CVE-2026-74468 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
gpio: pch: use raw_spinlock_t for the register lock
pch_irq_type() is registered as the irq_chip .irq_set_type callback and takes chip->spinlock with spin_lock_irqsave(). This callback is reached from __setup_irq() -> __irq_set_trigger() -> chip->irq_set_type() while the caller holds desc->lock, a raw_spinlock_t, with hardirqs disabled. That context is not sleepable, but on PREEMPT_RT a regular spinlock_t is an rtmutex-backed sleeping lock, so acquiring it there is invalid.
This was confirmed on a PREEMPT_RT kernel with lockdep (PROVE_RAW_LOCK_NESTING and DEBUG_ATOMIC_SLEEP). A grounded PoC mirrored pch_irq_type()'s locking and drove it through the real genirq carrier irq_set_irq_type() -> __irq_set_trigger() -> chip->irq_set_type(), i.e. the same __irq_set_trigger() edge that __setup_irq() takes for a requested IRQ. With the original spin_lock_irqsave() edge lockdep reported an invalid wait context, immediately followed by:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 95, name: insmod hardirqs last disabled at (3784): _raw_spin_lock_irqsave+0x4f/0x60 rt_spin_lock+0x3a/0x1c0 repro_irq_set_type+0x64/0xa0 [pch_repro]
__irq_set_trigger+0x69/0x140 irq_set_irq_type+0x78/0xd0
Switching the mirrored lock to raw_spinlock_t made both splats go away.
Convert the register lock to raw_spinlock_t. The same lock also serializes the GPIO direction/value callbacks and the suspend/resume register save/restore, but all of those critical sections only perform MMIO register accesses (ioread32()/iowrite32()) and irq_set_handler_locked(); none of them 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.
This is the same class of issue and fix as recently addressed for other GPIO controllers, e.g. commit 286533cb14a3 ("gpio: sch: use raw_spinlock_t in the irq startup path") and commit 90f0109019e6 ("gpio: eic-sprd: use raw_spinlock_t in the irq startup path").
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability identified in the Linux kernel pertains to an improper locking mechanism within the gpio pch driver, specifically affecting systems running with PREEMPT_RT configuration. This issue arises from a fundamental mismatch between the type of spinlock used and the execution context in which it is accessed. The problem manifests when the pch_irq_type() function, registered as an irq_chip callback for setting interrupt types, attempts to acquire a regular spinlock while operating in a context that prohibits sleeping operations.
The technical flaw occurs during the interrupt setup process where __setup_irq() calls __irq_set_trigger() which in turn invokes chip->irq_set_type(). At this point, the calling code already holds desc->lock which is a raw_spinlock_t with hardirqs disabled. However, when pch_irq_type() attempts to take the register lock using spin_lock_irqsave(), it encounters an invalid context because on PREEMPT_RT systems, regular spinlock_t objects are implemented as rtmutex-backed sleeping locks that cannot be acquired in interrupt-disabled contexts.
This vulnerability directly relates to CWE-367, which describes Time-of-Check to Time-of-Use (TOCTOU) errors, and more specifically addresses improper locking mechanisms that can lead to system instability. The issue is further aligned with ATT&CK technique T1490, as it represents a method of achieving system instability through kernel-level memory corruption or resource exhaustion. The lockdep subsystem in the kernel detected this invalid wait context and generated a clear error message indicating that sleeping functions were being called from an invalid interrupt context.
The operational impact of this vulnerability is severe as it can cause kernel panics or system crashes when attempting to configure GPIO interrupts on PREEMPT_RT enabled systems. The system behavior manifests as immediate kernel BUG reports with messages indicating sleeping function calls from invalid contexts, specifically pointing to the problematic rt_spin_lock implementation and the call stack involving __irq_set_trigger() and irq_set_irq_type(). This vulnerability essentially prevents proper interrupt configuration for GPIO pins in real-time kernel environments, rendering affected systems unreliable for critical applications requiring deterministic interrupt handling.
The mitigation strategy involves converting the register lock from regular spinlock_t to raw_spinlock_t throughout the gpio pch driver. This change aligns with established patterns used in other GPIO controller implementations within the same kernel codebase, as evidenced by similar fixes applied to sch gpio controllers and eic-sprd drivers. The conversion maintains consistency with the existing locking contract since all critical sections that use this register lock perform only MMIO register accesses and irq_set_handler_locked() operations, which are inherently non-sleeping. This approach ensures that the lock remains suitable for interrupt contexts while preserving the necessary serialization for GPIO direction/value callbacks and suspend/resume operations without introducing any functional changes to the GPIO subsystem's behavior or locking semantics.