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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 1FC8AC7618B for ; Fri, 26 Jul 2019 13:58:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECE8C22CEB for ; Fri, 26 Jul 2019 13:58:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564149534; bh=uIbs0tM0t17lsosykX6s17QGS1UOz8ioMvBtnf/X32M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0v0yoDzbcumKYpcUPCWHCq+FxlpnqXQdbmtFPFnSj+Z/xsjlg970e3/VyExqVxdjj iBpNiJvYjQVN48O8pdBaKOEb5cwfbkUIvpj9a+4Cnnw/n4PTGUde9j/8fyIgX9Va/V MgY8jAHhMwuvD8hsQz6Xj64GSxkwS57cpd34UXf8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387517AbfGZNkh (ORCPT ); Fri, 26 Jul 2019 09:40:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:46552 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727681AbfGZNk3 (ORCPT ); Fri, 26 Jul 2019 09:40:29 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C905C22BF5; Fri, 26 Jul 2019 13:40:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564148428; bh=uIbs0tM0t17lsosykX6s17QGS1UOz8ioMvBtnf/X32M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FftBAWT4UBRYlUsRHErC51i0REzoW9YSSn/oHmPvUk7OLEtW6mzNl5/0SWX1RdvNy hKaPiaRyhSjdivoam+PdqwY9u8RQeZ7r+tAK4JVBPmVNvKK1OI0PTTq5ny8r7n+G82 YU9eWlxHcw5583yhzYY83/+qtE795FxyVMw6IeK4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ronnie Sahlberg , Pavel Shilovsky , Steve French , Sasha Levin , linux-cifs@vger.kernel.org Subject: [PATCH AUTOSEL 5.2 31/85] cifs: Fix a race condition with cifs_echo_request Date: Fri, 26 Jul 2019 09:38:41 -0400 Message-Id: <20190726133936.11177-31-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190726133936.11177-1-sashal@kernel.org> References: <20190726133936.11177-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 8dd6637a3cbb..0872188ce3c6 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