Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755043Ab3H2OBz (ORCPT ); Thu, 29 Aug 2013 10:01:55 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:9727 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754822Ab3H2OBx (ORCPT ); Thu, 29 Aug 2013 10:01:53 -0400 From: Libin To: , , , , , , , , , , , CC: , , , , , , Subject: [PATCH 03/14] audit: Fix invalid wakeup in wait_for_auditd Date: Thu, 29 Aug 2013 21:57:38 +0800 Message-ID: <1377784669-28140-4-git-send-email-huawei.libin@huawei.com> X-Mailer: git-send-email 1.8.1.msysgit.1 In-Reply-To: <1377784669-28140-1-git-send-email-huawei.libin@huawei.com> References: <1377784669-28140-1-git-send-email-huawei.libin@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.135.74.57] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2308 Lines: 83 If this thread is preempted at(or before) location a, and the other thread set the condition followed with wake_up_process. After that when this thread is re-scheduled, calling set_current_state to set itself as state TASK_UNINTERRUPTIBLE, if it is preempted again after that and before __set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem. ---------------- wait_for_auditd() ---------------- ... //location a set_current_state(TASK_UNINTERRUPTIBLE); ... if (audit_backlog_limit && skb_queue_len(&audit_skb_queue) > audit_backlog_limit) //location b schedule_timeout(sleep_time); //location c __set_current_state(TASK_RUNNING); //location d ... To solve this problem, using preempt_disable() to bound the operaion that setting the task state and the conditions(set by the wake thread) validation. ---------------- wait_for_auditd() ---------------- ... preempt_disable(); set_current_state(TASK_UNINTERRUPTIBLE); ... if (audit_backlog_limit && skb_queue_len(&audit_skb_queue) > audit_backlog_limit) { preempt_enable(); schedule_timeout(sleep_time); preempt_disable(); } __set_current_state(TASK_RUNNING); preempt_enable(); ... Signed-off-by: Libin --- kernel/audit.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/audit.c b/kernel/audit.c index a7d1346..48d2f76 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1060,14 +1060,19 @@ static inline void audit_get_stamp(struct audit_context *ctx, static void wait_for_auditd(unsigned long sleep_time) { DECLARE_WAITQUEUE(wait, current); + preempt_disable(); set_current_state(TASK_UNINTERRUPTIBLE); add_wait_queue(&audit_backlog_wait, &wait); if (audit_backlog_limit && - skb_queue_len(&audit_skb_queue) > audit_backlog_limit) + skb_queue_len(&audit_skb_queue) > audit_backlog_limit) { + preempt_enable(); schedule_timeout(sleep_time); + preempt_disable(); + } __set_current_state(TASK_RUNNING); + preempt_enable(); remove_wait_queue(&audit_backlog_wait, &wait); } -- 1.8.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/