CVE-2025-38105 in Linux
Summary
by MITRE • 07/03/2025
In the Linux kernel, the following vulnerability has been resolved:
ALSA: usb-audio: Kill timer properly at removal
The USB-audio MIDI code initializes the timer, but in a rare case, the driver might be freed without the disconnect call. This leaves the timer in an active state while the assigned object is released via snd_usbmidi_free(), which ends up with a kernel warning when the debug configuration is enabled, as spotted by fuzzer.
For avoiding the problem, put timer_shutdown_sync() at snd_usbmidi_free(), so that the timer can be killed properly. While we're at it, replace the existing timer_delete_sync() at the disconnect callback with timer_shutdown_sync(), too.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-2025-38105 represents a critical resource management issue within the Linux kernel's USB audio subsystem, specifically affecting the Advanced Linux Sound Architecture ALSA driver. This flaw manifests in the usb-audio module where MIDI functionality is handled, creating a potential kernel panic or system instability through improper timer cleanup operations. The issue stems from a race condition between driver initialization and cleanup processes, where the timer structure remains active even after the associated driver object has been freed, leading to kernel warnings and potential memory corruption scenarios.
The technical implementation flaw occurs within the snd_usbmidi_free() function which is responsible for cleaning up USB audio MIDI driver resources. When the USB audio device is removed from the system, the driver initialization process creates a timer object to manage MIDI data transmission timing. However, under specific conditions involving rare race scenarios during device removal, the disconnect callback may not be invoked properly, leaving the timer in an active state while the underlying snd_usbmidi structure is freed. This creates a dangling timer reference that can cause kernel warnings when debug configurations are enabled, as detected by automated fuzzing tools during kernel testing.
The operational impact of this vulnerability extends beyond simple kernel warnings to potentially compromise system stability and security. When the timer_shutdown_sync() function is not properly invoked before driver cleanup, it can lead to memory corruption patterns that may be exploited by malicious actors to execute arbitrary code within kernel space. This represents a significant concern for systems running Linux kernels with USB audio devices, particularly in server environments or embedded systems where audio functionality is critical. The vulnerability aligns with CWE-410: Insufficient Resource Management, specifically addressing improper resource cleanup in kernel-level drivers. From an ATT&CK framework perspective, this vulnerability could be leveraged as a privilege escalation vector through kernel memory corruption, potentially enabling an attacker to gain root access or disrupt system operations.
The mitigation strategy implemented in the fix involves replacing the existing timer_delete_sync() function call with timer_shutdown_sync() within both the disconnect callback and the snd_usbmidi_free() cleanup routine. This ensures proper synchronization and cleanup of timer resources regardless of the execution path taken during driver removal. The solution addresses the root cause by guaranteeing that timer destruction occurs before memory deallocation, preventing the dangling reference scenario that led to kernel warnings. The fix demonstrates proper kernel resource management practices by ensuring that all timer objects are properly synchronized and shut down before their associated structures are freed, thereby preventing potential use-after-free conditions and memory corruption. This remediation approach aligns with kernel security best practices and follows established patterns for safe timer management in kernel modules, particularly those handling USB device communications and audio data processing.