From patchwork Thu Jul 5 16:46:34 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paulo Alcantara (SUSE)" X-Patchwork-Id: 10510011 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 9E395600F5 for ; Thu, 5 Jul 2018 16:46:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BFD7F28F95 for ; Thu, 5 Jul 2018 16:46:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B308F28FFC; Thu, 5 Jul 2018 16:46:55 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI, T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2D91528F95 for ; Thu, 5 Jul 2018 16:46:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753512AbeGEQqy (ORCPT ); Thu, 5 Jul 2018 12:46:54 -0400 Received: from mail.paulo.ac ([34.238.86.106]:52226 "EHLO mail.paulo.ac" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753250AbeGEQqx (ORCPT ); Thu, 5 Jul 2018 12:46:53 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.paulo.ac (Postfix) with ESMTP id EB8ADC78F25; Thu, 5 Jul 2018 16:46:52 +0000 (UTC) X-Virus-Scanned: amavisd-new at paulo.ac Authentication-Results: mail.paulo.ac (amavisd-new); dkim=pass (1024-bit key) header.d=paulo.ac Received: from mail.paulo.ac ([127.0.0.1]) by localhost (mail.paulo.ac [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tCYdK6xNfiKu; Thu, 5 Jul 2018 16:46:50 +0000 (UTC) Received: from localhost.localdomain (unknown [177.18.142.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.paulo.ac (Postfix) with ESMTPSA id 7497EC78F24; Thu, 5 Jul 2018 16:46:48 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 mail.paulo.ac 7497EC78F24 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=paulo.ac; s=default; t=1530809210; bh=DATKxmOk2/cUiGTiCNLI67whYGQK67JHv2AfDz2wj30=; h=From:To:Cc:Subject:Date:From; b=fLcYsko+6+2Q8yfM0pVzfY0WTmbquv80latRpNzkPIiifsCTcejmmw4CxPZ8VWX8V u2k144azBswPR4l8ZvHNIUdonVdQNVIw6MvBN8TqVYSC6H0lRu5pXC3XVNegs1xN60 2qvCfDkcmNI+3txKIyUnxcF/eQLFBH7hZJIQHZCQ= From: Paulo Alcantara To: linux-cifs@vger.kernel.org Cc: smfrench@gmail.com, Paulo Alcantara , Paulo Alcantara , stable@vger.kernel.org Subject: [PATCH] cifs: Fix infinite loop when using hard mount option Date: Thu, 5 Jul 2018 13:46:34 -0300 Message-Id: <20180705164634.12288-1-paulo@paulo.ac> X-Mailer: git-send-email 2.18.0 Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP For every request we send, whether it is SMB1 or SMB2+, we attempt to reconnect tcon (cifs_reconnect_tcon or smb2_reconnect) before carrying out the request. So, while server->tcpStatus != CifsNeedReconnect, we wait for the reconnection to succeed on wait_event_interruptible_timeout(). If it returns, that means that either the condition was evaluated to true, or timeout elapsed, or it was interrupted by a signal. Since we're not handling the case where the process woke up due to a received signal (-ERESTARTSYS), the next call to wait_event_interruptible_timeout() will _always_ fail and we end up looping forever inside either cifs_reconnect_tcon() or smb2_reconnect(). Here's an example of how to trigger that: $ mount.cifs //foo/share /mnt/test -o username=foo,password=foo,vers=1.0,hard (break connection to server before executing bellow cmd) $ stat -f /mnt/test & sleep 140 [1] 2511 $ ps -aux -q 2511 USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 2511 0.0 0.0 12892 1008 pts/0 S 12:24 0:00 stat -f /mnt/test $ kill -9 2511 (wait for a while; process is stuck in the kernel) $ ps -aux -q 2511 USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 2511 83.2 0.0 12892 1008 pts/0 R 12:24 30:01 stat -f /mnt/test By using 'hard' mount point means that cifs.ko will keep retrying indefinitely, however we must allow the process to be killed otherwise it would hang the system. Signed-off-by: Paulo Alcantara Cc: stable@vger.kernel.org Reviewed-by: Aurelien Aptel --- fs/cifs/cifssmb.c | 10 ++++++++-- fs/cifs/smb2pdu.c | 18 ++++++++++++------ 2 files changed, 20 insertions(+), 8 deletions(-) diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c index d352da325de3..93408eab92e7 100644 --- a/fs/cifs/cifssmb.c +++ b/fs/cifs/cifssmb.c @@ -157,8 +157,14 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command) * greater than cifs socket timeout which is 7 seconds */ while (server->tcpStatus == CifsNeedReconnect) { - wait_event_interruptible_timeout(server->response_q, - (server->tcpStatus != CifsNeedReconnect), 10 * HZ); + rc = wait_event_interruptible_timeout(server->response_q, + (server->tcpStatus != CifsNeedReconnect), + 10 * HZ); + if (rc < 0) { + cifs_dbg(FYI, "%s: aborting reconnect due to a received" + " signal by the process\n", __func__); + return -ERESTARTSYS; + } /* are we still trying to reconnect? */ if (server->tcpStatus != CifsNeedReconnect) diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index 810b85787c91..086629b0d59c 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -155,7 +155,7 @@ smb2_hdr_assemble(struct smb2_sync_hdr *shdr, __le16 smb2_cmd, static int smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon) { - int rc = 0; + int rc; struct nls_table *nls_codepage; struct cifs_ses *ses; struct TCP_Server_Info *server; @@ -166,10 +166,10 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon) * for those three - in the calling routine. */ if (tcon == NULL) - return rc; + return 0; if (smb2_command == SMB2_TREE_CONNECT) - return rc; + return 0; if (tcon->tidStatus == CifsExiting) { /* @@ -212,8 +212,14 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon) return -EAGAIN; } - wait_event_interruptible_timeout(server->response_q, - (server->tcpStatus != CifsNeedReconnect), 10 * HZ); + rc = wait_event_interruptible_timeout(server->response_q, + (server->tcpStatus != CifsNeedReconnect), + 10 * HZ); + if (rc < 0) { + cifs_dbg(FYI, "%s: aborting reconnect due to a received" + " signal by the process\n", __func__); + return -ERESTARTSYS; + } /* are we still trying to reconnect? */ if (server->tcpStatus != CifsNeedReconnect) @@ -231,7 +237,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon) } if (!tcon->ses->need_reconnect && !tcon->need_reconnect) - return rc; + return 0; nls_codepage = load_nls_default();