Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756551Ab2BAPIs (ORCPT ); Wed, 1 Feb 2012 10:08:48 -0500 Received: from mail-tul01m020-f174.google.com ([209.85.214.174]:59842 "EHLO mail-tul01m020-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754714Ab2BAPIr convert rfc822-to-8bit (ORCPT ); Wed, 1 Feb 2012 10:08:47 -0500 MIME-Version: 1.0 In-Reply-To: References: <1327269381-20748-1-git-send-email-richard@nod.at> <1327269381-20748-2-git-send-email-richard@nod.at> Date: Wed, 1 Feb 2012 16:08:46 +0100 Message-ID: Subject: Re: [PATCH 1/6] Netfilter: Merge ipt_LOG and ip6_LOG into xt_LOG From: richard -rw- weinberger To: Jan Engelhardt Cc: Netfilter Developer Mailing List , Linux Networking Developer Mailing List , Linux Kernel Mailing List , eric.dumazet@gmail.com, Pablo Neira Ayuso Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3100 Lines: 97 On Wed, Feb 1, 2012 at 3:47 PM, Jan Engelhardt wrote: > > On Wednesday 2012-02-01 10:14, richard -rw- weinberger wrote: >>> >>> Do you have the patchset as a retrievable git tree, btw? >> >>Only for kernel stuff: >>git://git.kernel.org/pub/scm/linux/kernel/git/rw/misc.git xt_LOG >> >>If you want it for the user space part too, I can setup something... > > That would be welcome. Okay, will do! >>>>[PATCH 6/6] iptables: xt_LOG: Add ring buffer support >>>> >>>>in libxt_LOG.c: >>>>+.size = XT_ALIGN(sizeof(struct xt_log_info_v1) + sizeof(void *)), >>> >>> Why the extra void*? >> >>The kernel space part of ?xt_log_info_v1 differs from the user space struct, >>it contains an extra pointer to the ring buffer context. >>Iptables must not see this extra pointer because the kernel writes to it. > > I don't see that extra pointer (outside xt_log_info_v1) that you talk about. > > +struct xt_log_info_v1 { > + ? ? ? unsigned char level; > + ? ? ? unsigned char logflags; > + ? ? ? char prefix[30]; > + > + ? ? ? char ring_name[30]; > + ? ? ? unsigned long ring_size; > + ? ? ? struct xt_LOG_ring_ctx *rctx; > +}; > > This is the struct as you defined it. First, you must not use > unsigned long (due to its flexible size, which is an ABI breaker; cf. > "Writing Netfilter Modules" PDF), and the pointer must be tagged for > 8-alignment as well for the same reason. See: include/linux/netfilter/xt_LOG.h (user space part). +struct xt_log_info_v1 { + unsigned char level; + unsigned char logflags; + char prefix[30]; + + char ring_name[30]; + unsigned long ring_siVs.ze; +}; Here is no context pointer. I'll fix the unsigned long issue. > Second, the kernel will reject a ruleset if (kernel) .targetsize != (user) > .size. This is likely to occur, since you essentially have > .targetsize=72 in xt_LOG.c and .size=72+sizeof(void*) > in libxt_LOG. > > > > Check commit 8a252e8941cd50e4390e6fedf280ba1c7ff9ac43 for > trailing whitespace, git log -p shows them. > > + ? ? ? if (par->family == NFPROTO_IPV4) > + ? ? ? ? ? ? ? m = ipt_log_packet(NFPROTO_IPV4, par->hooknum, skb, par->in, > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?par->out, &li, loginfo->prefix); > +#if IS_ENABLED(CONFIG_IPV6) > + ? ? ? else if (par->family == NFPROTO_IPV6) > + ? ? ? ? ? ? ? m = ip6t_log_packet(NFPROTO_IPV6, par->hooknum, skb, par->in, > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? par->out, &li, loginfo->prefix); > +#endif > + ? ? ? else > + ? ? ? ? ? ? ? BUG(); > > Please avoid BUG. Either do nothing in the 'else' case, or print > a courtesy message with some unkn_log_packet() or > WARN_ON_ONCE(). The same goes for xt_LOG_ring_exit, which I vote > for being reduced to WARN_ON as well. If the condition triggers, > one will have a little memory leak, but at least the machine > still runs. Will fix! -- Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/