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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 BFB56C54FCB for ; Wed, 22 Apr 2020 16:08:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 79D6B20776 for ; Wed, 22 Apr 2020 16:08:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="frLUi5ar" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726937AbgDVQI0 (ORCPT ); Wed, 22 Apr 2020 12:08:26 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:26509 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726006AbgDVQIZ (ORCPT ); Wed, 22 Apr 2020 12:08:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587571703; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=R35aCgtTp2T6zHwz/j/qjTydyXlhLxZnyI5/178mz/E=; b=frLUi5arwuFWUyV5cKUk/m2mfogWDfYukAi8oPPg/MATU+U4ptcs4sn+cr7e8IOrZBC98r fS/Nh/v1sZUYmk1qDW80mYQHpUqiKSIlCp51wEFVYH4XdHShwfaooKJZKRDBKU3d2wbDth pEGpPhbBYUARZ7gk2q0quqdbhBDAllI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-239-BE0LcpEmMcKl3jU2kXppag-1; Wed, 22 Apr 2020 12:08:22 -0400 X-MC-Unique: BE0LcpEmMcKl3jU2kXppag-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5C8E418C8C01; Wed, 22 Apr 2020 16:08:19 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.3]) by smtp.corp.redhat.com (Postfix) with ESMTP id A63C110190D6; Wed, 22 Apr 2020 16:08:07 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id CB82830000272; Wed, 22 Apr 2020 18:08:06 +0200 (CEST) Subject: [PATCH net-next 09/33] veth: adjust hard_start offset on redirect XDP frames From: Jesper Dangaard Brouer To: sameehj@amazon.com Cc: Toshiaki Makita , Mao Wenan , Toshiaki Makita , Jesper Dangaard Brouer , netdev@vger.kernel.org, bpf@vger.kernel.org, zorik@amazon.com, akiyano@amazon.com, gtzalik@amazon.com, =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , Daniel Borkmann , Alexei Starovoitov , John Fastabend , Alexander Duyck , Jeff Kirsher , David Ahern , Willem de Bruijn , Ilias Apalodimas , Lorenzo Bianconi , Saeed Mahameed , steffen.klassert@secunet.com Date: Wed, 22 Apr 2020 18:08:06 +0200 Message-ID: <158757168676.1370371.9335548837047528670.stgit@firesoul> In-Reply-To: <158757160439.1370371.13213378122947426220.stgit@firesoul> References: <158757160439.1370371.13213378122947426220.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org When native XDP redirect into a veth device, the frame arrives in the xdp_frame structure. It is then processed in veth_xdp_rcv_one(), which can run a new XDP bpf_prog on the packet. Doing so requires converting xdp_frame to xdp_buff, but the tricky part is that xdp_frame memory area is located in the top (data_hard_start) memory area that xdp_buff will point into. The current code tried to protect the xdp_frame area, by assigning xdp_buff.data_hard_start past this memory. This results in 32 bytes less headroom to expand into via BPF-helper bpf_xdp_adjust_head(). This protect step is actually not needed, because BPF-helper bpf_xdp_adjust_head() already reserve this area, and don't allow BPF-prog to expand into it. Thus, it is safe to point data_hard_start directly at xdp_frame memory area. Cc: Toshiaki Makita Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring") Reported-by: Mao Wenan Signed-off-by: Jesper Dangaard Brouer Acked-by: Toshiaki Makita --- drivers/net/veth.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/net/veth.c b/drivers/net/veth.c index aece0e5eec8c..d5691bb84448 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -564,13 +564,15 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq, struct veth_stats *stats) { void *hard_start = frame->data - frame->headroom; - void *head = hard_start - sizeof(struct xdp_frame); int len = frame->len, delta = 0; struct xdp_frame orig_frame; struct bpf_prog *xdp_prog; unsigned int headroom; struct sk_buff *skb; + /* bpf_xdp_adjust_head() assures BPF cannot access xdp_frame area */ + hard_start -= sizeof(struct xdp_frame); + rcu_read_lock(); xdp_prog = rcu_dereference(rq->xdp_prog); if (likely(xdp_prog)) { @@ -592,7 +594,6 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq, break; case XDP_TX: orig_frame = *frame; - xdp.data_hard_start = head; xdp.rxq->mem = frame->mem; if (unlikely(veth_xdp_tx(rq, &xdp, bq) < 0)) { trace_xdp_exception(rq->dev, xdp_prog, act); @@ -605,7 +606,6 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq, goto xdp_xmit; case XDP_REDIRECT: orig_frame = *frame; - xdp.data_hard_start = head; xdp.rxq->mem = frame->mem; if (xdp_do_redirect(rq->dev, &xdp, xdp_prog)) { frame = &orig_frame; @@ -629,7 +629,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq, rcu_read_unlock(); headroom = sizeof(struct xdp_frame) + frame->headroom - delta; - skb = veth_build_skb(head, headroom, len, 0); + skb = veth_build_skb(hard_start, headroom, len, 0); if (!skb) { xdp_return_frame(frame); stats->rx_drops++;