From: Jason Gunthorpe <jgg@nvidia.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Tony Krowiak <akrowiak@linux.ibm.com>,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
cohuck@redhat.com, pasic@linux.vnet.ibm.com,
jjherne@linux.ibm.com, alex.williamson@redhat.com,
kwankhede@nvidia.com, stable@vger.kernel.org,
Tony Krowiak <akrowiak@stny.rr.com>
Subject: Re: [PATCH] s390/vfio-ap: fix memory leak in mdev remove callback
Date: Wed, 5 May 2021 15:00:38 -0300 [thread overview]
Message-ID: <20210505180038.GK1370958@nvidia.com> (raw)
In-Reply-To: <7b20afce-5782-53c6-beab-ae852ae69b40@de.ibm.com>
On Wed, May 05, 2021 at 07:44:55PM +0200, Christian Borntraeger wrote:
>
>
> On 05.05.21 19:28, Tony Krowiak wrote:
> > The mdev remove callback for the vfio_ap device driver bails out with
> > -EBUSY if the mdev is in use by a KVM guest. The intended purpose was
> > to prevent the mdev from being removed while in use; however, returning a
> > non-zero rc does not prevent removal. This could result in a memory leak
> > of the resources allocated when the mdev was created. In addition, the
> > KVM guest will still have access to the AP devices assigned to the mdev
> > even though the mdev no longer exists.
> >
> > To prevent this scenario, cleanup will be done - including unplugging the
> > AP adapters, domains and control domains - regardless of whether the mdev
> > is in use by a KVM guest or not.
> [...]
> > static int vfio_ap_mdev_create(struct mdev_device *mdev)
> > {
> > struct ap_matrix_mdev *matrix_mdev;
> > @@ -366,16 +392,9 @@ static int vfio_ap_mdev_remove(struct mdev_device *mdev)
> > struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> > mutex_lock(&matrix_dev->lock);
> > -
> > - /*
> > - * If the KVM pointer is in flux or the guest is running, disallow
> > - * un-assignment of control domain.
> > - */
> > - if (matrix_mdev->kvm_busy || matrix_mdev->kvm) {
> > - mutex_unlock(&matrix_dev->lock);
> > - return -EBUSY;
> > - }
> > -
> > + WARN(vfio_ap_mdev_has_crycb(matrix_mdev),
> > + "Removing mdev leaves KVM guest without any crypto devices");
> > + vfio_ap_mdev_clear_apcb(matrix_mdev);
>
> Triggering a kernel warning due to an administrative task is not good.
> Can't you simply clear the crycb? Maybe do a printk, but not a WARN.
+1
Jason
next prev parent reply other threads:[~2021-05-05 18:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 17:28 [PATCH] s390/vfio-ap: fix memory leak in mdev remove callback Tony Krowiak
2021-05-05 17:44 ` Christian Borntraeger
2021-05-05 18:00 ` Jason Gunthorpe [this message]
2021-05-10 17:22 ` Tony Krowiak
2021-05-06 10:22 ` Cornelia Huck
2021-05-06 10:45 ` Cornelia Huck
2021-05-10 17:50 ` Tony Krowiak
2021-05-10 17:44 ` Tony Krowiak
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