CVE-2026-97478 (GCVE-0-2026-97478)
Vulnerability from cvelistv5
Published
2026-09-24 16:04
Modified
2026-10-30 12:36
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
virt: acrn: Fix irqfd use-after-free during eventfd shutdown
acrn_irqfd_deassign() and the eventfd EPOLLHUP wakeup can race and free
the same struct hsm_irqfd:
CPU0 CPU1
---- ----
eventfd_release()
wake_up_poll(EPOLLHUP)
hsm_irqfd_wakeup()
queue_work(&irqfd->shutdown)
acrn_irqfd_deassign()
hsm_irqfd_shutdown()
list_del_init()
eventfd_ctx_remove_wait_queue()
eventfd_ctx_put()
kfree(irqfd)
hsm_irqfd_shutdown_work()
container_of(work, ..., shutdown)
irqfd->vm <-- use-after-free
The deassign path freed the irqfd while a shutdown work item was
already queued by EPOLLHUP (or vice versa), so the work item could
resurrect a dangling pointer through container_of().
Switch to the lifetime model used by KVM irqfds:
- Deassign/deinit only deactivate the irqfd: remove it from vm->irqfds
under irqfds_lock and queue the cleanup work.
- hsm_irqfd_shutdown_work() becomes the sole owner that unhooks the
eventfd waitqueue entry, drops the eventfd reference and frees the
irqfd.
- A new HSM_IRQFD_FLAG_SHUTDOWN bit guarded by test_and_set_bit()
ensures the cleanup work is queued at most once, no matter how many
of {EPOLLHUP, deassign, deinit} fire concurrently. This is safe to
call from the waitqueue callback, which runs with wqh->lock held and
IRQs disabled and therefore cannot take irqfds_lock.
- acrn_irqfd_deassign() flushes vm->irqfd_wq before returning so the
eventfd is fully detached on return. acrn_irqfd_deinit() deactivates
every irqfd, flushes the workqueue and only then destroys it, so no
path can queue_work() onto a torn-down workqueue.
- acrn_irqfd_assign() now installs the eventfd waitqueue entry and
publishes the irqfd to vm->irqfds under irqfds_lock, so the irqfd is
never visible to deassign/deinit before its waitqueue entry is in
place, and any EPOLLHUP that fires in the assign window queues
cleanup work that blocks on irqfds_lock until publication is done.
References
Impacted products
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"drivers/virt/acrn/irqfd.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "dccf23a72a6c5ec8d9eab2a7f98e186af6eaff48",
"status": "affected",
"version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71",
"versionType": "git"
},
{
"lessThan": "6e9e007ee1dfb54bc2d070550308077ec28dbaec",
"status": "affected",
"version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71",
"versionType": "git"
},
{
"lessThan": "0e1152f689847b9db2f05454775d34610c1424c2",
"status": "affected",
"version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71",
"versionType": "git"
},
{
"lessThan": "d8156aacfcabb81f52c20ef89094945434d08079",
"status": "affected",
"version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71",
"versionType": "git"
},
{
"lessThan": "666c7f9e07925aa0863348f960e09bb89f8f05a3",
"status": "affected",
"version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"drivers/virt/acrn/irqfd.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.12"
},
{
"lessThan": "5.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.191",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.114",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.53",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.191",
"versionStartIncluding": "5.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.160",
"versionStartIncluding": "5.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.114",
"versionStartIncluding": "5.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.53",
"versionStartIncluding": "5.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "5.12",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvirt: acrn: Fix irqfd use-after-free during eventfd shutdown\n\nacrn_irqfd_deassign() and the eventfd EPOLLHUP wakeup can race and free\nthe same struct hsm_irqfd:\n\n CPU0 CPU1\n ---- ----\n eventfd_release()\n wake_up_poll(EPOLLHUP)\n hsm_irqfd_wakeup()\n queue_work(\u0026irqfd-\u003eshutdown)\n acrn_irqfd_deassign()\n hsm_irqfd_shutdown()\n list_del_init()\n eventfd_ctx_remove_wait_queue()\n eventfd_ctx_put()\n kfree(irqfd)\n hsm_irqfd_shutdown_work()\n container_of(work, ..., shutdown)\n irqfd-\u003evm \u003c-- use-after-free\n\nThe deassign path freed the irqfd while a shutdown work item was\nalready queued by EPOLLHUP (or vice versa), so the work item could\nresurrect a dangling pointer through container_of().\n\nSwitch to the lifetime model used by KVM irqfds:\n\n - Deassign/deinit only deactivate the irqfd: remove it from vm-\u003eirqfds\n under irqfds_lock and queue the cleanup work.