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