From patchwork Tue Jun 2 14:58:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Borkmann X-Patchwork-Id: 218037 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C839C433E0 for ; Tue, 2 Jun 2020 14:58:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 265F82074B for ; Tue, 2 Jun 2020 14:58:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728091AbgFBO6o (ORCPT ); Tue, 2 Jun 2020 10:58:44 -0400 Received: from www62.your-server.de ([213.133.104.62]:37380 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726311AbgFBO6n (ORCPT ); Tue, 2 Jun 2020 10:58:43 -0400 Received: from 75.57.196.178.dynamic.wline.res.cust.swisscom.ch ([178.196.57.75] helo=localhost) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1jg8NE-0007bm-Ii; Tue, 02 Jun 2020 16:58:40 +0200 From: Daniel Borkmann To: alexei.starovoitov@gmail.com Cc: lmb@cloudflare.com, alan.maguire@oracle.com, bpf@vger.kernel.org, netdev@vger.kernel.org, Daniel Borkmann Subject: [PATCH bpf 1/3] bpf: Fix up bpf_skb_adjust_room helper's skb csum setting Date: Tue, 2 Jun 2020 16:58:32 +0200 Message-Id: <11a90472e7cce83e76ddbfce81fdfce7bfc68808.1591108731.git.daniel@iogearbox.net> X-Mailer: git-send-email 2.21.0 In-Reply-To: References: MIME-Version: 1.0 X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.2/25831/Tue Jun 2 14:41:03 2020) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Lorenz recently reported: In our TC classifier cls_redirect [0], we use the following sequence of helper calls to decapsulate a GUE (basically IP + UDP + custom header) encapsulated packet: bpf_skb_adjust_room(skb, -encap_len, BPF_ADJ_ROOM_MAC, BPF_F_ADJ_ROOM_FIXED_GSO) bpf_redirect(skb->ifindex, BPF_F_INGRESS) It seems like some checksums of the inner headers are not validated in this case. For example, a TCP SYN packet with invalid TCP checksum is still accepted by the network stack and elicits a SYN ACK. [...] That is, we receive the following packet from the driver: | ETH | IP | UDP | GUE | IP | TCP | skb->ip_summed == CHECKSUM_UNNECESSARY ip_summed is CHECKSUM_UNNECESSARY because our NICs do rx checksum offloading. On this packet we run skb_adjust_room_mac(-encap_len), and get the following: | ETH | IP | TCP | skb->ip_summed == CHECKSUM_UNNECESSARY Note that ip_summed is still CHECKSUM_UNNECESSARY. After bpf_redirect()'ing into the ingress, we end up in tcp_v4_rcv(). There, skb_checksum_init() is turned into a no-op due to CHECKSUM_UNNECESSARY. The bpf_skb_adjust_room() helper is not aware of protocol specifics. Internally, it handles the CHECKSUM_COMPLETE case via skb_postpull_rcsum(), but that does not cover CHECKSUM_UNNECESSARY. In this case skb->csum_level of the original skb prior to bpf_skb_adjust_room() call was 0, that is, covering UDP. Right now there is no way to adjust the skb->csum_level. NICs that have checksum offload disabled (CHECKSUM_NONE) or that support CHECKSUM_COMPLETE are not affected. Use a safe default for CHECKSUM_UNNECESSARY by resetting to CHECKSUM_NONE and add a flag to the helper called BPF_F_ADJ_ROOM_NO_CSUM_RESET that allows users from opting out. Opting out is useful for the case where we don't remove/add full protocol headers, or for the case where a user wants to adjust the csum level manually e.g. through bpf_csum_level() helper that is added in subsequent patch. The bpf_skb_proto_{4_to_6,6_to_4}() for NAT64/46 translation from the BPF