{"id":"AZL-101528","summary":"CVE-2026-89960 affecting package kernel 6.6.150.1-1","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":"2026-09-17T14:15:58.940673410Z","published":"2026-09-16T11:17:06Z","upstream":["CVE-2026-89960"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89960"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.150.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-101528.json"}}],"schema_version":"1.9.0"}