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Mon, 10 May 2021 17:50:57 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4078C112062; Mon, 10 May 2021 17:50:57 +0000 (GMT) Received: from cpe-172-100-179-72.stny.res.rr.com (unknown [9.85.140.234]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 10 May 2021 17:50:57 +0000 (GMT) Subject: Re: [PATCH] s390/vfio-ap: fix memory leak in mdev remove callback To: Cornelia Huck Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com, jgg@nvidia.com, alex.williamson@redhat.com, kwankhede@nvidia.com, stable@vger.kernel.org, Tony Krowiak References: <20210505172826.105304-1-akrowiak@linux.ibm.com> <20210506122245.20f4ba21.cohuck@redhat.com> <20210506124541.63e98b64.cohuck@redhat.com> From: Tony Krowiak Message-ID: <8fd7f138-8544-c38b-fb0f-fa12e3c8ef06@linux.ibm.com> Date: Mon, 10 May 2021 13:50:56 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210506124541.63e98b64.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: fn1s1Fw8-6KwfJBCFQJumBHeVpCIw-u8 X-Proofpoint-GUID: bieBX1xk9QSJv723mce2mabqDZJHBUEn X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-05-10_11:2021-05-10,2021-05-10 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 phishscore=0 mlxlogscore=999 spamscore=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 mlxscore=0 priorityscore=1501 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105100118 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/6/21 6:45 AM, Cornelia Huck wrote: > On Thu, 6 May 2021 12:22:45 +0200 > Cornelia Huck wrote: > >> On Wed, 5 May 2021 13:28:26 -0400 >> 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. >>> >>> Fixes: 258287c994de ("s390: vfio-ap: implement mediated device open callback") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Tony Krowiak >>> Signed-off-by: Tony Krowiak >>> --- >>> drivers/s390/crypto/vfio_ap_ops.c | 39 +++++++++++++++++++++++-------- >>> 1 file changed, 29 insertions(+), 10 deletions(-) >>> >>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c >>> index b2c7e10dfdcd..757166da947e 100644 >>> --- a/drivers/s390/crypto/vfio_ap_ops.c >>> +++ b/drivers/s390/crypto/vfio_ap_ops.c >>> @@ -335,6 +335,32 @@ static void vfio_ap_matrix_init(struct ap_config_info *info, >>> matrix->adm_max = info->apxa ? info->Nd : 15; >>> } >>> >>> +static bool vfio_ap_mdev_has_crycb(struct ap_matrix_mdev *matrix_mdev) >>> +{ >>> + return (matrix_mdev->kvm && matrix_mdev->kvm->arch.crypto.crycbd); >>> +} >>> + >>> +static void vfio_ap_mdev_clear_apcb(struct ap_matrix_mdev *matrix_mdev) >>> +{ >>> + /* >>> + * If the KVM pointer is in the process of being set, wait until the >>> + * process has completed. >>> + */ >>> + wait_event_cmd(matrix_mdev->wait_for_kvm, >>> + !matrix_mdev->kvm_busy, >>> + mutex_unlock(&matrix_dev->lock), >>> + mutex_lock(&matrix_dev->lock)); >>> + >>> + if (vfio_ap_mdev_has_crycb(matrix_mdev)) { >>> + matrix_mdev->kvm_busy = true; >>> + mutex_unlock(&matrix_dev->lock); >>> + kvm_arch_crypto_clear_masks(matrix_mdev->kvm); >>> + mutex_lock(&matrix_dev->lock); >>> + matrix_mdev->kvm_busy = false; >>> + wake_up_all(&matrix_mdev->wait_for_kvm); >>> + } >>> +} >> Looking at vfio_ap_mdev_unset_kvm(), do you need to unhook the kvm here >> as well? >> >> (Or can you maybe even combine the two functions into one?) > Staring at the code some more, the rules where you unset the kvm stuff > seem pretty confusing (at least to me). Does this partial unhooking in > the remove callback make sense? If you stare at it too long, you'll go blind:) As I stated in my response to your previous review comment, I'm going to remove the function above and call the vfio_ap_mdev_unset_kvm() function from the remove callback. > >>> + >>> 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); >>> vfio_ap_mdev_reset_queues(mdev); >>> list_del(&matrix_mdev->node); >>> kfree(matrix_mdev);