CVE-2023-52821 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/panel: fix a possible null pointer dereference
In versatile_panel_get_modes(), the return value of drm_mode_duplicate() is assigned to mode, which will lead to a NULL pointer dereference on failure of drm_mode_duplicate(). Add a check to avoid npd.
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Analysis
by VulDB Data Team • 12/18/2024
The vulnerability identified as CVE-2023-52821 represents a critical null pointer dereference flaw within the Linux kernel's display subsystem, specifically affecting the drm/panel driver component. This issue manifests in the versatile_panel_get_modes() function where the drm_mode_duplicate() API call's return value is directly assigned to a mode variable without proper validation. When drm_mode_duplicate() fails to allocate or duplicate the display mode structure, it returns a NULL pointer which subsequently gets dereferenced, leading to a kernel panic or system crash. The vulnerability stems from inadequate error handling in the display mode management code path that governs how panel drivers interact with the drm subsystem to enumerate supported display modes.
The technical implementation of this flaw demonstrates a classic programming error pattern where function return values are not properly validated before being used in subsequent operations. The drm_mode_duplicate() function is designed to create a copy of a display mode structure, but when this operation fails due to memory allocation issues or other internal errors, it returns NULL. The vulnerable code path in versatile_panel_get_modes() fails to check this return value, directly proceeding to use the NULL pointer in downstream operations that expect a valid mode structure pointer. This type of error falls under CWE-476 which specifically addresses null pointer dereference vulnerabilities, representing a fundamental failure in defensive programming practices.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the entire display functionality of affected Linux systems. When triggered, the null pointer dereference causes kernel panic conditions that result in system crashes and forced reboots, disrupting user sessions and potentially causing data loss. Systems running kernel versions containing this vulnerability are particularly at risk during display mode enumeration processes, which typically occur during system boot, display configuration changes, or when connecting external display devices. The vulnerability affects any system utilizing the versatile panel driver framework within the drm subsystem, making it a widespread concern across various Linux distributions and embedded systems that rely on proper display management.
Mitigation strategies for CVE-2023-52821 primarily focus on applying the official kernel patch that introduces proper null pointer validation before dereferencing the mode variable. The fix implements a straightforward conditional check to verify that drm_mode_duplicate() returns a valid pointer before proceeding with operations that require a non-null mode structure. This approach aligns with the ATT&CK framework's defensive techniques for preventing code injection and memory corruption attacks by ensuring proper input validation and error handling. System administrators should prioritize updating to kernel versions containing the patched code, typically those released after the vulnerability disclosure, and conduct thorough testing to ensure compatibility with existing display configurations. Additionally, monitoring systems for kernel panic events and implementing proper system logging can help detect exploitation attempts or identify affected systems that have not yet been patched. The vulnerability highlights the importance of robust error handling in kernel space code and demonstrates how seemingly minor oversight in return value validation can lead to critical system stability issues.