mshv: Order pt_vp_array publish against irqfd assertion path
Summary
| CVE | CVE-2026-80895 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-04 18:17:57 UTC |
| Updated | 2026-09-04 18:17:57 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: mshv: Order pt_vp_array publish against irqfd assertion path mshv_partition_ioctl_create_vp() initialises a VP struct (allocations, mutex_init, init_waitqueue_head, page mappings) and then publishes the pointer into partition->pt_vp_array. Several ISR paths read this array locklessly: the intercept ISR, the two scheduler ISRs, and mshv_try_assert_irq_fast() on the irqfd fast path. Of these, only mshv_try_assert_irq_fast() can structurally race the publish. It runs from an eventfd waker without holding pt_mutex, and MSHV_IRQFD does not require the target lapic_apic_id (== vp_index) to refer to an existing VP at registration time. A user can therefore register an irqfd targeting a yet-to-be-created VP, then trigger mshv_try_assert_irq_fast() concurrently with MSHV_CREATE_VP for the same index. On weakly-ordered architectures the reader can observe a non-NULL pointer in pt_vp_array before the initialising stores to the VP struct become visible, leading to use of partially-initialised fields (e.g. vp_register_page). The other ISR readers cannot reach this race: the hypervisor will not generate intercept or scheduler messages for a VP that has never been told to run, and the user can only call MSHV_RUN_VP on the VP fd returned by MSHV_CREATE_VP, which by construction is returned after the publish. Leave those readers as plain loads. Use smp_store_release() in mshv_partition_ioctl_create_vp() to publish the pointer, and pair it with smp_load_acquire() in mshv_try_assert_irq_fast(). On x86 these compile to plain accesses under TSO; on ARM64 they emit one-instruction acquire/release barriers, acceptable on this fast path. The destroy-side path (destroy_partition() clearing pt_vp_array[i] to NULL after kfree(vp)) has a separate ordering and lifetime concern that is out of scope here. |
Risk And Classification
EPSS: 0.001660000 probability, percentile 0.061770000 (date 2026-09-07)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 621191d709b14882270dfd8ea5d7d6cdfebe2c35 062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 git | Not specified |
| CNA | Linux | Linux | affected 621191d709b14882270dfd8ea5d7d6cdfebe2c35 eba2bf5daa7933f94c53ebbbf0f567d4274716df git | Not specified |
| CNA | Linux | Linux | affected 621191d709b14882270dfd8ea5d7d6cdfebe2c35 b098dc869219c15dc49bf9cf63fb5fc1481d3373 git | Not specified |
| CNA | Linux | Linux | affected 6.15 | Not specified |
| CNA | Linux | Linux | unaffected 6.15 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.44 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1.8 7.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/eba2bf5daa7933f94c53ebbbf0f567d4274716df | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/b098dc869219c15dc49bf9cf63fb5fc1481d3373 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.