From mboxrd@z Thu Jan 1 00:00:00 1970 From: "gregkh@linuxfoundation.org" Subject: Re: [PATCH] scsi: fix race condition when removing target Date: Wed, 29 Nov 2017 17:39:47 +0000 Message-ID: <20171129173947.GC20581@kroah.com> References: <20171129030556.47833-1-yanaijie@huawei.com> <1511972310.2671.7.camel@wdc.com> <20171129162050.GA32071@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:57708 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934667AbdK2Rjo (ORCPT ); Wed, 29 Nov 2017 12:39:44 -0500 Content-Disposition: inline In-Reply-To: <20171129162050.GA32071@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "hch@lst.de" Cc: Bart Van Assche , "zhaohongjiang@huawei.com" , "jthumshirn@suse.de" , "martin.petersen@oracle.com" , "hare@suse.de" , "linux-scsi@vger.kernel.org" , "yanaijie@huawei.com" , "jejb@linux.vnet.ibm.com" , "miaoxie@huawei.com" On Wed, Nov 29, 2017 at 05:20:50PM +0100, hch@lst.de wrote: > On Wed, Nov 29, 2017 at 04:18:30PM +0000, Bart Van Assche wrote: > > As the above patch description shows it can happen that the SCSI core calls > > get_device() after the device reference count has reached zero and before > > the memory for struct device is freed. Although the above patch looks fine > > to me, would you consider it acceptable to modify get_device() such that it > > uses kobject_get_unless_zero() instead of kobject_get()? I'm asking this > > because that change would help to reduce the complexity of the already too > > complicated SCSI core. > > I don't think we can just modify get_device, but we can add a new > get_device_unless_zero. In fact I have an open coded variant of that > in nvme, and was planning to submit one for the current merge window.. I feel like that is just delaying the real fix, shouldn't there be a bus lock somewhere on the put_device path for this bus to prevent this? thanks, greg k-h