From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752477AbdIWBJT (ORCPT ); Fri, 22 Sep 2017 21:09:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:57820 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751995AbdIWBJR (ORCPT ); Fri, 22 Sep 2017 21:09:17 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 70D1E21482 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Fri, 22 Sep 2017 21:09:14 -0400 From: Steven Rostedt To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, ngo Molnar , Andrew Morton , stable@vger.kernel.org Subject: Re: [PATCH 3/4] extable: Enable RCU if it is not watching in kernel_text_address() Message-ID: <20170922210914.041a5f14@gandalf.local.home> In-Reply-To: <20170922224406.GZ3521@linux.vnet.ibm.com> References: <20170922221543.900812109@goodmis.org> <20170922221837.736806508@goodmis.org> <20170922224406.GZ3521@linux.vnet.ibm.com> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 22 Sep 2017 15:44:06 -0700 "Paul E. McKenney" wrote: > On Fri, Sep 22, 2017 at 06:15:46PM -0400, Steven Rostedt wrote: > > From: "Steven Rostedt (VMware)" > > > > If kernel_text_address() is called when RCU is not watching, it can cause an > > RCU bug because is_module_text_address() and the is_kprobe_*insn_slot() > > functions require the use of RCU. > > > > Only enable RCU if it is not currently watching before it calls > > is_module_text_address(). The use of rcu_nmi_enter() is used to enable RCU > > because kernel_text_address() can happen pretty much anywhere (like an NMI), > > and even from within an NMI. It is called via save_stack_trace() that can be > > called by any WARN() or tracing function, which can happen while RCU is not > > watching (for example, going to or coming from idle, or during CPU take down > > or bring up). > > > > Cc: Paul E. McKenney > > Cc: stable@vger.kernel.org > > Do we need something calling out the dependency on the first two patches, > or is that implied these days? I believe the stable folks will simply apply patches marked for stable in the order they are applied. This is a patch series, so I don't think it will be an issue for them. > > > Fixes: 0be964be0 ("module: Sanitize RCU usage and locking") > > Signed-off-by: Steven Rostedt (VMware) > > Give or take Josh's feedback on the commit log and comment: Yep. > > Acked-by: Paul E. McKenney Thanks! -- Steve