From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756017Ab3A0Ttj (ORCPT ); Sun, 27 Jan 2013 14:49:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49445 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755876Ab3A0Ttg (ORCPT ); Sun, 27 Jan 2013 14:49:36 -0500 Date: Sun, 27 Jan 2013 20:48:37 +0100 From: Oleg Nesterov To: Ingo Molnar , Srikar Dronamraju , Steven Rostedt Cc: Anton Arapov , Frank Eigler , Josh Stone , Masami Hiramatsu , "Suzuki K. Poulose" , linux-kernel@vger.kernel.org Subject: [PATCH 2/4] uprobes: Fully initialize uprobe_trace_consumer before uprobe_register() Message-ID: <20130127194837.GA25402@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130127194814.GA25377@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org probe_event_enable() does uprobe_register() and only after that sets utc->tu and tu->consumer/flags. This can race with uprobe_dispatcher() which can miss these assignments or see them out of order. Nothing really bad can happen, but this doesn't look clean/safe. And this does not allow to use uprobe_consumer->filter() we are going to add, it is called by uprobe_register() and it needs utc->tu. Change this code to initialize everything before uprobe_register(), and reset tu->consumer/flags if it fails. We can't race with event_disable(), the caller holds event_mutex, and if we could the code would be wrong anyway. In fact I think uprobe_trace_consumer should die, it buys nothing but complicate the code. We can simply add uprobe_consumer into trace_uprobe. Signed-off-by: Oleg Nesterov --- kernel/trace/trace_uprobe.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 53afabe..94d4ea2 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -552,17 +552,18 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag) return -EINTR; utc->cons.handler = uprobe_dispatcher; + utc->tu = tu; + tu->consumer = utc; + tu->flags |= flag; + ret = uprobe_register(tu->inode, tu->offset, &utc->cons); if (ret) { + tu->consumer = NULL; + tu->flags &= ~flag; kfree(utc); - return ret; } - tu->flags |= flag; - utc->tu = tu; - tu->consumer = utc; - - return 0; + return ret; } static void probe_event_disable(struct trace_uprobe *tu, int flag) -- 1.5.5.1