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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 3A849C433B4 for ; Tue, 27 Apr 2021 16:25:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16FA4613DD for ; Tue, 27 Apr 2021 16:25:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237534AbhD0QZv (ORCPT ); Tue, 27 Apr 2021 12:25:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:50374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238039AbhD0QWp (ORCPT ); Tue, 27 Apr 2021 12:22:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4BE7261164; Tue, 27 Apr 2021 16:12:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619539939; bh=rw5bt2WGIYOK4tOkpbS0fGPf8sq1EDlW2gLyssfB1fE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZpAOGtkoAGlYY6zCcvB8yxCqSlFGG9Zfu7BqGhRvUhwd8mHD0rLiOZ0eQcY5J3uyp /Ee3+lfrpwqdResUeqO2vMKgt/FGnnJxwPrJ7+vpuuTLOjA6ISGTJEJPAA+C/BRu++ dH1XZXR1iiG85L5Ye1qv5CSHr/sP7BLIzsFBG79w= Date: Tue, 27 Apr 2021 18:12:17 +0200 From: Greg KH To: Jens Axboe Cc: Peter Rosin , linux-kernel@vger.kernel.org Subject: Re: [PATCH 167/190] Revert "gdrom: fix a memory leak bug" Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 27, 2021 at 08:39:15AM -0600, Jens Axboe wrote: > 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 > I'll add this fix to the tree after the revert, and give you the credit for the fix :) thanks, greg k-h