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,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 7023EC0650F for ; Mon, 5 Aug 2019 13:06:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40E892075B for ; Mon, 5 Aug 2019 13:06:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565010411; bh=zFjRGFPNjIL768K9LktA6/YMA4FYV3GlrLodHMBX6Ac=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=N5Cr8YkC6VvJNOCQHOwIlLZhDu0dcaon1UzJfHWDuVz9X/VbDaQdaAJPcmQqgYTLu /kvO9BF0cvFW6AV89sYWY4mUWM2d/v+gMh98Ag1P6tkh2IyvZZXacIX1r6ILv40KAM snWtYEUNJ9mojGzvAkq3W7Q4jR9SSRPqnCJnA3to= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729699AbfHENGu (ORCPT ); Mon, 5 Aug 2019 09:06:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:43796 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729195AbfHENGr (ORCPT ); Mon, 5 Aug 2019 09:06:47 -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 B87DF206C1; Mon, 5 Aug 2019 13:06:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565010407; bh=zFjRGFPNjIL768K9LktA6/YMA4FYV3GlrLodHMBX6Ac=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2MU+dOH1ZUOASpvjS0H9fmHpvJJBoaj+u83IQA8dCYoxOS4NsDJ9vlobsYG57aKhm Y8tD57XzsRKm20Tlq67hY5oHjfoADN+8aKpn0mKZzzSs8cZppVarDIXrdpPnT5KxsC hx4NYuA3f0iGipapLfhklnP/uVQwrSlM8NGpVpn8= 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 4.14 12/53] cifs: Fix a race condition with cifs_echo_request Date: Mon, 5 Aug 2019 15:02:37 +0200 Message-Id: <20190805124929.478819677@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190805124927.973499541@linuxfoundation.org> References: <20190805124927.973499541@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 33cd844579aed..57c62ff4e8d6d 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -554,10 +554,10 @@ 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 * ... @@ -566,9 +566,9 @@ 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