CVE-2026-74594 (GCVE-0-2026-74594)
Vulnerability from cvelistv5
Published
2026-08-22 15:31
Modified
2026-08-25 05:40
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
sched/psi: Shut down rtpoll_timer in psi_cgroup_free()
psi_schedule_rtpoll_work() is called locklessly from the scheduler hotpath
and can race psi_trigger_destroy() taking down the last rtpoll trigger under
rtpoll_trigger_lock:
psi_schedule_rtpoll_work() psi_trigger_destroy()
rcu_read_lock();
task = rcu_dereference(rtpoll_task);
rcu_assign_pointer(rtpoll_task, NULL);
timer_delete(&rtpoll_timer);
mod_timer(&rtpoll_timer, ...);
rcu_read_unlock();
synchronize_rcu();
kthread_stop(task_to_destroy);
The group can then be freed with the re-armed timer still pending, and
poll_timer_fn() runs on freed memory.
461daba06bdc ("psi: eliminate kthread_worker from psi trigger scheduling
mechanism") deleted the timer synchronously after the synchronize_rcu(),
which prevented this but raced trigger creation instead: the deletion could
cancel the timer that a new trigger set armed during the grace period and,
as creation also reinitialized the timer at the time, corrupt it.
8f91efd870ea ("psi: Fix race between psi_trigger_create/destroy") moved the
initialization into group_init() and the deletion into the locked section,
trading the creation races for the window above.
Neither placement in the destruction path works. A pending timer firing
while the group is alive is harmless though. poll_timer_fn() just wakes the
rtpoll waitqueue and doesn't re-arm itself. Bind the timer to the group's
lifetime instead and shut it down in psi_cgroup_free(). Nothing can arm it
by then. timer_shutdown_sync() because the timer is never armed again.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 6bfcb6178925b1fd28c102e53d403091b8f49396 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 Version: e1e5e263bbe0e6e9c3db36aa48a3c8acf546fa49 Version: 979965c33f734a1666af67900408f997ac669c23 Version: 5.10.50 ≤ Version: 5.12.17 ≤ Version: 5.13.2 ≤ |
||
{
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]
},
{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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{
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"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/psi: Shut down rtpoll_timer in psi_cgroup_free()\n\npsi_schedule_rtpoll_work() is called locklessly from the scheduler hotpath\nand can race psi_trigger_destroy() taking down the last rtpoll trigger under\nrtpoll_trigger_lock:\n\n psi_schedule_rtpoll_work() psi_trigger_destroy()\n\n rcu_read_lock();\n task = rcu_dereference(rtpoll_task);\n rcu_assign_pointer(rtpoll_task, NULL);\n timer_delete(\u0026rtpoll_timer);\n mod_timer(\u0026rtpoll_timer, ...);\n rcu_read_unlock();\n synchronize_rcu();\n kthread_stop(task_to_destroy);\n\nThe group can then be freed with the re-armed timer still pending, and\npoll_timer_fn() runs on freed memory.\n\n461daba06bdc (\"psi: eliminate kthread_worker from psi trigger scheduling\nmechanism\") deleted the timer synchronously after the synchronize_rcu(),\nwhich prevented this but raced trigger creation instead: the deletion could\ncancel the timer that a new trigger set armed during the grace period and,\nas creation also reinitialized the timer at the time, corrupt it.\n8f91efd870ea (\"psi: Fix race between psi_trigger_create/destroy\") moved the\ninitialization into group_init() and the deletion into the locked section,\ntrading the creation races for the window above.\n\nNeither placement in the destruction path works. A pending timer firing\nwhile the group is alive is harmless though. poll_timer_fn() just wakes the\nrtpoll waitqueue and doesn\u0027t re-arm itself. Bind the timer to the group\u0027s\nlifetime instead and shut it down in psi_cgroup_free(). Nothing can arm it\nby then. timer_shutdown_sync() because the timer is never armed again."
}
],
"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 - Reachable only via local kernel interfaces: writing cgroup *.pressure or /proc/pressure/*, closing the trigger fd, and removing the cgroup; the race involves scheduler hotpath callbacks, not any network protocol.\nAC:L - The attacker controls both race participants\u2014closing/destroying the last privileged PSI trigger while concurrently driving psi_schedule_rtpoll_work() via cgroup task scheduling or the psimon worker\u2014so the mod_timer-after-timer_delete window is reliably winnable.\nPR:L - The vulnerable rtpoll path requires CAP_SYS_RESOURCE (non-2s PSI windows); that capability is available to an unprivileged user who creates a user namespace, and cgroup pressure files are writable under delegated cgroup v2 hierarchies in that namespace.\nUI:N - Exploitation is fully self-driven: the attacker creates the trigger, races its teardown against scheduler activity, and deletes the cgroup; no separate victim action such as mounting a filesystem or opening a file is required.\nS:U - Impact is confined to kernel memory corruption and potential local privilege escalation within the same kernel security authority; it does not cross a VM, container runtime, or IOMMU trust boundary.\nC:H - After psi_cgroup_free() the pending rtpoll_timer fires poll_timer_fn() on a freed psi_group, a classic use-after-free that can expose or corrupt adjacent slab contents and be developed into arbitrary kernel memory read primitives.\nI:H - poll_timer_fn() performs atomic_set() on group-\u003ertpoll_wakeup and wake_up_interruptible() on group-\u003ertpoll_wait after the psi_group is freed, giving attacker-influenced writes into a recycled kmem object suitable for control-flow hijacking.\nA:H - Timer execution on freed psi_group memory can cause immediate kernel oops/panic from invalid pointer dereferences or list corruption, and the race can be retriggered for sustained denial of service on shared cloud/container hosts."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-25T05:40:21.246Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/4addb102154b7cf6e2310ccbe20c3c08619e520d"
},
{
"url": "https://git.kernel.org/stable/c/894a9300d7fb2e2951da92e565ae6de7ddfb0a69"
},
{
"url": "https://git.kernel.org/stable/c/1e5ca82eee59caca6988f9d6e859786aab8a5fa0"
},
{
"url": "https://git.kernel.org/stable/c/310b5a537a78c358a4cd244bd767c1a517a05459"
},
{
"url": "https://git.kernel.org/stable/c/806fcff98c1d7cb3c1dc0015e55ebdbe819e6b08"
},
{
"url": "https://git.kernel.org/stable/c/8037c5b2b2a447df52542f4d8535895d837bdcbd"
},
{
"url": "https://git.kernel.org/stable/c/611e7821c4f83a671455658797336faecc3a5196"
},
{
"url": "https://git.kernel.org/stable/c/5457025fa8ca3c0d2732109513de839e3e797190"
}
],
"title": "sched/psi: Shut down rtpoll_timer in psi_cgroup_free()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74594",
"datePublished": "2026-08-22T15:31:44.894Z",
"dateReserved": "2026-08-15T05:44:03.919Z",
"dateUpdated": "2026-08-25T05:40:21.246Z",
"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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