From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.netfilter.org (mail.netfilter.org [217.70.190.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CC5374CDA22; Wed, 16 Sep 2026 23:17:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.190.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789600624; cv=none; b=FsgXpTXTxfNPpivp8tke85aTOZN7YmXF8IgJyWZ02C/BL1A47SI3MjJMS7bycnSe2BZ8iGZ9pemrr7UsDYWfjJ/QhxOSN3YrJiYU5C+EO668u/qp4FSraWfQdfzxszf206afrQ7sZNYpfAudeqJzwVIzwl+qAk4RHsj0KStQX+4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789600624; c=relaxed/simple; bh=Me8xftH3rOGBjQhK+kMtrkecExm6eS0RQgg9t8Stnjc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=J0JcfZNAw6ZEBmtuo8Q7BP0pCeXPg5GRoJMoo4DwOdqoCnQLHiDhB4KCGohmwFJ7Q9a0ZfAV9VIN3WJnh/VEF7lwsYwkTif8UfJNJAvlPHT0Jl2DrqLNWmJBTljTrPkFedgiPje2mT8y9OO27hDdwGevu4SeDDh4015DGtqsOgQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b=IJWh4bAv; arc=none smtp.client-ip=217.70.190.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netfilter.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b="IJWh4bAv" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1789600620; bh=08cxZCjDbFNhxjzhJ9tap9ER4pgFbk5CK7pyqmcuhAs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IJWh4bAvlKdwjVrjlPmHrbZxnz75iw1ieoaI9Ww2OiBwLn4zTWDx44Zsndq9hnc5S sCSIZXWLErFdZiHC2gjKiFkgpEfNknfBb8bpAqlCG3lKCZGwR5w/b5l1gXbzmEOLoI eXoB4IfVoFnx/kk5eCvGT058/vID8jK+WyNTvaXd8JFZLoL0b0Yy8oP797LtXJ05oJ NoONbHv0nCIMONBbt7VyR/aQXOTCzSL/vooiGzzgMj54g9TfxCjsdXODhzr1gi9Zny LCHakH9PcBej3AsDqxCXv29lP3jrJEXi1ul4t6qBpSa4YcHw3Q4ALo/KsjmkZDbAIB 0vL9G6UXdwfhg== Received: from localhost.localdomain (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with ESMTPSA id 51E556008F; Thu, 17 Sep 2026 01:17:00 +0200 (CEST) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, horms@kernel.org, fw@strlen.de, ja@ssi.bg Subject: [PATCH net 03/10] netfilter: ip6t_rpfilter: reject routes without inet6_dev Date: Thu, 17 Sep 2026 01:16:44 +0200 Message-ID: <20260916231652.127456-4-pablo@netfilter.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260916231652.127456-1-pablo@netfilter.org> References: <20260916231652.127456-1-pablo@netfilter.org> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Weiming Shi ip6_route_lookup() can return an error-free route whose rt6i_idev is NULL. Lowering an external nexthop device's MTU below IPV6_MIN_MTU tears down its inet6_dev while fib6_ifdown() leaves routes using nexthop objects in the FIB. An unprivileged user can construct this state with rtnetlink in a private user and network namespace, then trigger a NULL dereference through an IPv6 rpfilter lookup: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: rpfilter_mt (net/ipv6/netfilter/ip6t_rpfilter.c:75) Call Trace: ip6t_do_table (net/ipv6/netfilter/ip6_tables.c:316) nf_hook_slow (net/netfilter/core.c:619) ipv6_rcv (net/ipv6/ip6_input.c:351) __netif_receive_skb_one_core (net/core/dev.c:6216) process_backlog (net/core/dev.c:6680) __napi_poll (net/core/dev.c:7739) net_rx_action (net/core/dev.c:7959) handle_softirqs (kernel/softirq.c:622) do_softirq.part.0 (kernel/softirq.c:523) __local_bh_enable_ip (kernel/softirq.c:450) __dev_queue_xmit (net/core/dev.c:4913) packet_sendmsg (net/packet/af_packet.c:3139) __sys_sendto (net/socket.c:2252) __x64_sys_sendto (net/socket.c:2259) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt Reject routes without an inet6_dev immediately after lookup. Such routes are not eligible for reverse-path filtering, and the check protects all later rt6i_idev dereferences. Fixes: e26f9a480fb6 ("netfilter: add ipv6 reverse path filter match") Reported-by: co+459f67f4d8af8ce6@bugs.sh Closes: https://lore.kernel.org/all/VtWUkE8QzJt5CroTj2V2v3ZQ0gwbXZ7nq7I3@bugs.sh/ Suggested-by: Florian Westphal Assisted-by: Claude:gpt-5 Cc: stable@vger.kernel.org Signed-off-by: Weiming Shi Signed-off-by: Pablo Neira Ayuso --- net/ipv6/netfilter/ip6t_rpfilter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/netfilter/ip6t_rpfilter.c b/net/ipv6/netfilter/ip6t_rpfilter.c index 67c87a88cde4..b5def30c3127 100644 --- a/net/ipv6/netfilter/ip6t_rpfilter.c +++ b/net/ipv6/netfilter/ip6t_rpfilter.c @@ -61,7 +61,7 @@ static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb, fl6.flowi6_oif = dev->ifindex; rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags); - if (rt->dst.error) + if (rt->dst.error || !rt->rt6i_idev) goto out; if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST)) -- 2.47.3