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// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
__u32 target_ancestor_level;
__u64 target_ancestor_cgid;
int target_pid, target_hid;
struct cgroup *bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) __ksym;
struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) __ksym;
void bpf_cgroup_release(struct cgroup *cgrp) __ksym;
static int bpf_link_create_verify(int cmd)
{
struct cgroup *cgrp, *ancestor;
struct task_struct *task;
int ret = 0;
if (cmd != BPF_LINK_CREATE)
return 0;
task = bpf_get_current_task_btf();
/* Then it can run in parallel with others */
if (task->pid != target_pid)
return 0;
cgrp = bpf_task_get_cgroup1(task, target_hid);
if (!cgrp)
return 0;
/* Refuse it if its cgid or its ancestor's cgid is the target cgid */
if (cgrp->kn->id == target_ancestor_cgid)
ret = -1;
ancestor = bpf_cgroup_ancestor(cgrp, target_ancestor_level);
if (!ancestor)
goto out;
if (ancestor->kn->id == target_ancestor_cgid)
ret = -1;
bpf_cgroup_release(ancestor);
out:
bpf_cgroup_release(cgrp);
return ret;
}
SEC("lsm/bpf")
int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
{
return bpf_link_create_verify(cmd);
}
SEC("lsm.s/bpf")
int BPF_PROG(lsm_s_run, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
{
return bpf_link_create_verify(cmd);
}
SEC("fentry")
int BPF_PROG(fentry_run)
{
return 0;
}
char _license[] SEC("license") = "GPL";
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