{"id":"CVE-2026-98473","summary":"s390/vfio-ap: fix KVM GISC and page leak when queue removed from host config","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: fix KVM GISC and page leak when queue removed from host config\n\nThree related problems exist in the handling of KVM interrupt and page\nresources when a queue is removed from the host's AP configuration\nwhile assigned to a mediated device (mdev).\n\nProblem 1:\n~~~~~~~~~\nAP_RESPONSE_Q_NOT_AVAIL not handled in vfio_ap_mdev_reset_queue()\n\nWhen the AP bus removes a queue device whose adapter or domain has\nbeen removed from the host's AP configuration,\nvfio_ap_mdev_remove_queue() is called. If the queue is still in the\nhost's AP configuration at that point, it calls\nvfio_ap_mdev_reset_queue(), which issues a PQAP(ZAPQ). Since the\nadapter is already gone from the host configuration, ap_zapq() returns\nAP_RESPONSE_Q_NOT_AVAIL (0x01). This response code is not handled in\nvfio_ap_mdev_reset_queue()'s switch statement and falls through to\nthe default case, which issues a WARN but does not call\nvfio_ap_free_aqic_resources(). As a result, if IRQ handling was\nenabled for the queue by the guest, the KVM GISC registration and\nthe pinned guest page holding the notification indicator byte (NIB)\nare both leaked.\n\nThis is fixed by adding AP_RESPONSE_Q_NOT_AVAIL to the same case as\nAP_RESPONSE_DECONFIGURED and AP_RESPONSE_CHECKSTOPPED in\nvfio_ap_mdev_reset_queue(). Like those response codes, Q_NOT_AVAIL\nindicates the queue is not operational and no further reset attempts\nare possible; the correct action is to free the IRQ resources\nimmediately.\n\nProblem 2:\n~~~~~~~~~\n AP_RESPONSE_Q_NOT_AVAIL not handled in apq_status_check()\n\nIn vfio_ap_mdev_reset_queue(), there are four cases that indicate a queue\nreset has not yet completed, in which case apq_reset_check() is queued to\na work queue to verify completion of the reset operation. This function\nuses the PQAP(TAPQ) function to get the queue's status and calls\napq_status_check() to verify whether the reset has completed, failed or\nneeds to be executed again. As described in Problem #1 above,\napq_reset_check() does not specifically check for AP_RESPONSE_Q_NOT_AVAIL,\nthereby potentially leaking KVM GISC registration and the pinned guest page\nholding the NIB.\n\nThis is fixed by adding a case statement for AP_RESPONSE_Q_NOT_AVAIL to\napq_status_check() and returning -ENODEV for that case. The caller,\napq_reset_check() will then check for this return code and call\nvfio_ap_free_aqic_resources() to prevent the leak.\n\nProblem 3:\n~~~~~~~~~\nvfio_ap_free_aqic_resources() leaks saved_isc when kvm is NULL\n\nvfio_ap_free_aqic_resources() guards the call to\nkvm_s390_gisc_unregister() with:\n\n    if (q-\u003esaved_isc != VFIO_AP_ISC_INVALID &&\n        !WARN_ON(!(q-\u003ematrix_mdev && q-\u003ematrix_mdev-\u003ekvm)))\n\nIf matrix_mdev-\u003ekvm is NULL -- which can happen when\nvfio_ap_mdev_unset_kvm() has already run and cleared kvm before a\nsubsequent cleanup path reaches this function -- the WARN_ON fires\nand the entire block is skipped. This leaves q-\u003esaved_isc set to a\nnon-invalid value, creating a potential double-free on any subsequent\ncall to this function.\n\nWhen kvm is NULL the KVM guest is already torn down, so\nkvm_s390_gisc_unregister() need not and cannot be called; however,\nq-\u003esaved_isc must always be cleared. Fix this by separating the\nkvm_s390_gisc_unregister() call from the q-\u003esaved_isc reset. The\nWARN_ON now guards only the genuinely impossible case of matrix_mdev\nbeing NULL. A NULL kvm is handled gracefully by skipping only the\nunregister call, and q-\u003esaved_isc = VFIO_AP_ISC_INVALID is set\nunconditionally whenever saved_isc was not already invalid.