From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:59788 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933580AbbIZVSJ (ORCPT ); Sat, 26 Sep 2015 17:18:09 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , "David S. Miller" Subject: [PATCH 4.1 157/159] inet: fix races with reqsk timers Date: Sat, 26 Sep 2015 13:56:43 -0700 Message-Id: <20150926205322.306609629@linuxfoundation.org> In-Reply-To: <20150926205313.363686083@linuxfoundation.org> References: <20150926205313.363686083@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: stable-owner@vger.kernel.org List-ID: 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 2235f2ac75fd2501c251b0b699a9632e80239a6d ] reqsk_queue_destroy() and reqsk_queue_unlink() should use del_timer_sync() instead of del_timer() before calling reqsk_put(), otherwise we could free a req still used by another cpu. But before doing so, reqsk_queue_destroy() must release syn_wait_lock spinlock or risk a dead lock, as reqsk_timer_handler() might need to take this same spinlock from reqsk_queue_unlink() (called from inet_csk_reqsk_queue_drop()) Fixes: fa76ce7328b2 ("inet: get rid of central tcp/dccp listener timer") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/request_sock.c | 8 +++++++- net/ipv4/inet_connection_sock.c | 2 +- 2 files changed, 8 insertions(+), 2 deletions(-) --- a/net/core/request_sock.c +++ b/net/core/request_sock.c @@ -103,10 +103,16 @@ void reqsk_queue_destroy(struct request_ spin_lock_bh(&queue->syn_wait_lock); while ((req = lopt->syn_table[i]) != NULL) { lopt->syn_table[i] = req->dl_next; + /* Because of following del_timer_sync(), + * we must release the spinlock here + * or risk a dead lock. + */ + spin_unlock_bh(&queue->syn_wait_lock); atomic_inc(&lopt->qlen_dec); - if (del_timer(&req->rsk_timer)) + if (del_timer_sync(&req->rsk_timer)) reqsk_put(req); reqsk_put(req); + spin_lock_bh(&queue->syn_wait_lock); } spin_unlock_bh(&queue->syn_wait_lock); } --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -584,7 +584,7 @@ static bool reqsk_queue_unlink(struct re } spin_unlock(&queue->syn_wait_lock); - if (del_timer(&req->rsk_timer)) + if (del_timer_sync(&req->rsk_timer)) reqsk_put(req); return found; }