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CVE-2022-49882

KVM: Reject attempts to consume or refresh inactive gfn_to_pfn_cache

High7.8EPSS 0.19%
Published
Updated
Reserved
Assigned by
Linux

Description

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 gpc->valid = true gpc->khva = not NULL Result: active = false, valid = true 3. Race ioctl KVM_XEN_HVM_EVTCHN_SEND against ioctl KVM_XEN_ATTR_TYPE_SHARED_INFO: kvm_arch_vm_ioctl case KVM_XEN_HVM_EVTCHN_SEND kvm_xen_hvm_evtchn_send kvm_xen_set_evtchn kvm_xen_set_evtchn_fast read_lock gpc->lock kvm_xen_hvm_set_attr case KVM_XEN_ATTR_TYPE_SHARED_INFO mutex_lock kvm->lock kvm_xen_shared_info_init kvm_gpc_activate gpc->khva = NULL kvm_gpc_check [ Check passes because gpc->valid is still true, even though gpc->khva is already NULL. ] shinfo = gpc->khva pending_bits = shinfo->evtchn_pending CRASH: test_and_set_bit(..., pending_bits)

Timeline

  1. ID reserved

    By Linux

  2. Published

  3. · 18 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2022-49882, by who scored it
Scored byCVSSScoreVector
LinuxCNA (assigner)3.1High7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVDNVD · Modified3.1High7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.19% · top 91% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: total
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Weakness

Affected products

  • Linux · Linux

    • affected 982ed0de4753ed6e71dbd40f82a5a066baf133ed – < bfa9672f8fc9eb118124bab61899d2dd497f95ba
    • affected 982ed0de4753ed6e71dbd40f82a5a066baf133ed – < ecbcf030b45666ad11bc98565e71dfbcb7be4393

  • Linux · Linux

    • affected 5.17
    • unaffected < 5.17
    • unaffected 6.0.8 – ≤ 6.0.*
    • unaffected 6.1 – ≤ *

References (2)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .