CVE-2024-40919 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
bnxt_en: Adjust logging of firmware messages in case of released token in __hwrm_send()
In case of token is released due to token->state == BNXT_HWRM_DEFERRED, released token (set to NULL) is used in log messages. This issue is expected to be prevented by HWRM_ERR_CODE_PF_UNAVAILABLE error code. But this error code is returned by recent firmware. So some firmware may not return it. This may lead to NULL pointer dereference. Adjust this issue by adding token pointer check.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
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Analysis
by VulDB Data Team • 11/19/2024
The vulnerability identified as CVE-2024-40919 affects the Linux kernel's bnxt_en driver, which manages Broadcom network adapters. This issue stems from improper handling of firmware communication tokens within the __hwrm_send() function, creating a potential null pointer dereference condition that could compromise system stability. The problem specifically occurs when a token is released due to the token->state being set to BNXT_HWRM_DEFERRED, yet the code continues to reference the released token in subsequent logging operations.
The technical flaw manifests in the driver's firmware message handling mechanism where the code fails to properly validate whether a token pointer remains valid before using it in log messages. When firmware returns HWRM_ERR_CODE_PF_UNAVAILABLE error codes, the system should prevent further operations on released tokens, but recent firmware versions may not consistently return this error code. This inconsistency creates a scenario where a NULL pointer is dereferenced during logging operations, potentially causing kernel panics or system crashes. The vulnerability represents a classic null pointer dereference issue that falls under CWE-476, specifically targeting improper null pointer handling in kernel space operations.
The operational impact of this vulnerability extends beyond simple system instability to potentially enable denial of service conditions within network operations. When the bnxt_en driver encounters firmware communication issues, particularly with token management, the system may experience unexpected crashes or hangs that affect network connectivity for affected systems. This vulnerability is particularly concerning in server environments where network reliability is critical, as it could lead to complete network service outages. The issue affects systems running Linux kernels with the bnxt_en driver, particularly those managing Broadcom network hardware where firmware communication protocols may not consistently return expected error codes.
Mitigation strategies for CVE-2024-40919 involve implementing proper null pointer checks before referencing token pointers in logging operations within the __hwrm_send() function. The fix requires adding explicit validation to ensure token pointers remain valid before use in log messages, preventing the NULL pointer dereference scenario. System administrators should prioritize applying kernel updates that include the patched bnxt_en driver, as this vulnerability represents a critical kernel-level issue that could be exploited to cause system instability. Additionally, monitoring systems should be configured to detect unusual network adapter behavior that might indicate token management issues. The remediation aligns with ATT&CK technique T1499.004 for network denial of service attacks, as this vulnerability could be leveraged to disrupt network services through kernel-level instability. Organizations should also implement comprehensive testing procedures to validate firmware compatibility with the patched kernel versions, ensuring that the fix properly addresses the token validation issue without introducing regressions in network functionality.