{"id":"CVE-2026-89960","summary":"s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()\n\nIn vfio_ap_mdev_set_kvm(), kvm-\u003earch.crypto.pqap_hook is set to\n&matrix_mdev-\u003epqap_hook before the update locks are acquired and the\nmdev list is checked for a conflicting assignment. If another mdev is\nalready attached to the same KVM instance, the function returns -EPERM\nwithout restoring the hook pointer, leaving kvm-\u003earch.crypto.pqap_hook\npointing at the failing matrix_mdev instead of the mdev that legitimately\nowns the KVM.\n\nSince matrix_mdev-\u003ekvm is never set on this error path,\nvfio_ap_mdev_unset_kvm() will not clean up the hook when matrix_mdev\nis later closed. If matrix_mdev is subsequently freed, any PQAP\ninstruction executed by the guest will dereference the stale pointer\nthrough pqap_hook_rwsem, resulting in a use-after-free.\n\nSince kvm-\u003earch.crypto.pqap_hook is only set in the vfio_ap_mdev_set_kvm()\nfunction and is cleared in the vfio_ap_mdev_unset_kvm() function, a check\nfor 'kvm-\u003earch.crypto.pqap_hook != NULL' is all that is needed to determine\nwhether it belongs to another mdev. This will alleviate the need to iterate\nthe matrix_dev-\u003emdev_list list to see if the kvm object is assigned to\nanother mdev.This was introduced in v3 to alleviate the need to take the\nmdevs_lock while iterating the list; however, this did not prevent a\npotential race condition.\n\nThe pqap_hook_rwsem(write) is now performed inside\nget_update_locks_for_kvm(), which is updated to acquire\npqap_hook_rwsem(write) between kvm-\u003elock and mdevs_lock. This ordering\nis consistent with the PQAP intercept path, which acquires pqap_hook_rwsem\nin read mode while srcu is held under vcpu-\u003emutex, establishing the\ndependency: kvm-\u003elock -\u003e vcpu-\u003emutex -\u003e srcu -\u003e pqap_hook_rwsem(read).\n\nThe pqap_hook_rwsem is now released inside the\nrelease_update_locks_for_kvm(), which is updated to release\npqap_hook_rwsem(write) between mdevs_lock and kvm-\u003elock.\n\nAdditionally, kvm_put_kvm() in vfio_ap_mdev_unset_kvm() is moved\nafter release_update_locks_for_kvm(). Previously it was called while\nkvm-\u003elock was held; if it were ever the last reference, kvm_destroy_vm()\nwould run under kvm-\u003elock, which would deadlock.","modified":"2026-09-18T03:48:34.320392709Z","published":"2026-09-16T10:32:42.618Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89960.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/13bfc94eef389bd664ffc67b00184919902c938a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4400270ec0348d05dc0439d8f0130853ce7f9e20"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6a180adafc2a8a5fbe815985c71b2201e93ab5e1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/eb6cc898501a004c0fa8aab951351d9c959b91cc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fc069d00a0dbef40042fd681554d48dcd5a1d524"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89960.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89960"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"86956e70761b3292156d668e87126844334dd71b"},{"fixed":"eb6cc898501a004c0fa8aab951351d9c959b91cc"},{"fixed":"6a180adafc2a8a5fbe815985c71b2201e93ab5e1"},{"fixed":"fc069d00a0dbef40042fd681554d48dcd5a1d524"},{"fixed":"13bfc94eef389bd664ffc67b00184919902c938a"},{"fixed":"4400270ec0348d05dc0439d8f0130853ce7f9e20"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89960.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.15.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.51"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89960.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"}]}