CVE-2026-89889 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
media: i2c: imx415: Release runtime PM reference on VBLANK error
The VBLANK path returned immediately when programming VMAX failed after pm_runtime_get_if_in_use() had taken a runtime PM reference. Break out of the switch instead so the common pm_runtime_put() path is used.
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel media subsystem contains a driver for the Sony IMX415 image sensor, which interfaces with hardware via the I2C bus and manages power states through the runtime PM framework. A specific flaw was identified in the vertical blanking interrupt handling logic within this driver. The issue arises during the programming of the VMAX register, which defines the total number of lines per frame for video output. When an error occurs while attempting to write to this hardware register, the existing code path incorrectly returns immediately from the function without releasing a previously acquired runtime power management reference. This behavior violates the fundamental principle that every successful acquisition of a resource must be matched by its corresponding release upon completion or failure.
The technical root cause lies in the control flow structure surrounding the pm_runtime_get_if_in_use call. When this function succeeds, it indicates that the device is currently active and increments its usage counter to prevent it from being suspended. However, if subsequent operations such as setting VMAX fail due to hardware errors or communication issues with the I2C bus, the code path exits prematurely via a direct return statement rather than breaking out of the switch case to reach the common cleanup routine. This structural oversight means that the pm_runtime_put call, which is responsible for decrementing the usage counter and potentially allowing the device to enter a low-power state if no other references exist, is skipped entirely in error scenarios.
This imbalance results in a reference leak within the runtime PM subsystem. Each time an I2C write operation fails during VBLANK handling, the kernel retains an extra reference count on the IMX415 sensor's power domain. Over time, particularly under conditions where such errors occur frequently or persistently, this accumulation of unreleased references prevents the device from ever reaching a zero usage counter state. Consequently, the hardware remains powered on indefinitely even when it is not actively being used for video capture or processing. This leads to unnecessary battery drain in mobile devices and increased thermal output in embedded systems where power efficiency is critical.
From an industry standards perspective, this vulnerability aligns with CWE-401, which describes a missing release of resource after effective use. The failure to properly manage the lifecycle of hardware resources represents a classic resource management error common in low-level system programming. Furthermore, while not directly exploitable for remote code execution or privilege escalation by an external attacker, such leaks contribute to local denial-of-service conditions through resource exhaustion. In the context of ATT&CK techniques related to impact and persistence on Linux systems, this type of flaw can be leveraged indirectly if an attacker can trigger repeated hardware errors to degrade system performance or stability over time, although it primarily falls under poor software design practices rather than active exploitation vectors for immediate compromise.
The operational impact is characterized by reduced power efficiency and potential instability in long-running media applications. Devices relying on the IMX415 sensor may experience faster battery depletion during idle periods if the driver fails to suspend properly due to these leaked references. In severe cases, persistent reference leaks could theoretically lead to memory pressure or other subsystem instabilities within the kernel's power management framework, although this is less common than simple battery drain. For enterprise environments utilizing embedded Linux for surveillance or industrial imaging, such issues can compromise uptime guarantees and increase maintenance costs associated with device reboots required to clear stuck states.
Mitigation strategies primarily involve applying the upstream kernel patch that corrects the control flow logic. The fix ensures that regardless of whether VMAX programming succeeds or fails, execution proceeds to a common exit path where pm_runtime_put is reliably invoked. This guarantees symmetry in resource acquisition and release operations. Administrators should ensure their systems are updated with the latest stable Linux kernel versions containing this media subsystem correction. Additionally, developers integrating custom drivers based on similar patterns should audit their code for matching get-put pairs across all error paths to prevent analogous reference leaks. Regular static analysis using tools capable of detecting resource management inconsistencies can also help identify such structural flaws before deployment in production environments.