CVE-2025-71313 in Linux
Summary
by MITRE • 06/03/2026
In the Linux kernel, the following vulnerability has been resolved:
PCI: endpoint: Add missing NULL check for alloc_workqueue()
alloc_workqueue() can return NULL on memory allocation failure. Without proper error checking, this may lead to a NULL pointer dereference when queue_work() is later called with the NULL workqueue pointer in epf_ntb_epc_init().
Add a NULL check immediately after alloc_workqueue() and return -ENOMEM on failure to prevent the driver from loading with an invalid workqueue pointer.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability identified in the Linux kernel represents a critical null pointer dereference flaw within the PCI endpoint framework that could potentially lead to system instability or denial of service conditions. This issue specifically affects the endpoint function driver implementation where the alloc_workqueue() function is utilized to create a workqueue for asynchronous processing operations. The flaw occurs when the kernel attempts to allocate memory for a workqueue structure but fails due to insufficient memory resources, resulting in alloc_workqueue() returning a NULL pointer instead of a valid workqueue handle. The absence of proper error handling in the epf_ntb_epc_init() function means that this NULL return value propagates through the system without being validated, creating a dangerous condition where subsequent calls to queue_work() attempt to operate on a non-existent workqueue structure. This particular vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a fundamental security weakness that can be exploited to crash system processes or potentially enable privilege escalation attacks. The attack surface is primarily limited to systems utilizing PCI endpoint functionality, particularly those implementing the NTB (Non-Transparent Bridge) endpoint controller driver where the endpoint function driver is initialized.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the stability of the entire system during PCI endpoint initialization processes. When the kernel driver attempts to initialize the endpoint controller and encounters memory allocation failure during workqueue creation, the lack of proper error handling causes the driver to continue execution with a NULL workqueue pointer. This condition manifests when queue_work() is invoked later in the initialization sequence, resulting in immediate system panic or kernel oops due to the attempt to dereference a NULL pointer. The flaw demonstrates a classic pattern of inadequate resource management where memory allocation failure is not properly accounted for in the driver's error handling path. The vulnerability is particularly concerning because it occurs during driver initialization, meaning that any system utilizing PCI endpoint functionality could become unstable upon loading the affected driver. This type of error handling failure represents a violation of the principle of defensive programming where all potentially failing operations must be checked for success before proceeding with dependent operations. The specific context of this vulnerability aligns with ATT&CK technique T1499.004 which involves system network configuration modification through kernel-level attacks, where improper error handling can create conditions that allow for system instability or crash conditions.
The mitigation strategy for this vulnerability requires implementing immediate null pointer validation following the alloc_workqueue() call within the epf_ntb_epc_init() function. This approach directly addresses the root cause by ensuring that any memory allocation failure is properly detected and handled before proceeding with driver initialization. The fix involves adding a simple conditional check immediately after the alloc_workqueue() call to verify that the returned pointer is not NULL, and if it is, returning the appropriate error code -ENOMEM to prevent the driver from continuing with an invalid workqueue handle. This solution follows established kernel development practices and aligns with the Linux kernel's documented error handling conventions where allocation failures should be propagated up the call stack through appropriate error codes. The implementation must be carefully considered to maintain backward compatibility while ensuring that the driver fails gracefully when memory resources are insufficient, rather than causing system crashes or unpredictable behavior. This type of error handling fix is consistent with the kernel's approach to resource management and demonstrates the importance of proper error checking in kernel-space drivers where memory allocation failures can have catastrophic consequences for system stability. The fix also reinforces the principle that all kernel subsystems should validate their resources before attempting to use them, which is a fundamental requirement for maintaining system integrity and preventing exploitation of similar vulnerabilities in other kernel components.