CVE-2021-29648 : Security Advisory and Response

An issue was discovered in the Linux kernel before 5.11.11, where the BPF subsystem does not properly consider that resolved_ids and resolved_sizes are intentionally uninitialized in the vmlinux BPF Type Format (BTF). This can lead to a system crash upon an unexpected access attempt, specifically in map_create in kernel/bpf/syscall.c or check_btf_info in kernel/bpf/verifier.c, identified as CID-350a5c4dd245.

Understanding CVE-2021-29648

This section will provide insights into the nature and impact of CVE-2021-29648.

What is CVE-2021-29648?

CVE-2021-29648 is a vulnerability found in the Linux kernel affecting versions prior to 5.11.11. It arises from a lack of proper initialization in the BPF subsystem, which can result in a system crash during unexpected access attempts.

The Impact of CVE-2021-29648

The vulnerability can be exploited by triggering an unexpected access attempt in specific kernel functions, potentially leading to a system crash and denial of service.

Technical Details of CVE-2021-29648

This section will delve deeper into the technical aspects of CVE-2021-29648.

Vulnerability Description

The issue stems from the improper handling of resolved_ids and resolved_sizes, which are left uninitialized in the BPF Type Format (BTF) of the vmlinux kernel.

Affected Systems and Versions

Systems running Linux kernel versions before 5.11.11 are vulnerable to this issue due to the uninitialized variables in the BPF subsystem.

Exploitation Mechanism

The vulnerability can be exploited through specific actions triggering access attempts in map_create within kernel/bpf/syscall.c or check_btf_info in kernel/bpf/verifier.c.

Mitigation and Prevention

Protecting systems from CVE-2021-29648 involves immediate actions and long-term security practices.

Immediate Steps to Take

Promptly apply available patches provided by the Linux kernel maintainers to mitigate the risk of exploitation.

Long-Term Security Practices

Regularly update the Linux kernel to newer versions that include fixes for known vulnerabilities, ensuring system security.

Patching and Updates

Stay informed about security advisories from Linux distributions and the kernel community to apply relevant patches and updates in a timely manner.