1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
3
4 #include "vmlinux.h"
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_tracing.h>
7 #include <bpf/bpf_core_read.h>
8
9 __u32 target_ancestor_level;
10 __u64 target_ancestor_cgid;
11 int target_pid, target_hid;
12
13 struct cgroup *bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) __ksym;
14 struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) __ksym;
15 void bpf_cgroup_release(struct cgroup *cgrp) __ksym;
16
17 static int bpf_link_create_verify(int cmd)
18 {
19 struct cgroup *cgrp, *ancestor;
20 struct task_struct *task;
21 int ret = 0;
22
23 if (cmd != BPF_LINK_CREATE)
24 return 0;
25
26 task = bpf_get_current_task_btf();
27
28 /* Then it can run in parallel with others */
29 if (task->pid != target_pid)
30 return 0;
31
32 cgrp = bpf_task_get_cgroup1(task, target_hid);
33 if (!cgrp)
34 return 0;
35
36 /* Refuse it if its cgid or its ancestor's cgid is the target cgid */
37 if (cgrp->kn->id == target_ancestor_cgid)
38 ret = -1;
39
40 ancestor = bpf_cgroup_ancestor(cgrp, target_ancestor_level);
41 if (!ancestor)
42 goto out;
43
44 if (ancestor->kn->id == target_ancestor_cgid)
45 ret = -1;
46 bpf_cgroup_release(ancestor);
47
48 out:
49 bpf_cgroup_release(cgrp);
50 return ret;
51 }
52
53 SEC("lsm/bpf")
54 int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
55 {
56 return bpf_link_create_verify(cmd);
57 }
58
59 SEC("lsm.s/bpf")
60 int BPF_PROG(lsm_s_run, int cmd, union bpf_attr *attr, unsigned int size)
61 {
62 return bpf_link_create_verify(cmd);
63 }
64
65 SEC("fentry")
66 int BPF_PROG(fentry_run)
67 {
68 return 0;
69 }
70
71 char _license[] SEC("license") = "GPL";
72
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