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 0EEB7C433FF for ; Mon, 5 Aug 2019 13:10:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6A5D216F4 for ; Mon, 5 Aug 2019 13:10:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565010608; bh=QZ+aaWTUIyXJ7C1ky9bKKBHcnbAsyEgHKKuQWgsNePI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gIfvWaH+Bcf3KUtjIXU10gErmSkUJGPC2uaQiA8lgObsfkgPks+Onp/AaPdTyWZld s8ZCrxgGPCKx04/UOsw669m6IW5Twh2zY/yHeaCkja6gj3bSORc/u2vVYn5kmxK3wL BkbDFBUeWakonfh9eZ3a4YBy4y/qxcjmSWLaUG+0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730294AbfHENKH (ORCPT ); Mon, 5 Aug 2019 09:10:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:48898 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730278AbfHENKG (ORCPT ); Mon, 5 Aug 2019 09:10:06 -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 1068720880; Mon, 5 Aug 2019 13:10:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565010605; bh=QZ+aaWTUIyXJ7C1ky9bKKBHcnbAsyEgHKKuQWgsNePI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nGcw2QCaA+FDc41lyF8HEkXh1jvPBPVlIBMso3tIaM+Um6Jz08cJllKSM8zoinmqO VFIWckgVXgvmIHN1xuPjEX1xe80ry7A8AFo53tYXivoczG5UpaNf5qYrErv70iOgFw 1A3M/3eWh2O5RAmlLemn8Lkbhzqcxsuoc5mQy+NQ= 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 4.19 17/74] cifs: Fix a race condition with cifs_echo_request Date: Mon, 5 Aug 2019 15:02:30 +0200 Message-Id: <20190805124937.192021152@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190805124935.819068648@linuxfoundation.org> References: <20190805124935.819068648@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 f31339db45fdb..c53a2e86ed544 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -563,10 +563,10 @@ 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 * ... @@ -575,9 +575,9 @@ 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