1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * Copyright 2020 Google LLC.
5 */
6
7#include "vmlinux.h"
8#include <errno.h>
9#include <bpf/bpf_helpers.h>
10#include <bpf/bpf_tracing.h>
11
12char _license[] SEC("license") = "GPL";
13
14#define DUMMY_STORAGE_VALUE 0xdeadbeef
15
16__u32 monitored_pid = 0;
17int inode_storage_result = -1;
18int sk_storage_result = -1;
19int task_storage_result = -1;
20
21struct local_storage {
22	struct inode *exec_inode;
23	__u32 value;
24};
25
26struct {
27	__uint(type, BPF_MAP_TYPE_INODE_STORAGE);
28	__uint(map_flags, BPF_F_NO_PREALLOC);
29	__type(key, int);
30	__type(value, struct local_storage);
31} inode_storage_map SEC(".maps");
32
33struct {
34	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
35	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
36	__type(key, int);
37	__type(value, struct local_storage);
38} sk_storage_map SEC(".maps");
39
40struct {
41	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
42	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
43	__type(key, int);
44	__type(value, struct local_storage);
45} sk_storage_map2 SEC(".maps");
46
47struct {
48	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
49	__uint(map_flags, BPF_F_NO_PREALLOC);
50	__type(key, int);
51	__type(value, struct local_storage);
52} task_storage_map SEC(".maps");
53
54struct {
55	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
56	__uint(map_flags, BPF_F_NO_PREALLOC);
57	__type(key, int);
58	__type(value, struct local_storage);
59} task_storage_map2 SEC(".maps");
60
61SEC("lsm/inode_unlink")
62int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim)
63{
64	__u32 pid = bpf_get_current_pid_tgid() >> 32;
65	struct bpf_local_storage *local_storage;
66	struct local_storage *storage;
67	struct task_struct *task;
68	bool is_self_unlink;
69
70	if (pid != monitored_pid)
71		return 0;
72
73	task = bpf_get_current_task_btf();
74	if (!task)
75		return 0;
76
77	task_storage_result = -1;
78
79	storage = bpf_task_storage_get(&task_storage_map, task, 0, 0);
80	if (!storage)
81		return 0;
82
83	/* Don't let an executable delete itself */
84	is_self_unlink = storage->exec_inode == victim->d_inode;
85
86	storage = bpf_task_storage_get(&task_storage_map2, task, 0,
87				       BPF_LOCAL_STORAGE_GET_F_CREATE);
88	if (!storage || storage->value)
89		return 0;
90
91	if (bpf_task_storage_delete(&task_storage_map, task))
92		return 0;
93
94	/* Ensure that the task_storage_map is disconnected from the storage.
95	 * The storage memory should not be freed back to the
96	 * bpf_mem_alloc.
97	 */
98	local_storage = task->bpf_storage;
99	if (!local_storage || local_storage->smap)
100		return 0;
101
102	task_storage_result = 0;
103
104	return is_self_unlink ? -EPERM : 0;
105}
106
107SEC("lsm.s/inode_rename")
108int BPF_PROG(inode_rename, struct inode *old_dir, struct dentry *old_dentry,
109	     struct inode *new_dir, struct dentry *new_dentry,
110	     unsigned int flags)
111{
112	struct local_storage *storage;
113	int err;
114
115	/* new_dentry->d_inode can be NULL when the inode is renamed to a file
116	 * that did not exist before. The helper should be able to handle this
117	 * NULL pointer.
118	 */
119	bpf_inode_storage_get(&inode_storage_map, new_dentry->d_inode, 0,
120			      BPF_LOCAL_STORAGE_GET_F_CREATE);
121
122	storage = bpf_inode_storage_get(&inode_storage_map, old_dentry->d_inode,
123					0, 0);
124	if (!storage)
125		return 0;
126
127	if (storage->value != DUMMY_STORAGE_VALUE)
128		inode_storage_result = -1;
129
130	err = bpf_inode_storage_delete(&inode_storage_map, old_dentry->d_inode);
131	if (!err)
132		inode_storage_result = err;
133
134	return 0;
135}
136
137SEC("lsm.s/socket_bind")
138int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address,
139	     int addrlen)
140{
141	__u32 pid = bpf_get_current_pid_tgid() >> 32;
142	struct local_storage *storage;
143
144	if (pid != monitored_pid)
145		return 0;
146
147	storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0, 0);
148	if (!storage)
149		return 0;
150
151	sk_storage_result = -1;
152	if (storage->value != DUMMY_STORAGE_VALUE)
153		return 0;
154
155	/* This tests that we can associate multiple elements
156	 * with the local storage.
157	 */
158	storage = bpf_sk_storage_get(&sk_storage_map2, sock->sk, 0,
159				     BPF_LOCAL_STORAGE_GET_F_CREATE);
160	if (!storage)
161		return 0;
162
163	if (bpf_sk_storage_delete(&sk_storage_map2, sock->sk))
164		return 0;
165
166	storage = bpf_sk_storage_get(&sk_storage_map2, sock->sk, 0,
167				     BPF_LOCAL_STORAGE_GET_F_CREATE);
168	if (!storage)
169		return 0;
170
171	if (bpf_sk_storage_delete(&sk_storage_map, sock->sk))
172		return 0;
173
174	/* Ensure that the sk_storage_map is disconnected from the storage. */
175	if (!sock->sk->sk_bpf_storage || sock->sk->sk_bpf_storage->smap)
176		return 0;
177
178	sk_storage_result = 0;
179	return 0;
180}
181
182SEC("lsm.s/socket_post_create")
183int BPF_PROG(socket_post_create, struct socket *sock, int family, int type,
184	     int protocol, int kern)
185{
186	__u32 pid = bpf_get_current_pid_tgid() >> 32;
187	struct local_storage *storage;
188
189	if (pid != monitored_pid)
190		return 0;
191
192	storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0,
193				     BPF_LOCAL_STORAGE_GET_F_CREATE);
194	if (!storage)
195		return 0;
196
197	storage->value = DUMMY_STORAGE_VALUE;
198
199	return 0;
200}
201
202/* This uses the local storage to remember the inode of the binary that a
203 * process was originally executing.
204 */
205SEC("lsm.s/bprm_committed_creds")
206void BPF_PROG(exec, struct linux_binprm *bprm)
207{
208	__u32 pid = bpf_get_current_pid_tgid() >> 32;
209	struct local_storage *storage;
210
211	if (pid != monitored_pid)
212		return;
213
214	storage = bpf_task_storage_get(&task_storage_map,
215				       bpf_get_current_task_btf(), 0,
216				       BPF_LOCAL_STORAGE_GET_F_CREATE);
217	if (storage)
218		storage->exec_inode = bprm->file->f_inode;
219
220	storage = bpf_inode_storage_get(&inode_storage_map, bprm->file->f_inode,
221					0, BPF_LOCAL_STORAGE_GET_F_CREATE);
222	if (!storage)
223		return;
224
225	storage->value = DUMMY_STORAGE_VALUE;
226}
227