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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 0CDD5C3524A for ; Tue, 4 Feb 2020 07:51:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D24E720730 for ; Tue, 4 Feb 2020 07:51:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="gstJsAL8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726578AbgBDHv0 (ORCPT ); Tue, 4 Feb 2020 02:51:26 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:51972 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726000AbgBDHv0 (ORCPT ); Tue, 4 Feb 2020 02:51:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=yUiImlhwcIpiW7cZCXnZDPMFY1pVbnQvFpHqcngYJpA=; b=gstJsAL8wCfEyAUHmus+6yyWTS FTJf8/HqAHwAoYF3+90KrznEc26VGSwMoQjghTds08H67I2DqucLSFAGKoRURFqhgAbPoJlMyPFpy TAQ2aL1XrcAx00X1sLx+A0G7bBQkRNfDr+NcL9HP7IbFWHUbsIKl82akG0UGwyLdlKbUmTPXpISm4 jkEePYDhBrk2NXbJaXa2+5lOYwB+FfFUziY5EQWBTs7wzZXAerzVhQ8mzqjzeF7+Y1JTuKdmXBvdy WcgvXnEKK/ZNE5PP7qzo8kgpvk1i4cMNGhd1G9DuTqkKGCKAsd0vvPpDuLWCDgT7nlVeqxSwIN2At dpNbF2iw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iyszU-0000Wx-HQ; Tue, 04 Feb 2020 07:51:24 +0000 Date: Mon, 3 Feb 2020 23:51:24 -0800 From: Christoph Hellwig To: Bijan Mottahedeh Cc: Christoph Hellwig , axboe@kernel.dk, linux-block@vger.kernel.org, io-uring@vger.kernel.org Subject: Re: [PATCH 1/1] block: Manage bio references so the bio persists until necessary Message-ID: <20200204075124.GA29349@infradead.org> References: <1580441022-59129-1-git-send-email-bijan.mottahedeh@oracle.com> <1580441022-59129-2-git-send-email-bijan.mottahedeh@oracle.com> <20200131064230.GA28151@infradead.org> <9f29fbc7-baf3-00d1-a20c-d2a115439db2@oracle.com> <20200203083422.GA2671@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Mon, Feb 03, 2020 at 01:07:48PM -0800, Bijan Mottahedeh wrote: > My concern is with the code below for the single bio async case: > >                            qc = submit_bio(bio); > >                            if (polled) >                                    WRITE_ONCE(iocb->ki_cookie, qc); > > The bio/dio can be freed before the the cookie is written which is what I'm > seeing, and I thought this may lead to a scenario where that iocb request > could be completed, freed, reallocated, and resubmitted in io_uring layer; > i.e., I thought the cookie could be written into the wrong iocb. I think we do have a potential use after free of the iocb here. But taking a bio reference isn't going to help with that, as the iocb and bio/dio life times are unrelated. I vaguely remember having that discussion with Jens a while ago, and tried to pass a pointer to the qc to submit_bio so that we can set it at submission time, but he came up with a reason why that might not be required. I'd have to dig out all notes unless Jens remembers better.