From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout12.his.huawei.com (canpmsgout12.his.huawei.com [113.46.200.227]) (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 366054949F2 for ; Thu, 10 Sep 2026 13:52:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.227 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789048344; cv=none; b=kZBwvfuBUZuZgde1Nnn7nrniEr3J0kAizD+mhFoVaUE/I4FUxs3RihUa/9qeitjjNB95nMCQc6aglGmC7/ZPvXLYqZXPY/b8e533D+EFHGtjpn4J4YUhMDZ4gWPo+ICMUYh15fc1Jz1O7ji8AU8msd1o4EzMecL199TDqWADnM8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789048344; c=relaxed/simple; bh=FWNkayyt98XWizn+TnLX4IeeWjcWx693RzsE5aZPFOU=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=DQQc4OgbFh4AMiXX/ZftYaf6nvhp5K8ZbpPaGYKPaNha9ltKelXU+WAEtV/0LCmPVJp8fCSAwSm9JZd4vWTTAOLb0MFQKkI8HbM74128h7ZaA6/UHR5JHewckXygKZcYwq9r0qOVO1GM+UVIKKnOGJaSPVb6kVlXZpSZAE8Znd0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=hoB8B5Oi; arc=none smtp.client-ip=113.46.200.227 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="hoB8B5Oi" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=CezzRRH2VOMxiELJvJIAlqhXHUwdxVIitGvfkBQTXuw=; b=hoB8B5OiMzIeTExhQ2Zv1/eQlTlMt6m7sRQdhHCVgJfKWaevECSpKfKbZ/bTPUtaL+5SCuKWK nO17t5bUC0n6YfR3098pErN3/bF/uaq0JYllvSnXN+5PXSpLzIT9iXGvZRJB5fTT7yudYscwuit pIVEbyG/ixOTLd7TLJ1DxUE= Received: from mail.maildlp.com (unknown [172.19.163.127]) by canpmsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4hgf2l4RrsznTVd; Thu, 10 Sep 2026 21:41:03 +0800 (CST) Received: from whupemk100012.china.huawei.com (unknown [7.152.185.0]) by mail.maildlp.com (Postfix) with ESMTPS id 126DE402AB; Thu, 10 Sep 2026 21:52:12 +0800 (CST) Received: from localhost.localdomain (10.50.85.175) by whupemk100012.china.huawei.com (7.152.185.0) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Thu, 10 Sep 2026 21:52:10 +0800 From: Dong Chenchen To: , , , , , , , , CC: , , Dong Chenchen Subject: [PATCH net v5] ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup Date: Thu, 10 Sep 2026 22:00:42 +0800 Message-ID: <20260910140042.1880242-1-dongchenchen2@huawei.com> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To whupemk100012.china.huawei.com (7.152.185.0) When the forward output route cannot be used in icmp_route_lookup(), it enters the "reverse path" and calls ip_route_input() on fl4_dec.daddr, the original packet's source address. ip_route_input() only returns an error for truly invalid packets. For unreachable addresses it will succeed and return an input route whose dst.output is set to ip_rt_bug(). The existing check only rejects RTN_LOCAL routes, so the RTN_UNREACHABLE route types can still be returned and later used for output, syzkaller triggering a WARN_ON_ONCE() in ip_rt_bug() as bellow: ------------[ cut here ]------------ WARNING: net/ipv4/route.c:1273 at ip_rt_bug+0x14/0x20 RIP: 0010:ip_rt_bug+0x14/0x20 Call Trace: ip_push_pending_frames+0xfa/0x100 __icmp_send+0x905/0xf10 ip_options_compile+0xc0/0xd0 ip_rcv_finish_core+0x321/0xae0 ip_rcv+0x1de/0x260 __netif_receive_skb_one_core+0x11a/0x130 netif_receive_skb+0x7b/0x260 tun_get_user+0x11bf/0x1c10 ------------[ cut here ]------------ Reject input route that is RTN_UNREACHABLE to fix it. The net warning is only printed for RTN_LOCAL, as RTN_UNREACHABLE is not the result of a race condition. Fixes: 8b7817f3a959 ("[IPSEC]: Add ICMP host relookup support") Suggested-by: Ido Schimmel Reviewed-by: Jiayuan Chen Reviewed-by: Ido Schimmel Signed-off-by: Dong Chenchen --- v2: - RTN_UNICAST judgement will reject bforward packet. Only reject RTN_UNREACHABLE v3: - RTN_UNREACHABLE dont need warn log. v4: - Modify the comments and commit msg to make them more accurate. v5: - avoid going over 80 chars --- net/ipv4/icmp.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 0caedfc7ca92..90c0e22c29be 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -581,16 +581,19 @@ static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4, skb_dstref_restore(skb_in, orefdst); /* - * At this point, fl4_dec.daddr should NOT be local (we - * checked fl4_dec.saddr above). However, a race condition - * may occur if the address is added to the interface - * concurrently. In that case, ip_route_input() returns a - * LOCAL route with dst.output=ip_rt_bug, which must not - * be used for output. + * fl4_dec.daddr is not expected to be local here, but it can be + * added to an interface concurrently, in which case + * ip_route_input() returns a LOCAL route. It can also fail to + * build a forwarding route towards fl4_dec.daddr, for example, + * when forwarding is disabled, and return an UNREACHABLE route. + * Both cases will result in a route with dst.output=ip_rt_bug, + * which must not be used for output. */ - if (!err && rt2 && rt2->rt_type == RTN_LOCAL) { + if (!err && rt2 && rt2->rt_type == RTN_LOCAL) net_warn_ratelimited("detected local route for %pI4 during ICMP sending, src %pI4\n", &fl4_dec.daddr, &fl4_dec.saddr); + if (!err && rt2 && + (rt2->rt_type == RTN_LOCAL || rt2->rt_type == RTN_UNREACHABLE)) { dst_release(&rt2->dst); err = -EINVAL; } -- 2.25.1