From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752365AbdKTTMa (ORCPT ); Mon, 20 Nov 2017 14:12:30 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:34324 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752298AbdKTTM2 (ORCPT ); Mon, 20 Nov 2017 14:12:28 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 2ECCA607E8 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=sboyd@codeaurora.org Date: Mon, 20 Nov 2017 11:12:19 -0800 From: Stephen Boyd To: Chunyan Zhang Cc: Michael Turquette , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, Cai Li , Orson Zhai , Chunyan Zhang Subject: Re: [PATCH] clk: fix a panic error caused by accessing NULL pointer Message-ID: <20171120191219.GD18379@codeaurora.org> References: <20171120033816.28414-1-chunyan.zhang@spreadtrum.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171120033816.28414-1-chunyan.zhang@spreadtrum.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/20, Chunyan Zhang wrote: > From: Cai Li > > In some cases the clock parent would be set NULL when doing re-parent, > it will cause a NULL pointer accessing if clk_set trace event is enabled, > since the trace event function would not check the input parameter. > > Signed-off-by: Cai Li > Signed-off-by: Chunyan Zhang Fixes: tag? > --- > drivers/clk/clk.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index c8d83ac..64efaf0 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -1242,13 +1242,12 @@ static int __clk_set_parent(struct clk_core *core, struct clk_core *parent, > > old_parent = __clk_set_parent_before(core, parent); > > - trace_clk_set_parent(core, parent); > - > /* change clock input source */ > - if (parent && core->ops->set_parent) > + if (parent && core->ops->set_parent) { > + trace_clk_set_parent(core, parent); > ret = core->ops->set_parent(core->hw, p_index); > - > - trace_clk_set_parent_complete(core, parent); > + trace_clk_set_parent_complete(core, parent); > + } Is the problem that parent may be NULL and the tracepoint dereferences it? Perhaps we need to update the tracepoint code instead so that we always see that the tracepoint is called even if we don't actually touch the hardware. Something like the patch below instead. ---8<---- diff --git a/include/trace/events/clk.h b/include/trace/events/clk.h index 758607226bfd..5a85ea2090c4 100644 --- a/include/trace/events/clk.h +++ b/include/trace/events/clk.h @@ -139,7 +139,7 @@ DECLARE_EVENT_CLASS(clk_parent, TP_fast_assign( __assign_str(name, core->name); - __assign_str(pname, parent->name); + __assign_str(pname, parent ? parent->name : NULL); ), TP_printk("%s %s", __get_str(name), __get_str(pname)) -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project