CVE-2026-31734

/// Technical description

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

sched_ext: Fix is_bpf_migration_disabled() false negative on non-PREEMPT_RCU

Since commit 8e4f0b1ebcf2 ("bpf: use rcu_read_lock_dont_migrate() for

trampoline.c"), the BPF prolog (__bpf_prog_enter) calls migrate_disable()

only when CONFIG_PREEMPT_RCU is enabled, via rcu_read_lock_dont_migrate().

Without CONFIG_PREEMPT_RCU, the prolog never touches migration_disabled,

so migration_disabled == 1 always means the task is truly

migration-disabled regardless of whether it is the current task.

The old unconditional p == current check was a false negative in this

case, potentially allowing a migration-disabled task to be dispatched to

a remote CPU and triggering scx_error in task_can_run_on_remote_rq().

Only apply the p == current disambiguation when CONFIG_PREEMPT_RCU is

enabled, where the ambiguity with the BPF prolog still exists.

/// 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