bpf_skb_change_proto() helper uses bpf_skb_net_hdr_{push,pop}() pair internally as well but doesn't change layers, only transitions between v4 to v6 and vice versa, therefore no adoption is required there. [0] https://lore.kernel.org/bpf/20200424185556.7358-1-lmb@cloudflare.com/ Fixes: 2be7e212d541 ("bpf: add bpf_skb_adjust_room helper") Reported-by: Lorenz Bauer Reported-by: Alan Maguire Signed-off-by: Daniel Borkmann Signed-off-by: Lorenz Bauer Reviewed-by: Alan Maguire Link: https://lore.kernel.org/bpf/CACAyw9-uU_52esMd1JjuA80fRPHJv5vsSg8GnfW3t_qDU4aVKQ@mail.gmail.com/ --- include/linux/skbuff.h | 8 ++++++++ include/uapi/linux/bpf.h | 8 ++++++++ net/core/filter.c | 8 ++++++-- tools/include/uapi/linux/bpf.h | 8 ++++++++ 4 files changed, 30 insertions(+), 2 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index a0d5c2760103..0c0377fc00c2 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -3919,6 +3919,14 @@ static inline void __skb_incr_checksum_unnecessary(struct sk_buff *skb) } } +static inline void __skb_reset_checksum_unnecessary(struct sk_buff *skb) +{ + if (skb->ip_summed == CHECKSUM_UNNECESSARY) { + skb->ip_summed = CHECKSUM_NONE; + skb->csum_level = 0; + } +} + /* Check if we need to perform checksum complete validation. * * Returns true if checksum complete is needed, false otherwise diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index b9ed9f14f2a2..3ba2bbbed80c 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -1635,6 +1635,13 @@ union bpf_attr { * Grow or shrink the room for data in the packet associated to * *skb* by *len_diff*, and according to the selected *mode*. * + * By default, the helper will reset any offloaded checksum + * indicator of the skb to CHECKSUM_NONE. This can be avoided + * by the following flag: + * + * * **BPF_F_ADJ_ROOM_NO_CSUM_RESET**: Do not reset offloaded + * checksum data of the skb to CHECKSUM_NONE. + * * There are two supported modes at this time: * * * **BPF_ADJ_ROOM_MAC**: Adjust room at the mac layer @@ -3433,6 +3440,7 @@ enum { BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 = (1ULL << 2), BPF_F_ADJ_ROOM_ENCAP_L4_GRE = (1ULL << 3), BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4), + BPF_F_ADJ_ROOM_NO_CSUM_RESET = (1ULL << 5), }; enum { diff --git a/net/core/filter.c b/net/core/filter.c index ae82bcb03124..278dcc0af961 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3113,7 +3113,8 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff, { int ret; - if (flags & ~BPF_F_ADJ_ROOM_FIXED_GSO) + if (unlikely(flags & ~(BPF_F_ADJ_ROOM_FIXED_GSO | + BPF_F_ADJ_ROOM_NO_CSUM_RESET))) return -EINVAL; if (skb_is_gso(skb) && !skb_is_gso_tcp(skb)) { @@ -3163,7 +3164,8 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, u32 off; int ret; - if (unlikely(flags & ~BPF_F_ADJ_ROOM_MASK)) + if (unlikely(flags & ~(BPF_F_ADJ_ROOM_MASK | + BPF_F_ADJ_ROOM_NO_CSUM_RESET))) return -EINVAL; if (unlikely(len_diff_abs > 0xfffU)) return -EFAULT; @@ -3191,6 +3193,8 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, ret = shrink ? bpf_skb_net_shrink(skb, off, len_diff_abs, flags) : bpf_skb_net_grow(skb, off, len_diff_abs, flags); + if (!ret && !