linux-kernel - Re: [PATCH V5 2/2] nvme-pci: fixup the timeout case when reset is ongoing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180119060521.GD12043@localhost.localdomain>
Date:   Thu, 18 Jan 2018 23:05:21 -0700
From:   Keith Busch <keith.busch@...el.com>
To:     "jianchao.wang" <jianchao.w.wang@...cle.com>
Cc:     axboe@...com, hch@....de, sagi@...mberg.me, maxg@...lanox.com,
        james.smart@...adcom.com, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 2/2] nvme-pci: fixup the timeout case when reset is
 ongoing

On Fri, Jan 19, 2018 at 01:55:29PM +0800, jianchao.wang wrote:
> On 01/19/2018 12:59 PM, Keith Busch wrote:
> > On Thu, Jan 18, 2018 at 06:10:02PM +0800, Jianchao Wang wrote:
> >> +	 * - When the ctrl.state is NVME_CTRL_RESETTING, the expired
> >> +	 *   request should come from the previous work and we handle
> >> +	 *   it as nvme_cancel_request.
> >> +	 * - When the ctrl.state is NVME_CTRL_RECONNECTING, the expired
> >> +	 *   request should come from the initializing procedure such as
> >> +	 *   setup io queues, because all the previous outstanding
> >> +	 *   requests should have been cancelled.
> >>  	 */
> >> -	if (dev->ctrl.state == NVME_CTRL_RESETTING) {
> >> -		dev_warn(dev->ctrl.device,
> >> -			 "I/O %d QID %d timeout, disable controller\n",
> >> -			 req->tag, nvmeq->qid);
> >> -		nvme_dev_disable(dev, false);
> >> +	switch (dev->ctrl.state) {
> >> +	case NVME_CTRL_RESETTING:
> >> +		nvme_req(req)->status = NVME_SC_ABORT_REQ;
> >> +		return BLK_EH_HANDLED;
> >> +	case NVME_CTRL_RECONNECTING:
> >> +		WARN_ON_ONCE(nvmeq->qid);
> >>  		nvme_req(req)->flags |= NVME_REQ_CANCELLED;
> >>  		return BLK_EH_HANDLED;
> >> +	default:
> >> +		break;
> >>  	}
> > 
> > The driver may be giving up on the command here, but that doesn't mean
> > the controller has. We can't just end the request like this because that
> > will release the memory the controller still owns. We must wait until
> > after nvme_dev_disable clears bus master because we can't say for sure
> > the controller isn't going to write to that address right after we end
> > the request.
> > 
> Yes, but the controller is going to be reseted or shutdown at the moment,
> even if the controller accesses a bad address and goes wrong, everything will
> be ok after reset or shutdown. :)

Hm, I don't follow. DMA access after free is never okay.