CVE-2024-42151 in Linux
Summary
by MITRE • 07/30/2024
In the Linux kernel, the following vulnerability has been resolved:
bpf: mark bpf_dummy_struct_ops.test_1 parameter as nullable
Test case dummy_st_ops/dummy_init_ret_value passes NULL as the first parameter of the test_1() function. Mark this parameter as nullable to make verifier aware of such possibility. Otherwise, NULL check in the test_1() code:
SEC("struct_ops/test_1") int BPF_PROG(test_1, struct bpf_dummy_ops_state *state) {
if (!state) return ...;
... access state ... }
Might be removed by verifier, thus triggering NULL pointer dereference under certain conditions.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/19/2025
The vulnerability described in CVE-2024-42151 resides within the Linux kernel's eBPF (extended Berkeley Packet Filter) subsystem, specifically affecting the struct_ops functionality that enables dynamic attachment of BPF programs to kernel data structures. This issue represents a critical flaw in the BPF verifier component that governs program validation and execution safety. The vulnerability manifests when the bpf_dummy_struct_ops.test_1 test case attempts to pass a NULL parameter to the test_1() function, which is invoked through the struct_ops mechanism that allows BPF programs to interact with kernel data structures dynamically. The problem occurs because the verifier lacks explicit awareness that the first parameter of the test_1 function can legitimately be NULL, creating a potential for null pointer dereference conditions during program execution.
The technical flaw stems from insufficient parameter annotation within the BPF program definition, specifically in the struct_ops test case implementation. When the test_1 function is defined with the signature int BPF_PROG(test_1, struct bpf_dummy_ops_state *state), the verifier does not recognize that the state parameter may be NULL, despite the test case explicitly passing NULL as the first argument. This omission causes the verifier to optimize away the NULL check that the programmer explicitly included in the code, which is a fundamental safety mechanism to prevent dereferencing uninitialized or invalid pointers. The verifier's optimization removes the conditional check that should protect against accessing memory through a NULL pointer, leading to potential kernel crashes or undefined behavior when the program attempts to access members of the state structure.
The operational impact of this vulnerability extends beyond simple program execution issues, potentially compromising system stability and security. When the verifier incorrectly optimizes away the NULL check, it creates a scenario where a BPF program can attempt to access kernel memory through a NULL pointer reference, which could result in kernel panic, system crashes, or in more severe cases, potential privilege escalation opportunities. The vulnerability affects the broader BPF subsystem functionality, particularly when struct_ops are used to attach BPF programs to kernel data structures, which is a common pattern in network filtering, monitoring, and security enforcement mechanisms. This type of flaw could be exploited by malicious actors to destabilize systems or potentially gain elevated privileges within the kernel context, making it particularly concerning for production environments.
The vulnerability aligns with CWE-476, which addresses NULL pointer dereference issues, and demonstrates a clear failure in proper parameter validation within the BPF verifier system. From an ATT&CK perspective, this vulnerability could be leveraged as part of a broader attack chain targeting kernel-level security controls, potentially enabling techniques such as privilege escalation or denial of service through kernel exploitation. The fix implemented addresses this by explicitly marking the bpf_dummy_struct_ops.test_1 parameter as nullable, ensuring that the verifier maintains awareness of the potential NULL value and preserves the necessary safety checks. This remediation approach follows established security practices for kernel-level programming where explicit parameter annotations are crucial for proper verification and execution safety. The fix ensures that the verifier correctly handles the NULL parameter case and maintains the integrity of the program validation process, preventing optimization artifacts that could lead to security vulnerabilities or system instability.