CVE-2026-90432sched_ext: Abort directly from the hardlockup handler

Official description

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Abort directly from the hardlockup handler scx_hardlockup() defers the abort to an irq_work because exit claiming used to take scx_sched_lock and couldn't run from NMI. The deferral is now unnecessary - claiming is NMI-safe and asserting ->aborting is exactly what breaks the live-locks that hard-lock CPUs. Call handle_lockup() directly and drop the irq_work. This also makes the self-detected case recoverable: the perf watchdog fires on the hard-locked CPU itself, where a queued irq_work never runs with IRQs off. Also fix the return value: %true used to be returned whenever sched_ext was loaded, suppressing the kernel's hardlockup report even when the abort was refused. Return %true only when this call initiated the abort.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4d6270bbb4e083a4d2d39f3c36f30f5c939c06ed
• https://git.kernel.org/stable/c/3c4b38064937a761ebbf85b1649e812db85eb59e