfLGzs4IF5hclA81YCZgElWve9acQKY+vLNrJlyMiRBz rGoUSnaPGQS4x4tBHkiJnhzzHdKqWoWz6Prx3NWUhAAXIjlwQpV0RXSMguOEGkd6MRg7 y8hMnwE66Hj9skpBdbwQDAWJxpFdIlGkhQ3lCq/kk3y+TcjkSBE6KgLp5KaBTqXpxic5 8rkQDfPBGOBwxRtBiBXmEV1REo86MPiDFzMB98MDsEtaIsK2psGuTSwP4pblL3kj8HUW 9ULg== X-Gm-Message-State: AOAM5315y+cnw1iKzrfe6EukcEBXHpoxeaauPL77jS3nVyQpBPcuEUUi BxVa/voL5z037CuY8BWWsI9FhA== X-Google-Smtp-Source: ABdhPJypFjd84ljN3wDRQmnbFvf1otGCfCVscA2ErlmfqM+U8CwukKDeMXqwq/W9hVIZBoRnIEVYIw== X-Received: by 2002:a17:902:b943:: with SMTP id h3mr4977097pls.286.1598303478248; Mon, 24 Aug 2020 14:11:18 -0700 (PDT) Received: from exodia.localdomain ([2620:10d:c090:400::5:8d5d]) by smtp.gmail.com with ESMTPSA id t63sm10560733pgt.50.2020.08.24.14.11.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2020 14:11:17 -0700 (PDT) Date: Mon, 24 Aug 2020 14:11:15 -0700 From: Omar Sandoval To: Josef Bacik Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig , Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v5 2/9] fs: add O_ALLOW_ENCODED open flag Message-ID: <20200824211115.GB197795@exodia.localdomain> References: <3c44cdf2-e0fd-cea1-4028-d6315ba3b7fd@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3c44cdf2-e0fd-cea1-4028-d6315ba3b7fd@toxicpanda.com> Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Aug 24, 2020 at 02:28:39PM -0400, Josef Bacik wrote: > On 8/21/20 3:38 AM, Omar Sandoval wrote: > > From: Omar Sandoval > > > > The upcoming RWF_ENCODED operation introduces some security concerns: > > > > 1. Compressed writes will pass arbitrary data to decompression > > algorithms in the kernel. > > 2. Compressed reads can leak truncated/hole punched data. > > > > Therefore, we need to require privilege for RWF_ENCODED. It's not > > possible to do the permissions checks at the time of the read or write > > because, e.g., io_uring submits IO from a worker thread. So, add an open > > flag which requires CAP_SYS_ADMIN. It can also be set and cleared with > > fcntl(). The flag is not cleared in any way on fork or exec; it should > > probably be used with O_CLOEXEC in most cases. > > > > Note that the usual issue that unknown open flags are ignored doesn't > > really matter for O_ALLOW_ENCODED; if the kernel doesn't support > > O_ALLOW_ENCODED, then it doesn't support RWF_ENCODED, either. > > It seemed like you agreed to require O_CLOEXEC to be set when using > O_ALLOW_ENCODED in your last go around, what happened to that? I know I'd > feel better if we had that requirement, and if we aren't I'd like to know > why we can't. Thanks, > > Josef Yup I was still on the fence about it since it's a bit of an awkward requirement, but I'm convinced now that we might as well be safe and require it.