Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753953Ab2HDJBg (ORCPT ); Sat, 4 Aug 2012 05:01:36 -0400 Received: from relay02ant.iops.be ([212.53.4.35]:35398 "EHLO relay02ant.iops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752220Ab2HDJBc (ORCPT ); Sat, 4 Aug 2012 05:01:32 -0400 Message-ID: <501CE4E5.20604@acm.org> Date: Sat, 04 Aug 2012 09:01:25 +0000 From: Bart Van Assche User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: Chanho Min CC: James Bottomley , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe , Tejun Heo , Mike Christie Subject: Re: [PATCH] fix NULL-pointer dereference on scsi_run_queue References: In-Reply-To: X-Enigmail-Version: 1.5a1pre Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2312 Lines: 63 On 08/02/12 08:41, Chanho Min wrote: > This patch is to fix a oops from a torn down device. When > scsi_run_queue process starved queues, scsi_request_fn can race with > scsi_remove_device. In this case, rarely, scsi_request_fn release the > last reference and set sdev->request_queue to NULL. It result in > NULL-pointer dereference when spin_unlock is tried with (NULL)-> > queue_lock. We need to add an extra reference to the device on both > sides of the __blk_run_queue to hold reference until scsi_request_fn > is finished. Good catch. So far I haven't been able to trigger this issue in my tests. So it would be appreciated if you could verify whether the patch below helps (patch is based on 3.6-rc1): --- drivers/scsi/scsi_sysfs.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 093d4f6..59e523c 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -348,7 +348,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) starget->reap_ref++; list_del(&sdev->siblings); list_del(&sdev->same_target_siblings); - list_del(&sdev->starved_entry); spin_unlock_irqrestore(sdev->host->host_lock, flags); cancel_work_sync(&sdev->event_work); @@ -956,6 +955,8 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev) void __scsi_remove_device(struct scsi_device *sdev) { struct device *dev = &sdev->sdev_gendev; + struct Scsi_Host *shost = sdev->host; + unsigned long flags; if (sdev->is_visible) { if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0) @@ -977,6 +978,11 @@ void __scsi_remove_device(struct scsi_device *sdev) blk_cleanup_queue(sdev->request_queue); cancel_work_sync(&sdev->requeue_work); + spin_lock_irqsave(shost->host_lock, flags); + if (!list_empty(&sdev->starved_entry)) + list_del(&sdev->starved_entry); + spin_unlock_irqrestore(shost->host_lock, flags); + if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy(sdev); transport_destroy_device(dev); -- 1.7.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/