From nobody Wed Dec 17 17:58:23 2025 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 E705BC7113D for ; Fri, 18 Aug 2023 02:59:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357359AbjHRC63 (ORCPT ); Thu, 17 Aug 2023 22:58:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357342AbjHRC6P (ORCPT ); Thu, 17 Aug 2023 22:58:15 -0400 Received: from mail-qt1-x832.google.com (mail-qt1-x832.google.com [IPv6:2607:f8b0:4864:20::832]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C35D01BB for ; Thu, 17 Aug 2023 19:58:14 -0700 (PDT) Received: by mail-qt1-x832.google.com with SMTP id d75a77b69052e-40ff796e8ddso3446021cf.2 for ; Thu, 17 Aug 2023 19:58:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; t=1692327494; x=1692932294; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=B//PxqTOcLRZSFYVWOXGViYC9OULMJhe+RhXHERECls=; b=tmv/IW4eAJDthaFDwjvi9IaSF4Rcud5RPAMq/Cw6bY18saA/WzMcE2wsVXdr2M9HuI ELfdKCcPerKH0tBnpuC8ZnlQx1DdOGyQU12dGiagEAyQZXRak7SX8KpqDsdc4b4Igmcw 3dfj9Vwi3iaCkZkmtpe6IaOU7anpUGK0uLf/0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692327494; x=1692932294; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=B//PxqTOcLRZSFYVWOXGViYC9OULMJhe+RhXHERECls=; b=Wb6WTD25VIlnRn6ooSPYD3frKqrSai9Si4EcyEUdN/iRHaN+0SyQL+5JWVvsJzAK0v ubxK+Bn4n8pVhRMoFInt+zouR1LVf3Nww2DzwHeCo9Z3rCJj2yDETlRam/LOhYZ7jbQ5 TfaQx6uMFbC+YpzZaY1PVqtR6uG01UkuB893T3XPqIm96gDERTn1Eo2niJe4gs2rKiw4 ECY7MB2pZZwgxCOHwmfGjOstxPT6bIm9XnifqyRwGAv7D1QOX8+vRWUZMQf61nZ97WS4 nuUJg52bBThgQAHQiNxhxVdG/IvLTvJddH7+RulBk85tYUusWwfXYlGg35+EEWqBdtfL KBug== X-Gm-Message-State: AOJu0YwUgP9NNJmfeKFDyj0dckeGT7P4YoXX5qc0hUFtcgR4vZC1dfOg NgPmY02MdcLfRPrYIDL/d5PI9A== X-Google-Smtp-Source: AGHT+IH7rjUWj757WVMp0Qqu31Vckq9gjzUG4qfABg1kPLHXqiniH9ZGEnmCzeHgJSsJdQ3Rc6uMDA== X-Received: by 2002:ac8:5742:0:b0:408:2e66:3a1b with SMTP id 2-20020ac85742000000b004082e663a1bmr2008883qtx.3.1692327493979; Thu, 17 Aug 2023 19:58:13 -0700 (PDT) Received: from debian.debian ([140.141.197.139]) by smtp.gmail.com with ESMTPSA id m17-20020a0cdb91000000b0063d3744c5c5sm350536qvk.5.2023.08.17.19.58.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Aug 2023 19:58:13 -0700 (PDT) Date: Thu, 17 Aug 2023 19:58:11 -0700 From: Yan Zhai To: bpf@vger.kernel.org Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Ahern , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , Yan Zhai , Thomas Graf , Jordan Griege , Dan Carpenter , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v6 bpf 1/4] lwt: fix return values of BPF xmit ops Message-ID: <0d2b878186cfe215fec6b45769c1cd0591d3628d.1692326837.git.yan@cloudflare.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" BPF encap ops can return different types of positive values, such like NET_RX_DROP, NET_XMIT_CN, NETDEV_TX_BUSY, and so on, from function skb_do_redirect and bpf_lwt_xmit_reroute. At the xmit hook, such return values would be treated implicitly as LWTUNNEL_XMIT_CONTINUE in ip(6)_finish_output2. When this happens, skbs that have been freed would continue to the neighbor subsystem, causing use-after-free bug and kernel crashes. To fix the incorrect behavior, skb_do_redirect return values can be simply discarded, the same as tc-egress behavior. On the other hand, bpf_lwt_xmit_reroute returns useful errors to local senders, e.g. PMTU information. Thus convert its return values to avoid the conflict with LWTUNNEL_XMIT_CONTINUE. Fixes: 3a0af8fd61f9 ("bpf: BPF for lightweight tunnel infrastructure") Suggested-by: Martin KaFai Lau Suggested-by: Stanislav Fomichev Reported-by: Jordan Griege Signed-off-by: Yan Zhai --- * v5: discards skb_do_redirect return instead; convert bpf_lwt_xmit_reroute return; * v4: minor commit message changes * v3: converts skb_do_redirect statuses from both ingress and egress * v2: code style amend --- net/core/lwt_bpf.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c index 8b6b5e72b217..4a0797f0a154 100644 --- a/net/core/lwt_bpf.c +++ b/net/core/lwt_bpf.c @@ -60,9 +60,8 @@ static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lw= t_prog *lwt, ret =3D BPF_OK; } else { skb_reset_mac_header(skb); - ret =3D skb_do_redirect(skb); - if (ret =3D=3D 0) - ret =3D BPF_REDIRECT; + skb_do_redirect(skb); + ret =3D BPF_REDIRECT; } break; =20 @@ -255,7 +254,7 @@ static int bpf_lwt_xmit_reroute(struct sk_buff *skb) =20 err =3D dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb); if (unlikely(err)) - return err; + return net_xmit_errno(err); =20 /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */ return LWTUNNEL_XMIT_DONE; --=20 2.30.2