CVE-2026-98842 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
module: fix lost error code from codetag_load_module()
If codetag_load_module() fails, err is not set to reflect the failure and load_module() returns 0 after the module has been torn down.
Also, if the module is a livepatch, mod->klp_info allocated by copy_module_elf() leaks on this error path. Free it via a new livepatch_cleanup label.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel contains a critical logic flaw within the module loading subsystem that results in improper error handling and resource leakage during dynamic module initialization. Specifically, the function codetag_load_module is responsible for setting up code tags required for profiling and tracing features such as ftrace or kprobes. When this function encounters an error condition, it returns a negative error code to indicate failure; however, the calling function load_module fails to capture and propagate this return value correctly. Instead of preserving the non-zero error status that signifies the root cause of the initialization failure, the variable err remains unset or retains its previous state, which often defaults to zero in C programming contexts when not explicitly assigned a negative integer upon failure.
This oversight leads to a severe operational impact where load_module proceeds under the false assumption that codetag_load_module succeeded. Consequently, the kernel continues with module teardown procedures but ultimately returns success status code zero to the user space caller or the invoking subsystem. This misrepresentation of state can cause dependent services or system components to believe that the kernel module has been successfully loaded and is operational, when in reality it was never fully initialized due to the underlying codetag failure. Such a discrepancy creates an inconsistent internal state where resources may be partially allocated while others are freed, potentially leading to undefined behavior during subsequent interactions with the supposedly active but actually inactive module structures.
Furthermore, this error path exhibits a distinct resource management vulnerability characterized by memory leaks associated with livepatch modules. When load_module processes a kernel module designated for live patching, it allocates specific metadata structures via copy_module_elf, specifically populating mod->klp_info to manage the live patch context. Under normal execution paths where codetag_load_module succeeds, these resources are properly cleaned up during standard module unloading or initialization completion routines. However, when codetag_load_module fails and triggers an early exit from load_module, the existing cleanup logic does not account for this specific allocation path. As a result, the memory allocated for mod->klp_info is never released because the original error handling labels did not include instructions to free livepatch-specific data structures.
The resolution of this vulnerability involves correcting the control flow within load_module to ensure that any non-zero return value from codetag_load_module is properly captured and returned as a failure status, thereby preventing the module from being treated as successfully loaded despite its incomplete initialization. Additionally, developers introduced a new cleanup label designated for livepatch scenarios which ensures that mod->klp_info is explicitly freed before returning an error code. This patch aligns with standard defensive programming practices by ensuring symmetry between allocation and deallocation routines across all execution paths, including exceptional ones triggered by hardware or configuration errors during module loading.
From a vulnerability classification perspective, this issue maps directly to CWE-252 which describes unchecked return values where the software does not check for errors or warnings from functions that can indicate failure. The improper handling of error codes allows the system state to become inconsistent with observable outcomes, facilitating potential confusion in diagnostic tools and management interfaces. Additionally, the memory leak component corresponds closely to CWE-401 regarding missing release of memory after effective allocation. While this specific instance does not immediately grant remote code execution or privilege escalation, it contributes to resource exhaustion over time if modules are frequently loaded and failed during testing or dynamic configuration changes in production environments.
In terms of threat modeling and detection methodologies, this type of logic error is often difficult to detect through static analysis alone without sophisticated data flow tracking that follows return values across function boundaries. It relates to ATT&CK techniques involving resource hijacking where system resources are consumed unnecessarily due to poor lifecycle management. Although the immediate impact is limited to memory leaks and incorrect status reporting rather than direct exploitation, such flaws can serve as precursors to more severe issues if they lead to use-after-free conditions or heap corruption in adjacent code paths that assume valid module structures exist.
Mitigation strategies for this vulnerability primarily involve applying the upstream kernel patch that corrects the error propagation logic and adds the necessary cleanup routines for livepatch information blocks. System administrators should ensure their kernels are updated to versions where these specific fixes have been merged into stable release branches. For organizations running custom or out-of-tree modules, rigorous testing of module loading sequences under failure conditions is recommended to verify that error codes are correctly propagated and resources are properly released. Continuous integration pipelines should include checks for memory leaks using tools like KASAN or Valgrind when simulating module load failures to catch similar patterns in proprietary kernel extensions before deployment.