CVE-2024-49954 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
static_call: Replace pointless WARN_ON() in static_call_module_notify()
static_call_module_notify() triggers a WARN_ON(), when memory allocation fails in __static_call_add_module().
That's not really justified, because the failure case must be correctly handled by the well known call chain and the error code is passed through to the initiating userspace application.
A memory allocation fail is not a fatal problem, but the WARN_ON() takes the machine out when panic_on_warn is set.
Replace it with a pr_warn().
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Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2024-49954 resides within the Linux kernel's static call mechanism, specifically in the static_call_module_notify() function. This issue represents a problematic approach to error handling that can lead to system instability under certain conditions. The static call infrastructure is a kernel feature designed to optimize function call dispatching by using indirect calls through a centralized mechanism, which helps reduce overhead in kernel code execution paths. The function in question serves as a notification handler for module loading events within this static call framework, where it processes module-related notifications and manages the registration of static call sites.
The technical flaw manifests in the implementation of error handling within static_call_module_notify() where a WARN_ON() macro is employed to signal memory allocation failures that occur during the __static_call_add_module() function call. This particular implementation pattern creates a significant operational risk because it treats memory allocation failures as critical system errors rather than recoverable conditions. The WARN_ON() macro, when triggered, generates a kernel warning message and can cause system panic when the panic_on_warn kernel parameter is enabled, leading to complete system termination. This behavior is fundamentally flawed because memory allocation failures, while undesirable, are common occurrences in operating systems and should not result in system-wide crashes.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise system availability and reliability. When panic_on_warn is enabled, which is a common configuration in production environments for debugging purposes, the mere occurrence of a memory allocation failure within the static call module notification process can cause complete system shutdown. This scenario represents a denial-of-service condition that can be triggered by legitimate module loading operations, particularly in resource-constrained environments where memory allocation failures are more likely to occur. The vulnerability affects the kernel's ability to gracefully handle memory pressure conditions and maintain system stability during normal operation.
The remediation approach for this vulnerability involves replacing the WARN_ON() macro with a pr_warn() macro, which provides appropriate warning-level logging without triggering system panic behavior. This change aligns with established kernel development practices and security standards that emphasize graceful degradation of system functionality rather than complete system failure in response to recoverable errors. The pr_warn() approach maintains visibility of the error condition for system administrators while ensuring that the system continues operating normally. This modification follows the principle of least privilege and system resilience, where the kernel should continue functioning even when encountering non-fatal conditions that do not compromise system integrity. The fix addresses the core issue identified in CWE-703, which deals with improper handling of error conditions, and aligns with ATT&CK technique T1490 for system destruction through denial-of-service attacks, by preventing an otherwise recoverable condition from becoming a system-wide failure.
The vulnerability demonstrates a critical understanding of kernel error handling principles and the distinction between fatal and non-fatal system conditions. Memory allocation failures are inherently non-fatal in kernel space, as the kernel is designed to handle such conditions gracefully through various memory management strategies including memory compaction, swapping, and other recovery mechanisms. The inappropriate use of WARN_ON() in this context violates kernel design principles that require error handling to be proportional to the severity of the condition. This issue also reflects broader concerns about kernel robustness and the importance of avoiding panic-inducing error conditions in critical system components that handle module loading and dynamic code execution. The fix ensures that the static call infrastructure maintains its intended functionality while avoiding unnecessary system instability that could impact the reliability of kernel-based systems in production environments.