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Tue, 17 Mar 2020 05:27:18 +0000 Date: Mon, 16 Mar 2020 22:27:15 -0700 From: Martin KaFai Lau To: Andrii Nakryiko CC: , , , , , Subject: Re: [Potential Spoof] [PATCH bpf-next 1/3] selftests/bpf: fix race in tcp_rtt test Message-ID: <20200317052715.xnof2rdecrmkep7v@kafai-mbp> References: <20200314013932.4035712-1-andriin@fb.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200314013932.4035712-1-andriin@fb.com> User-Agent: NeoMutt/20180716 X-ClientProxiedBy: MWHPR1201CA0006.namprd12.prod.outlook.com (2603:10b6:301:4a::16) To BYAPR15MB2278.namprd15.prod.outlook.com (2603:10b6:a02:8e::17) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp (2620:10d:c090:400::5:e745) by MWHPR1201CA0006.namprd12.prod.outlook.com (2603:10b6:301:4a::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2814.21 via Frontend Transport; Tue, 17 Mar 2020 05:27:17 +0000 X-Originating-IP: [2620:10d:c090:400::5:e745] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: fc9a2282-f889-45b3-3af9-08d7ca33dc21 X-MS-TrafficTypeDiagnostic: BYAPR15MB2664: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:7691; X-Forefront-PRVS: 0345CFD558 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(39860400002)(346002)(366004)(396003)(136003)(376002)(199004)(52116002)(16526019)(186003)(1076003)(5660300002)(6496006)(4326008)(66946007)(66476007)(66556008)(316002)(33716001)(8676002)(81156014)(81166006)(55016002)(86362001)(478600001)(2906002)(6636002)(8936002)(6862004)(9686003);DIR:OUT;SFP:1102;SCL:1;SRVR:BYAPR15MB2664;H:BYAPR15MB2278.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1; Received-SPF: None (protection.outlook.com: fb.com does not designate permitted sender hosts) X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: dmxtDggogPrfn6Y/PSzkmtLfTUFBqrCOv4CGvLxgKKJEaRHKnAOFo+lO5i5ysN8K6pDCd+kRURLBu02mb43F9Cpp4wAPiO/nJC8MwbMNHEjQaQ3M7oaaoR10QUCHYm5aGVub+9QLUbu8y7z6SQFXokm0quwtpDayHM9s7KEOxnhjsiAZZxnkdsKlzv0YffIhce7K8vBPUPWeWYQGwVmLWbUmlSj4bHQiHLb91Fkh6X9w06yLiUNYPZqT0mnhPsDkaqdhGpfFXLllVVAt6x2LkVJnYLuy4OuT3UpXRXux0ToMFBp9Vf+NIJG/SZjHJlPpZVIR0Jd0vGMgOFtZVkmAFmfabqIarwXs9+130yXrfCAUSclSLaSS0gldwkAEO2trd14n2/bGpwEYNU1LGGGerEVXMZC6PxUtm7m4iUbWn0TONqaZIM77pTC2r8WRS7I3 X-MS-Exchange-AntiSpam-MessageData: ljcV30xRlNw+AEnxNSf3BojcBcvLYdCqoSh0oJCU2xfoCnmPekTPepJ4Es5pBnPOs3mPCHhzuQGyyd2YGL21u2rjcpqX1CQ6FPAYfYiohdmt8TR2Gu3wob0R1TtvvD/07uQrthqPY3FZjN98lhK4UGIWoAQ+CT6pToW98DuB+wsCLxdI6/L4xXn834gRI/WO X-MS-Exchange-CrossTenant-Network-Message-Id: fc9a2282-f889-45b3-3af9-08d7ca33dc21 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Mar 2020 05:27:18.7999 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: lZnDjamuU3PeTwXYc9bMFfZeK2FDLbLhTOU5xLoHObmUiLQ1Z62Ouw2gm4vQvWyb X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2664 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-17_01:2020-03-12,2020-03-17 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=897 adultscore=0 bulkscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 suspectscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003170023 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Mar 13, 2020 at 06:39:30PM -0700, Andrii Nakryiko wrote: > Previous attempt to make tcp_rtt more robust introduced a new race, in which > server_done might be set to true before server can actually accept any > connection. Fix this by unconditionally waiting for accept(). Given socket is > non-blocking, if there are any problems with client side, it should eventually > close listening FD and let server thread exit with failure. > > Fixes: 4cd729fa022c ("selftests/bpf: Make tcp_rtt test more robust to failures") > Signed-off-by: Andrii Nakryiko > --- > tools/testing/selftests/bpf/prog_tests/tcp_rtt.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c > index e08f6bb17700..e56b52ab41da 100644 > --- a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c > +++ b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c > @@ -226,7 +226,7 @@ static void *server_thread(void *arg) > return ERR_PTR(err); > } > > - while (!server_done) { > + while (true) { > client_fd = accept(fd, (struct sockaddr *)&addr, &len); > if (client_fd == -1 && errno == EAGAIN) { > usleep(50); > @@ -272,7 +272,7 @@ void test_tcp_rtt(void) > CHECK_FAIL(run_test(cgroup_fd, server_fd)); > > server_done = true; > - pthread_join(tid, &server_res); > + CHECK_FAIL(pthread_join(tid, &server_res)); >From looking at run_test(), I suspect without accept and server_thread, this may also work: listen(server_fd, 1); run_test(cgroup_fd, server_fd); close(server_fd); This change lgtm since it is NONBLOCK. Ideally, may be it should also be time limited by epoll or setsockopt(SO_RCVTIMEO) in the future. Acked-by: Martin KaFai Lau