From patchwork Tue Aug 21 19:19:31 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sage Weil X-Patchwork-Id: 1357391 Return-Path: X-Original-To: patchwork-ceph-devel@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork2.kernel.org (Postfix) with ESMTP id 8CD44DFB34 for ; Tue, 21 Aug 2012 19:07:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756618Ab2HUTH1 (ORCPT ); Tue, 21 Aug 2012 15:07:27 -0400 Received: from cobra.newdream.net ([66.33.216.30]:42593 "EHLO cobra.newdream.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756630Ab2HUTHT (ORCPT ); Tue, 21 Aug 2012 15:07:19 -0400 Received: from fatty.ops.newdream.net (unknown [38.122.20.226]) by cobra.newdream.net (Postfix) with ESMTPA id 831228132D; Tue, 21 Aug 2012 12:07:18 -0700 (PDT) From: Sage Weil To: ceph-devel@vger.kernel.org Cc: Jim Schutt Subject: [PATCH 3/4] libceph: avoid truncation due to racing banners Date: Tue, 21 Aug 2012 12:19:31 -0700 Message-Id: <1345576772-3284-4-git-send-email-sage@inktank.com> X-Mailer: git-send-email 1.7.9 In-Reply-To: <1345576772-3284-1-git-send-email-sage@inktank.com> References: <1345576772-3284-1-git-send-email-sage@inktank.com> Sender: ceph-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org From: Jim Schutt Because the Ceph client messenger uses a non-blocking connect, it is possible for the sending of the client banner to race with the arrival of the banner sent by the peer. When ceph_sock_state_change() notices the connect has completed, it schedules work to process the socket via con_work(). During this time the peer is writing its banner, and arrival of the peer banner races with con_work(). If con_work() calls try_read() before the peer banner arrives, there is nothing for it to do, after which con_work() calls try_write() to send the client's banner. In this case Ceph's protocol negotiation can complete succesfully. The server-side messenger immediately sends its banner and addresses after accepting a connect request, *before* actually attempting to read or verify the banner from the client. As a result, it is possible for the banner from the server to arrive before con_work() calls try_read(). If that happens, try_read() will read the banner and prepare protocol negotiation info via prepare_write_connect(). prepare_write_connect() calls con_out_kvec_reset(), which discards the as-yet-unsent client banner. Next, con_work() calls try_write(), which sends the protocol negotiation info rather than the banner that the peer is expecting. The result is that the peer sees an invalid banner, and the client reports "negotiation failed". Fix this by moving con_out_kvec_reset() out of prepare_write_connect() to its callers at all locations except the one where the banner might still need to be sent. [elder@inktak.com: added note about server-side behavior] Signed-off-by: Jim Schutt Reviewed-by: Alex Elder --- net/ceph/messenger.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-) diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c index b979675..24c5eea 100644 --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -915,7 +915,6 @@ static int prepare_write_connect(struct ceph_connection *con) con->out_connect.authorizer_len = auth ? cpu_to_le32(auth->authorizer_buf_len) : 0; - con_out_kvec_reset(con); con_out_kvec_add(con, sizeof (con->out_connect), &con->out_connect); if (auth && auth->authorizer_buf_len) @@ -1557,6 +1556,7 @@ static int process_connect(struct ceph_connection *con) return -1; } con->auth_retry = 1; + con_out_kvec_reset(con); ret = prepare_write_connect(con); if (ret < 0) return ret; @@ -1577,6 +1577,7 @@ static int process_connect(struct ceph_connection *con) ENTITY_NAME(con->peer_name), ceph_pr_addr(&con->peer_addr.in_addr)); reset_connection(con); + con_out_kvec_reset(con); ret = prepare_write_connect(con); if (ret < 0) return ret; @@ -1601,6 +1602,7 @@ static int process_connect(struct ceph_connection *con) le32_to_cpu(con->out_connect.connect_seq), le32_to_cpu(con->in_reply.connect_seq)); con->connect_seq = le32_to_cpu(con->in_reply.connect_seq); + con_out_kvec_reset(con); ret = prepare_write_connect(con); if (ret < 0) return ret; @@ -1617,6 +1619,7 @@ static int process_connect(struct ceph_connection *con) le32_to_cpu(con->in_reply.global_seq)); get_global_seq(con->msgr, le32_to_cpu(con->in_reply.global_seq)); + con_out_kvec_reset(con); ret = prepare_write_connect(con); if (ret < 0) return ret; @@ -2135,7 +2138,11 @@ more: BUG_ON(con->state != CON_STATE_CONNECTING); con->state = CON_STATE_NEGOTIATING; - /* Banner is good, exchange connection info */ + /* + * Received banner is good, exchange connection info. + * Do not reset out_kvec, as sending our banner raced + * with receiving peer banner after connect completed. + */ ret = prepare_write_connect(con); if (ret < 0) goto out;