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 41D15C77B7F for ; Fri, 5 May 2023 14:51:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232090AbjEEOvc (ORCPT ); Fri, 5 May 2023 10:51:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232221AbjEEOvb (ORCPT ); Fri, 5 May 2023 10:51:31 -0400 Received: from Chamillionaire.breakpoint.cc (unknown [IPv6:2a0a:51c0:0:237:300::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E08731635B for ; Fri, 5 May 2023 07:51:29 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1puwm9-0006cb-EO; Fri, 05 May 2023 16:51:13 +0200 Date: Fri, 5 May 2023 16:51:13 +0200 From: Florian Westphal To: Pablo Neira Ayuso Cc: Florian Westphal , netfilter-devel@vger.kernel.org Subject: Re: [PATCH nf-next 0/3] netfilter: nf_tables: reject loads from uninitialized registers Message-ID: <20230505145113.GD6126@breakpoint.cc> References: <20230505111656.32238-1-fw@strlen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Pablo Neira Ayuso wrote: > On Fri, May 05, 2023 at 01:16:53PM +0200, Florian Westphal wrote: > > Keep a per-rule bitmask that tracks registers that have seen a store, > > then reject loads when the accessed registers haven't been flagged. > > > > This changes uabi contract, because we previously allowed this. > > Neither nftables nor iptables-nft create such rules. > > > > In case there is breakage, we could insert an 'store 0 to x' > > immediate expression into the ruleset automatically, but this > > isn't done here. > > > > Let me know if you think the "refuse" approach is too risky. > > Might the NFT_BREAK case defeat this approach? Sequence is: > > 1) expression that writes on register hits NFT_BREAK (nothing is written) > 2) expression that read from register, it reads uninitialized data. > > From ruleset load step, we cannot know if the write fails, because it > is subject to NFT_BREAK. Yes, but its irrelevant: If 1) issues NFT_BREAK, 2) won't execute.