From nobody Sat Feb 7 20:41:02 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0982CEB64DC for ; Tue, 18 Jul 2023 18:23:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229934AbjGRSXZ (ORCPT ); Tue, 18 Jul 2023 14:23:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229888AbjGRSXQ (ORCPT ); Tue, 18 Jul 2023 14:23:16 -0400 Received: from mail-qk1-x731.google.com (mail-qk1-x731.google.com [IPv6:2607:f8b0:4864:20::731]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F5902133 for ; Tue, 18 Jul 2023 11:22:51 -0700 (PDT) Received: by mail-qk1-x731.google.com with SMTP id af79cd13be357-76754b9eac0so565824085a.0 for ; Tue, 18 Jul 2023 11:22:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; t=1689704569; x=1692296569; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :from:to:cc:subject:date:message-id:reply-to; bh=8AccF1SH0Y/JdOIILtRJfpt1KSbJ1RJLB1Gr9T87MgQ=; b=y55DQ0ccRWb6COUVaYx73KAnztfT22L6tm0bmuaM50598rvJ5Y6eD7a8Et8Mvnxr4v 2apMRynnMF1C3N9iuaHqnlHa6dMxDpRuPJiaxWWYtaPTgV+e9kUf5Pfjg0bX6xK1Tt91 KlUrfzFAwy2kOwP3ylFCArl6WDG/yTJx2SdJ4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689704569; x=1692296569; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=8AccF1SH0Y/JdOIILtRJfpt1KSbJ1RJLB1Gr9T87MgQ=; b=ObVXCtO8+F0TM3KqVjnyu/jtKGuEzd1X1Ggo0CeocjCS09do9+12jPVq/gk2XpEGki sKTZlfPYUdZheATznRXEdE8htUrTuaqkIPzUT7IEJVUJtxxx0WaPZTGcUt7VNQ2KFdFz WBeK/j3XjJdUUronOGNVZI1upIDczU0HhLOyqCOhbbFWnBZVWGVKqhxsJ0MNlR9QUbY0 exkYCiLyahq0i8gvdPCaD85Z2n2wxWzhz9gxk36VWSQigAWOd6OIjuJhS5E2DN/KjDEy 7gqAFVn3NlgavNjtZyEBZk82gAVGqWskjlX1IW66pBUAl0rLvZ74NgRPRNq/My69sVhI m46A== X-Gm-Message-State: ABy/qLbGVcdS6d9u3YLK2PMQKiz79H8q3aZVsvmNHYoYDb12Ef3d6TAF hSSo1aIQd7PoiAkOb6oX6Qdytw== X-Google-Smtp-Source: APBJJlEteunjPjWOeYmnXJKjAGsOAYEHHNQfxFRrs9W3n0YlOAsgaxljr7z5c21XZHsvYlbYTc+FTw== X-Received: by 2002:a05:620a:4512:b0:767:1938:93c7 with SMTP id t18-20020a05620a451200b00767193893c7mr682655qkp.43.1689704569008; Tue, 18 Jul 2023 11:22:49 -0700 (PDT) Received: from debian.debian ([140.141.197.139]) by smtp.gmail.com with ESMTPSA id pi30-20020a05620a379e00b00767d572d651sm762073qkn.87.2023.07.18.11.22.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Jul 2023 11:22:48 -0700 (PDT) Date: Tue, 18 Jul 2023 11:22:46 -0700 From: Yan Zhai To: "open list:BPF [NETWORKING] (tc BPF, sock_addr)" Cc: kernel-team@cloudflare.com, Martin KaFai Lau , Daniel Borkmann , John Fastabend , Alexei Starovoitov , Andrii Nakryiko , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "open list:BPF [NETWORKING] (tc BPF, sock_addr)" , open list , Jordan Griege Subject: [PATCH] bpf: lwt: do not return NET_XMIT_xxx values on bpf_redirect Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" skb_do_redirect handles returns error code from both rx and tx path. The tx path codes are special, e.g. NET_XMIT_CN: they are non-negative, and can conflict with LWTUNNEL_XMIT_xxx values. Directly returning such code can cause unexpected behavior. We found at least one bug that will panic the kernel through KASAN report when we accidentally redirect packets to a down or carrier-down device at lwt xmit hook: https://gist.github.com/zhaiyan920/8fbac245b261fe316a7ef04c9b1eba48 Above bug is hit because NET_XMIT_CN is returned by noop_qdisc of the down device, and it propagates from dev_queue_xmit all way to the lwt logic. Although skb has been freed by the qdisc, it still continues to neighbor subsystem and triggers the bug. This change converts the tx code to proper errors that lwt can consume. Reported-by: Jordan Griege Signed-off-by: Yan Zhai --- net/core/filter.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/core/filter.c b/net/core/filter.c index 06ba0e56e369..c9cc501ecdc0 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2129,6 +2129,11 @@ static inline int __bpf_tx_skb(struct net_device *de= v, struct sk_buff *skb) ret =3D dev_queue_xmit(skb); dev_xmit_recursion_dec(); =20 + // We should not return NET_XMIT_xxx here since it will conflict with + // LWTUNNEL_XMIT_xxx values. Convert the return value to errno instead. + if (unlikely(ret !=3D NET_XMIT_SUCCESS)) + ret =3D net_xmit_errno(ret); + return ret; } =20 --=20 2.30.2