CVE-2023-53221

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix memleak due to fentry attach failure

If it fails to attach fentry, the allocated bpf trampoline image will be

left in the system. That can be verified by checking /proc/kallsyms.

This meamleak can be verified by a simple bpf program as follows:

SEC("fentry/trap_init")

int fentry_run()

{

return 0;

}

It will fail to attach trap_init because this function is freed after

kernel init, and then we can find the trampoline image is left in the

system by checking /proc/kallsyms.

$ tail /proc/kallsyms

ffffffffc0613000 t bpf_trampoline_6442453466_1 [bpf]

ffffffffc06c3000 t bpf_trampoline_6442453466_1 [bpf]

$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep "FUNC 'trap_init'"

[2522] FUNC 'trap_init' type_id=119 linkage=static

$ echo $((6442453466 & 0x7fffffff))

2522

Note that there are two left bpf trampoline images, that is because the

libbpf will fallback to raw tracepoint if -

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References