CVE-2023-52840 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
Input: synaptics-rmi4 - fix use after free in rmi_unregister_function()
The put_device() calls rmi_release_function() which frees "fn" so the dereference on the next line "fn->num_of_irqs" is a use after free. Move the put_device() to the end to fix this.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability identified as CVE-2023-52840 represents a critical use after free condition within the Linux kernel's synaptics-rmi4 driver subsystem. This flaw specifically affects the rmi_unregister_function() function where improper device reference management creates a scenario that can lead to arbitrary code execution or system instability. The vulnerability stems from a fundamental error in the sequence of operations during device cleanup, where the device reference is released before all dependent operations are completed. The synaptics-rmi4 driver handles touchpad and touchscreen devices from Synaptics, making this issue particularly concerning for laptop and tablet systems that rely on these input devices.
The technical root cause of this vulnerability lies in the improper ordering of function calls within the device unregistration process. When the rmi_unregister_function() function executes, it calls put_device() which subsequently invokes rmi_release_function() to free the function structure memory. However, the code then attempts to access fn->num_of_irqs on the following line, creating a use after free condition where memory that has already been freed is being dereferenced. This memory corruption pattern represents a classic software vulnerability that can be exploited by malicious actors to gain elevated privileges or cause system crashes. The flaw directly maps to CWE-416 which defines use after free vulnerabilities as a condition where memory is accessed after it has been freed by a program.
The operational impact of this vulnerability extends across various Linux distributions that utilize the synaptics-rmi4 driver for input device management, particularly affecting systems with Synaptics touchpad and touchscreen hardware. Attackers could potentially exploit this condition to execute arbitrary code with kernel-level privileges, leading to complete system compromise. The vulnerability is especially dangerous because it occurs during normal device removal operations, meaning that any legitimate device unregistration process could trigger the exploit. Systems running affected kernel versions are at risk, with the attack surface including laptops, tablets, and other devices with Synaptics input hardware. This vulnerability can also contribute to denial of service conditions where system stability is compromised through memory corruption.
Mitigation strategies for CVE-2023-52840 focus on immediate kernel updates that implement the fix by reordering the device reference management operations. The solution involves moving the put_device() call to the end of the function execution sequence, ensuring that all references to the function structure are processed before memory deallocation occurs. System administrators should prioritize applying the patched kernel versions from their respective distribution vendors, as the fix directly addresses the problematic code flow without requiring additional configuration changes. Additionally, monitoring for unusual device removal patterns or system stability issues can help identify potential exploitation attempts, though the primary defense remains the kernel patch itself. Organizations should also consider implementing device access controls and monitoring to limit potential attack vectors, while the fix aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel vulnerabilities. The resolution of this vulnerability demonstrates the importance of proper memory management in kernel space operations and serves as a reminder of the critical nature of input validation and resource cleanup in security-sensitive code paths.