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Wed, 12 Aug 2026 11:52:01 +0000 (GMT) Received: from li-4c4c4544-004d-4810-8043-b7c04f423534.ibm.com.com (unknown [9.61.9.29]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 12 Aug 2026 11:52:01 +0000 (GMT) From: Anthony Krowiak To: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: jjherne@linux.ibm.com, borntraeger@de.ibm.com, mjrosato@linux.ibm.com, pasic@linux.ibm.com, alex@shazbot.org, kwankhede@nvidia.com, fiuczy@linux.ibm.com, pbonzini@redhat.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, agordeev@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, stable@vger.kernel.org Subject: [PATCH v3 8/9] s390/vfio-ap: Fix NULL deref in status_show() during queue probe Date: Wed, 12 Aug 2026 07:51:38 -0400 Message-ID: <20260812115139.576303-9-akrowiak@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260812115139.576303-1-akrowiak@linux.ibm.com> References: <20260812115139.576303-1-akrowiak@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=RsP16imK c=1 sm=1 tr=0 ts=6a7c5e66 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=6WrCTVO_FsqHOomzZFMA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: PqUgwOKVG8DvLq-ShdSHh5bt1-vC5vdr X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEyMDA5MyBTYWx0ZWRfX4ruds9+vR1Ct 8kcL7N2fuWSVuKZ3utuJjkYiBxJa20HItHCHCN70+DLL+ko+BhjsAeGe8IXe0C+B8qXYKikzDdk xG7RJcULq2y/RAQU9Y1d5q+XZDR7Qau21OOJp6XFNOfpwXiDx0zJWDoyuuyFDYS24ijUMEaC4tC 8MAQVNmS2SnKj4STA74pomNjJLe4X3UkzHbIMDVlVUh9gkflFlE9AEjprdU02Uu7wyABlmOuYWG Bgz5Bj5dZGYb/zhmSTXUQmflCL/g8soJeascA6Vw6buYCB9KCiMVMhBvZ7uWn0QV9ymAWOxS9IE b0wcxJGVPtWiweaYR41ATu1Qb78zwNrbPWAGRgMDL2VYQiO6qrkwrQsUuzcN9GERGhLqFuGSRyS Ddgsonv41rAx8NvcMbBtq30nU/+SCgpqgVjqcG6ejecVqRy6MxyNjeoqmeotuXEpNEbH0gtl7fF h88phAz29Vl20FapJXg== X-Proofpoint-ORIG-GUID: PqUgwOKVG8DvLq-ShdSHh5bt1-vC5vdr X-Proofpoint-Spam-Info: AW1haW4tMjYwODEyMDA5MyBTYWx0ZWRfX4TMGatPsesG5 l1fWo9QSDw1AVrrR8BmAc/VfceW8oMv5MmppGkTi43yksqrz7J4HZiTQx4WVOXGviifFXCSdgMU Zb9O1rf4fld8qNu0Zbj84A+rECI/w/E= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-12_03,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 suspectscore=0 clxscore=1015 malwarescore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608120093 When vfio_ap_mdev_probe_queue() creates the sysfs attribute group, the queue's driver data has not yet been set. A concurrent read of the 'status' attribute can therefore call dev_get_drvdata() and get NULL, which is then passed directly to vfio_ap_mdev_for_queue() where q->apqn is unconditionally dereferenced, causing a NULL pointer dereference. Fix this by acquiring the update locks before calling sysfs_create_group(). The status_show() function acquires guests_lock before reading the driver data, so any concurrent read will block until after dev_set_drvdata() has been called and the update locks are released. As a bonus, the APQN no longer needs to be read from the queue struct after allocation — it can be read directly from apdev before allocation and stored in a local variable, which is then assigned to q->apqn once the allocation succeeds. Fixes: 260f3ea141382 ("s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c") Cc: stable@vger.kernel.org Signed-off-by: Anthony Krowiak --- drivers/s390/crypto/vfio_ap_ops.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c index cb1e5db69d8a..3652ba792be7 100644 --- a/drivers/s390/crypto/vfio_ap_ops.c +++ b/drivers/s390/crypto/vfio_ap_ops.c @@ -2419,14 +2419,17 @@ void vfio_ap_mdev_unregister(void) int vfio_ap_mdev_probe_queue(struct ap_device *apdev) { - int ret; + int ret, apqn; struct vfio_ap_queue *q; DECLARE_BITMAP(apm_filtered, AP_DEVICES); struct ap_matrix_mdev *matrix_mdev; + apqn = to_ap_queue(&apdev->device)->qid; + matrix_mdev = get_update_locks_by_apqn(apqn); + ret = sysfs_create_group(&apdev->device.kobj, &vfio_queue_attr_group); if (ret) - return ret; + goto err_release_locks; q = kzalloc_obj(*q); if (!q) { @@ -2434,11 +2437,10 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev) goto err_remove_group; } - q->apqn = to_ap_queue(&apdev->device)->qid; + q->apqn = apqn; q->saved_isc = VFIO_AP_ISC_INVALID; memset(&q->reset_status, 0, sizeof(q->reset_status)); INIT_WORK(&q->reset_work, apq_reset_check); - matrix_mdev = get_update_locks_by_apqn(q->apqn); if (matrix_mdev) { vfio_ap_mdev_link_queue(matrix_mdev, q); @@ -2468,6 +2470,8 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev) err_remove_group: sysfs_remove_group(&apdev->device.kobj, &vfio_queue_attr_group); +err_release_locks: + release_update_locks_for_mdev(matrix_mdev); return ret; } -- 2.53.0