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 
9 char _license[] SEC("license") = "GPL";
10 
11 struct {
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 __u32 target_pid;
19 __u64 cgroup_id;
20 
21 void bpf_rcu_read_lock(void) __ksym;
22 void bpf_rcu_read_unlock(void) __ksym;
23 
24 SEC("?iter.s/cgroup")
cgroup_iter(struct bpf_iter__cgroup * ctx)25 int cgroup_iter(struct bpf_iter__cgroup *ctx)
26 {
27 	struct cgroup *cgrp = ctx->cgroup;
28 	long *ptr;
29 
30 	if (cgrp == NULL)
31 		return 0;
32 
33 	ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0,
34 				   BPF_LOCAL_STORAGE_GET_F_CREATE);
35 	if (ptr)
36 		cgroup_id = cgrp->kn->id;
37 	return 0;
38 }
39 
40 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
no_rcu_lock(void * ctx)41 int no_rcu_lock(void *ctx)
42 {
43 	struct task_struct *task;
44 	struct cgroup *cgrp;
45 	long *ptr;
46 
47 	task = bpf_get_current_task_btf();
48 	if (task->pid != target_pid)
49 		return 0;
50 
51 	/* task->cgroups is untrusted in sleepable prog outside of RCU CS */
52 	cgrp = task->cgroups->dfl_cgrp;
53 	ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0,
54 				   BPF_LOCAL_STORAGE_GET_F_CREATE);
55 	if (ptr)
56 		cgroup_id = cgrp->kn->id;
57 	return 0;
58 }
59 
60 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
yes_rcu_lock(void * ctx)61 int yes_rcu_lock(void *ctx)
62 {
63 	struct task_struct *task;
64 	struct cgroup *cgrp;
65 	long *ptr;
66 
67 	task = bpf_get_current_task_btf();
68 	if (task->pid != target_pid)
69 		return 0;
70 
71 	bpf_rcu_read_lock();
72 	cgrp = task->cgroups->dfl_cgrp;
73 	/* cgrp is trusted under RCU CS */
74 	ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE);
75 	if (ptr)
76 		cgroup_id = cgrp->kn->id;
77 	bpf_rcu_read_unlock();
78 	return 0;
79 }
80