CVE-2019-15924 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 5.0.11. fm10k_init_module in drivers/net/ethernet/intel/fm10k/fm10k_main.c has a NULL pointer dereference because there is no -ENOMEM upon an alloc_workqueue failure.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability CVE-2019-15924 represents a critical NULL pointer dereference flaw in the Linux kernel version 5.0.11 and earlier, specifically within the fm10k network driver module. This issue resides in the fm10k_init_module function located at drivers/net/ethernet/intel/fm10k/fm10k_main.c, where the kernel fails to properly handle memory allocation failures during workqueue initialization. The flaw stems from inadequate error checking mechanisms that do not account for the possibility of alloc_workqueue returning NULL when memory allocation fails, leading to a potential system crash or denial of service condition.
The technical root cause of this vulnerability aligns with CWE-476, which identifies NULL pointer dereference as a common weakness in software development. When alloc_workqueue fails to allocate memory for the workqueue structure, it returns NULL instead of a valid pointer, but the fm10k driver code does not verify this condition before proceeding with subsequent operations that assume the workqueue pointer is valid. This particular flaw falls under the broader category of improper error handling in kernel space, where the absence of proper memory allocation validation creates a path for system instability. The vulnerability manifests when the network driver attempts to initialize the fm10k module, particularly during system boot or network interface activation, where the kernel's memory management subsystem encounters allocation failures that are not gracefully handled.
The operational impact of CVE-2019-15924 extends beyond simple denial of service, as it can potentially lead to complete system crashes or lockups in environments where the fm10k network driver is actively used. Attackers could exploit this vulnerability by triggering network interface initialization sequences that force the kernel to allocate workqueues, thereby causing the system to crash when attempting to dereference the NULL pointer. This vulnerability affects systems running Linux kernel versions prior to 5.0.11, making it particularly concerning for enterprise environments that may be running older kernel versions or have delayed patching cycles. The attack surface is limited to systems utilizing Intel fm10k network adapters, but given the widespread deployment of these network interfaces in data centers and enterprise networks, the potential impact remains significant. The flaw demonstrates the importance of robust error handling in kernel space, where memory allocation failures can cascade into system-wide instability.
Mitigation strategies for CVE-2019-15924 primarily focus on upgrading to Linux kernel version 5.0.11 or later, where the vulnerability has been addressed through proper error handling mechanisms. System administrators should prioritize patching efforts, particularly in production environments where fm10k network adapters are deployed, as the vulnerability can be exploited to cause system crashes. Additional defensive measures include implementing proper monitoring and alerting for system crashes or unexpected reboots that could indicate exploitation attempts. Organizations should also consider implementing kernel lockdown mechanisms and ensuring that only trusted code can be loaded into kernel space, as recommended by the ATT&CK framework for kernel-level threats. The fix typically involves adding proper NULL pointer checks after alloc_workqueue calls and implementing appropriate error return codes to prevent the system from attempting to use invalid pointers, thereby aligning with best practices for secure kernel development as outlined in industry standards and security frameworks.