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 12 char _license[] SEC("license") = "GPL"; 13 14 #define DUMMY_STORAGE_VALUE 0xdeadbeef 15 16 int monitored_pid = 0; 17 int inode_storage_result = -1; 18 int sk_storage_result = -1; 19 20 struct local_storage { 21 struct inode *exec_inode; 22 __u32 value; 23 }; 24 25 struct { 26 __uint(type, BPF_MAP_TYPE_INODE_STORAGE); 27 __uint(map_flags, BPF_F_NO_PREALLOC); 28 __type(key, int); 29 __type(value, struct local_storage); 30 } inode_storage_map SEC(".maps"); 31 32 struct { 33 __uint(type, BPF_MAP_TYPE_SK_STORAGE); 34 __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE); 35 __type(key, int); 36 __type(value, struct local_storage); 37 } sk_storage_map SEC(".maps"); 38 39 struct { 40 __uint(type, BPF_MAP_TYPE_SK_STORAGE); 41 __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE); 42 __type(key, int); 43 __type(value, struct local_storage); 44 } sk_storage_map2 SEC(".maps"); 45 46 struct { 47 __uint(type, BPF_MAP_TYPE_TASK_STORAGE); 48 __uint(map_flags, BPF_F_NO_PREALLOC); 49 __type(key, int); 50 __type(value, struct local_storage); 51 } task_storage_map SEC(".maps"); 52 53 SEC("lsm/inode_unlink") 54 int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim) 55 { 56 __u32 pid = bpf_get_current_pid_tgid() >> 32; 57 struct local_storage *storage; 58 bool is_self_unlink; 59 60 if (pid != monitored_pid) 61 return 0; 62 63 storage = bpf_task_storage_get(&task_storage_map, 64 bpf_get_current_task_btf(), 0, 0); 65 if (storage) { 66 /* Don't let an executable delete itself */ 67 is_self_unlink = storage->exec_inode == victim->d_inode; 68 if (is_self_unlink) 69 return -EPERM; 70 } 71 72 return 0; 73 } 74 75 SEC("lsm.s/inode_rename") 76 int BPF_PROG(inode_rename, struct inode *old_dir, struct dentry *old_dentry, 77 struct inode *new_dir, struct dentry *new_dentry, 78 unsigned int flags) 79 { 80 __u32 pid = bpf_get_current_pid_tgid() >> 32; 81 struct local_storage *storage; 82 int err; 83 84 /* new_dentry->d_inode can be NULL when the inode is renamed to a file 85 * that did not exist before. The helper should be able to handle this 86 * NULL pointer. 87 */ 88 bpf_inode_storage_get(&inode_storage_map, new_dentry->d_inode, 0, 89 BPF_LOCAL_STORAGE_GET_F_CREATE); 90 91 storage = bpf_inode_storage_get(&inode_storage_map, old_dentry->d_inode, 92 0, 0); 93 if (!storage) 94 return 0; 95 96 if (storage->value != DUMMY_STORAGE_VALUE) 97 inode_storage_result = -1; 98 99 err = bpf_inode_storage_delete(&inode_storage_map, old_dentry->d_inode); 100 if (!err) 101 inode_storage_result = err; 102 103 return 0; 104 } 105 106 SEC("lsm.s/socket_bind") 107 int BPF_PROG(socket_bind, struct socket *sock, struct sockaddr *address, 108 int addrlen) 109 { 110 __u32 pid = bpf_get_current_pid_tgid() >> 32; 111 struct local_storage *storage; 112 int err; 113 114 if (pid != monitored_pid) 115 return 0; 116 117 storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0, 118 BPF_LOCAL_STORAGE_GET_F_CREATE); 119 if (!storage) 120 return 0; 121 122 if (storage->value != DUMMY_STORAGE_VALUE) 123 sk_storage_result = -1; 124 125 /* This tests that we can associate multiple elements 126 * with the local storage. 127 */ 128 storage = bpf_sk_storage_get(&sk_storage_map2, sock->sk, 0, 129 BPF_LOCAL_STORAGE_GET_F_CREATE); 130 if (!storage) 131 return 0; 132 133 err = bpf_sk_storage_delete(&sk_storage_map, sock->sk); 134 if (err) 135 return 0; 136 137 err = bpf_sk_storage_delete(&sk_storage_map2, sock->sk); 138 if (!err) 139 sk_storage_result = err; 140 141 return 0; 142 } 143 144 SEC("lsm.s/socket_post_create") 145 int BPF_PROG(socket_post_create, struct socket *sock, int family, int type, 146 int protocol, int kern) 147 { 148 __u32 pid = bpf_get_current_pid_tgid() >> 32; 149 struct local_storage *storage; 150 151 if (pid != monitored_pid) 152 return 0; 153 154 storage = bpf_sk_storage_get(&sk_storage_map, sock->sk, 0, 155 BPF_LOCAL_STORAGE_GET_F_CREATE); 156 if (!storage) 157 return 0; 158 159 storage->value = DUMMY_STORAGE_VALUE; 160 161 return 0; 162 } 163 164 /* This uses the local storage to remember the inode of the binary that a 165 * process was originally executing. 166 */ 167 SEC("lsm.s/bprm_committed_creds") 168 void BPF_PROG(exec, struct linux_binprm *bprm) 169 { 170 __u32 pid = bpf_get_current_pid_tgid() >> 32; 171 struct local_storage *storage; 172 173 if (pid != monitored_pid) 174 return; 175 176 storage = bpf_task_storage_get(&task_storage_map, 177 bpf_get_current_task_btf(), 0, 178 BPF_LOCAL_STORAGE_GET_F_CREATE); 179 if (storage) 180 storage->exec_inode = bprm->file->f_inode; 181 182 storage = bpf_inode_storage_get(&inode_storage_map, bprm->file->f_inode, 183 0, BPF_LOCAL_STORAGE_GET_F_CREATE); 184 if (!storage) 185 return; 186 187 storage->value = DUMMY_STORAGE_VALUE; 188 } 189