From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932714AbcBXEns (ORCPT ); Tue, 23 Feb 2016 23:43:48 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:53001 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932124AbcBXEOV (ORCPT ); Tue, 23 Feb 2016 23:14:21 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rabin Vincent , Shirish Pargaonkar , Steve French Subject: [PATCH 4.4 052/137] cifs: fix race between call_async() and reconnect() Date: Tue, 23 Feb 2016 19:33:03 -0800 Message-Id: <20160224033418.939782339@linuxfoundation.org> X-Mailer: git-send-email 2.7.1 In-Reply-To: <20160224033417.270530882@linuxfoundation.org> References: <20160224033417.270530882@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rabin Vincent commit 820962dc700598ffe8cd21b967e30e7520c34748 upstream. cifs_call_async() queues the MID to the pending list and calls smb_send_rqst(). If smb_send_rqst() performs a partial send, it sets the tcpStatus to CifsNeedReconnect and returns an error code to cifs_call_async(). In this case, cifs_call_async() removes the MID from the list and returns to the caller. However, cifs_call_async() releases the server mutex _before_ removing the MID. This means that a cifs_reconnect() can race with this function and manage to remove the MID from the list and delete the entry before cifs_call_async() calls cifs_delete_mid(). This leads to various crashes due to the use after free in cifs_delete_mid(). Task1 Task2 cifs_call_async(): - rc = -EAGAIN - mutex_unlock(srv_mutex) cifs_reconnect(): - mutex_lock(srv_mutex) - mutex_unlock(srv_mutex) - list_delete(mid) - mid->callback() cifs_writev_callback(): - mutex_lock(srv_mutex) - delete(mid) - mutex_unlock(srv_mutex) - cifs_delete_mid(mid) <---- use after free Fix this by removing the MID in cifs_call_async() before releasing the srv_mutex. Also hold the srv_mutex in cifs_reconnect() until the MIDs are moved out of the pending list. Signed-off-by: Rabin Vincent Acked-by: Shirish Pargaonkar Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/cifs/connect.c | 2 +- fs/cifs/transport.c | 6 ++++-- 2 files changed, 5 insertions(+), 3 deletions(-) --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -368,7 +368,6 @@ cifs_reconnect(struct TCP_Server_Info *s server->session_key.response = NULL; server->session_key.len = 0; server->lstrp = jiffies; - mutex_unlock(&server->srv_mutex); /* mark submitted MIDs for retry and issue callback */ INIT_LIST_HEAD(&retry_list); @@ -381,6 +380,7 @@ cifs_reconnect(struct TCP_Server_Info *s list_move(&mid_entry->qhead, &retry_list); } spin_unlock(&GlobalMid_Lock); + mutex_unlock(&server->srv_mutex); cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); list_for_each_safe(tmp, tmp2, &retry_list) { --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -576,14 +576,16 @@ cifs_call_async(struct TCP_Server_Info * cifs_in_send_dec(server); cifs_save_when_sent(mid); - if (rc < 0) + if (rc < 0) { server->sequence_number -= 2; + cifs_delete_mid(mid); + } + mutex_unlock(&server->srv_mutex); if (rc == 0) return 0; - cifs_delete_mid(mid); add_credits_and_wake_if(server, credits, optype); return rc; }