CVE-2026-89980 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
ALSA: harmony: initialize locks before requesting IRQ
snd_harmony_create() registers the IRQ before initializing h->lock and h->mixer_lock. A pending interrupt can invoke the handler while these locks are uninitialized.
Initialize both locks before requesting the IRQ so the handler always sees valid lock state.
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel's Advanced Linux Sound Architecture (ALSA) subsystem contains a synchronization vulnerability within the snd_harmony_create function, specifically affecting drivers for VIA Harmony audio hardware. This issue stems from an incorrect initialization order where interrupt request registration precedes the setup of critical mutex locks. In concurrent systems, proper sequencing is paramount to prevent race conditions and undefined behavior during device operation. The flaw arises because the kernel registers the interrupt handler with the system before initializing h->lock and h->mixer_lock, which are essential for protecting shared data structures from concurrent access.
When an interrupt occurs immediately after registration but before lock initialization completes, the hardware triggers the associated interrupt service routine. This handler attempts to acquire or utilize these uninitialized mutex locks to synchronize access to audio buffers and configuration states. Since the memory backing these locks has not been properly set up by the kernel's locking primitives, any attempt to operate on them results in undefined behavior. Depending on the specific state of the memory at that moment, this can lead to a system crash, data corruption within the sound subsystem, or potentially allow an attacker with local access to exploit the race condition for privilege escalation if other security boundaries are bypassed.
From a technical classification perspective, this vulnerability aligns closely with CWE-362, which describes concurrent execution using shared resources with inadequate synchronization. The core issue is not merely that locks exist but that their initialization is decoupled from the point at which they become accessible to asynchronous code paths like interrupt handlers. This violates fundamental principles of safe concurrency in kernel development where all shared state must be fully initialized and protected before any external agent, including hardware interrupts, can interact with it. The ATT&CK framework does not have a direct single entry for this specific race condition but relates broadly to techniques involving exploitation of timing vulnerabilities or resource management errors that lead to denial of service through system instability.
The operational impact of this vulnerability is primarily stability-related rather than directly exploitable for remote code execution in most standard configurations. However, local users with the ability to trigger audio device initialization under high interrupt load could potentially cause a kernel panic, leading to a Denial of Service against the entire host system. In more complex scenarios involving other vulnerabilities or specific hardware behaviors, such race conditions can sometimes be leveraged to corrupt memory structures in ways that might facilitate further exploitation attempts. The unpredictability of uninitialized lock states makes consistent reproduction difficult but does not diminish the severity of the potential for system instability.
To mitigate this risk, the fix involves reordering the initialization sequence within snd_harmony_create so that both h->lock and h->mixer_lock are fully initialized before calling request_irq or equivalent functions to register the interrupt handler. This ensures that when an interrupt fires, all synchronization primitives are in a valid state capable of protecting shared data. Developers should adhere strictly to patterns where resource allocation is followed by immediate initialization and protection setup prior to enabling any asynchronous event sources. Regular code audits focusing on lock ordering and interrupt registration sequences can help prevent similar issues across the kernel tree. Maintaining strict adherence to these synchronization protocols ensures that concurrent access paths remain safe even under high-load conditions or rapid device enumeration scenarios.