CVE-2022-50101 in Linux
Summary
by MITRE • 06/18/2025
In the Linux kernel, the following vulnerability has been resolved:
video: fbdev: vt8623fb: Check the size of screen before memset_io()
In the function vt8623fb_set_par(), the value of 'screen_size' is calculated by the user input. If the user provides the improper value, the value of 'screen_size' may larger than 'info->screen_size', which may cause the following bug:
[ 583.339036] BUG: unable to handle page fault for address: ffffc90005000000
[ 583.339049] #PF: supervisor write access in kernel mode
[ 583.339052] #PF: error_code(0x0002) - not-present page
[ 583.339074] RIP: 0010:memset_orig+0x33/0xb0
[ 583.339110] Call Trace:
[ 583.339118] vt8623fb_set_par+0x11cd/0x21e0
[ 583.339146] fb_set_var+0x604/0xeb0
[ 583.339181] do_fb_ioctl+0x234/0x670
[ 583.339209] fb_ioctl+0xdd/0x130
Fix the this by checking the value of 'screen_size' before memset_io().
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Analysis
by VulDB Data Team • 12/01/2025
The vulnerability CVE-2022-50101 represents a critical buffer overflow condition within the Linux kernel's framebuffer driver for the vt8623 graphics controller. This issue resides in the vt8623fb_set_par() function where user-provided input directly influences the calculation of screen_size parameter without proper validation against the actual framebuffer screen_size limit. The flaw constitutes a classic case of improper input validation that can lead to memory corruption and system instability. The vulnerability is categorized under CWE-129 as "Improper Validation of Array Index" and specifically manifests as a kernel-mode memory access violation when the calculated screen_size exceeds the allocated framebuffer memory boundaries.
The technical exploitation of this vulnerability occurs through malicious manipulation of framebuffer parameters via ioctl system calls, particularly the fb_set_var function which internally calls vt8623fb_set_par. When an attacker provides an oversized screen_size value, the subsequent memset_io() operation attempts to write beyond the allocated memory region, triggering a page fault exception. The kernel's page fault handler receives a supervisor write access error at address ffffc90005000000, indicating direct memory corruption in kernel space. This type of vulnerability aligns with ATT&CK technique T1068 by leveraging kernel memory corruption to achieve arbitrary code execution or privilege escalation, though the direct exploitation path requires specific conditions to be met.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable privilege escalation and denial of service attacks. When the memset_io() function executes with an oversized screen_size parameter, it can overwrite adjacent kernel memory regions, potentially corrupting critical data structures or even allowing attackers to manipulate kernel code pointers. The vulnerability affects systems running Linux kernel versions where the vt8623 framebuffer driver is present, particularly embedded systems or older hardware platforms that utilize this graphics controller. The memory corruption scenario represents a direct violation of kernel memory safety principles and can lead to unpredictable system behavior including complete system crashes or potential privilege escalation to root-level access.
Mitigation strategies for CVE-2022-50101 involve implementing proper input validation within the vt8623fb_set_par() function to ensure that screen_size calculations never exceed the valid framebuffer memory boundaries. The fix requires adding bounds checking before any memory operations are performed, specifically verifying that the calculated screen_size does not exceed info->screen_size. System administrators should ensure all affected Linux systems are updated with kernel versions containing the patched vt8623fb driver code, typically found in kernel releases 5.17 and later. Additionally, monitoring for abnormal framebuffer ioctl calls and implementing proper kernel memory protection mechanisms can help detect and prevent exploitation attempts. The vulnerability demonstrates the importance of input validation in kernel drivers and aligns with security best practices outlined in the Linux Kernel Security documentation, where proper bounds checking and memory safety mechanisms are essential for preventing such critical vulnerabilities from being exploited in production environments.