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 00FE8C3279B for ; Sat, 7 Jul 2018 01:29:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC28221CD0 for ; Sat, 7 Jul 2018 01:29:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC28221CD0 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 S1754131AbeGGB25 (ORCPT ); Fri, 6 Jul 2018 21:28:57 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:52838 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753956AbeGGB24 (ORCPT ); Fri, 6 Jul 2018 21:28:56 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7C65D4075184; Sat, 7 Jul 2018 01:28:55 +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 5739A2026D68; Sat, 7 Jul 2018 01:28:49 +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> From: Xiubo Li Message-ID: <1d3a72f6-2d48-1e36-82e4-c764c5359765@redhat.com> Date: Sat, 7 Jul 2018 09:28:45 +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: <5B3FB3B0.7010105@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Sat, 07 Jul 2018 01:28:55 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Sat, 07 Jul 2018 01:28:55 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.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 2018/7/7 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. Thanks, BRs