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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E7F7C4332F for ; Thu, 21 Oct 2021 10:08:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3645F610FF for ; Thu, 21 Oct 2021 10:08:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231741AbhJUKKr (ORCPT ); Thu, 21 Oct 2021 06:10:47 -0400 Received: from mail.netfilter.org ([217.70.188.207]:33826 "EHLO mail.netfilter.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231447AbhJUKKo (ORCPT ); Thu, 21 Oct 2021 06:10:44 -0400 Received: from localhost.localdomain (unknown [78.30.32.163]) by mail.netfilter.org (Postfix) with ESMTPSA id AB90463F3C; Thu, 21 Oct 2021 12:06:45 +0200 (CEST) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org Subject: [PATCH net 3/8] netfilter: nf_tables: skip netdev events generated on netns removal Date: Thu, 21 Oct 2021 12:08:16 +0200 Message-Id: <20211021100821.964677-4-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211021100821.964677-1-pablo@netfilter.org> References: <20211021100821.964677-1-pablo@netfilter.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Florian Westphal syzbot reported following (harmless) WARN: WARNING: CPU: 1 PID: 2648 at net/netfilter/core.c:468 nft_netdev_unregister_hooks net/netfilter/nf_tables_api.c:230 [inline] nf_tables_unregister_hook include/net/netfilter/nf_tables.h:1090 [inline] __nft_release_basechain+0x138/0x640 net/netfilter/nf_tables_api.c:9524 nft_netdev_event net/netfilter/nft_chain_filter.c:351 [inline] nf_tables_netdev_event+0x521/0x8a0 net/netfilter/nft_chain_filter.c:382 reproducer: unshare -n bash -c 'ip link add br0 type bridge; nft add table netdev t ; \ nft add chain netdev t ingress \{ type filter hook ingress device "br0" \ priority 0\; policy drop\; \}' Problem is that when netns device exit hooks create the UNREGISTER event, the .pre_exit hook for nf_tables core has already removed the base hook. Notifier attempts to do this again. The need to do base hook unregister unconditionally was needed in the past, because notifier was last stage where reg->dev dereference was safe. Now that nf_tables does the hook removal in .pre_exit, this isn't needed anymore. Reported-and-tested-by: syzbot+154bd5be532a63aa778b@syzkaller.appspotmail.com Fixes: 767d1216bff825 ("netfilter: nftables: fix possible UAF over chains from packet path in netns") Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_chain_filter.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c index 5b02408a920b..3ced0eb6b7c3 100644 --- a/net/netfilter/nft_chain_filter.c +++ b/net/netfilter/nft_chain_filter.c @@ -342,12 +342,6 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, return; } - /* UNREGISTER events are also happening on netns exit. - * - * Although nf_tables core releases all tables/chains, only this event - * handler provides guarantee that hook->ops.dev is still accessible, - * so we cannot skip exiting net namespaces. - */ __nft_release_basechain(ctx); } @@ -366,6 +360,9 @@ static int nf_tables_netdev_event(struct notifier_block *this, event != NETDEV_CHANGENAME) return NOTIFY_DONE; + if (!check_net(ctx.net)) + return NOTIFY_DONE; + nft_net = nft_pernet(ctx.net); mutex_lock(&nft_net->commit_mutex); list_for_each_entry(table, &nft_net->tables, list) { -- 2.30.2