linux-kernel - Re: [RFC 02/20] vfio: Add device class for /dev/vfio/devices

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]

Date:   Wed, 3 Nov 2021 10:25:47 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>
Cc:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "hch@....de" <hch@....de>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "parav@...lanox.com" <parav@...lanox.com>,
        "lkml@...ux.net" <lkml@...ux.net>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "lushenming@...wei.com" <lushenming@...wei.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "yi.l.liu@...ux.intel.com" <yi.l.liu@...ux.intel.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "david@...son.dropbear.id.au" <david@...son.dropbear.id.au>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>
Subject: Re: [RFC 02/20] vfio: Add device class for /dev/vfio/devices

On Tue, Nov 02, 2021 at 09:53:29AM +0000, Liu, Yi L wrote:

> > 	vfio_uninit_group_dev(&mdev_state->vdev);
> > 	kfree(mdev_state->pages);
> > 	kfree(mdev_state->vconfig);
> > 	kfree(mdev_state);
> > 
> > pages/vconfig would logically be in a release function
> 
> I see. So the criteria is: the pointer fields pointing to a memory buffer
> allocated by the device driver should be logically be free in a release
> function. right? 

Often yes, that is usually a good idea

>I can see there are such fields in struct vfio_pci_core_device
> and mdev_state (both mbochs and mdpy). So we may go with your option #2.
> Is it? otherwise, needs to add release callback for all the related drivers.

Yes, that is the approx trade off

> > On the other hand ccw needs to rcu free the vfio_device, so that would
> > have to be global overhead with this api design.
> 
> not quite get. why ccw is special here? could you elaborate?

I added a rcu usage to it in order to fix a race

+static inline struct vfio_ccw_private *vfio_ccw_get_priv(struct subchannel *sch)
+{
+       struct vfio_ccw_private *private;
+
+       rcu_read_lock();
+       private = dev_get_drvdata(&sch->dev);
+       if (private && !vfio_device_try_get(&private->vdev))
+               private = NULL;
+       rcu_read_unlock();
+       return private;
+}
 

Jason