GHSA-5GHQ-73F5-5J56
Vulnerability from github – Published: 2026-09-17 18:32 – Updated: 2026-09-18 18:31In the Linux kernel, the following vulnerability has been resolved:
blk-cgroup: skip dying blkg in blkcg_activate_policy()
When switching IO schedulers on a block device, blkcg_activate_policy() can race with concurrent blkcg deletion, leading to a use-after-free in rcu_accelerate_cbs.
T1: T2: blkg_destroy kill(&blkg->refcnt) // blkg->refcnt=1->0 blkg_release // call_rcu(__blkg_release) ... blkg_free_workfn ->pd_free_fn(pd) elv_iosched_store elevator_switch ... iterate blkg list blkg_get(blkg) // blkg->refcnt=0->1 list_del_init(&blkg->q_node) blkg_put(pinned_blkg) // blkg->refcnt=1->0 blkg_release // call_rcu again rcu_accelerate_cbs // uaf
Fix this by checking hlist_unhashed(&blkg->blkcg_node) before getting a reference to the blkg. This is the same check used in blkg_destroy() to detect if a blkg has already been destroyed. If the blkg is already unhashed, skip processing it since it's being destroyed.
{
"affected": [],
"aliases": [
"CVE-2026-90325"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:30Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-cgroup: skip dying blkg in blkcg_activate_policy()\n\nWhen switching IO schedulers on a block device, blkcg_activate_policy()\ncan race with concurrent blkcg deletion, leading to a use-after-free in\nrcu_accelerate_cbs.\n\nT1: T2:\n blkg_destroy\n kill(\u0026blkg-\u003erefcnt) // blkg-\u003erefcnt=1-\u003e0\n blkg_release // call_rcu(__blkg_release)\n ...\n blkg_free_workfn\n -\u003epd_free_fn(pd)\nelv_iosched_store\nelevator_switch\n...\niterate blkg list\nblkg_get(blkg) // blkg-\u003erefcnt=0-\u003e1\n list_del_init(\u0026blkg-\u003eq_node)\nblkg_put(pinned_blkg) // blkg-\u003erefcnt=1-\u003e0\nblkg_release // call_rcu again\nrcu_accelerate_cbs // uaf\n\nFix this by checking hlist_unhashed(\u0026blkg-\u003eblkcg_node) before getting\na reference to the blkg. This is the same check used in blkg_destroy()\nto detect if a blkg has already been destroyed. If the blkg is already\nunhashed, skip processing it since it\u0027s being destroyed.",
"id": "GHSA-5ghq-73f5-5j56",
"modified": "2026-09-18T18:31:29Z",
"published": "2026-09-17T18:32:01Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90325"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/083b58373463a6e5ee60ecb135269348f68ad7df"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1a267295b1ea6a6477963f3fda84adfecd48fcad"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3d8c3da95c75a4d312e272fc7b4076dd3ba9115c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5e9220389920f33b6a804d50c548cd0cd1b04634"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7337d012ca3fc3a6a2d1c8e2a19c6d97c38b410d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b5dae1cd0d8368b4338430ff93403df67f0b8bcc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d8c872901e6459339374e9eea80aa919176c2ccd"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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