From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout07.his.huawei.com (canpmsgout07.his.huawei.com [113.46.200.222]) (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 A17EB2E54B6 for ; Sat, 29 Aug 2026 09:25:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.222 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787995538; cv=none; b=SqBwQWGApBxmfTOuWV3PRc1lZWRZT7r+b+SsnvuIPc7ERjXtJBiRH0+gWKo6C3jW8qrM9WESonqQEuJmNN1kQxFikV1+QE8zttyg27C0z+urPbyW234VGy70eppvJe63pCw3VaSuA5k9vvEpAJVlWdAa0/gmLmnPkJuCsbxo/Dk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787995538; c=relaxed/simple; bh=KpwPoGz4OlkHZ/v32iX4PcHbee6r/0XA5ykjKt9KfNE=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=Xur4uYqM/fbXPCSip05aY6hqwkm6uvldQEBTbhPJA38XwOjmAaYNT1TWQiABk77vVcFQyYdrPzQGHGxcwSNtDc/3vQH0dhusThnFE/CAO5uz6ZykWM686YHUtZR2YT724xuO6ZpL/FPx+QxpHdIaLdrG1edUku1Gvj9Hr2zPy+U= 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=ntp3OZ46; arc=none smtp.client-ip=113.46.200.222 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="ntp3OZ46" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=Emdl/f/ACtPAcDMHpGez4HrIl0NLe0ft3uByr8TE4Yw=; b=ntp3OZ46vqqlgWrbgQhYYXMvB8klNL8Ua8l7PI6HyKweHfIDsWjO0aAbWJvDF9gW2g6NDriMd TIgRHVNslcXV58TNMO2tEV6t27SHH1MHlz9JPeFY3/Wec9tetbm0dv4j2/LTwnlLYNj0sChVRBg GBL73f+kw6Xh41A6ItzVtPI= Received: from mail.maildlp.com (unknown [172.19.163.163]) by canpmsgout07.his.huawei.com (SkyGuard) with ESMTPS id 4hX8hn3GnDzLlTk; Sat, 29 Aug 2026 17:14:33 +0800 (CST) Received: from whupemk200012.china.huawei.com (unknown [7.152.185.169]) by mail.maildlp.com (Postfix) with ESMTPS id E69924048B; Sat, 29 Aug 2026 17:25:20 +0800 (CST) Received: from localhost.localdomain (10.50.85.175) by whupemk200012.china.huawei.com (7.152.185.169) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Sat, 29 Aug 2026 17:25:19 +0800 From: Dong Chenchen To: , , , , , , , , CC: , , Dong Chenchen Subject: [PATCH net v4] ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup Date: Sat, 29 Aug 2026 17:34:00 +0800 Message-ID: <20260829093400.1531398-1-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: kwepems500002.china.huawei.com (7.221.188.17) To whupemk200012.china.huawei.com (7.152.185.169) 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 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. --- net/ipv4/icmp.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 0caedfc7ca92..288da11c5de8 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -581,16 +581,17 @@ 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) { - 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)) { + if (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); dst_release(&rt2->dst); err = -EINVAL; } -- 2.25.1