GHSA-49M4-J2FJ-6QVH
Vulnerability from github – Published: 2025-02-27 03:34 – Updated: 2025-10-28 21:30In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix incorrect autogroup migration detection
scx_move_task() is called from sched_move_task() and tells the BPF scheduler that cgroup migration is being committed. sched_move_task() is used by both cgroup and autogroup migrations and scx_move_task() tried to filter out autogroup migrations by testing the destination cgroup and PF_EXITING but this is not enough. In fact, without explicitly tagging the thread which is doing the cgroup migration, there is no good way to tell apart scx_move_task() invocations for racing migration to the root cgroup and an autogroup migration.
This led to scx_move_task() incorrectly ignoring a migration from non-root cgroup to an autogroup of the root cgroup triggering the following warning:
WARNING: CPU: 7 PID: 1 at kernel/sched/ext.c:3725 scx_cgroup_can_attach+0x196/0x340 ... Call Trace: cgroup_migrate_execute+0x5b1/0x700 cgroup_attach_task+0x296/0x400 __cgroup_procs_write+0x128/0x140 cgroup_procs_write+0x17/0x30 kernfs_fop_write_iter+0x141/0x1f0 vfs_write+0x31d/0x4a0 __x64_sys_write+0x72/0xf0 do_syscall_64+0x82/0x160 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fix it by adding an argument to sched_move_task() that indicates whether the moving is for a cgroup or autogroup migration. After the change, scx_move_task() is called only for cgroup migrations and renamed to scx_cgroup_move_task().
{
"affected": [],
"aliases": [
"CVE-2025-21771"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-27T03:15:17Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix incorrect autogroup migration detection\n\nscx_move_task() is called from sched_move_task() and tells the BPF scheduler\nthat cgroup migration is being committed. sched_move_task() is used by both\ncgroup and autogroup migrations and scx_move_task() tried to filter out\nautogroup migrations by testing the destination cgroup and PF_EXITING but\nthis is not enough. In fact, without explicitly tagging the thread which is\ndoing the cgroup migration, there is no good way to tell apart\nscx_move_task() invocations for racing migration to the root cgroup and an\nautogroup migration.\n\nThis led to scx_move_task() incorrectly ignoring a migration from non-root\ncgroup to an autogroup of the root cgroup triggering the following warning:\n\n WARNING: CPU: 7 PID: 1 at kernel/sched/ext.c:3725 scx_cgroup_can_attach+0x196/0x340\n ...\n Call Trace:\n \u003cTASK\u003e\n cgroup_migrate_execute+0x5b1/0x700\n cgroup_attach_task+0x296/0x400\n __cgroup_procs_write+0x128/0x140\n cgroup_procs_write+0x17/0x30\n kernfs_fop_write_iter+0x141/0x1f0\n vfs_write+0x31d/0x4a0\n __x64_sys_write+0x72/0xf0\n do_syscall_64+0x82/0x160\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFix it by adding an argument to sched_move_task() that indicates whether the\nmoving is for a cgroup or autogroup migration. After the change,\nscx_move_task() is called only for cgroup migrations and renamed to\nscx_cgroup_move_task().",
"id": "GHSA-49m4-j2fj-6qvh",
"modified": "2025-10-28T21:30:28Z",
"published": "2025-02-27T03:34:05Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21771"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/75bf2f80c046d2ec5a07455891ea0a9fb6d8b5f6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d8b510d0ddc65d8a71e0f9a3acc9ed5f010fc514"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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