CVE-2024-40908 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
bpf: Set run context for rawtp test_run callback
syzbot reported crash when rawtp program executed through the test_run interface calls bpf_get_attach_cookie helper or any other helper that touches task->bpf_ctx pointer.
Setting the run context (task->bpf_ctx pointer) for test_run callback.
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Analysis
by VulDB Data Team • 10/03/2025
The vulnerability identified as CVE-2024-40908 resides within the Linux kernel's eBPF (extended Berkeley Packet Filter) subsystem, specifically affecting the raw tracepoint (rawtp) test_run interface implementation. This issue represents a critical flaw in the kernel's handling of BPF program execution contexts, where the system fails to properly initialize the execution context for programs run through the test_run interface. The vulnerability manifests when BPF programs executed via this interface attempt to invoke helpers that interact with the task->bpf_ctx pointer, which serves as a crucial data structure for maintaining BPF execution context information for individual tasks. The root cause stems from the absence of proper context initialization during test_run callback execution, leading to potential memory access violations and system instability.
The technical implementation flaw occurs at the kernel level where the test_run interface for rawtp programs does not establish the necessary run context through the task->bpf_ctx pointer before executing BPF helper functions. This pointer is essential for maintaining per-task BPF execution state and is typically initialized during normal BPF program execution flows. When programs execute through test_run, however, this initialization step is omitted, causing subsequent helper calls like bpf_get_attach_cookie to access an uninitialized or improperly set pointer. The vulnerability aligns with CWE-476 which addresses NULL pointer dereferences, and more specifically relates to improper initialization of critical kernel data structures. The syzbot automated testing system first identified this issue through crash reports generated when such helper functions attempted to access the unpopulated task->bpf_ctx structure.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable privilege escalation and arbitrary code execution within the kernel context. When BPF programs execute through the test_run interface and attempt to utilize BPF helpers that access task->bpf_ctx, the system may experience memory corruption or segmentation faults leading to kernel panics. This creates a potential attack surface where malicious actors could exploit the uninitialized context to gain elevated privileges or disrupt system operations. The vulnerability affects systems running Linux kernels with eBPF support, particularly those utilizing the test_run interface for BPF program testing and validation. From an ATT&CK framework perspective, this vulnerability maps to T1059.006 (System Scripting) and T1068 (Exploitation for Privilege Escalation), as it enables potential privilege escalation through kernel-level memory corruption. The impact is particularly severe in environments where BPF programs are used for system monitoring, security policy enforcement, or network packet filtering, as these systems may be vulnerable to exploitation through crafted test_run calls.
Mitigation strategies for CVE-2024-40908 involve applying the official kernel patch that ensures proper initialization of the task->bpf_ctx pointer during test_run callback execution. System administrators should prioritize updating to kernel versions that contain the fix, typically those released after the vulnerability disclosure. The patch implementation specifically addresses the missing context setup by ensuring that the run context is properly established before BPF helper functions attempt to access the task->bpf_ctx structure. Additionally, organizations should implement monitoring for abnormal BPF program execution patterns and consider restricting access to the test_run interface where possible. Security teams should also conduct vulnerability assessments to identify systems running affected kernel versions and implement proper patch management procedures to ensure timely deployment of the security fix. The mitigation approach aligns with the principle of least privilege and follows standard security practices for kernel-level vulnerability remediation.