CVE-2021-47331 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
usb: common: usb-conn-gpio: fix NULL pointer dereference of charger
When power on system with OTG cable, IDDIG's interrupt arises before the charger registration, it will cause a NULL pointer dereference, fix the issue by registering the power supply before requesting IDDIG/VBUS irq.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 12/24/2024
The vulnerability identified as CVE-2021-47331 represents a critical NULL pointer dereference flaw within the Linux kernel's USB subsystem, specifically affecting the usb-conn-gpio driver component. This issue manifests during system power-on sequences when an OTG (On-The-Go) cable is connected, creating a race condition that can lead to system instability and potential denial of service conditions. The vulnerability stems from improper initialization order within the USB power management framework, where interrupt handling occurs before necessary power supply components are properly registered.
The technical root cause of this vulnerability lies in the improper sequence of operations within the USB connector GPIO driver implementation. When a system boots with an OTG cable already connected, the IDDIG (Input Digital Interrupt Generator) interrupt signal is generated before the charger registration process completes. This timing issue creates a scenario where the system attempts to dereference a NULL pointer when processing the interrupt, as the charger object reference has not yet been established. The flaw specifically affects the usb-conn-gpio driver which manages USB connector detection and power supply state transitions, making it a fundamental component of USB power management in Linux-based embedded systems and mobile devices.
From an operational perspective, this vulnerability presents significant security and reliability risks to systems relying on USB OTG functionality, particularly mobile devices, embedded systems, and IoT platforms that utilize Linux kernels. The NULL pointer dereference can result in immediate system crashes, kernel oops messages, or more subtle instability that may persist until system reboot. Attackers could potentially exploit this vulnerability to cause denial of service conditions by connecting OTG cables during system boot, or in more sophisticated scenarios, leverage the instability to execute arbitrary code or escalate privileges. The vulnerability is particularly concerning in automotive, industrial, and mobile computing environments where USB connectivity is essential and system reliability is paramount.
The fix for CVE-2021-47331 implements a proper initialization sequence by ensuring that power supply registration occurs before requesting IDDIG/VBUS interrupt handlers are set up. This approach follows fundamental software engineering principles of proper resource management and initialization ordering, preventing the race condition that leads to the NULL pointer dereference. The mitigation strategy aligns with security best practices outlined in the CWE (Common Weakness Enumeration) catalog under CWE-476 which addresses NULL pointer dereference vulnerabilities, and incorporates defensive programming techniques recommended in the ATT&CK framework for kernel-level security hardening. System administrators should prioritize applying the kernel patches that implement this fix, particularly in environments where USB OTG functionality is actively used or where system stability is critical. The resolution demonstrates the importance of proper initialization ordering in kernel drivers and serves as a reminder of the potential security implications of seemingly minor timing issues in low-level system components.