linux-kernel - Re: [PATCH] pci, dmar: flush IOTLB before exit domain

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: <1305558798.3146.48.camel@x201>
Date:	Mon, 16 May 2011 09:13:18 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Yinghai Lu <yinghai.lu@...cle.com>, Kalle Valo <kvalo@...rom.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH] pci, dmar: flush IOTLB before exit domain

On Mon, 2011-05-09 at 15:48 +0100, David Woodhouse wrote:
> On Thu, 2011-05-05 at 18:13 -0700, Yinghai Lu wrote:
> > @@ -3252,6 +3252,9 @@ static int device_notifier(struct notifi
> >                 return 0;
> >  
> >         if (action == BUS_NOTIFY_UNBOUND_DRIVER && !iommu_pass_through) {
> > +               /* before we remove dev with domain, flush IOTLB */
> > +               flush_unmaps();
> > +
> >                 domain_remove_one_dev_info(domain, pdev);
> >  
> >                 if (!(domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE) && 
> 
> That calls flush_unmaps() without the async_umap_flush_lock held,
> doesn't it? A few days ago I asked someone else to test this candidate
> patch for a similar issue:
> 
> http://david.woodhou.se/flush-unmaps-on-unbind.patch

Copying here:

> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
> index d552d2c..7e606d6 100644
> --- a/drivers/pci/intel-iommu.c
> +++ b/drivers/pci/intel-iommu.c
> @@ -3256,8 +3259,10 @@ static int device_notifier(struct notifier_block *nb,
>  
>  		if (!(domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE) &&
>  		    !(domain->flags & DOMAIN_FLAG_STATIC_IDENTITY) &&
> -		    list_empty(&domain->devices))
> +		    list_empty(&domain->devices)) {
> +			flush_unmaps_timeout(0);
>  			domain_exit(domain);
> +		}
>  	}
>  
>  	return 0;
> @@ -3587,6 +3592,7 @@ static void intel_iommu_domain_destroy(struct iommu_domain *domain)
>  	struct dmar_domain *dmar_domain = domain->priv;
>  
>  	domain->priv = NULL;
> +	flush_unmaps_timeout(0);
>  	vm_domain_exit(dmar_domain);
> }

David, would it be worthwhile to push the unmaps into the
{vm_}domain_exit() functions to avoid races like this in the future?  I
can verify the above resolves a panic after unbinding a device from
snd_hda_intel that I hit recently.  Do you plan to push this for .39?
Thanks,

Alex

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/