\n\nAdditionally, add an else clause to the host-config check in\nvfio_ap_mdev_remove_queue() to call vfio_ap_free_aqic_resources()\ndirectly when the queue is not in the host's AP configuration. This\nserves as a backstop: when the AP bus fires the driver .remove\ncallback after an adapter is removed from the host config, the queue\nis by definition no longer addressable, so vfio_ap_mdev_reset_queue\n---truncated---","modified":"2026-10-19T02:46:19.934920071Z","published":"2026-10-18T15:15:35.479Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98473.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3c3433657c82f200dae36c29e2b80681c81b85be"},{"type":"WEB","url":"https://git.kernel.org/stable/c/65e05ec252a9b79e75930d3c4dd42d8877db04c5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cf441a0db681dfad5e89b015d6be11365159d7a9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/da69d3ac53490724eba0ade9deb4e539a6ae9034"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98473.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98473"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"b9bd10c43456d16abd97b717446f51afb3b88411"},{"fixed":"da69d3ac53490724eba0ade9deb4e539a6ae9034"},{"fixed":"cf441a0db681dfad5e89b015d6be11365159d7a9"},{"fixed":"3c3433657c82f200dae36c29e2b80681c81b85be"},{"fixed":"65e05ec252a9b79e75930d3c4dd42d8877db04c5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.6.15"},{"fixed":"6.7"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.7.3"},{"fixed":"6.8"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"582014b08cb83383cdd61f052cd81e8aa5023696"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7abe1494896c052d5dcf4ba910656777aff72fbb"}]}],"versions":["v6.6.159","v6.6.158","v6.6.157","v6.6.156","v6.6.155","v6.6.154","v6.6.153","v6.6.152","v6.6.151","v6.6.150","v6.6.149","v6.6.148","v6.6.147","v6.6.146","v6.6.145","v6.6.144","v6.6.143","v6.6.142","v6.6.141","v6.6.140","v6.6.139","v6.6.138","v6.6.137","v6.6.136","v6.6.135","v6.6.134","v6.6.133","v6.6.132","v6.6.131","v6.6.130","v6.6.129","v6.6.128","v6.6.127","v6.6.126","v6.6.125","v6.6.124","v6.6.123","v6.6.122","v6.6.121","v6.6.120","v6.6.119","v6.6.118","v6.6.117","v6.6.116","v6.6.115","v6.6.114","v6.6.113","v6.6.112","v6.6.111","v6.6.110","v6.6.109","v6.6.108","v6.6.107","v6.6.106","v6.6.105","v6.6.104","v6.6.103","v6.6.102","v6.6.101","v6.6.100","v6.6.99","v6.6.98","v6.6.97","v6.6.96","v6.6.95","v6.6.94","v6.6.93","v6.6.92","v6.6.91","v6.6.90","v6.6.89","v6.6.88","v6.6.87","v6.6.86","v6.6.85","v6.6.84","v6.6.83","v6.6.82","v6.6.81","v6.6.80","v6.6.79","v6.6.78","v6.6.77","v6.6.76","v6.6.75","v6.6.74","v6.6.73","v6.6.72","v6.6.71","v6.6.70","v6.6.69","v6.6.68","v6.6.67","v6.6.66","v6.6.65","v6.6.64","v6.6.63","v6.6.62","v6.6.61","v6.6.60","v6.6.59","v6.6.58","v6.6.57","v6.6.56","v6.6.55","v6.6.54","v6.6.53","v6.6.52","v6.6.51","v6.6.50","v6.6.49","v6.6.48","v6.6.47","v6.6.46","v6.6.45","v6.6.44","v6.6.43","v6.6.42","v6.6.41","v6.6.40","v6.6.39","v6.6.38","v6.6.37","v6.6.36","v6.6.35","v6.6.34","v6.6.33","v6.6.32","v6.6.31","v6.6.30","v6.6.29","v6.6.28","v6.6.27","v6.6.26","v6.6.25","v6.6.24","v6.6.23","v6.6.22","v6.6.21","v6.6.20","v6.6.19","v6.6.18","v6.6.17","v6.6.16","v6.6.15","v6.7.12","v6.7.11","v6.7.10","v6.7.9","v6.7.8","v6.7.7","v6.7.6","v6.7.5","v6.7.4","v6.7.3"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98473.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.8.0"},{"fixed":"6.12.112"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.55"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98473.json"}}],"schema_version":"1.9.0"}