CVE-2026-98220

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Fix NULL sched deref in kfunc sub-sched error paths

When the root scheduler has sub-scheds attached, the COMPAT kfunc

wrappers scx_bpf_select_cpu_and() and scx_bpf_dsq_insert_vtime() refuse

the call and report to @p's scheduler:

scx_error(scx_task_sched(p), "... must be used");

The wrappers are reachable with tasks that have no scheduler.

scx_bpf_select_cpu_and() is in the select_cpu kfunc group, which

scx_kfunc_context_filter() opens to BPF_PROG_TYPE_SYSCALL programs;

scx_bpf_dsq_insert_vtime() is in the enqueue_dispatch group, which

ops.enqueue() and ops.dispatch() may call with any KF_RCU task -- the

group has no kf_tasks validation, and scx_dsq_insert_preamble() checks

task ownership with scx_task_on_sched() precisely because @p may be an

arbitrary task.

scx_task_sched(p) is p->scx.sched, which is NULL for tasks past

sched_ext_dead() -- which clears it via scx_disable_and_exit_task() on

exit -- and

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References