From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52D45C43381 for ; Mon, 25 Mar 2019 11:55:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D4C720850 for ; Mon, 25 Mar 2019 11:55:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729831AbfCYLzC (ORCPT ); Mon, 25 Mar 2019 07:55:02 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:46066 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730730AbfCYLzB (ORCPT ); Mon, 25 Mar 2019 07:55:01 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ED09080D; Mon, 25 Mar 2019 04:55:00 -0700 (PDT) Received: from [10.1.196.69] (e112269-lin.cambridge.arm.com [10.1.196.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F30363F575; Mon, 25 Mar 2019 04:54:59 -0700 (PDT) Subject: Re: [PATCH] firmware: arm_scmi: check return value of idr_find To: Kangjie Lu Cc: Sudeep Holla , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, pakki001@umn.edu References: <20190309040239.32431-1-kjlu@umn.edu> From: Steven Price Message-ID: <225abd6e-4551-213d-367b-93d938789188@arm.com> Date: Mon, 25 Mar 2019 11:54:58 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190309040239.32431-1-kjlu@umn.edu> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/03/2019 04:02, Kangjie Lu wrote: > idr_find may return NULL, so check its return value and return an > error code. > > Signed-off-by: Kangjie Lu > --- > drivers/firmware/arm_scmi/driver.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c > index 8f952f2f1a29..35faa203d549 100644 > --- a/drivers/firmware/arm_scmi/driver.c > +++ b/drivers/firmware/arm_scmi/driver.c > @@ -709,6 +709,8 @@ scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id) > > if (scmi_mailbox_check(np)) { > cinfo = idr_find(&info->tx_idr, SCMI_PROTOCOL_BASE); > + if (!cinfo) > + return -EINVAL; > goto idr_alloc; > } > > I don't believe this situation can ever actually occur. The SCMI_PROTOCOL_BASE id is reserved just after the IDR is created in scmi_probe() in the first call to scmi_mbox_chan_setup(). That first call can't enter the above if() block because the scmi_mailbox_check() call has already been checked in scmi_probe(). It is only when processing the children in subsequent calls to scmi_mbox_chan_setup() that the check is on another node and so might fail. But by this time the SCMI_PROTOCOL_BASE id must exist. So there shouldn't be any way of reaching the situation where the IDR doesn't contain SCMI_PROTOCOL_BASE and idr_find() returns NULL. Having said that it did take me a while to understand the code well enough to reason that, and the above return should be handled appropriately, so you can add my Reviewed-by. But it would be worth expanding the commit message pointing out that there isn't actually a bug (yet). Steve