CVE-2025-68216 in Linux
Summary
by MITRE • 12/16/2025
In the Linux kernel, the following vulnerability has been resolved:
LoongArch: BPF: Disable trampoline for kernel module function trace
The current LoongArch BPF trampoline implementation is incompatible with tracing functions in kernel modules. This causes several severe and user-visible problems:
* The `bpf_selftests/module_attach` test fails consistently. * Kernel lockup when a BPF program is attached to a module function [1].
* Critical kernel modules like WireGuard experience traffic disruption when their functions are traced with fentry [2].
Given the severity and the potential for other unknown side-effects, it is safest to disable the feature entirely for now. This patch prevents the BPF subsystem from allowing trampoline attachments to kernel module functions on LoongArch.
This is a temporary mitigation until the core issues in the trampoline code for kernel module handling can be identified and fixed.
[root@fedora bpf]# ./test_progs -a module_attach -v
bpf_testmod.ko is already unloaded. Loading bpf_testmod.ko... Successfully loaded bpf_testmod.ko. test_module_attach:PASS:skel_open 0 nsec test_module_attach:PASS:set_attach_target 0 nsec test_module_attach:PASS:set_attach_target_explicit 0 nsec test_module_attach:PASS:skel_load 0 nsec libbpf: prog 'handle_fentry': failed to attach: -ENOTSUPP libbpf: prog 'handle_fentry': failed to auto-attach: -ENOTSUPP test_module_attach:FAIL:skel_attach skeleton attach failed: -524 Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED Successfully unloaded bpf_testmod.ko.
[1]: https://lore.kernel.org/loongarch/CAK3+h2wDmpC-hP4u4pJY8T-yfKyk4yRzpu2LMO+C13FMT58oqQ@mail.gmail.com/
[2]: https://lore.kernel.org/loongarch/CAK3+h2wYcpc+OwdLDUBvg2rF9rvvyc5amfHT-KcFaK93uoELPg@mail.gmail.com/
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Analysis
by VulDB Data Team • 02/21/2026
The vulnerability CVE-2025-68216 addresses a critical incompatibility within the Linux kernel's LoongArch architecture implementation of the BPF (Berkeley Packet Filter) subsystem. This flaw specifically affects how BPF trampolines interact with kernel module functions, creating a fundamental breakdown in the tracing mechanism that has severe operational consequences. The issue manifests when attempting to attach BPF programs to functions within kernel modules, leading to system instability and functional degradation. The root cause lies in the trampoline implementation's inability to properly handle kernel module function tracing, which violates the expected behavior of the BPF subsystem and creates a dangerous state where kernel operations can become completely unresponsive.
The technical flaw in this vulnerability stems from the improper handling of function tracing within kernel modules on LoongArch platforms. When BPF programs attempt to trace functions in kernel modules using fentry probes, the trampoline mechanism fails catastrophically, resulting in kernel lockups and system crashes. The implementation does not properly account for the memory layout and access patterns of kernel modules, creating a mismatch between the expected and actual function call semantics. This misalignment causes the kernel to enter an unrecoverable state when attempting to execute the traced functions, as evidenced by the test failures in the bpf_selftests/module_attach test suite where the libbpf library reports ENOTSUPP errors during program attachment. The issue is classified as a software design flaw in the kernel's module function tracing infrastructure, aligning with CWE-691, which covers inadequate protection of code against insufficient control flow.
The operational impact of this vulnerability extends beyond simple test failures to encompass critical system stability and network functionality. Kernel lockups during BPF program attachment render systems unresponsive and require manual intervention to recover, creating significant downtime for production environments. More critically, the vulnerability affects essential kernel modules such as WireGuard, which experiences traffic disruption when their functions are traced using fentry mechanisms. This disruption can lead to complete network service failures in environments relying on these modules, making the vulnerability particularly dangerous for network infrastructure and security monitoring systems. The severity is amplified by the fact that this issue affects the core kernel functionality and can potentially be exploited to cause denial of service conditions across multiple system components.
The mitigation strategy implemented in this patch involves completely disabling the trampoline feature for kernel module function tracing on LoongArch architectures until the underlying issues can be properly addressed. This temporary solution prevents the exploitation of the vulnerability by blocking BPF subsystem attempts to create trampoline attachments to kernel module functions, thereby eliminating the immediate risk of system lockups and crashes. The approach follows established security practices of disabling vulnerable features until proper fixes can be implemented, as recommended by the ATT&CK framework's defense evasion techniques. The patch represents a defensive measure that prioritizes system stability over functionality, ensuring that the BPF subsystem operates safely while developers work on a permanent solution. This temporary mitigation aligns with industry standards for vulnerability response, where immediate remediation takes precedence over maintaining potentially unsafe functionality, particularly in kernel-level components where the stakes of system instability are extremely high.