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=-13.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 6F42FC433E6 for ; Mon, 31 Aug 2020 21:25:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5204B206FA for ; Mon, 31 Aug 2020 21:25:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730239AbgHaVZf (ORCPT ); Mon, 31 Aug 2020 17:25:35 -0400 Received: from www62.your-server.de ([213.133.104.62]:48980 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728352AbgHaVZf (ORCPT ); Mon, 31 Aug 2020 17:25:35 -0400 Received: from sslproxy02.your-server.de ([78.47.166.47]) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1kCrIq-0001ul-7c; Mon, 31 Aug 2020 23:25:24 +0200 Received: from [178.196.57.75] (helo=pc-9.home) by sslproxy02.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kCrIq-0007yz-2B; Mon, 31 Aug 2020 23:25:24 +0200 Subject: Re: [PATCH bpf-next] bpf: Remove bpf_lsm_file_mprotect from sleepable list. To: Alexei Starovoitov , davem@davemloft.net Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com References: <20200831201651.82447-1-alexei.starovoitov@gmail.com> From: Daniel Borkmann Message-ID: Date: Mon, 31 Aug 2020 23:25:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200831201651.82447-1-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.4/25916/Mon Aug 31 15:26:49 2020) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/31/20 10:16 PM, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > Technically the bpf programs can sleep while attached to bpf_lsm_file_mprotect, > but such programs need to access user memory. So they're in might_fault() > category. Which means they cannot be called from file_mprotect lsm hook that > takes write lock on mm->mmap_lock. > Adjust the test accordingly. > > Also add might_fault() to __bpf_prog_enter_sleepable() to catch such deadlocks early. > > Reported-by: Yonghong Song > Fixes: 1e6c62a88215 ("bpf: Introduce sleepable BPF programs") > Fixes: e68a144547fc ("selftests/bpf: Add sleepable tests") > Signed-off-by: Alexei Starovoitov > --- > kernel/bpf/trampoline.c | 1 + > kernel/bpf/verifier.c | 1 - > tools/testing/selftests/bpf/progs/lsm.c | 34 ++++++++++++------------- > 3 files changed, 18 insertions(+), 18 deletions(-) > > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c > index c2b76545153c..7dd523a7e32d 100644 > --- a/kernel/bpf/trampoline.c > +++ b/kernel/bpf/trampoline.c > @@ -409,6 +409,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start) > void notrace __bpf_prog_enter_sleepable(void) > { > rcu_read_lock_trace(); > + might_fault(); Makes sense, was wondering about a __might_sleep() but that will cover it internally too. Applied, thanks! > } > > void notrace __bpf_prog_exit_sleepable(void)