CVE-2021-47487 in Linux
Summary
by MITRE • 05/22/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu: fix out of bounds write
Size can be any value and is user controlled resulting in overwriting the 40 byte array wr_buf with an arbitrary length of data from buf.
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Analysis
by VulDB Data Team • 01/06/2025
The vulnerability resides within the drm/amdgpu subsystem of the Linux kernel, specifically addressing an out-of-bounds write condition that can be exploited through improper input validation. This flaw manifests when user-controlled data is used to determine buffer sizes without adequate bounds checking, creating a scenario where arbitrary amounts of data can overwrite memory regions beyond their allocated boundaries.
The technical implementation involves a 40-byte array named wr_buf that serves as a write buffer for graphics processing operations. When the system processes user-supplied size parameters, it fails to validate whether these values remain within acceptable limits before proceeding with data copying operations. This lack of input sanitization allows attackers to specify buffer sizes that exceed the allocated 40-byte space, resulting in memory corruption that can overwrite adjacent memory locations.
This vulnerability directly maps to CWE-787, which describes out-of-bounds write conditions in software systems. The flaw represents a critical security issue that aligns with ATT&CK technique T1059 by enabling code execution through memory corruption attacks. The operational impact extends beyond simple data corruption as it can potentially allow privilege escalation or system instability.
The attack surface becomes particularly concerning when considering that graphics drivers operate with elevated privileges and handle sensitive data streams from user applications. An attacker could leverage this vulnerability to overwrite critical kernel memory structures, potentially leading to complete system compromise. The out-of-bounds write condition creates opportunities for exploitation through return-oriented programming or other advanced attack techniques that manipulate the execution flow of the graphics subsystem.
Mitigation strategies should focus on implementing robust input validation mechanisms within the amdgpu driver code. Developers must enforce strict bounds checking before any memory copying operations occur, ensuring that user-provided size parameters remain within expected ranges. Additionally, defensive programming practices such as using safe string handling functions and implementing proper buffer overflow detection can significantly reduce the risk of exploitation.
The fix requires careful examination of how buffer sizes are validated in graphics processing contexts, particularly where user applications interact with kernel-level drivers. System administrators should prioritize updating to patched kernel versions that address this specific vulnerability while maintaining monitoring for potential exploitation attempts. Regular security assessments of graphics subsystems and comprehensive input validation testing can help identify similar vulnerabilities that may exist in other driver components.
This vulnerability demonstrates the critical importance of memory safety practices in kernel space operations where user input directly influences system behavior. The complexity of graphics processing drivers creates multiple potential entry points for attackers, making thorough code review and security testing essential for maintaining system integrity and preventing exploitation of similar flaws across different subsystems.