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