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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 6FB68C0650F for ; Mon, 5 Aug 2019 13:21:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 467E920880 for ; Mon, 5 Aug 2019 13:21:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565011280; bh=6/aconRxdHSsHCvo34orQxhuarnf6NEQYSFYDAIaev8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=NVy0BgjcfvNlpblnj4+MfEKcQOhIRIqYBjcrjmBoFmHsKieVJOcw1Kyfv1Xtzo9wM c2Ua7VaVu3eIOqFHWemqEVXSPwICY++FBCDkdBI2TMXKPmF375yr3TsrN64AHw9q7u 6sbUDA2teCzOkQPYilsuTeY4USbJp50/lOdwKiCE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730488AbfHENVS (ORCPT ); Mon, 5 Aug 2019 09:21:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:57464 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730479AbfHENVR (ORCPT ); Mon, 5 Aug 2019 09:21:17 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ABD3B20880; Mon, 5 Aug 2019 13:21:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565011277; bh=6/aconRxdHSsHCvo34orQxhuarnf6NEQYSFYDAIaev8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MyrVRK4oBkjBNdLeE6E9grHFJR5t0WyVnRxKstSdnjalgI//2BxBP015mjAxFDrDM WUHTyvVF0TYl9kU6fQwoq93zQcvVJZ4jUxpVKA871nzlrnxmkrQNPCs1vIrNKqNbyA PI5i4y5O+S1hmGjgGp+KH93rn1qWzA/9c0CDM6YY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ronnie Sahlberg , Pavel Shilovsky , Steve French , Sasha Levin Subject: [PATCH 5.2 031/131] cifs: Fix a race condition with cifs_echo_request Date: Mon, 5 Aug 2019 15:01:58 +0200 Message-Id: <20190805124953.516186475@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190805124951.453337465@linuxfoundation.org> References: <20190805124951.453337465@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org [ Upstream commit f2caf901c1b7ce65f9e6aef4217e3241039db768 ] There is a race condition with how we send (or supress and don't send) smb echos that will cause the client to incorrectly think the server is unresponsive and thus needs to be reconnected. Summary of the race condition: 1) Daisy chaining scheduling creates a gap. 2) If traffic comes unfortunate shortly after the last echo, the planned echo is suppressed. 3) Due to the gap, the next echo transmission is delayed until after the timeout, which is set hard to twice the echo interval. This is fixed by changing the timeouts from 2 to three times the echo interval. Detailed description of the bug: https://lutz.donnerhacke.de/eng/Blog/Groundhog-Day-with-SMB-remount Signed-off-by: Ronnie Sahlberg Reviewed-by: Pavel Shilovsky Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/cifs/connect.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 59380dd546a1e..6ad43ac129d2f 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -706,10 +706,10 @@ static bool server_unresponsive(struct TCP_Server_Info *server) { /* - * We need to wait 2 echo intervals to make sure we handle such + * We need to wait 3 echo intervals to make sure we handle such * situations right: * 1s client sends a normal SMB request - * 2s client gets a response + * 3s client gets a response * 30s echo workqueue job pops, and decides we got a response recently * and don't need to send another * ... @@ -718,9 +718,9 @@ server_unresponsive(struct TCP_Server_Info *server) */ if ((server->tcpStatus == CifsGood || server->tcpStatus == CifsNeedNegotiate) && - time_after(jiffies, server->lstrp + 2 * server->echo_interval)) { + time_after(jiffies, server->lstrp + 3 * server->echo_interval)) { cifs_dbg(VFS, "Server %s has not responded in %lu seconds. Reconnecting...\n", - server->hostname, (2 * server->echo_interval) / HZ); + server->hostname, (3 * server->echo_interval) / HZ); cifs_reconnect(server); wake_up(&server->response_q); return true; -- 2.20.1