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=-10.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 34207C43460 for ; Tue, 27 Apr 2021 14:39:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0785613E2 for ; Tue, 27 Apr 2021 14:39:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238400AbhD0OkB (ORCPT ); Tue, 27 Apr 2021 10:40:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236173AbhD0OkA (ORCPT ); Tue, 27 Apr 2021 10:40:00 -0400 Received: from mail-io1-xd2b.google.com (mail-io1-xd2b.google.com [IPv6:2607:f8b0:4864:20::d2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B01CFC061574 for ; Tue, 27 Apr 2021 07:39:17 -0700 (PDT) Received: by mail-io1-xd2b.google.com with SMTP id t21so8990187iob.2 for ; Tue, 27 Apr 2021 07:39:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=VzCXi3U4cA43+FJ7G1wS5WnWPcFxc4C59R2q89RLAEE=; b=rbl6dGamxZbGTGVWIeflu0JeKPdpyqXU5lERJm2YuRbuWQ4IBGQgyC5N5Jk+OK8Pd3 lJ8s5kmJRPzbsiUvF/PGui3B5GwuMd0T8U0IpGpJ9zRHHJgF0cxBf3KW784WXOg/SSuD NOigYuR0uJHKHGebfcn4KK+dMIQyU9shTVQRPA7jhEc9nGwDFYshsTrHamB4s3cHA6Wh QcLJAvvMZcOsPK31OZctElfPa5maEqxkRz8gioNYGzlySu05XLNnmDsSvK3nOhjCGgwE wKzWjNC0SkNAKFzUSvXcELzt9zCb0a2i7FAXVcpSA3Tdb+TjM/PdMa0F/3lm4xAQ5Wy2 0ROQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=VzCXi3U4cA43+FJ7G1wS5WnWPcFxc4C59R2q89RLAEE=; b=QnViGnjJm76Vt4I+qwnG+044+0q7xzdR0zg6ZFLfwBq5/Os7Z9J/2P7RvNE3CbdMth 4D7hja8a8aB1xZmq6PpUNk0uDJicglIxhzx/YsjgTxo7QYs215javxFjT3mcZAzRohu9 VO52B9jOl63eo8JAg8Y0Ek8+poZ53r3URmDYWsPDwmNn4Mn9Fc3TAXQchZHmi9Hrkk+t 7a5L790bS5qDUe/qo/WdgDDwugGFPAgbmPrWIMI703wJIOyLB+8v2DGCgbPxZJPzzebm yAEmUiJA0m32++xzBxPy/9r1IiMGCdBnvMzGMIwwTG4D7J0RZUGr6sS98jIh0wcAI+TR gBYQ== X-Gm-Message-State: AOAM531cR7ojd+O7WcADa1o9apHdds8Ltf/83VWNMm8AFyW6s6N6Z2QK 0NUVVbWqXqgQWriVdj6VVm5ArVHQ2tZ49w== X-Google-Smtp-Source: ABdhPJypkkuMfeIIfnwojWMH/w7kva/yQUVsfqM5rhBnFR4H91CxAwXUaJfUjT9wW2z4tolwobejxQ== X-Received: by 2002:a5e:9801:: with SMTP id s1mr18976896ioj.194.1619534356857; Tue, 27 Apr 2021 07:39:16 -0700 (PDT) Received: from [192.168.1.30] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id l2sm1441489ilq.70.2021.04.27.07.39.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Apr 2021 07:39:16 -0700 (PDT) Subject: Re: [PATCH 167/190] Revert "gdrom: fix a memory leak bug" To: Peter Rosin , Greg KH Cc: linux-kernel@vger.kernel.org References: <20210421130105.1226686-168-gregkh@linuxfoundation.org> <23ffd3c5-0095-6a95-8c30-2b6f67377ce7@axentia.se> <14bdfbee-b8b9-d8ac-de34-b6d852d1485b@kernel.dk> <5a55e8d4-e9b6-1854-51bc-afacd3ca097c@axentia.se> From: Jens Axboe Message-ID: Date: Tue, 27 Apr 2021 08:39:15 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <5a55e8d4-e9b6-1854-51bc-afacd3ca097c@axentia.se> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/27/21 8:03 AM, Peter Rosin wrote: > On 2021-04-27 15:01, Greg KH wrote: >> On Fri, Apr 23, 2021 at 08:20:30AM -0600, Jens Axboe wrote: >>> On 4/22/21 3:29 PM, Peter Rosin wrote: >>>>> This reverts commit 093c48213ee37c3c3ff1cf5ac1aa2a9d8bc66017. >>>> >>>> The reverted patch looks fishy. >>>> >>>> gc.cd_info is kzalloc:ed on probe. In case probe fails after this allocation, the >>>> memory is kfree:d but the variable is NOT zeroed out. >>>> >>>> AFAICT, the above leads to a double-free on exit by the added line. >>>> >>>> I believe gd.cd_info should be kfree:d on remove instead. >>>> >>>> However, might not gc.toc also be kfree:d twice for similar reasons? >>>> >>>> I could easily be mistaken. >>> >>> >From taking a quick look the other day, that's my conclusion too. I >>> don't think the patch is correct, but I don't think the surrounding code >>> is correct right now either. >> >> Thanks for the review from both of you, I'll keep this commit in the >> tree. > Err, which commit is "this" and what tree are you keeping it in? I > think you mean that you are keeping the revert in your tree with > reverts, and not that you mean that we should keep the original > commit in Linus' tree. > > In any case, I'd think that the original memory leak is somewhat > better than the introduced double-free and therefore the revert > should be done. It should probably look like the below, though I doubt it matters since only one device is supported anyway. As long as the free happens post unregister, it likely won't make a difference. But it is cleaner and easier to verify, and should double device support ever be introduced, the existing code is buggy. But given that, I don't think we should keep the revert patch. diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c index 9874fc1c815b..02d369881165 100644 --- a/drivers/cdrom/gdrom.c +++ b/drivers/cdrom/gdrom.c @@ -831,6 +831,8 @@ static int remove_gdrom(struct platform_device *devptr) if (gdrom_major) unregister_blkdev(gdrom_major, GDROM_DEV_NAME); unregister_cdrom(gd.cd_info); + kfree(gd.toc); + kfree(gd.cd_info); return 0; } @@ -862,8 +864,6 @@ static void __exit exit_gdrom(void) { platform_device_unregister(pd); platform_driver_unregister(&gdrom_driver); - kfree(gd.toc); - kfree(gd.cd_info); } module_init(init_gdrom); -- Jens Axboe