In the Linux kernel, the following vulnerability has been resolved:

KVM: Reject attempts to consume or refresh inactive gfn_to_pfn_cache

Reject kvm_gpc_check() and kvm_gpc_refresh() if the cache is inactive. Not checking the active flag during refresh is particularly egregious, as KVM can end up with a valid, inactive cache, which can lead to a variety of use-after-free bugs, e.g. consuming a NULL kernel pointer or missing an mmu_notifier invalidation due to the cache not being on the list of gfns to invalidate.

Note, "active" needs to be set if and only if the cache is on the list of caches, i.e. is reachable via mmu_notifier events. If a relevant mmu_notifier event occurs while the cache is "active" but not on the list, KVM will not acquire the cache's lock and so will not serailize the mmu_notifier event with active users and/or kvm_gpc_refresh().

A race between KVM_XEN_ATTR_TYPE_SHARED_INFO and KVM_XEN_HVM_EVTCHN_SEND can be exploited to trigger the bug.

1. Deactivate shinfo cache:

kvm_xen_hvm_set_attr case KVM_XEN_ATTR_TYPE_SHARED_INFO kvm_gpc_deactivate kvm_gpc_unmap gpc->valid = false gpc->khva = NULL gpc->active = false

Result: active = false, valid = false

2. Cause cache refresh:

kvm_arch_vm_ioctl case KVM_XEN_HVM_EVTCHN_SEND kvm_xen_hvm_evtchn_send kvm_xen_set_evtchn kvm_xen_set_evtchn_fast kvm_gpc_check return -EWOULDBLOCK because !gpc->valid kvm_xen_set_evtchn_fast return -EWOULDBLOCK kvm_gpc_refresh hva_to_pfn_ret…

In the Linux kernel, the following vulnerability has been resolved:

KVM: Reject attempts to consume or refresh inactive gfn_to_pfn_cache

Reject kvm_gpc_check() and kvm_gpc_refresh() if the cache is inactive. Not checking the active flag during refresh is particularly egregious, as KVM can end up with a valid, inactive cache, which can lead to a variety of use-after-free bugs, e.g. consuming a NULL kernel pointer or missing an mmu_notifier invalidation due to the cache not being on the list of gfns to invalidate.

Note, "active" needs to be set if and only if the cache is on the list of caches, i.e. is reachable via mmu_notifier events. If a relevant mmu_notifier event occurs while the cache is "active" but not on the list, KVM will not acquire the cache's lock and so will not serailize the mmu_notifier event with active users and/or kvm_gpc_refresh().

A race between KVM_XEN_ATTR_TYPE_SHARED_INFO and KVM_XEN_HVM_EVTCHN_SEND can be exploited to trigger the bug.

1. Deactivate shinfo cache:

kvm_xen_hvm_set_attr case KVM_XEN_ATTR_TYPE_SHARED_INFO kvm_gpc_deactivate kvm_gpc_unmap gpc->valid = false gpc->khva = NULL gpc->active = false

Result: active = false, valid = false

2. Cause cache refresh:

kvm_arch_vm_ioctl case KVM_XEN_HVM_EVTCHN_SEND kvm_xen_hvm_evtchn_send kvm_xen_set_evtchn kvm_xen_set_evtchn_fast kvm_gpc_check return -EWOULDBLOCK because !gpc->valid kvm_xen_set_evtchn_fast return -EWOULDBLOCK kvm_gpc_refresh hva_to_pfn_ret…

kernel: seg6: fix the iif in the IPv6 socket control block Kernel: race when faulting a device private page in memory manager kernel: use-after-free in l1oip timer handlers kernel: Rate limit overflow messages in r8152 in intr_callback kernel: vmwgfx: use-after-free in vmw_cmd_res_check kernel: vmwgfx: use-after-free in vmw_execbuf_tie_context hw: Intel: Gather Data Sampling (GDS) side channel vulnerability kernel: Information leak in l2cap_parse_conf_req in net/bluetooth/l2cap_core.c kernel: perf: Fix perf_pending_task() UaF kernel: gpiolib: fix memory leak in gpiochip_setup_dev() kernel: memcg: fix possible use-after-free in memcg_write_event_control() kernel: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths kernel: char: tpm: Protect tpm_pm_suspend with locks kernel: ixgbevf: Fix resource leak in ixgbevf_init_module() kernel: dax: make sure inodes are flushed before destroy cache kernel: watch_queue: Actually free the watch kernel: watch_queue: Fix NULL dereference in error cleanup kernel: rtc: pl031: fix rtc features null pointer dereference kernel: tpm: fix reference counting for struct tpm_chip kernel: NFSv4: Don't hold the layoutget locks across multiple RPC calls kernel: xprtrdma: treat all calls not a bcall when bc_serv is NULL kernel: net: ipv6: unexport __init-annotated seg6_hmac_init() kernel: af_unix: Fix a data-race in unix_dgram_peer_wake_me(). kernel: regulator: scmi: Fix refcount leak in scmi_regulator_probe kernel: mm/mempolicy: fix uninit-v…

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 70 more

In the Linux kernel, the following vulnerability has been resolved: KVM: Reject attempts to consume or refresh inactive gfn_to_pfn_cache Reject kvm_gpc_check() and kvm_gpc_refresh() if the cache is inactive. Not checking the active flag during refresh is particularly egregious, as KVM can end up with a valid, inactive cache, which can lead to a variety of use-after-free bugs, e.g. consuming a NULL kernel pointer or missing an mmu_notifier invalidation due to the cache not being on the list of gfns to invalidate. Note, "active" needs to be set if and only if the cache is on the list of caches, i.e. is reachable via mmu_notifier events. If a relevant mmu_notifier event occurs while the cache is "active" but not on the list, KVM will not acquire the cache's lock and so will not serailize the mmu_notifier event with active users and/or kvm_gpc_refresh(). A race between KVM_XEN_ATTR_TYPE_SHARED_INFO and KVM_XEN_HVM_EVTCHN_SEND can be exploited to trigger the bug. 1. Deactivate shinfo cache: kvm_xen_hvm_set_attr case KVM_XEN_ATTR_TYPE_SHARED_INFO kvm_gpc_deactivate kvm_gpc_unmap gpc->valid = false gpc->khva = NULL gpc->active = false Result: active = false, valid = false 2. Cause cache refresh: kvm_arch_vm_ioctl case KVM_XEN_HVM_EVTCHN_SEND kvm_xen_hvm_evtchn_send kvm_xen_set_evtchn kvm_xen_set_evtchn_fast kvm_gpc_check return -EWOULDBLOCK because !gpc->valid kvm_xen_set_evtchn_fast return -EWOULDBLOCK kvm_gpc_refresh hva_to_pfn_retry g…

Ein Angreifer kann mehrere Schwachstellen in Linux Kernel ausnutzen, um einen Denial of Service Angriff und nicht näher spezifizierte Angriffe durchzuführen.