UBUNTU-CVE-2026-64428: Medium severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: gpio: sch: use rawspinlockt in the irq startup path schirqunmask() enables the GPIO IRQ and then updates the controller state through schirqmaskunmask(), which takes sch->lock with spinlockirqsave(). The callback can be reached from irqstartup() while setting up a requested IRQ. That path is not sleepable, but on PREEMPTRT a regular spinlockt becomes a sleeping lock. This issue was found by our static analysis tool and then manually reviewed against the current tree. The grounded PoC kept the requestthreadedirq() -> setupirq() -> irqstartup() -> schirqunmask() -> schirqmaskunmask() carrier and used the original spinlockirqsave(&sch->lock) edge. Lockdep reported: BUG: sleeping function called from invalid context hardirqs last disabled at ... setupirq.constprop.0 ... [vulnmsv] schrtspinlockirqsave+0x1c/0x30 [vulnmsv] schirqmaskunmask.constprop.0+0x31/0x70 [vulnmsv] setupirq.constprop.0+0xd/0x30 [vulnmsv] Convert the SCH controller lock to rawspinlockt. The same lock is also used by the GPIO direction and value callbacks, but those critical sections only update MMIO-backed GPIO registers and do not contain sleepable operations. Keeping this register lock non-sleeping is therefore appropriate for the irqchip callbacks and does not change the GPIO-side locking contract.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Convert the SCH controller lock from spinlock_t to raw_spinlock_t so sch_irq_mask_unmask() remains non-sleeping when reached through the irq_startup() path, including on PREEMPT_RT.
Linux kernel SCH GPIO controller sch->lock type = raw_spinlock_t
Event History
Frequently Asked Questions
Which systems are most likely to encounter this issue?
Systems using an affected Ubuntu Linux kernel with the SCH GPIO controller and PREEMPT_RT are the relevant exposure case. The failure occurs during GPIO IRQ startup, when a requested IRQ reaches the SCH GPIO unmask callback.
What access or conditions are needed to trigger the problem?
A local actor needs the ability to request and start a GPIO interrupt through the affected driver path. The reported reproducer used request_threaded_irq(), which led through IRQ setup and startup into the problematic locking path.
What is the expected impact if the issue is triggered?
On PREEMPT_RT, the IRQ startup path can attempt to acquire a sleeping lock from a non-sleepable context. Lockdep reports a sleeping-function-in-invalid-context error; the provided severity vector indicates availability impact only, with no stated confidentiality or integrity impact.
How can administrators identify a likely occurrence?
Look for lockdep reports stating "BUG: sleeping function called from invalid context" with stack frames including sch_rt_spin_lock_irqsave, sch_irq_mask_unmask, and __setup_irq. The issue is associated with GPIO IRQ setup or startup.