\n - hsm_irqfd_shutdown_work() becomes the sole owner that unhooks the\n eventfd waitqueue entry, drops the eventfd reference and frees the\n irqfd.\n - A new HSM_IRQFD_FLAG_SHUTDOWN bit guarded by test_and_set_bit()\n ensures the cleanup work is queued at most once, no matter how many\n of {EPOLLHUP, deassign, deinit} fire concurrently. This is safe to\n call from the waitqueue callback, which runs with wqh-\u003elock held and\n IRQs disabled and therefore cannot take irqfds_lock.\n - acrn_irqfd_deassign() flushes vm-\u003eirqfd_wq before returning so the\n eventfd is fully detached on return. acrn_irqfd_deinit() deactivates\n every irqfd, flushes the workqueue and only then destroys it, so no\n path can queue_work() onto a torn-down workqueue.\n - acrn_irqfd_assign() now installs the eventfd waitqueue entry and\n publishes the irqfd to vm-\u003eirqfds under irqfds_lock, so the irqfd is\n never visible to deassign/deinit before its waitqueue entry is in\n place, and any EPOLLHUP that fires in the assign window queues\n cleanup work that blocks on irqfds_lock until publication is done."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The UAF is reached from ioctl(ACRN_IOCTL_IRQFD) on /dev/acrn_hsm: acrn_dev_ioctl() copy_from_user()s struct acrn_irqfd and calls acrn_irqfd_config() \u2192 acrn_irqfd_assign()/acrn_irqfd_deassign(), while close() of that eventfd hits eventfd_release() \u2192 hsm_irqfd_wakeup(). No remote protocol carries the fd, flags, or EPOLLHUP.\nAC:L - The attacker owns both sides: one thread ioctl(ACRN_IOCTL_IRQFD) with ACRN_IRQFD_FLAG_DEASSIGN so acrn_irqfd_deassign() \u2192 hsm_irqfd_shutdown() kfree()s the hsm_irqfd, while another close()s a dup of the same eventfd so eventfd_release() \u2192 wake_up_poll(EPOLLHUP) \u2192 hsm_irqfd_wakeup() queues hsm_irqfd_shutdown_work(); the window is retryable.\nPR:L - acrn_dev_open(), acrn_dev_ioctl() and acrn_irqfd_config() have no capable()/CAP_* gate; only /dev/acrn_hsm DAC applies. ACRN Service VM deployments grant that node to the deprivileged acrn-dm device-model account (as with /dev/kvm), so a local user with that fd can CREATE_VM and IRQFD without init-namespace root.\nUI:N - The attacker opens /dev/acrn_hsm, ioctl(ACRN_IOCTL_CREATE_VM) then ACRN_IOCTL_IRQFD assign, and races close() of its own eventfd against deassign (or acrn_dev_release() \u2192 acrn_irqfd_deinit()); no other user must mount, open, or click.\nS:U - hsm_irqfd_shutdown_work() uses the freed struct hsm_irqfd in the Service VM kernel that runs acrn_dev_ioctl(). The attacker is already a Service VM process issuing HSM ioctls, not a User VM guest crossing into the ACRN hypervisor, so impact stays in one kernel authority.\nC:H - After acrn_irqfd_deassign() kfree()s the hsm_irqfd, hsm_irqfd_shutdown_work() container_of()s the queued work_struct and reads irqfd-\u003evm (and later irqfd-\u003eeventfd) from the freed kmalloc object. Reclaiming that slot lets the attacker disclose reallocated kernel heap through those dangling loads.\nI:H - The same UAF lets hsm_irqfd_shutdown_work() mutex_lock(\u0026irqfd-\u003evm-\u003eirqfds_lock), list_del_init(\u0026irqfd-\u003elist) and eventfd_ctx_put(irqfd-\u003eeventfd) on attacker-reclaimed hsm_irqfd fields, which is an arbitrary write / wait-queue function-pointer hijack, plus a second kfree of the sprayed object.\nA:H - hsm_irqfd_shutdown_work() loading irqfd-\u003evm after hsm_irqfd_shutdown() kfree()s it oopses on a dangling pointer or corrupts the irqfds mutex/list; the EPOLLHUP work versus deassign kfree race in the commit is a Service VM kernel panic even without a successful spray."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:36:59.771Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/dccf23a72a6c5ec8d9eab2a7f98e186af6eaff48"
},
{
"url": "https://git.kernel.org/stable/c/6e9e007ee1dfb54bc2d070550308077ec28dbaec"
},
{
"url": "https://git.kernel.org/stable/c/0e1152f689847b9db2f05454775d34610c1424c2"
},
{
"url": "https://git.kernel.org/stable/c/d8156aacfcabb81f52c20ef89094945434d08079"
},
{
"url": "https://git.kernel.org/stable/c/666c7f9e07925aa0863348f960e09bb89f8f05a3"
}
],
"title": "virt: acrn: Fix irqfd use-after-free during eventfd shutdown",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-97478",
"datePublished": "2026-09-24T16:04:20.263Z",
"dateReserved": "2026-09-24T16:01:01.149Z",
"dateUpdated": "2026-10-30T12:36:59.771Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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