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 EE969C46467 for ; Tue, 3 Jan 2023 12:42:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233156AbjACMmF (ORCPT ); Tue, 3 Jan 2023 07:42:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230437AbjACMmE (ORCPT ); Tue, 3 Jan 2023 07:42:04 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73AC89FD3; Tue, 3 Jan 2023 04:42:03 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 2390D671AC; Tue, 3 Jan 2023 12:42:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1672749722; h=from:from:reply-to: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; bh=pTRmPLN+nKDxpkvAuy7xPSj+P5EUaykcz/bu6SdbF0o=; b=gGorrRDau2nrUcCwnX8wbC7EN9jCz8eEPUV/e/66YNbDy15+B96B7v6eDHuv8KlU5byjMy IkeQvcaTZ4GBJIWnRymFXp5NTMwvcGMdUg6gP8wJfiR1vEafV4JUIluIKO2f4hCn33VJKW OZTxz++wX6FNhylZKDz0G2m2ndshblM= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1672749722; h=from:from:reply-to: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; bh=pTRmPLN+nKDxpkvAuy7xPSj+P5EUaykcz/bu6SdbF0o=; b=osD1MW9Rp24AQxdfGkeuER8PF8qI1TxQbQPYHisjuff44K9ufUJwbC0hxa4YHJ3XGtDwhG wc7NwZkZ/vtuXxDg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0F5211392B; Tue, 3 Jan 2023 12:42:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id f1ewA5oitGN9DgAAMHmgww (envelope-from ); Tue, 03 Jan 2023 12:42:02 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 7D9B8A0742; Tue, 3 Jan 2023 13:42:01 +0100 (CET) Date: Tue, 3 Jan 2023 13:42:01 +0100 From: Jan Kara To: Richard Guy Briggs Cc: Jan Kara , Linux-Audit Mailing List , LKML , linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Paul Moore , Eric Paris , Steve Grubb , Amir Goldstein Subject: Re: [PATCH v5 2/3] fanotify: define struct members to hold response decision context Message-ID: <20230103124201.iopasddbtb6vi362@quack3> References: <45da8423b9b1e8fc7abd68cd2269acff8cf9022a.1670606054.git.rgb@redhat.com> <20221216164342.ojcbdifdmafq5njw@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu 22-12-22 15:47:21, Richard Guy Briggs wrote: > On 2022-12-16 17:43, Jan Kara wrote: > > On Mon 12-12-22 09:06:10, Richard Guy Briggs wrote: > > > This patch adds a flag, FAN_INFO and an extensible buffer to provide > > > additional information about response decisions. The buffer contains > > > one or more headers defining the information type and the length of the > > > following information. The patch defines one additional information > > > type, FAN_RESPONSE_INFO_AUDIT_RULE, to audit a rule number. This will > > > allow for the creation of other information types in the future if other > > > users of the API identify different needs. > > > > > > Suggested-by: Steve Grubb > > > Link: https://lore.kernel.org/r/2745105.e9J7NaK4W3@x2 > > > Suggested-by: Jan Kara > > > Link: https://lore.kernel.org/r/20201001101219.GE17860@quack2.suse.cz > > > Signed-off-by: Richard Guy Briggs > > > > Thanks for the patches. They look very good to me. Just two nits below. I > > can do the small updates on commit if there would be no other changes. But > > I'd like to get some review from audit guys for patch 3/3 before I commit > > this. > > I'd prefer to send a followup patch based on your recommendations rather > than have you modify it. It does save some back and forth though... OK, since there are updates to patch 3 as well, I agree this is a better way forward. > > > diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c > > > index caa1211bac8c..cf3584351e00 100644 > > > --- a/fs/notify/fanotify/fanotify_user.c > > > +++ b/fs/notify/fanotify/fanotify_user.c > > > @@ -283,19 +283,44 @@ static int create_fd(struct fsnotify_group *group, const struct path *path, > > > return client_fd; > > > } > > > > > > +static int process_access_response_info(int fd, const char __user *info, size_t info_len, > > > + struct fanotify_response_info_audit_rule *friar) > > > > I prefer to keep lines within 80 columns, unless there is really good > > reason (like with strings) to have them longer. > > Sure. In this case, it buys us little since the last line is lined up > with the arguments openning bracket and it one long struct name unless I > unalign that argument and back up the indent by one. Yeah, that's what I'd generally do. > > BTW, why do you call the info structure 'friar'? I feel some language twist > > escapes me ;) > > Fanotify_Response_Info_Audit_Rule, it is a pronounceable word, and > besides they have a long reputation for making good beer. :-D Aha, ok :) Thanks for explanation. > > > +{ > > > + if (fd == FAN_NOFD) > > > + return -ENOENT; > > > > I would not test 'fd' in this function at all. After all it is not part of > > the response info structure and you do check it in > > process_access_response() anyway. > > I wrestled with that. I was even tempted to swallow the following fd > check too, but the flow would not have made as much sense for the > non-INFO case. > > My understanding from Amir was that FAN_NOFD was only to be sent in in > conjuction with FAN_INFO to test if a newer kernel was present. Yes, that is correct. But we not only want to check that FAN_INFO flag is understood (as you do in your patch) but also whether a particular response type is understood (which you don't verify for FAN_NOFD). Currently, there is only one response type (FAN_RESPONSE_INFO_AUDIT_RULE) but if there are more in the future we need old kernels to refuse new response types even for FAN_NOFD case. > I presumed that if FAN_NOFD was present without FAN_INFO that was an > invalid input to an old kernel. Yes, that is correct and I agree the conditions I've suggested below are wrong in that regard and need a bit of tweaking. Thanks for catching it. > > > + > > > + 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? Honza -- Jan Kara SUSE Labs, CR