1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
3
4#include "bpf_iter.h"
5#include <bpf/bpf_helpers.h>
6#include <bpf/bpf_tracing.h>
7#include "bpf_misc.h"
8
9char _license[] SEC("license") = "GPL";
10
11struct {
12	__uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
13	__uint(map_flags, BPF_F_NO_PREALLOC);
14	__type(key, int);
15	__type(value, long);
16} map_a SEC(".maps");
17
18__s32 target_pid;
19__u64 cgroup_id;
20int target_hid;
21bool is_cgroup1;
22
23struct cgroup *bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) __ksym;
24void bpf_cgroup_release(struct cgroup *cgrp) __ksym;
25void bpf_rcu_read_lock(void) __ksym;
26void bpf_rcu_read_unlock(void) __ksym;
27
28SEC("?iter.s/cgroup")
29int cgroup_iter(struct bpf_iter__cgroup *ctx)
30{
31	struct cgroup *cgrp = ctx->cgroup;
32	long *ptr;
33
34	if (cgrp == NULL)
35		return 0;
36
37	ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0,
38				   BPF_LOCAL_STORAGE_GET_F_CREATE);
39	if (ptr)
40		cgroup_id = cgrp->kn->id;
41	return 0;
42}
43
44static void __no_rcu_lock(struct cgroup *cgrp)
45{
46	long *ptr;
47
48	/* Note that trace rcu is held in sleepable prog, so we can use
49	 * bpf_cgrp_storage_get() in sleepable prog.
50	 */
51	ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0,
52				   BPF_LOCAL_STORAGE_GET_F_CREATE);
53	if (ptr)
54		cgroup_id = cgrp->kn->id;
55}
56
57SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
58int cgrp1_no_rcu_lock(void *ctx)
59{
60	struct task_struct *task;
61	struct cgroup *cgrp;
62
63	task = bpf_get_current_task_btf();
64	if (task->pid != target_pid)
65		return 0;
66
67	/* bpf_task_get_cgroup1 can work in sleepable prog */
68	cgrp = bpf_task_get_cgroup1(task, target_hid);
69	if (!cgrp)
70		return 0;
71
72	__no_rcu_lock(cgrp);
73	bpf_cgroup_release(cgrp);
74	return 0;
75}
76
77SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
78int no_rcu_lock(void *ctx)
79{
80	struct task_struct *task;
81
82	task = bpf_get_current_task_btf();
83	if (task->pid != target_pid)
84		return 0;
85
86	/* task->cgroups is untrusted in sleepable prog outside of RCU CS */
87	__no_rcu_lock(task->cgroups->dfl_cgrp);
88	return 0;
89}
90
91SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
92int yes_rcu_lock(void *ctx)
93{
94	struct task_struct *task;
95	struct cgroup *cgrp;
96	long *ptr;
97
98	task = bpf_get_current_task_btf();
99	if (task->pid != target_pid)
100		return 0;
101
102	if (is_cgroup1) {
103		bpf_rcu_read_lock();
104		cgrp = bpf_task_get_cgroup1(task, target_hid);
105		if (!cgrp) {
106			bpf_rcu_read_unlock();
107			return 0;
108		}
109
110		ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE);
111		if (ptr)
112			cgroup_id = cgrp->kn->id;
113		bpf_cgroup_release(cgrp);
114		bpf_rcu_read_unlock();
115		return 0;
116	}
117
118	bpf_rcu_read_lock();
119	cgrp = task->cgroups->dfl_cgrp;
120	/* cgrp is trusted under RCU CS */
121	ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE);
122	if (ptr)
123		cgroup_id = cgrp->kn->id;
124	bpf_rcu_read_unlock();
125	return 0;
126}
127