{"id":"CVE-2025-21771","summary":"sched_ext: Fix incorrect autogroup migration detection","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().","modified":"2026-04-02T12:45:13.862103Z","published":"2025-02-27T02:18:19.050Z","related":["ALSA-2025:20095"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21771.json"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21771.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21771"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8195136669661fdfe54e9a8923c33b31c92fc1da"},{"fixed":"75bf2f80c046d2ec5a07455891ea0a9fb6d8b5f6"},{"fixed":"d8b510d0ddc65d8a71e0f9a3acc9ed5f010fc514"},{"fixed":"d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21771.json"}}],"schema_version":"1.7.5"}