CVE-2023-53842

Vulnerability

In the Linux kernel ASoC codecs subsystem, the wcd-mbhc-v2 driver tied MBHC (Multi-Button Headset Control) resources to the lifetime of the component device. This meant that resources were not properly released on component probe failure or removal, leading to stale interrupt registrations and resource leaks.

Exploitation

The vulnerability is triggered during sound card initialization when probe deferrals occur. When the codec component is reprobed, the driver attempts to request interrupts that are still registered from a previous probe attempt. This results in a genirq flags mismatch error: "Flags mismatch irq 299. 00002001 (mbhc sw intr) vs. 00002001 (mbhc sw intr)" [1]. The failure is observed in the kernel log as "Failed to request mbhc interrupts -16" and "mbhc initialization failed", ultimately causing the sound card instantiation to fail with -16 (EBUSY).

Impact

An attacker with local access to trigger reprobe events on affected systems can cause persistent denial of service by preventing the sound card from being instantiated. The error is reproducible by triggering probe deferral of the sound card via snd-sc8280xp driver, which leads to complete loss of audio functionality until the kernel is rebooted.

Mitigation

The fix is included in Linux kernel stable releases via commits [1] and [2]. The patch ensures that MBHC resources are released on component probe failure and removal, decoupling them from the component device lifetime. Users should update to a kernel version containing these commits.