CVE-2021-38783 in R818 SoC Android Q SDK
Summary
by MITRE • 01/18/2022
There is a Out-of-Bound Write in the Allwinner R818 SoC Android Q SDK V1.0 camera driver "/dev/cedar_dev" through iotcl cmd IOCTL_SET_PROC_INFO and IOCTL_COPY_PROC_INFO, which could cause a system crash or EoP.
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Analysis
by VulDB Data Team • 01/20/2022
The vulnerability identified as CVE-2021-38783 represents a critical out-of-bounds write condition within the Allwinner R818 System-on-Chip Android Q SDK V1.0 camera driver implementation. This flaw exists in the device file "/dev/cedar_dev" which serves as the primary interface for camera functionality within the embedded Android system. The vulnerability manifests specifically through two ioctl commands: IOCTL_SET_PROC_INFO and IOCTL_COPY_PROC_INFO, which are designed to manage process information within the camera subsystem. The out-of-bounds write occurs when these commands process user-supplied data without proper bounds checking, allowing malicious actors to write data beyond the allocated memory boundaries. This type of vulnerability falls under CWE-787, which specifically addresses out-of-bounds writes in software implementations. The attack surface is particularly concerning as it operates within the camera driver context, which typically runs with elevated privileges and has direct access to hardware components.
The technical execution of this vulnerability requires an attacker to establish a valid connection to the camera driver through the /dev/cedar_dev device node and then issue the specific ioctl commands with maliciously crafted parameters. When the driver processes these commands, it fails to validate the size or bounds of the data being written, allowing an attacker to overwrite adjacent memory locations. This memory corruption can lead to unpredictable behavior including system crashes, which represents a denial of service condition, or more critically, privilege escalation that could allow an attacker to execute arbitrary code with kernel-level privileges. The potential for privilege escalation stems from the fact that kernel drivers typically operate with the highest privilege level in the system, making any memory corruption vulnerabilities particularly dangerous from a security standpoint.
The operational impact of CVE-2021-38783 extends beyond simple system instability to encompass potential complete system compromise. When exploited, this vulnerability can result in persistent denial of service conditions that prevent normal camera functionality, or more severely, provide attackers with kernel-level access that could enable full system compromise. The Allwinner R818 SoC is commonly found in various embedded devices including tablets, set-top boxes, and IoT devices, meaning this vulnerability affects a wide range of products. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1068, which involves local privilege escalation through kernel exploits, and T1499, which covers endpoint denial of service attacks. The exploitation chain typically begins with privilege escalation from a regular user context to kernel space, potentially allowing attackers to bypass security controls and gain administrative access to affected devices.
Mitigation strategies for CVE-2021-38783 must address both immediate defensive measures and long-term architectural improvements. The most effective immediate solution involves applying vendor-provided patches that implement proper bounds checking within the ioctl command handlers for both IOCTL_SET_PROC_INFO and IOCTL_COPY_PROC_INFO. Additionally, implementing kernel mitigations such as stack canaries, kernel address space layout randomization, and memory protection mechanisms can significantly reduce exploitability. System administrators should also consider disabling camera functionality when not required, particularly in embedded environments where the attack surface can be minimized. The vulnerability demonstrates the critical importance of input validation in kernel drivers, as highlighted by industry best practices in secure coding standards. Organizations should implement comprehensive monitoring for suspicious ioctl activity and establish incident response procedures specifically tailored to handle kernel-level exploits. Regular security assessments of embedded system components and adherence to secure development lifecycle practices are essential to prevent similar vulnerabilities from emerging in future implementations.