GHSA-QJ9W-QWPX-8WFP
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: fix race between policy activation and blkg destruction
When switching an IO scheduler on a block device, blkcg_activate_policy() allocates blkg_policy_data (pd) for all blkgs attached to the queue. However, blkcg_activate_policy() may race with concurrent blkcg deletion, leading to use-after-free and memory leak issues.
The use-after-free occurs in the following race:
T1 (blkcg_activate_policy): - Successfully allocates pd for blkg1 (loop0->queue, blkcgA) - Fails to allocate pd for blkg2 (loop0->queue, blkcgB) - Enters the enomem rollback path to release blkg1 resources
T2 (blkcg deletion): - blkcgA is deleted concurrently - blkg1 is freed via blkg_free_workfn() - blkg1->pd is freed
T1 (continued): - Rollback path accesses blkg1->pd->online after pd is freed - Triggers use-after-free
In addition, blkg_free_workfn() frees pd before removing the blkg from q->blkg_list. This allows blkcg_activate_policy() to allocate a new pd for a blkg that is being destroyed, leaving the newly allocated pd unreachable when the blkg is finally freed.
Fix these races by extending blkcg_mutex coverage to serialize blkcg_activate_policy() rollback and blkg destruction, ensuring pd lifecycle is synchronized with blkg list visibility.
{
"affected": [],
"aliases": [
"CVE-2026-90326"
],
"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: fix race between policy activation and blkg destruction\n\nWhen switching an IO scheduler on a block device, blkcg_activate_policy()\nallocates blkg_policy_data (pd) for all blkgs attached to the queue.\nHowever, blkcg_activate_policy() may race with concurrent blkcg deletion,\nleading to use-after-free and memory leak issues.\n\nThe use-after-free occurs in the following race:\n\nT1 (blkcg_activate_policy):\n - Successfully allocates pd for blkg1 (loop0-\u003equeue, blkcgA)\n - Fails to allocate pd for blkg2 (loop0-\u003equeue, blkcgB)\n - Enters the enomem rollback path to release blkg1 resources\n\nT2 (blkcg deletion):\n - blkcgA is deleted concurrently\n - blkg1 is freed via blkg_free_workfn()\n - blkg1-\u003epd is freed\n\nT1 (continued):\n - Rollback path accesses blkg1-\u003epd-\u003eonline after pd is freed\n - Triggers use-after-free\n\nIn addition, blkg_free_workfn() frees pd before removing the blkg from\nq-\u003eblkg_list. This allows blkcg_activate_policy() to allocate a new pd\nfor a blkg that is being destroyed, leaving the newly allocated pd\nunreachable when the blkg is finally freed.\n\nFix these races by extending blkcg_mutex coverage to serialize\nblkcg_activate_policy() rollback and blkg destruction, ensuring pd\nlifecycle is synchronized with blkg list visibility.",
"id": "GHSA-qj9w-qwpx-8wfp",
"modified": "2026-09-18T18:31:30Z",
"published": "2026-09-17T18:32:01Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90326"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/083b58373463a6e5ee60ecb135269348f68ad7df"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2cf9f50a38c1839e549a08e22aa35e8d69e2c8fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5313d4d41739b0cb63000747c97bb1217ac45f3e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ac34e655dffa74349d885a43d098115336f53842"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b5dae1cd0d8368b4338430ff93403df67f0b8bcc"
}
],
"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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