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