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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 401F8C43215 for ; Tue, 26 Nov 2019 10:49:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E9D320862 for ; Tue, 26 Nov 2019 10:49:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727889AbfKZKs7 (ORCPT ); Tue, 26 Nov 2019 05:48:59 -0500 Received: from foss.arm.com ([217.140.110.172]:32796 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727855AbfKZKs6 (ORCPT ); Tue, 26 Nov 2019 05:48:58 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3F88530E; Tue, 26 Nov 2019 02:48:58 -0800 (PST) Received: from bogus (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 766FF3F52E; Tue, 26 Nov 2019 02:48:57 -0800 (PST) Date: Tue, 26 Nov 2019 10:48:50 +0000 From: Sudeep Holla To: Wen Yang Cc: Arnd Bergmann , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sudeep Holla Subject: Re: [PATCH] firmware: arm_scmi: avoid double free in error flow Message-ID: <20191126104850.GA5784@bogus> References: <20191125155409.9948-1-wenyang@linux.alibaba.com> <20191125161313.GA1157@bogus> <21f4f7d6-9085-382d-42d3-a63484aca8a2@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <21f4f7d6-9085-382d-42d3-a63484aca8a2@linux.alibaba.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 26, 2019 at 06:24:47PM +0800, Wen Yang wrote: > > > On 2019/11/26 12:13 上午, Sudeep Holla wrote: > > On Mon, Nov 25, 2019 at 11:54:09PM +0800, Wen Yang wrote: > > > If device_register() fails, both put_device() and kfree() > > > are called, ending with a double free of the scmi_dev. > > > > > > > Correct. > > > > > Calling kfree() is needed only when a failure happens between the > > > allocation of the scmi_dev and its registration, so move it to > > > there and remove it from the error flow. > > > > > > > kstrdup_const can fail and in that case device is not yet registered, > > so we need to free. Since device_register() calls put_device() on failure > > too, I would just drop it as it's unnecessary, not sure why I have added > > it in the first place. Can you re-spin the patch dropping put_device > > and renaming put_dev label to something like free_const. > > Please ignore the above completely. I have made some changes locally and got completely confused when I looked at your patch and compared with the modified context locally. > > Hi Sudeep, > Thanks for your comments. > Let's check the code like this: > > int device_register(struct device *dev) > { > device_initialize(dev); --> Initialize kobj-> kref to 1 > return device_add(dev); > } > > int device_add(struct device *dev) > { > ... > dev = get_device(dev); --> kobj-> kref increases by 1 > ... > done: > put_device(dev); --> kobj-> kref decreases by 1 and is now 1 > return error; > ... > } > > So we also need to call put_device (), > and the original patch should be fine. > Please kindly help to check again, thank you. > You are right, sorry for the confusion. I will apply your original patch. Thanks again for the patch. -- Regards, Sudeep