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Wed, 12 Aug 2026 17:09:55 +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 17:09:55 +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 v4 8/9] s390/vfio-ap: Fix NULL deref in status_show() during queue probe Date: Wed, 12 Aug 2026 13:09:44 -0400 Message-ID: <20260812170945.738351-9-akrowiak@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260812170945.738351-1-akrowiak@linux.ibm.com> References: <20260812170945.738351-1-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=6a7ca8e6 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==: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: K7iGlC2GYiPsQDmEdEOuthVcXZVgM2BT X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEyMDEzOCBTYWx0ZWRfX02q7y0UgZvNs Vn+EOL/0GQvbNDRaNDW2gf313ahGjjZbJW68TvPFkzyTJs5VrBWfwWRSf/10/oB/YrU3AHgvyP9 cL+c2CGZXYS30FICsgyDJe123fyReWSsrOYO5+pBK/gU9B8yq+e5TkroaZ8mT2mPsRer9rI+MZT qBPvqgZq8zQb8xjuXVUXh8tRB/u0s5gOVvu9Gs2/SSQw4AklTYP+PxkogC6p3bPSGGuopOGYCZ4 p6jv3FedJNfRJvy0wROwcZxVAI5q6b6b11Kt59H7U+Xlvfd9VJKErf7OsjdI5hdM5bAZUGoT+rv 2Pc/VokIFE1DJwS8/IXxcVPfTglYB24tworiipzvrJ3yKIRYSF8a30S6EOqPaJd/DTDBH6X5LXx l8+38cKwY4QwCN8iBwp7Rnmp3uzEbp5QfVARdjIywnArdRmzGbVMQlGrPFf6x3AXx8alV4/oC7C 96ugf471ds0qsAuh2Ow== X-Proofpoint-ORIG-GUID: K7iGlC2GYiPsQDmEdEOuthVcXZVgM2BT X-Proofpoint-Spam-Info: AW1haW4tMjYwODEyMDEzOCBTYWx0ZWRfX0zaFcGmB3NeR lhgsGFTs/b26V2Ip480vwViKQT+46YmEyzyDDmqec+GiGb3Ds4f5G/bcsvWhEQ8Gq8/qn3McZkm +Fwc76Drba/sg/lb1jhVKEv5PLO6Zec= 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_05,2026-08-12_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-2608120138 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 | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c index 16779cfc64e8..b0454a296c67 100644 --- a/drivers/s390/crypto/vfio_ap_ops.c +++ b/drivers/s390/crypto/vfio_ap_ops.c @@ -2424,14 +2424,17 @@ 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) { @@ -2439,11 +2442,10 @@ 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); @@ -2472,8 +2474,13 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev) return ret; err_remove_group: + release_update_locks_for_mdev(matrix_mdev); sysfs_remove_group(&apdev->device.kobj, &vfio_queue_attr_group); return ret; + +err_release_locks: + release_update_locks_for_mdev(matrix_mdev); + return ret; } void vfio_ap_mdev_remove_queue(struct ap_device *apdev) -- 2.53.0