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Mon, 10 Aug 2026 19:23:06 +0000 (GMT) Received: from li-4c4c4544-004d-4810-8043-b7c04f423534.ibm.com.com (unknown [9.61.71.153]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 10 Aug 2026 19:23:06 +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 v2 7/8] s390/vfio-ap: Fix required lock not held during display of sysfs status attribute Date: Mon, 10 Aug 2026 15:22:56 -0400 Message-ID: <20260810192257.1208410-8-akrowiak@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260810192257.1208410-1-akrowiak@linux.ibm.com> References: <20260810192257.1208410-1-akrowiak@linux.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=AMtp2X5w c=1 sm=1 tr=0 ts=6a7a251d cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=6H0jsFd48SEkPfM2B64A:9 a=+jEqtf1s3R9VXZ0wqowq2kgwd+I=:19 a=0bXxn9q0MV6snEgNplNhOjQmxlI=:19 X-Proofpoint-GUID: IMZ-6LHey7m8dSwygWrcJizEmS6Pf2gl X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEwMDE2MiBTYWx0ZWRfX96UB1fOsio0P en7IMOUm0MLtuS9sXjdiazB2dpnbpNZpixu9mIg48UVZygQACwGmrpddvoIg2rffMK3jTBUvJbG OIhg2XRGD+OLEMupUhIoD3J+s/NIZcWY87cCD0o/escMDRRb235DJgPueC3RZsZyi9MvLrT61x+ sXEegCiG2lKEaCqNDvHAUsjrhu8vJpl2kB4mD+QA9i7gw4oXgYqGLJoTc0K9DVXQ93pbYeOr8cQ 3apPx3XpIGiG4w5dXekiqZBGnnv8ENxxjZRRa/qZCkZLBp4QTxyHZvH1yIYbqia/3UQmmF3sOp2 n5lkAbe1VgQVPV79AVYh7ore0AUcEXJwg0gxjfAMbotzZIvXKY1BGVEvaVm2dxWBNQIxwS2SBwk zEjZauBDgPOdyfX3MUaJwNUOuN36K8iOtePpfjaPJQWIsNT4Udc1UHxyilZUeME4mApiMlAbKyg 3hyAirGaJ4+yknTFb1Q== X-Proofpoint-ORIG-GUID: IMZ-6LHey7m8dSwygWrcJizEmS6Pf2gl X-Proofpoint-Spam-Info: AW1haW4tMjYwODEwMDE2MiBTYWx0ZWRfX/72p5bf8vsEN SzKFzJkbpmXG9+mmFI6A/Kq9br8CfivtMyrdUIqPzjAMv9/9CV3NIpG3yovCV2RHlqcnUCWd2nX kT8N1ks+sNsD10D0vBZNTe8eRVv/OXI= 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=2026-08-10_05,2026-08-10_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 lowpriorityscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 phishscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608100162 The status_show function that supports display of the status attribute of the devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue function which iterates the matrix_dev->mdev_list to find the object representing the queue device whose status is to be displayed. In order to traverse this list, the matrix_dev->guests_lock mutex must be held which is not the case. To fix this, the guests_lock mutex is taken prior to taking the matrix_dev->mdevs_lock mutex in the status_show function. It is taken there rather than the vfio_ap_mdev_for_queue function - where it is needed - because it must be taken prior to the mdevs_lock mutex in order to adhere to the proper locking order and prevent a lockdep splat; also because the mdevs_lock is needed there to access fields within the matrix_mdev object in that function. Fixes: f139862b92cf ("s390/vfio-ap: add status attribute to AP queue device's sysfs dir") Cc: stable@vger.kernel.org Signed-off-by: Anthony Krowiak --- drivers/s390/crypto/vfio_ap_ops.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c index 061bbad20291..cdc9bf5c5e53 100644 --- a/drivers/s390/crypto/vfio_ap_ops.c +++ b/drivers/s390/crypto/vfio_ap_ops.c @@ -2297,6 +2297,8 @@ static struct ap_matrix_mdev *vfio_ap_mdev_for_queue(struct vfio_ap_queue *q) unsigned long apid = AP_QID_CARD(q->apqn); unsigned long apqi = AP_QID_QUEUE(q->apqn); + lockdep_assert_held(&matrix_dev->guests_lock); + list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) { if (test_bit_inv(apid, matrix_mdev->matrix.apm) && test_bit_inv(apqi, matrix_mdev->matrix.aqm)) @@ -2316,6 +2318,7 @@ static ssize_t status_show(struct device *dev, struct ap_matrix_mdev *matrix_mdev; struct ap_device *apdev = to_ap_dev(dev); + mutex_lock(&matrix_dev->guests_lock); mutex_lock(&matrix_dev->mdevs_lock); q = dev_get_drvdata(&apdev->device); matrix_mdev = vfio_ap_mdev_for_queue(q); @@ -2343,6 +2346,7 @@ static ssize_t status_show(struct device *dev, } mutex_unlock(&matrix_dev->mdevs_lock); + mutex_unlock(&matrix_dev->guests_lock); return nchars; } -- 2.53.0