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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D3C3C54E76 for ; Tue, 17 Jan 2023 21:11:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229728AbjAQVLw (ORCPT ); Tue, 17 Jan 2023 16:11:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229742AbjAQVJ4 (ORCPT ); Tue, 17 Jan 2023 16:09:56 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C4C1917D0 for ; Tue, 17 Jan 2023 11:33:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673984032; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; 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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230117082723.7g3ig6ernoslt7ub@quack3> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-01-17 09:27, Jan Kara wrote: > On Mon 16-01-23 15:42:29, Richard Guy Briggs wrote: > > On 2023-01-03 13:42, Jan Kara wrote: > > > On Thu 22-12-22 15:47:21, Richard Guy Briggs wrote: > > > > > > + > > > > > > + if (info_len != sizeof(*friar)) > > > > > > + return -EINVAL; > > > > > > + > > > > > > + if (copy_from_user(friar, info, sizeof(*friar))) > > > > > > + return -EFAULT; > > > > > > + > > > > > > + if (friar->hdr.type != FAN_RESPONSE_INFO_AUDIT_RULE) > > > > > > + return -EINVAL; > > > > > > + if (friar->hdr.pad != 0) > > > > > > + return -EINVAL; > > > > > > + if (friar->hdr.len != sizeof(*friar)) > > > > > > + return -EINVAL; > > > > > > + > > > > > > + return info_len; > > > > > > +} > > > > > > + > > > > > > > > > > ... > > > > > > > > > > > @@ -327,10 +359,18 @@ static int process_access_response(struct fsnotify_group *group, > > > > > > return -EINVAL; > > > > > > } > > > > > > > > > > > > - if (fd < 0) > > > > > > + if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT)) > > > > > > return -EINVAL; > > > > > > > > > > > > - if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT)) > > > > > > + if (response & FAN_INFO) { > > > > > > + ret = process_access_response_info(fd, info, info_len, &friar); > > > > > > + if (ret < 0) > > > > > > + return ret; > > > > > > + } else { > > > > > > + ret = 0; > > > > > > + } > > > > > > + > > > > > > + if (fd < 0) > > > > > > return -EINVAL; > > > > > > > > > > And here I'd do: > > > > > > > > > > if (fd == FAN_NOFD) > > > > > return 0; > > > > > if (fd < 0) > > > > > return -EINVAL; > > > > > > > > > > As we talked in previous revisions we'd specialcase FAN_NOFD to just verify > > > > > extra info is understood by the kernel so that application writing fanotify > > > > > responses has a way to check which information it can provide to the > > > > > kernel. > > > > > > > > The reason for including it in process_access_response_info() is to make > > > > sure that it is included in the FAN_INFO case to detect this extension. > > > > If it were included here > > > > > > I see what you're getting at now. So the condition > > > > > > if (fd == FAN_NOFD) > > > return 0; > > > > > > needs to be moved into > > > > > > if (response & FAN_INFO) > > > > > > branch after process_access_response_info(). I still prefer to keep it > > > outside of the process_access_response_info() function itself as it looks > > > more logical to me. Does it address your concerns? > > > > Ok. Note that this does not return zero to userspace, since this > > function's return value is added to the size of the struct > > fanotify_response when there is no error. > > Right, good point. 0 is not a good return value in this case. > > > For that reason, I think it makes more sense to return -ENOENT, or some > > other unused error code that fits, unless you think it is acceptable to > > return sizeof(struct fanotify_response) when FAN_INFO is set to indicate > > this. > > Yeah, my intention was to indicate "success" to userspace so I'd like to > return whatever we return for the case when struct fanotify_response is > accepted for a normal file descriptor - looks like info_len is the right > value. Thanks! Ok, I hadn't thought of that. So, to confirm, when FAN_INFO is set, if FAN_NOFD is also set, return info_len from process_access_response() and then immediately return sizeof(struct fanotify_response) plus info_len to userspace without issuing an audit record should indicate support for FAN_INFO and the specific info type supplied. Thanks for helping work through this. > Honza > -- > Jan Kara - RGB -- Richard Guy Briggs Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635