From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <stable-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 48495C3527A
	for <stable@archiver.kernel.org>; Tue,  5 Apr 2022 12:11:21 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1351391AbiDEMIW (ORCPT <rfc822;stable@archiver.kernel.org>);
        Tue, 5 Apr 2022 08:08:22 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33040 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1358211AbiDEK2G (ORCPT
        <rfc822;stable@vger.kernel.org>); Tue, 5 Apr 2022 06:28:06 -0400
Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 831C320BD8;
        Tue,  5 Apr 2022 03:17:07 -0700 (PDT)
Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140])
        (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
        (No client certificate requested)
        by ams.source.kernel.org (Postfix) with ESMTPS id 36A51B81C98;
        Tue,  5 Apr 2022 10:17:06 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B39AC385A2;
        Tue,  5 Apr 2022 10:17:03 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org;
        s=korg; t=1649153824;
        bh=CgVWNZ4s6TTDhylBTZIbCfgSt6/RIwAvVCsnksuYJjI=;
        h=From:To:Cc:Subject:Date:In-Reply-To:References:From;
        b=BgaAMXIapjOVu43bP6pt5SBlFvImqdEUVx7E5BCru64Kj0r+azVZyTcdFNuMyPFsg
         pm2sD9Kj5lEv1rXF45b/FqSyt5fck3g2hHORHA3xVpEHiXYzlVLsr9RdwAUavNFreD
         x32BeayWMdqP/g9S/lpIIa9NA9VD+aFLzvjBnRV8=
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        =?UTF-8?q?Niklas=20S=C3=B6derlund?= <niklas.soderlund@corigine.com>,
        Simon Horman <simon.horman@corigine.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 359/599] samples/bpf, xdpsock: Fix race when running for fix duration of time
Date:   Tue,  5 Apr 2022 09:30:53 +0200
Message-Id: <20220405070309.515064687@linuxfoundation.org>
X-Mailer: git-send-email 2.35.1
In-Reply-To: <20220405070258.802373272@linuxfoundation.org>
References: <20220405070258.802373272@linuxfoundation.org>
User-Agent: quilt/0.66
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk
List-ID: <stable.vger.kernel.org>
X-Mailing-List: stable@vger.kernel.org

From: Niklas Söderlund <niklas.soderlund@corigine.com>

[ Upstream commit 8fa42d78f6354bb96ad3a079dcbef528ca9fa9e0 ]

When running xdpsock for a fix duration of time before terminating
using --duration=<n>, there is a race condition that may cause xdpsock
to terminate immediately.

When running for a fixed duration of time the check to determine when to
terminate execution is in is_benchmark_done() and is being executed in
the context of the poller thread,

    if (opt_duration > 0) {
            unsigned long dt = (get_nsecs() - start_time);

            if (dt >= opt_duration)
                    benchmark_done = true;
    }

However start_time is only set after the poller thread have been
created. This leaves a small window when the poller thread is starting
and calls is_benchmark_done() for the first time that start_time is not
yet set. In that case start_time have its initial value of 0 and the
duration check fails as it do not correlate correctly for the
applications start time and immediately sets benchmark_done which in
turn terminates the xdpsock application.

Fix this by setting start_time before creating the poller thread.

Fixes: d3f11b018f6c ("samples/bpf: xdpsock: Add duration option to specify how long to run")
Signed-off-by: Niklas Söderlund <niklas.soderlund@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220315102948.466436-1-niklas.soderlund@corigine.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 samples/bpf/xdpsock_user.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index 2e4508a6cb3a..cf5b0a895225 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -1520,14 +1520,15 @@ int main(int argc, char **argv)
 
 	setlocale(LC_ALL, "");
 
+	prev_time = get_nsecs();
+	start_time = prev_time;
+
 	if (!opt_quiet) {
 		ret = pthread_create(&pt, NULL, poller, NULL);
 		if (ret)
 			exit_with_error(ret);
 	}
 
-	prev_time = get_nsecs();
-	start_time = prev_time;
 
 	if (opt_bench == BENCH_RXDROP)
 		rx_drop_all();
-- 
2.34.1