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=unavailable 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 63663C433E1 for ; Mon, 18 May 2020 17:39:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 466072086A for ; Mon, 18 May 2020 17:39:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589823596; bh=zZkOHLlY0C4rzlyING27MznEU+bpSrDuBYLW1QwahNw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZMsNOhcYcEJchWnNlK+4UYEzUxIwod0zfgkZ4dVKrQCFaHtrNhh4lxJVoOmcfBpNA Xdjv8u4lCCuf77fQFSaBEl15CQpFyt47dZNkybr25Fz1aZ0JSVeRyMbprb8qB3zUMt zkO45urHTn9jTIxwyXRyAj5WaIUwTT6IHqoooY7I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728923AbgERRjz (ORCPT ); Mon, 18 May 2020 13:39:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:34862 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728883AbgERRjv (ORCPT ); Mon, 18 May 2020 13:39:51 -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 6CE4F2083E; Mon, 18 May 2020 17:39:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589823590; bh=zZkOHLlY0C4rzlyING27MznEU+bpSrDuBYLW1QwahNw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O7C9j1xblen4afFFbUZ1HXPgwfRDwbN85anoy8EmLvxE1ImDRCd3HHQEOJJwo0hMt en0gbPJGnVnAaJe9GkyFuW+cNNbx/1n2M4pnE/5IKn8eRpxDzwvSpVSPhToUGbguVX m7bAseA5bGH+ZqEU/s9x7ud2iFMugUDJficz9jDs= 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 4.4 42/86] cifs: Fix a race condition with cifs_echo_request Date: Mon, 18 May 2020 19:36:13 +0200 Message-Id: <20200518173458.913521023@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200518173450.254571947@linuxfoundation.org> References: <20200518173450.254571947@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 From: Ronnie Sahlberg [ 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 7022750cae2fd..21ddfd77966eb 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -548,10 +548,10 @@ 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 * ... @@ -560,9 +560,9 @@ server_unresponsive(struct TCP_Server_Info *server) */ if ((server->tcpStatus == CifsGood || server->tcpStatus == CifsNeedNegotiate) && - time_after(jiffies, server->lstrp + 2 * SMB_ECHO_INTERVAL)) { + time_after(jiffies, server->lstrp + 3 * SMB_ECHO_INTERVAL)) { cifs_dbg(VFS, "Server %s has not responded in %d seconds. Reconnecting...\n", - server->hostname, (2 * SMB_ECHO_INTERVAL) / HZ); + server->hostname, (3 * SMB_ECHO_INTERVAL) / HZ); cifs_reconnect(server); wake_up(&server->response_q); return true; -- 2.20.1