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 79EB0EE8012 for ; Fri, 8 Sep 2023 14:42:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243857AbjIHOml (ORCPT ); Fri, 8 Sep 2023 10:42:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230385AbjIHOmj (ORCPT ); Fri, 8 Sep 2023 10:42:39 -0400 Received: from orbyte.nwl.cc (orbyte.nwl.cc [IPv6:2001:41d0:e:133a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E8381BF1; Fri, 8 Sep 2023 07:42:35 -0700 (PDT) Received: from n0-1 by orbyte.nwl.cc with local (Exim 4.94.2) (envelope-from ) id 1qecgr-0007kz-34; Fri, 08 Sep 2023 16:42:33 +0200 Date: Fri, 8 Sep 2023 16:42:33 +0200 From: Phil Sutter To: Pablo Neira Ayuso Cc: Florian Westphal , netfilter-devel@vger.kernel.org, audit@vger.kernel.org Subject: Re: [nf PATCH v2] netfilter: nf_tables: Fix entries val in rule reset audit log Message-ID: Mail-Followup-To: Phil Sutter , Pablo Neira Ayuso , Florian Westphal , netfilter-devel@vger.kernel.org, audit@vger.kernel.org References: <20230908081033.30806-1-phil@nwl.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Fri, Sep 08, 2023 at 04:01:02PM +0200, Pablo Neira Ayuso wrote: > Hi Phil, > > On Fri, Sep 08, 2023 at 10:10:33AM +0200, Phil Sutter wrote: > > The value in idx and the number of rules handled in that particular > > __nf_tables_dump_rules() call is not identical. The former is a cursor > > to pick up from if multiple netlink messages are needed, so its value is > > ever increasing. > > My (buggy) intention was to display this audit log once per chain, at > the end of the chain dump. Ah, I wasn't aware you did that on purpose. > > Fixing this is not just a matter of subtracting s_idx > > from it, though: When resetting rules in multiple chains, > > __nf_tables_dump_rules() is called for each and cb->args[0] is not > > adjusted in between. > > > > The audit notification in __nf_tables_dump_rules() had another problem: > > If nf_tables_fill_rule_info() failed (e.g. due to buffer exhaustion), no > > notification was sent - despite the rules having been reset already. > > Hm. that should not happen, when nf_tables_fill_rule_info() fails, > that means buffer is full and userspace will invoke recvmsg() again. > The next buffer resumes from the last entry that could not fit into > the buffer. I didn't explicitly test for this case, but __nf_tables_dump_rules() calls nf_tables_fill_rule_info() in a loop for reach rule. If it fails, the function immediately returns 1 without calling audit_log_rule_reset(). So while the last (failing) rule dump/reset will be repeated after the detour to user space, the preceding rules successfully dumped/reset slip through. > > To catch all the above and return to a single (if possible) notification > > per table again, move audit logging back into the caller but into the > > table loop instead of past it to avoid the potential null-pointer > > deref. > > > > This requires to trigger the notification in two spots. Care has to be > > taken in the second case as cb->args[0] is also not updated in between > > tables. This requires a helper variable as either it is the first table > > (with potential non-zero cb->args[0] cursor) or a consecutive one (with > > idx holding the current cursor already). > > Your intention is to trigger one single audit log per table, right? > Did you test a chain with a large ruleset that needs several buffers > to be delivered to userspace in the netlink dump? Yes, see the last part in the proposed kselftest[1]: Resetting rules in a chain with 503 rules causes three notifications to be sent, for 189, 188 and 126 rules each. > I would be inclined to do this once per-chain, so this can be extended > later on to display the chain. Yes, that means this will send one > audit log per chain, but this is where follow up updates will go? If you prefer that, no problem. I'll prepare a v3 then. Cheers, Phil [1] https://lore.kernel.org/netfilter-devel/20230908002229.1409-3-phil@nwl.cc/