CVE-2024-49899 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Initialize denominators' default to 1
[WHAT & HOW]
Variables used as denominators and maybe not assigned to other values, should not be 0. Change their default to 1 so they are never 0.
This fixes 10 DIVIDE_BY_ZERO issues reported by Coverity.
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Analysis
by VulDB Data Team • 01/19/2026
The vulnerability identified as CVE-2024-49899 resides within the Linux kernel's graphics subsystem, specifically affecting the AMD display driver component under the direct rendering manager framework. This issue represents a fundamental programming error that manifests as potential division by zero conditions during display configuration operations. The flaw occurs in the drm/amd/display driver module where certain variables intended to serve as denominators in mathematical operations are not properly initialized before use. When these uninitialized variables retain their default memory values, they may evaluate to zero, creating dangerous conditions that can lead to system crashes or unpredictable behavior during graphics processing. The vulnerability was detected through static analysis tools and specifically flagged by Coverity as representing ten distinct divide-by-zero scenarios that could potentially be exploited to disrupt system operations. This type of error falls under the category of improper initialization, where variables that are expected to hold non-zero values are not properly established before being used in arithmetic operations.
The technical implementation of this vulnerability stems from inadequate variable initialization practices within the AMD display driver code. During display mode setting operations, the driver computes various timing parameters and scaling factors that require division operations to determine proper display characteristics. Variables representing denominators in these calculations are declared but not explicitly initialized to non-zero values, leaving them vulnerable to containing zero or invalid data from memory. This particular flaw demonstrates a common software engineering oversight where developers assume that variables will be properly assigned before use, but fail to account for scenarios where initialization might be skipped or overlooked. The consequence of this oversight is that when the division operations execute, they encounter zero denominators, causing arithmetic exceptions that can result in kernel panics, system hangs, or other critical failures. This vulnerability directly relates to CWE-457, which addresses the use of uninitialized variables, and represents a specific instance of improper initialization that can lead to system instability.
The operational impact of CVE-2024-49899 extends beyond simple system crashes to potentially compromise the stability and reliability of graphics-intensive applications and display operations. When a system encounters a divide-by-zero condition during display processing, the kernel may panic and reboot the system, resulting in data loss and service interruption for users engaged in graphics-intensive tasks such as video rendering, gaming, or professional display work. The vulnerability affects systems running Linux kernels with AMD graphics hardware, particularly those utilizing the direct rendering manager framework for display management. Attackers could potentially exploit this vulnerability to cause denial-of-service conditions, forcing users to restart their systems repeatedly or preventing proper display functionality. The impact is particularly concerning in server environments or embedded systems where continuous display operation is critical, as these systems may experience unexpected shutdowns or fail to maintain proper visual output. From an attack surface perspective, this vulnerability aligns with ATT&CK technique T1490, which involves data destruction through system instability, and represents a foundational security weakness that could be leveraged as a stepping stone for more complex attacks.
The remediation approach for CVE-2024-49899 involves implementing proper default initialization for all variables that will be used as denominators in division operations. The fix ensures that these variables are explicitly initialized to the value of 1 rather than leaving them uninitialized, thereby preventing any possibility of zero denominators during arithmetic operations. This solution directly addresses the root cause by eliminating the potential for uninitialized memory values to result in division by zero errors. The change represents a defensive programming practice that should be applied to all similar variables throughout the codebase where division operations might occur. Security practitioners should monitor for similar patterns in other kernel subsystems and ensure that all arithmetic operations with potential zero denominators are properly safeguarded. The fix also emphasizes the importance of comprehensive static analysis and code review processes to identify and prevent such initialization errors before they can be exploited in production environments. This vulnerability serves as a reminder of the critical importance of proper variable initialization and the potential consequences of seemingly minor programming oversights in kernel space code.