CVE-2024-42121 in Linux
Summary
by MITRE • 07/30/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Check index msg_id before read or write
[WHAT]
msg_id is used as an array index and it cannot be a negative value, and therefore cannot be equal to MOD_HDCP_MESSAGE_ID_INVALID (-1).
[HOW]
Check whether msg_id is valid before reading and setting.
This fixes 4 OVERRUN issues reported by Coverity.
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Analysis
by VulDB Data Team • 09/29/2025
The vulnerability identified as CVE-2024-42121 resides within the Linux kernel's AMD display driver subsystem, specifically within the display rendering management component. This issue affects the direct rendering manager framework responsible for handling display operations on AMD graphics hardware. The flaw manifests as a potential out-of-bounds memory access condition that could be exploited to compromise system integrity or availability. The vulnerability was discovered through static analysis tools and subsequently reported to the Linux kernel development community, where it was addressed through a targeted code modification.
The technical root cause of this vulnerability stems from inadequate input validation within the display message handling logic. The msg_id parameter, which serves as an array index for accessing display message structures, lacks proper validation checks before being used for memory operations. According to the fix implementation, msg_id should never assume negative values since it represents a valid message identifier that must be non-negative. The specific validation requirement mandates that msg_id cannot equal MOD_HDCP_MESSAGE_ID_INVALID which is defined as -1, indicating that any negative value would represent an invalid state that should not be processed. This oversight creates a scenario where the driver could attempt to access memory locations outside the intended array boundaries, leading to potential memory corruption or system instability.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential attack vector for privilege escalation or denial of service conditions. When the display driver processes HDCP (High-bandwidth Digital Content Protection) messages, invalid msg_id values could cause the kernel to traverse memory locations that are not properly allocated for the intended operation. This type of out-of-bounds access could potentially allow malicious actors with appropriate privileges to manipulate kernel memory structures or cause system crashes. The vulnerability affects systems utilizing AMD graphics hardware with the Linux kernel's direct rendering manager framework, particularly those implementing HDCP message handling. The fix addresses four distinct overrun issues identified by Coverity static analysis, suggesting that this represents a broader class of validation problems within the display driver subsystem that required systematic review and remediation.
The resolution implemented for this vulnerability follows established security best practices and aligns with CWE-129, which addresses improper validation of array indices. The fix requires explicit validation of the msg_id parameter before any read or write operations are performed, ensuring that only valid indices are processed. This approach directly addresses the ATT&CK technique T1068, which involves exploiting privilege escalation through kernel vulnerabilities, by preventing unauthorized memory access patterns. The solution also reflects the principle of least privilege by ensuring that all input parameters are validated before being used in memory operations. The patch demonstrates proper defensive programming practices that should be applied throughout kernel subsystems to prevent similar vulnerabilities from manifesting in other components. This type of validation is particularly critical in kernel space operations where memory corruption can lead to complete system compromise, making the fix essential for maintaining overall system security and stability.