(flags & BPF_F_ADJ_ROOM_NO_CSUM_RESET)) + __skb_reset_checksum_unnecessary(skb); bpf_compute_data_pointers(skb); return ret; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index b9ed9f14f2a2..3ba2bbbed80c 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -1635,6 +1635,13 @@ union bpf_attr { * Grow or shrink the room for data in the packet associated to * *skb* by *len_diff*, and according to the selected *mode*. * + * By default, the helper will reset any offloaded checksum + * indicator of the skb to CHECKSUM_NONE. This can be avoided + * by the following flag: + * + * * **BPF_F_ADJ_ROOM_NO_CSUM_RESET**: Do not reset offloaded + * checksum data of the skb to CHECKSUM_NONE. + * * There are two supported modes at this time: * * * **BPF_ADJ_ROOM_MAC**: Adjust room at the mac layer @@ -3433,6 +3440,7 @@ enum { BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 = (1ULL << 2), BPF_F_ADJ_ROOM_ENCAP_L4_GRE = (1ULL << 3), BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4), + BPF_F_ADJ_ROOM_NO_CSUM_RESET = (1ULL << 5), }; enum { From patchwork Tue Jun 2 14:58:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Borkmann X-Patchwork-Id: 218038 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2E8FC433E0 for ; Tue, 2 Jun 2020 14:58:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D21D02074B for ; Tue, 2 Jun 2020 14:58:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728157AbgFBO6q (ORCPT ); Tue, 2 Jun 2020 10:58:46 -0400 Received: from www62.your-server.de ([213.133.104.62]:37388 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726867AbgFBO6n (ORCPT ); Tue, 2 Jun 2020 10:58:43 -0400 Received: from 75.57.196.178.dynamic.wline.res.cust.swisscom.ch ([178.196.57.75] helo=localhost) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1jg8NF-0007c5-HT; Tue, 02 Jun 2020 16:58:41 +0200 From: Daniel Borkmann To: alexei.starovoitov@gmail.com Cc: lmb@cloudflare.com, alan.maguire@oracle.com, bpf@vger.kernel.org, netdev@vger.kernel.org, Daniel Borkmann Subject: [PATCH bpf 3/3] bpf, selftests: Adapt cls_redirect to call csum_level helper Date: Tue, 2 Jun 2020 16:58:34 +0200 Message-Id: X-Mailer: git-send-email 2.21.0 In-Reply-To: References: MIME-Version: 1.0 X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.2/25831/Tue Jun 2 14:41:03 2020) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Adapt bpf_skb_adjust_room() to pass in BPF_F_ADJ_ROOM_NO_CSUM_RESET flag and use the new bpf_csum_level() helper to inc/dec the checksum level by one after the encap/decap. Signed-off-by: Daniel Borkmann --- tools/testing/selftests/bpf/progs/test_cls_redirect.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/test_cls_redirect.c b/tools/testing/selftests/bpf/progs/test_cls_redirect.c index 1668b993eb86..f0b72e86bee5 100644 --- a/tools/testing/selftests/bpf/progs/test_cls_redirect.c +++ b/tools/testing/selftests/bpf/progs/test_cls_redirect.c @@ -380,9 +380,10 @@ static ret_t accept_locally(struct __sk_buff *skb, encap_headers_t *encap) } if (bpf_skb_adjust_room(skb, -encap_overhead, BPF_ADJ_ROOM_MAC, - BPF_F_ADJ_ROOM_FIXED_GSO)) { + BPF_F_ADJ_ROOM_FIXED_GSO | + BPF_F_ADJ_ROOM_NO_CSUM_RESET) || + bpf_csum_level(skb, BPF_CSUM_LEVEL_DEC)) return TC_ACT_SHOT; - } return bpf_redirect(skb->ifindex, BPF_F_INGRESS); } @@ -472,7 +473,9 @@ static ret_t forward_with_gre(struct __sk_buff *skb, encap_headers_t *encap, } if (bpf_skb_adjust_room(skb, delta, BPF_ADJ_ROOM_NET, - BPF_F_ADJ_ROOM_FIXED_GSO)) { + BPF_F_ADJ_ROOM_FIXED_GSO | + BPF_F_ADJ_ROOM_NO_CSUM_RESET) || + bpf_csum_level(skb, BPF_CSUM_LEVEL_INC)) { metrics->errors_total_encap_adjust_failed++; return TC_ACT_SHOT; }