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=-13.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 AEF35C47404 for ; Mon, 7 Oct 2019 20:39:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 827F92084D for ; Mon, 7 Oct 2019 20:39:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728792AbfJGUjG (ORCPT ); Mon, 7 Oct 2019 16:39:06 -0400 Received: from www62.your-server.de ([213.133.104.62]:37738 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728187AbfJGUjF (ORCPT ); Mon, 7 Oct 2019 16:39:05 -0400 Received: from 55.249.197.178.dynamic.dsl-lte-bonding.lssmb00p-msn.res.cust.swisscom.ch ([178.197.249.55] helo=localhost) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1iHZmS-0005Sc-02; Mon, 07 Oct 2019 22:38:56 +0200 Date: Mon, 7 Oct 2019 22:38:55 +0200 From: Daniel Borkmann To: Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= Cc: Alexei Starovoitov , Martin KaFai Lau , Song Liu , Yonghong Song , Marek Majkowski , Lorenz Bauer , Alan Maguire , Jesper Dangaard Brouer , David Miller , netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH bpf-next v3 2/5] bpf: Add support for setting chain call sequence for programs Message-ID: <20191007203855.GE27307@pc-66.home> References: <157046883502.2092443.146052429591277809.stgit@alrua-x1> <157046883723.2092443.3902769602513209987.stgit@alrua-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <157046883723.2092443.3902769602513209987.stgit@alrua-x1> User-Agent: Mutt/1.12.1 (2019-06-15) X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.101.4/25595/Mon Oct 7 10:28:44 2019) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Oct 07, 2019 at 07:20:37PM +0200, Toke Høiland-Jørgensen wrote: > From: Toke Høiland-Jørgensen > > This adds support for setting and deleting bpf chain call programs through > a couple of new commands in the bpf() syscall. The CHAIN_ADD and CHAIN_DEL > commands take two eBPF program fds and a return code, and install the > 'next' program to be chain called after the 'prev' program if that program > returns 'retcode'. A retcode of -1 means "wildcard", so that the program > will be executed regardless of the previous program's return code. > > > The syscall command names are based on Alexei's prog_chain example[0], > which Alan helpfully rebased on current bpf-next. However, the logic and > program storage is obviously adapted to the execution logic in the previous > commit. > > [0] https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git/commit/?h=prog_chain&id=f54f45d00f91e083f6aec2abe35b6f0be52ae85b&context=15 > > Signed-off-by: Alan Maguire > Signed-off-by: Toke Høiland-Jørgensen > --- > include/uapi/linux/bpf.h | 10 ++++++ > kernel/bpf/syscall.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 88 insertions(+) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 1ce80a227be3..b03c23963af8 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -107,6 +107,9 @@ enum bpf_cmd { > BPF_MAP_LOOKUP_AND_DELETE_ELEM, > BPF_MAP_FREEZE, > BPF_BTF_GET_NEXT_ID, > + BPF_PROG_CHAIN_ADD, > + BPF_PROG_CHAIN_DEL, > + BPF_PROG_CHAIN_GET, > }; > > enum bpf_map_type { > @@ -516,6 +519,13 @@ union bpf_attr { > __u64 probe_offset; /* output: probe_offset */ > __u64 probe_addr; /* output: probe_addr */ > } task_fd_query; > + > + struct { /* anonymous struct used by BPF_PROG_CHAIN_* commands */ > + __u32 prev_prog_fd; > + __u32 next_prog_fd; > + __u32 retcode; > + __u32 next_prog_id; /* output: prog_id */ > + }; > } __attribute__((aligned(8))); > > /* The description below is an attempt at providing documentation to eBPF > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index b8a203a05881..be8112e08a88 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -2113,6 +2113,79 @@ static int bpf_prog_test_run(const union bpf_attr *attr, > return ret; > } > > +#define BPF_PROG_CHAIN_LAST_FIELD next_prog_id > + > +static int bpf_prog_chain(int cmd, const union bpf_attr *attr, > + union bpf_attr __user *uattr) > +{ > + struct bpf_prog *prog, *next_prog, *old_prog; > + struct bpf_prog **array; > + int ret = -EOPNOTSUPP; > + u32 index, prog_id; > + > + if (CHECK_ATTR(BPF_PROG_CHAIN)) > + return -EINVAL; > + > + /* Index 0 is wildcard, encoded as ~0 by userspace */ > + if (attr->retcode == ((u32) ~0)) > + index = 0; > + else > + index = attr->retcode + 1; > + > + if (index >= BPF_NUM_CHAIN_SLOTS) > + return -E2BIG; > + > + prog = bpf_prog_get(attr->prev_prog_fd); > + if (IS_ERR(prog)) > + return PTR_ERR(prog); > + > + /* If the chain_calls bit is not set, that's because the chain call flag > + * was not set on program load, and so we can't support chain calls. > + */ > + if (!prog->chain_calls) > + goto out; > + > + array = prog->aux->chain_progs; > + > + switch (cmd) { > + case BPF_PROG_CHAIN_ADD: > + next_prog = bpf_prog_get(attr->next_prog_fd); > + if (IS_ERR(next_prog)) { > + ret = PTR_ERR(next_prog); > + break; > + } > + old_prog = xchg(array + index, next_prog); > + if (old_prog) > + bpf_prog_put(old_prog); > + ret = 0; > + break; How are circular dependencies resolved here? Seems the situation is not prevented, so progs unloaded via XDP won't get the __bpf_prog_free() call where they then drop the references of all the other progs in the chain. > + case BPF_PROG_CHAIN_DEL: > + old_prog = xchg(array + index, NULL); > + if (old_prog) { > + bpf_prog_put(old_prog); > + ret = 0; > + } else { > + ret = -ENOENT; > + } > + break; > + case BPF_PROG_CHAIN_GET: > + old_prog = READ_ONCE(array[index]); > + if (old_prog) { > + prog_id = old_prog->aux->id; > + if (put_user(prog_id, &uattr->next_prog_id)) > + ret = -EFAULT; > + else > + ret = 0; > + } else > + ret = -ENOENT; > + break; > + } > + > +out: > + bpf_prog_put(prog); > + return ret; > +} > + > #define BPF_OBJ_GET_NEXT_ID_LAST_FIELD next_id > > static int bpf_obj_get_next_id(const union bpf_attr *attr, > @@ -2885,6 +2958,11 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz > case BPF_PROG_TEST_RUN: > err = bpf_prog_test_run(&attr, uattr); > break; > + case BPF_PROG_CHAIN_ADD: > + case BPF_PROG_CHAIN_DEL: > + case BPF_PROG_CHAIN_GET: > + err = bpf_prog_chain(cmd, &attr, uattr); > + break; > case BPF_PROG_GET_NEXT_ID: > err = bpf_obj_get_next_id(&attr, uattr, > &prog_idr, &prog_idr_lock); >