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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 165A4C433FE for ; Tue, 8 Dec 2020 13:50:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCB4523AAA for ; Tue, 8 Dec 2020 13:50:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729025AbgLHNuX (ORCPT ); Tue, 8 Dec 2020 08:50:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbgLHNuX (ORCPT ); Tue, 8 Dec 2020 08:50:23 -0500 Received: from mail-il1-x143.google.com (mail-il1-x143.google.com [IPv6:2607:f8b0:4864:20::143]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 113EFC061749; Tue, 8 Dec 2020 05:49:37 -0800 (PST) Received: by mail-il1-x143.google.com with SMTP id v3so15558022ilo.5; Tue, 08 Dec 2020 05:49:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MQXYbDMPL3yLYU7/kBOYlmtMsBjUqShGbSk3HBKaf8g=; b=qB1tZR3lpatG/0Zal3n5vfTlz2EOHV54ihJtai6PxbNg83npjonBDrtvWxoWqKEHMn boRmt5oXMbD5LvNj4OeZIaYR+ST5n8gpvHjkcbEIXqJUaprLoWbQkHTTjPeAci8N94HW loWBBpYEAkEob3/Cv/C1sDTjjxUvN4st0YeCB3Q7TQMzPQ2R19sISFXvvnF0zyV1kyGG 5w2kMfl/y3PE7p++iIOkxI/Zia39QDXZ+OQI8WiAlzXHgdbj92dbSCukLUIPqjMD5QM/ rvn5FhYjVTgU4PQvs1yECbhgurO+i+oCHAWjXh/zVWbgcNWS8WRzHjBnt5RoSNZ5bFhQ nhvw== 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; bh=MQXYbDMPL3yLYU7/kBOYlmtMsBjUqShGbSk3HBKaf8g=; b=jI0ul73ONQ1eM/zORf7+g7lsPQAkLiR5j7TpcJkcQzO7iT6wUzpmzX5RRHY9GyrYGk pYxzuH3Y2hZs/6+laaaAKVHfQu+se0VFgzGa/tKqvi83QHlafGlJLXYwfvjOShugFSel L7+vqwA3oyelO8LmT4Rzbz4NquqrmfNoSdxAwQ0aDN1nsDiA6419u4GF981NoUsifXGd k93boS5lvCjB30Ca/lmlLMGGwN7EwnxcRiE90whoiAYTKNF54DTdlLpLroKYGIa/+lAB USl+iFkF7RUtXQEU8EpFiRnnnB94ENSsOBLcN3+uGyykcqHS/ZwJPrX9sps4IrvMbyTd BwoA== X-Gm-Message-State: AOAM530DViDqOMsZgqiIKOuh2R9OYTYdztqt7+6+6s8jqW/ey24LgUTq X1WT6fmuWmclGtmJ1a33H+BpylK/13FyybNnmTudX1Cx410= X-Google-Smtp-Source: ABdhPJzs16Xbq9yXw4nMJe03SEuYZzH2JW3YVHgNPO0ogZUhHvZ9E49JOk1KNqGKQdSDMeXaSAPZ0uvc65/dx2fdz1w= X-Received: by 2002:a05:6e02:14ce:: with SMTP id o14mr27386946ilk.9.1607435376411; Tue, 08 Dec 2020 05:49:36 -0800 (PST) MIME-Version: 1.0 References: <20201207163255.564116-1-mszeredi@redhat.com> <20201207163255.564116-4-mszeredi@redhat.com> In-Reply-To: <20201207163255.564116-4-mszeredi@redhat.com> From: Amir Goldstein Date: Tue, 8 Dec 2020 15:49:25 +0200 Message-ID: Subject: Re: [PATCH v2 03/10] ovl: check privs before decoding file handle To: Miklos Szeredi Cc: "Eric W . Biederman" , linux-fsdevel , overlayfs , LSM List , linux-kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Dec 7, 2020 at 6:36 PM Miklos Szeredi wrote: > > CAP_DAC_READ_SEARCH is required by open_by_handle_at(2) so check it in > ovl_decode_real_fh() as well to prevent privilege escalation for > unprivileged overlay mounts. > > Signed-off-by: Miklos Szeredi > --- > fs/overlayfs/namei.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c > index a6162c4076db..82a55fdb1e7a 100644 > --- a/fs/overlayfs/namei.c > +++ b/fs/overlayfs/namei.c > @@ -156,6 +156,9 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt, > struct dentry *real; > int bytes; > > + if (!capable(CAP_DAC_READ_SEARCH)) > + return NULL; > + If the mounter is not capable in init ns, ovl_check_origin() and ovl_verify_index() will not function as expected and this will break index and nfs export features. So I think we need to also check capability in ovl_can_decode_fh(), to auto disable those features. Thanks, Amir.