The Linux kernel vulnerability (CVE-2026-64428) involved the gpio SCH controller's irq startup path where sch_irq_unmask() enabled the GPIO IRQ and updated controller state using sch_irq_mask_unmask() with a spin_lock_irqsave() on sch->lock. On PREEMPT_RT kernels, the regular spinlock_t could become a sleeping lock, which is invalid in this non-sleepable irq_startup() context, causing lockdep to report a sleeping function called from invalid context. The issue was fixed by converting the SCH controller lock to raw_spinlock_t, which is non-sleeping, ensuring proper locking behavior during IRQ setup without changing the GPIO-side locking contract.

The vulnerability could cause kernel warnings or bugs due to sleeping function calls in invalid contexts during IRQ startup on PREEMPT_RT kernels. This may lead to instability or unexpected behavior in interrupt handling. There is no indication of direct exploitation or broader impact beyond kernel locking correctness.

A fix is available that converts the SCH controller lock to raw_spinlock_t to prevent sleeping in irq_startup() context. Users should apply the official Linux kernel patch that addresses this issue. Patch status is not explicitly confirmed in the input data; therefore, check the vendor advisory or Linux kernel mailing lists for the current remediation guidance.