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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 82554C5CFE7 for ; Tue, 10 Jul 2018 02:40:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2CEA52089D for ; Tue, 10 Jul 2018 02:40:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2CEA52089D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933053AbeGJCkc (ORCPT ); Mon, 9 Jul 2018 22:40:32 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:35348 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932797AbeGJCk0 (ORCPT ); Mon, 9 Jul 2018 22:40:26 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D0240402347E; Tue, 10 Jul 2018 02:40:25 +0000 (UTC) Received: from [10.72.12.18] (ovpn-12-18.pek2.redhat.com [10.72.12.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6FA912156889; Tue, 10 Jul 2018 02:40:21 +0000 (UTC) Subject: Re: [PATCH v3 3/3] uio: fix crash after the device is unregistered To: Mike Christie , gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Cc: hamish.martin@alliedtelesis.co.nz, jannh@google.com, pkalever@redhat.com, pkarampu@redhat.com, atumball@redhat.com, sabose@redhat.com References: <1530845836-49101-1-git-send-email-xiubli@redhat.com> <1530845836-49101-4-git-send-email-xiubli@redhat.com> <5B3FB3B0.7010105@redhat.com> <1d3a72f6-2d48-1e36-82e4-c764c5359765@redhat.com> <5B439618.5060800@redhat.com> From: Xiubo Li Message-ID: <4f39f032-6ab4-2dff-346a-9c752aa16ed5@redhat.com> Date: Tue, 10 Jul 2018 10:40:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.0 MIME-Version: 1.0 In-Reply-To: <5B439618.5060800@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 10 Jul 2018 02:40:25 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 10 Jul 2018 02:40:25 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'xiubli@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/7/10 1:06, Mike Christie wrote: > On 07/06/2018 08:28 PM, Xiubo Li wrote: >> On 2018/7/7 2:23, Mike Christie wrote: >>> On 07/05/2018 09:57 PM, xiubli@redhat.com wrote: >>>> static irqreturn_t uio_interrupt(int irq, void *dev_id) >>>> { >>>> struct uio_device *idev = (struct uio_device *)dev_id; >>>> - irqreturn_t ret = idev->info->handler(irq, idev->info); >>>> + irqreturn_t ret; >>>> + >>>> + mutex_lock(&idev->info_lock); >>>> + if (!idev->info) { >>>> + ret = IRQ_NONE; >>>> + goto out; >>>> + } >>>> + ret = idev->info->handler(irq, idev->info); >>>> if (ret == IRQ_HANDLED) >>>> uio_event_notify(idev->info); >>>> +out: >>>> + mutex_unlock(&idev->info_lock); >>>> return ret; >>>> } >>> Do you need the interrupt related changes in this patch and the first >>> one? >> Actually, the NULL checking is not a must, we can remove this. But the >> lock/unlock is needed. >>> When we do uio_unregister_device -> free_irq does free_irq return >>> when there are no longer running interrupt handlers that we requested? >>> >>> If that is not the case then I think we can hit a similar bug. We do: >>> >>> __uio_register_device -> device_register -> device's refcount goes to >>> zero so we do -> uio_device_release -> kfree(idev) >>> >>> and if it is possible the interrupt handler could still run after >>> free_irq then we would end up doing: >>> >>> uio_interrupt -> mutex_lock(&idev->info_lock) -> idev access freed >>> memory. >> I think this shouldn't happen. Because the free_irq function does not >> return until any executing interrupts for this IRQ have completed. >> > If free_irq returns after executing interrupts and does not allow new > executions what is the lock protecting in uio_interrupt? > I meant idev->info->handler(irq, idev->info), it may should be protected by the related lock in each driver. Thanks，