GHSA-386Q-4477-2C5H
Vulnerability from github – Published: 2026-01-13 18:31 – Updated: 2026-01-19 15:30In the Linux kernel, the following vulnerability has been resolved:
sched/deadline: only set free_cpus for online runqueues
Commit 16b269436b72 ("sched/deadline: Modify cpudl::free_cpus to reflect rd->online") introduced the cpudl_set/clear_freecpu functions to allow the cpu_dl::free_cpus mask to be manipulated by the deadline scheduler class rq_on/offline callbacks so the mask would also reflect this state.
Commit 9659e1eeee28 ("sched/deadline: Remove cpu_active_mask from cpudl_find()") removed the check of the cpu_active_mask to save some processing on the premise that the cpudl::free_cpus mask already reflected the runqueue online state.
Unfortunately, there are cases where it is possible for the cpudl_clear function to set the free_cpus bit for a CPU when the deadline runqueue is offline. When this occurs while a CPU is connected to the default root domain the flag may retain the bad state after the CPU has been unplugged. Later, a different CPU that is transitioning through the default root domain may push a deadline task to the powered down CPU when cpudl_find sees its free_cpus bit is set. If this happens the task will not have the opportunity to run.
One example is outlined here: https://lore.kernel.org/lkml/20250110233010.2339521-1-opendmb@gmail.com
Another occurs when the last deadline task is migrated from a CPU that has an offlined runqueue. The dequeue_task member of the deadline scheduler class will eventually call cpudl_clear and set the free_cpus bit for the CPU.
This commit modifies the cpudl_clear function to be aware of the online state of the deadline runqueue so that the free_cpus mask can be updated appropriately.
It is no longer necessary to manage the mask outside of the cpudl_set/clear functions so the cpudl_set/clear_freecpu functions are removed. In addition, since the free_cpus mask is now only updated under the cpudl lock the code was changed to use the non-atomic __cpumask functions.
{
"affected": [],
"aliases": [
"CVE-2025-68780"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-01-13T16:15:57Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/deadline: only set free_cpus for online runqueues\n\nCommit 16b269436b72 (\"sched/deadline: Modify cpudl::free_cpus\nto reflect rd-\u003eonline\") introduced the cpudl_set/clear_freecpu\nfunctions to allow the cpu_dl::free_cpus mask to be manipulated\nby the deadline scheduler class rq_on/offline callbacks so the\nmask would also reflect this state.\n\nCommit 9659e1eeee28 (\"sched/deadline: Remove cpu_active_mask\nfrom cpudl_find()\") removed the check of the cpu_active_mask to\nsave some processing on the premise that the cpudl::free_cpus\nmask already reflected the runqueue online state.\n\nUnfortunately, there are cases where it is possible for the\ncpudl_clear function to set the free_cpus bit for a CPU when the\ndeadline runqueue is offline. When this occurs while a CPU is\nconnected to the default root domain the flag may retain the bad\nstate after the CPU has been unplugged. Later, a different CPU\nthat is transitioning through the default root domain may push a\ndeadline task to the powered down CPU when cpudl_find sees its\nfree_cpus bit is set. If this happens the task will not have the\nopportunity to run.\n\nOne example is outlined here:\nhttps://lore.kernel.org/lkml/20250110233010.2339521-1-opendmb@gmail.com\n\nAnother occurs when the last deadline task is migrated from a\nCPU that has an offlined runqueue. The dequeue_task member of\nthe deadline scheduler class will eventually call cpudl_clear\nand set the free_cpus bit for the CPU.\n\nThis commit modifies the cpudl_clear function to be aware of the\nonline state of the deadline runqueue so that the free_cpus mask\ncan be updated appropriately.\n\nIt is no longer necessary to manage the mask outside of the\ncpudl_set/clear functions so the cpudl_set/clear_freecpu\nfunctions are removed. In addition, since the free_cpus mask is\nnow only updated under the cpudl lock the code was changed to\nuse the non-atomic __cpumask functions.",
"id": "GHSA-386q-4477-2c5h",
"modified": "2026-01-19T15:30:35Z",
"published": "2026-01-13T18:31:03Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-68780"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/382748c05e58a9f1935f5a653c352422375566ea"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3ed049fbfb4d75b4e0b8ab54c934f485129d5dc8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9019e399684e3cc68c4a3f050e268f74d69c1317"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/91e448e69aca4bb0ba2e998eb3e555644db7322b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dbc61834b0412435df21c71410562d933e4eba49"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fb36846cbcc936954f2ad2bffdff13d16c0be08a"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
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Nomenclature
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