From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH bpf v2] xdp: Fix handling of devmap in generic XDP Date: Thu, 14 Jun 2018 10:49:59 +0200 Message-ID: <20180614104959.4e4e57b8@redhat.com> References: <1528942062-2353-1-git-send-email-makita.toshiaki@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Alexei Starovoitov , Daniel Borkmann , netdev@vger.kernel.org, brouer@redhat.com To: Toshiaki Makita Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51278 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752928AbeFNIuH (ORCPT ); Thu, 14 Jun 2018 04:50:07 -0400 In-Reply-To: <1528942062-2353-1-git-send-email-makita.toshiaki@lab.ntt.co.jp> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 14 Jun 2018 11:07:42 +0900 Toshiaki Makita wrote: > Commit 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") changed > the return value type of __devmap_lookup_elem() from struct net_device * > to struct bpf_dtab_netdev * but forgot to modify generic XDP code > accordingly. > Thus generic XDP incorrectly used struct bpf_dtab_netdev where struct > net_device is expected, then skb->dev was set to invalid value. > > v2: > - Fix compiler warning without CONFIG_BPF_SYSCALL. > > Fixes: 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") > Signed-off-by: Toshiaki Makita Thanks for catching this! Acked-by: Jesper Dangaard Brouer Notice, that the current code works (and does not crash), but it is pure luck. Because struct bpf_dtab_netdev happen to have the net_device as the first member. struct bpf_dtab_netdev { struct net_device *dev; /* must be first member, due to tracepoint */ struct bpf_dtab *dtab; unsigned int bit; struct xdp_bulk_queue __percpu *bulkq; struct rcu_head rcu; }; -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer