CVE-2021-47653 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
media: davinci: vpif: fix use-after-free on driver unbind
The driver allocates and registers two platform device structures during probe, but the devices were never deregistered on driver unbind.
This results in a use-after-free on driver unbind as the device structures were allocated using devres and would be freed by driver core when remove() returns.
Fix this by adding the missing deregistration calls to the remove() callback and failing probe on registration errors.
Note that the platform device structures must be freed using a proper release callback to avoid leaking associated resources like device names.
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Analysis
by VulDB Data Team • 03/25/2025
The vulnerability CVE-2021-47653 resides within the Linux kernel's media subsystem, specifically affecting the davinci video processing framework's VPIF (Video Processing Interface) driver. This issue represents a classic use-after-free vulnerability that occurs during driver unbinding operations, demonstrating a critical failure in resource management within the kernel's device driver framework. The flaw manifests when the driver properly allocates and registers two platform device structures during its probe phase, but fails to properly clean up these structures during the remove operation, creating a scenario where memory that should be freed becomes accessible after its intended lifetime.
The technical root cause of this vulnerability stems from improper device structure management within the Linux kernel's device model. During normal driver operation, the VPIF driver allocates platform device structures using the device resource management framework, which automatically handles memory cleanup when the driver is removed. However, the driver's remove callback lacks the necessary deregistration calls that would properly unregister these platform devices before their memory is freed. This creates a situation where the device structures remain registered in the kernel's device model while their underlying memory has been deallocated, leading to a use-after-free condition when the system attempts to access these now-invalid structures.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential vector for privilege escalation and system instability within embedded Linux systems that utilize the davinci video processing framework. Systems relying on the VPIF driver for video processing operations may experience kernel panics, memory corruption, or other unpredictable behavior when the driver is unbound, particularly in environments where the driver is dynamically loaded and unloaded during system operation. The vulnerability affects devices that implement the davinci platform and utilize the VPIF subsystem for video capture or output operations, making it relevant to various embedded multimedia applications and industrial systems.
The fix implemented for CVE-2021-47653 addresses the core issue by ensuring proper device deregistration within the driver's remove callback function, following established kernel development practices and security guidelines. This solution requires adding explicit deregistration calls to properly clean up the platform device structures that were allocated during probe, while also implementing proper error handling to fail the probe operation if device registration encounters failures. The mitigation approach specifically requires that platform device structures be freed using appropriate release callbacks to prevent resource leaks, a practice that aligns with CWE-415: Double Free and CWE-416: Use After Free vulnerability categories. The fix also demonstrates adherence to the ATT&CK framework's defense evasion techniques by preventing malicious actors from exploiting driver unbinding operations to gain unauthorized access to system resources, thereby maintaining system integrity and preventing potential privilege escalation scenarios.
This vulnerability exemplifies the importance of proper resource management in kernel space drivers and highlights the critical need for comprehensive testing of driver lifecycle operations. The fix emphasizes the necessity of following established kernel development patterns where allocation and deallocation operations are properly paired, and where device registration and deregistration are handled consistently throughout the driver's operational lifecycle. The resolution demonstrates that even seemingly simple driver operations require careful attention to memory management and resource cleanup to prevent security vulnerabilities that could be exploited by attackers with access to the system.