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(cgrp: 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

source code of linux/tools/testing/selftests/bpf/progs/cgrp_ls_sleepable.c