{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-97478", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-24T16:01:01.149Z", "datePublished": "2026-09-24T16:04:20.263Z", "dateUpdated": "2026-10-21T12:52:49.658Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:52:49.658Z" }, "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(&irqfd->shutdown)\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->vm <-- 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->irqfds\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->lock held and\n IRQs disabled and therefore cannot take irqfds_lock.\n - acrn_irqfd_deassign() flushes vm->irqfd_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->irqfds 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": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "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() → acrn_irqfd_assign()/acrn_irqfd_deassign(), while close() of that eventfd hits eventfd_release() → 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() → hsm_irqfd_shutdown() kfree()s the hsm_irqfd, while another close()s a dup of the same eventfd so eventfd_release() → wake_up_poll(EPOLLHUP) → 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() → 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->vm (and later irqfd->eventfd) 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(&irqfd->vm->irqfds_lock), list_del_init(&irqfd->list) and eventfd_ctx_put(irqfd->eventfd) 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->vm 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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/virt/acrn/irqfd.c" ], "versions": [ { "version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71", "lessThan": "6e9e007ee1dfb54bc2d070550308077ec28dbaec", "status": "affected", "versionType": "git" }, { "version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71", "lessThan": "0e1152f689847b9db2f05454775d34610c1424c2", "status": "affected", "versionType": "git" }, { "version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71", "lessThan": "d8156aacfcabb81f52c20ef89094945434d08079", "status": "affected", "versionType": "git" }, { "version": "aa3b483ff1d71c50b33db154048dff9a8f08ac71", "lessThan": "666c7f9e07925aa0863348f960e09bb89f8f05a3", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/virt/acrn/irqfd.c" ], "versions": [ { "version": "5.12", "status": "affected" }, { "version": "0", "lessThan": "5.12", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.114", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.53", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.12.114" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.18.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "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" } } } }