CVE-2026-89518

A flaw was found in the Linux kernel's sched_ext component. Under core scheduling, incorrect assumptions in dispatch kfuncs regarding this_rq() can lead to a deadlock. This occurs when an rq lock is acquired on a CPU different from the dispatched rq's, potentially causing the system to become unresponsive. This vulnerability could result in a Denial of Service (DoS).

A moderate-impact denial of service flaw was found in the Linux kernel's sched_ext scheduler framework. Under core scheduling, dispatch runs from within the core-wide pick and can target a sibling run queue (rq), so ops.dispatch() may execute on a CPU different from the dispatched rq's. Several sched_ext dispatch kfuncs incorrectly assumed the two always coincide: scx_dsq_move() could acquire the source rq lock while the dispatched rq lock was already held, resulting in a deadlock; scx_bpf_sub_dispatch() could dispatch this_rq() with a NULL sub_dispatch_prev; and finish_dispatch(), scx_bpf_dsq_reenq(), and scx_bpf_dsq_nr_queued() resolved SCX_DSQ_LOCAL to the executing CPU's local DSQ rather than the dispatched rq's. A local attacker able to run a sched_ext BPF scheduler on an affected kernel operating under core scheduling could trigger this deadlock and make the system unresponsive. Red Hat rated this flaw Moderate impact with a CVSS 3.1 score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), affecting availability only. The vulnerable sched_ext dispatch kfunc code is not present in the kernel versions shipped in any Red Hat Enterprise Linux or Red Hat OpenShift (RHCOS) builds, so all Red Hat products are marked NOT AFFECTED for this CVE.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.