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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 7054FC4360F for ; Mon, 25 Feb 2019 21:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4861020652 for ; Mon, 25 Feb 2019 21:39:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733118AbfBYVgJ (ORCPT ); Mon, 25 Feb 2019 16:36:09 -0500 Received: from www62.your-server.de ([213.133.104.62]:48168 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733107AbfBYVgJ (ORCPT ); Mon, 25 Feb 2019 16:36:09 -0500 Received: from [78.46.172.2] (helo=sslproxy05.your-server.de) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1gyNux-0007Yk-09; Mon, 25 Feb 2019 22:36:07 +0100 Received: from [178.197.249.32] (helo=linux.home) by sslproxy05.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1gyNuw-000Ase-Pv; Mon, 25 Feb 2019 22:36:06 +0100 Subject: Re: [PATCH bpf-next] bpf/test_run: fix unkillable BPF_PROG_TEST_RUN for flow dissector To: Stanislav Fomichev , netdev@vger.kernel.org Cc: davem@davemloft.net, ast@kernel.org, syzbot References: <20190219185417.145696-1-sdf@google.com> From: Daniel Borkmann Message-ID: <5f954e14-3dec-5e6e-56f0-aa7b32253c53@iogearbox.net> Date: Mon, 25 Feb 2019 22:36:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20190219185417.145696-1-sdf@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.2/25371/Mon Feb 25 11:48:47 2019) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 02/19/2019 07:54 PM, Stanislav Fomichev wrote: > Syzbot found out that running BPF_PROG_TEST_RUN with repeat=0xffffffff > makes process unkillable. The problem is that when CONFIG_PREEMPT is > enabled, we never see need_resched() return true. This is due to the > fact that preempt_enable() (which we do in bpf_test_run_one on each > iteration) now handles resched if it's needed. > > Let's disable preemption for the whole run, not per test. In this case > we can properly see whether resched is needed. > Let's also properly return -EINTR to the userspace in case of a signal > interrupt. > > This is a follow up for a recently fixed issue in bpf_test_run, see > commit df1a2cb7c74b ("bpf/test_run: fix unkillable > BPF_PROG_TEST_RUN"). > > Reported-by: syzbot > Signed-off-by: Stanislav Fomichev Applied, thanks! Would be nice to consolidate at least some of these bits so it's not duplicated, perhaps __always_inline might help for function args in avoiding indirect calls (iirc, perf's rb handling uses this heavily). > --- > net/bpf/test_run.c | 26 ++++++++++++++++++++------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c > index 2c5172b33209..619655db8d9e 100644 > --- a/net/bpf/test_run.c > +++ b/net/bpf/test_run.c > @@ -293,31 +293,45 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog, > if (!repeat) > repeat = 1; > > + rcu_read_lock(); > + preempt_disable(); > time_start = ktime_get_ns(); > for (i = 0; i < repeat; i++) { > - preempt_disable(); > - rcu_read_lock(); > retval = __skb_flow_bpf_dissect(prog, skb, > &flow_keys_dissector, > &flow_keys); > - rcu_read_unlock(); > - preempt_enable(); > + > + if (signal_pending(current)) { > + preempt_enable(); > + rcu_read_unlock(); > + > + ret = -EINTR; > + goto out; > + } > > if (need_resched()) { > - if (signal_pending(current)) > - break; > time_spent += ktime_get_ns() - time_start; > + preempt_enable(); > + rcu_read_unlock(); > + > cond_resched(); > + > + rcu_read_lock(); > + preempt_disable(); > time_start = ktime_get_ns(); > } > } > time_spent += ktime_get_ns() - time_start; > + preempt_enable(); > + rcu_read_unlock(); > + > do_div(time_spent, repeat); > duration = time_spent > U32_MAX ? U32_MAX : (u32)time_spent; > > ret = bpf_test_finish(kattr, uattr, &flow_keys, sizeof(flow_keys), > retval, duration); > > +out: > kfree_skb(skb); > kfree(sk); > return ret; >