{"cve":"CVE-2026-80895","nvd":{"published":"2026-09-04T18:17:57.727","modified":"2026-09-04T18:17:57.727","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmshv: Order pt_vp_array publish against irqfd assertion path\n\nmshv_partition_ioctl_create_vp() initialises a VP struct (allocations,\nmutex_init, init_waitqueue_head, page mappings) and then publishes the\npointer into partition->pt_vp_array.  Several ISR paths read this array\nlocklessly: the intercept ISR, the two scheduler ISRs, and\nmshv_try_assert_irq_fast() on the irqfd fast path.\n\nOf these, only mshv_try_assert_irq_fast() can structurally race the\npublish.  It runs from an eventfd waker without holding pt_mutex, and\nMSHV_IRQFD does not require the target lapic_apic_id (== vp_index) to\nrefer to an existing VP at registration time.  A user can therefore\nregister an irqfd targeting a yet-to-be-created VP, then trigger\nmshv_try_assert_irq_fast() concurrently with MSHV_CREATE_VP for the\nsame index.  On weakly-ordered architectures the reader can observe a\nnon-NULL pointer in pt_vp_array before the initialising stores to the\nVP struct become visible, leading to use of partially-initialised\nfields (e.g. vp_register_page).\n\nThe other ISR readers cannot reach this race: the hypervisor will not\ngenerate intercept or scheduler messages for a VP that has never been\ntold to run, and the user can only call MSHV_RUN_VP on the VP fd\nreturned by MSHV_CREATE_VP, which by construction is returned after\nthe publish.  Leave those readers as plain loads.\n\nUse smp_store_release() in mshv_partition_ioctl_create_vp() to publish\nthe pointer, and pair it with smp_load_acquire() in\nmshv_try_assert_irq_fast().  On x86 these compile to plain accesses\nunder TSO; on ARM64 they emit one-instruction acquire/release barriers,\nacceptable on this fast path.\n\nThe destroy-side path (destroy_partition() clearing pt_vp_array[i] to\nNULL after kfree(vp)) has a separate ordering and lifetime concern\nthat is out of scope here.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9","https://git.kernel.org/stable/c/b098dc869219c15dc49bf9cf63fb5fc1481d3373","https://git.kernel.org/stable/c/eba2bf5daa7933f94c53ebbbf0f567d4274716df"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:52:03.409947763+00:00"},"epss":{"cve":"CVE-2026-80895","score":0.00166,"percentile":0.05892,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}