From mboxrd@z Thu Jan 1 00:00:00 1970 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 E50BFC4332F for ; Thu, 27 Jan 2022 17:24:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238856AbiA0RYx (ORCPT ); Thu, 27 Jan 2022 12:24:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34542 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232315AbiA0RYx (ORCPT ); Thu, 27 Jan 2022 12:24:53 -0500 Received: from mail-wr1-x42c.google.com (mail-wr1-x42c.google.com [IPv6:2a00:1450:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1D54C061714 for ; Thu, 27 Jan 2022 09:24:52 -0800 (PST) Received: by mail-wr1-x42c.google.com with SMTP id c23so6091377wrb.5 for ; Thu, 27 Jan 2022 09:24:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=4OSnApzs5/dDYr7P92s+LuaWCqvDMi+S9AX1oUrs0vM=; b=RP5892c78EVoktgEsHSpYsIIxek1kSg6BAuAOkqlPIjeFN4Hke/6UgjJcuElKoGQro rEyR6H/9mi+lWFYwrMAVjP2SOscHXAeJ9QWyxzTZMTXThfoRxqIrJt+KMoSFgkEE9Bo4 trDshLbdFpQaJdVZNQPAM9T7bORJDYKkG19m8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=4OSnApzs5/dDYr7P92s+LuaWCqvDMi+S9AX1oUrs0vM=; b=e5a4ZKsltCH1CWqlcORG01Ks5eomwNV2ytQDBjy9uJtr4SYJR3sL3eFtVHWSpaFqo6 hoXs0Cb3EqWZHv+theXuuUPOSZNN3TSkjSedfJ2IHPMUfW/1Z5GEeIT1pemLddFwMCCS XlFSj9/Ta1MdvyIcUutVV66UviUjVFhsFrsztPuDWywwzZiqY2vAMKkxjuho4poe0Q7o kQWQconmFDUrUfSpXkHptHDvnKafu2uhgKjuZ+wny6RRXpHoZSa40/QViQLbsLUSP9RX wDTJk5sFZ53cUo7FbffY+XnR/MbP4sNRvnGruD+jiEyb3G3gHP7S4wEVkx6qFwbtny5I mdsA== X-Gm-Message-State: AOAM531u8WQ29F2zxgdiiU/fYZd+lHoxnZ8A8tfOjxLl7jNuf40Glx2s kr00GsUmysBx0h95+KVTyApONPgGMXUoZg== X-Google-Smtp-Source: ABdhPJz2YtgCt08zK7860NiSbkhG3MAIfhq1ATrD6sxfcP/kdwwwciS3paoWT14BIFRhEKSB9Pjzyg== X-Received: by 2002:adf:e54e:: with SMTP id z14mr3924419wrm.490.1643304291093; Thu, 27 Jan 2022 09:24:51 -0800 (PST) Received: from cloudflare.com ([2a01:110f:4809:d800::e00]) by smtp.gmail.com with ESMTPSA id j3sm2538616wrb.57.2022.01.27.09.24.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jan 2022 09:24:50 -0800 (PST) From: Jakub Sitnicki To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Menglong Dong , Martin KaFai Lau Subject: [PATCH bpf-next 1/2] bpf: Make dst_port field in struct bpf_sock 16-bit wide Date: Thu, 27 Jan 2022 18:24:47 +0100 Message-Id: <20220127172448.155686-2-jakub@cloudflare.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20220127172448.155686-1-jakub@cloudflare.com> References: <20220127172448.155686-1-jakub@cloudflare.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Menglong Dong reports that the documentation for the dst_port field in struct bpf_sock is inaccurate and confusing. From the BPF program PoV, the field is a zero-padded 16-bit integer in network byte order. The value appears to the BPF user as if laid out in memory as so: offsetof(struct bpf_sock, dst_port) + 0 + 8 +16 0x00 +24 0x00 32-, 16-, and 8-bit wide loads from the field are all allowed, but only if the offset into the field is 0. 32-bit wide loads from dst_port are especially confusing. The loaded value, after converting to host byte order with bpf_ntohl(dst_port), contains the port number in the upper 16-bits. Remove the confusion by splitting the field into two 16-bit fields. For backward compatibility, allow 32-bit wide loads from offsetof(struct bpf_sock, dst_port). While at it, allow loads 8-bit loads at offset [0] and [1] from dst_port. Reported-by: Menglong Dong Signed-off-by: Jakub Sitnicki --- include/uapi/linux/bpf.h | 3 ++- net/core/filter.c | 9 ++++++++- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 4a2f7041ebae..027e84b18b51 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5574,7 +5574,8 @@ struct bpf_sock { __u32 src_ip4; __u32 src_ip6[4]; __u32 src_port; /* host byte order */ - __u32 dst_port; /* network byte order */ + __be16 dst_port; /* network byte order */ + __u16 zero_padding; __u32 dst_ip4; __u32 dst_ip6[4]; __u32 state; diff --git a/net/core/filter.c b/net/core/filter.c index a06931c27eeb..ef8473163696 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8265,6 +8265,7 @@ bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, struct bpf_insn_access_aux *info) { const int size_default = sizeof(__u32); + int field_size; if (off < 0 || off >= sizeof(struct bpf_sock)) return false; @@ -8276,7 +8277,6 @@ bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, case offsetof(struct bpf_sock, family): case offsetof(struct bpf_sock, type): case offsetof(struct bpf_sock, protocol): - case offsetof(struct bpf_sock, dst_port): case offsetof(struct bpf_sock, src_port): case offsetof(struct bpf_sock, rx_queue_mapping): case bpf_ctx_range(struct bpf_sock, src_ip4): @@ -8285,6 +8285,13 @@ bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, case bpf_ctx_range_till(struct bpf_sock, dst_ip6[0], dst_ip6[3]): bpf_ctx_record_field_size(info, size_default); return bpf_ctx_narrow_access_ok(off, size, size_default); + case bpf_ctx_range(struct bpf_sock, dst_port): + field_size = size == size_default ? + size_default : sizeof_field(struct bpf_sock, dst_port); + bpf_ctx_record_field_size(info, field_size); + return bpf_ctx_narrow_access_ok(off, size, field_size); + case bpf_ctx_range(struct bpf_sock, zero_padding): + return false; } return size == size_default; -- 2.31.1