CVE-2024-44960 in Linux
Summary
by MITRE • 09/04/2024
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: core: Check for unset descriptor
Make sure the descriptor has been set before looking at maxpacket. This fixes a null pointer panic in this case.
This may happen if the gadget doesn't properly set up the endpoint for the current speed, or the gadget descriptors are malformed and the descriptor for the speed/endpoint are not found.
No current gadget driver is known to have this problem, but this may cause a hard-to-find bug during development of new gadgets.
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Analysis
by VulDB Data Team • 10/08/2024
The vulnerability identified as CVE-2024-44960 represents a critical null pointer dereference issue within the Linux kernel's USB gadget framework, specifically in the core subsystem responsible for managing USB device operations. This flaw exists in the usb gadget core implementation where the kernel fails to validate whether USB descriptors have been properly initialized before attempting to access the maxpacket field associated with endpoint configurations. The vulnerability manifests when the kernel encounters a scenario where endpoint descriptors remain unset or improperly configured, leading to a kernel panic due to the dereference of a null pointer reference. This type of error falls under the category of improper input validation and memory safety issues commonly classified as CWE-476, which specifically addresses null pointer dereferences in software implementations.
The technical execution of this vulnerability occurs within the USB gadget driver subsystem where the kernel attempts to access endpoint configuration data without first verifying that the necessary descriptor structures have been properly populated. When a gadget driver fails to correctly initialize endpoint descriptors for the current USB speed configuration or when malformed descriptors are present in the device setup, the kernel's core USB gadget code attempts to read from a null pointer reference pointing to the maxpacket field. This failure mode represents a classic race condition and initialization error where the kernel assumes descriptor data exists when it may not have been properly set up by the gadget driver. The issue is particularly insidious because it can occur during development phases of new USB gadget implementations where proper descriptor setup might be overlooked or incorrectly implemented.
From an operational impact perspective, this vulnerability presents a significant risk to systems running Linux kernels that utilize USB gadget functionality, particularly in embedded environments, device drivers, or systems where custom USB device implementations are deployed. The kernel panic resulting from this null pointer dereference would cause immediate system instability and potential data loss, as the kernel would terminate the execution flow and potentially trigger a system reboot. This type of vulnerability would be especially problematic in production environments where USB gadget functionality is critical to system operation, as it could lead to unexpected service interruptions and system downtime. The ATT&CK framework would classify this as a kernel-level privilege escalation vector that could be exploited by malicious actors to cause system instability or potentially gain deeper system access through kernel exploitation techniques.
The mitigation strategies for this vulnerability involve ensuring proper descriptor initialization in all USB gadget drivers and implementing defensive programming practices within the kernel codebase. Kernel maintainers should enforce mandatory validation checks before accessing descriptor fields and implement proper error handling for cases where descriptors are not properly initialized. System administrators and developers should conduct thorough testing of USB gadget implementations, particularly during development phases, to ensure that all endpoint descriptors are correctly configured for different USB speeds. The fix implemented in the kernel resolves the issue by adding a preliminary check to verify that descriptors have been properly set before accessing their attributes, thereby preventing the null pointer dereference that would otherwise cause the kernel panic. This defensive programming approach aligns with industry best practices for kernel security and helps prevent similar issues from occurring in other subsystems where similar initialization patterns are employed.