1 #include <linux/bpf.h> 2 #include <linux/vmalloc.h> 3 #include <linux/fdtable.h> 4 #include <linux/file.h> 5 #include <linux/fs.h> 6 #include <linux/kernel.h> 7 #include <linux/idr.h> 8 #include <linux/namei.h> 9 #include <linux/user_namespace.h> 10 #include <linux/security.h> 11 12 static bool bpf_ns_capable(struct user_namespace *ns, int cap) 13 { 14 return ns_capable(ns, cap) || (cap != CAP_SYS_ADMIN && ns_capable(ns, CAP_SYS_ADMIN)); 15 } 16 17 bool bpf_token_capable(const struct bpf_token *token, int cap) 18 { 19 struct user_namespace *userns; 20 21 /* BPF token allows ns_capable() level of capabilities */ 22 userns = token ? token->userns : &init_user_ns; 23 if (!bpf_ns_capable(userns, cap)) 24 return false; 25 if (token && security_bpf_token_capable(token, cap) < 0) 26 return false; 27 return true; 28 } 29 30 void bpf_token_inc(struct bpf_token *token) 31 { 32 atomic64_inc(&token->refcnt); 33 } 34 35 static void bpf_token_free(struct bpf_token *token) 36 { 37 security_bpf_token_free(token); 38 put_user_ns(token->userns); 39 kfree(token); 40 } 41 42 static void bpf_token_put_deferred(struct work_struct *work) 43 { 44 struct bpf_token *token = container_of(work, struct bpf_token, work); 45 46 bpf_token_free(token); 47 } 48 49 void bpf_token_put(struct bpf_token *token) 50 { 51 if (!token) 52 return; 53 54 if (!atomic64_dec_and_test(&token->refcnt)) 55 return; 56 57 INIT_WORK(&token->work, bpf_token_put_deferred); 58 schedule_work(&token->work); 59 } 60 61 static int bpf_token_release(struct inode *inode, struct file *filp) 62 { 63 struct bpf_token *token = filp->private_data; 64 65 bpf_token_put(token); 66 return 0; 67 } 68 69 static void bpf_token_show_fdinfo(struct seq_file *m, struct file *filp) 70 { 71 struct bpf_token *token = filp->private_data; 72 u64 mask; 73 74 BUILD_BUG_ON(__MAX_BPF_CMD >= 64); 75 mask = (1ULL << __MAX_BPF_CMD) - 1; 76 if ((token->allowed_cmds & mask) == mask) 77 seq_printf(m, "allowed_cmds:\tany\n"); 78 else 79 seq_printf(m, "allowed_cmds:\t0x%llx\n", token->allowed_cmds); 80 81 BUILD_BUG_ON(__MAX_BPF_MAP_TYPE >= 64); 82 mask = (1ULL << __MAX_BPF_MAP_TYPE) - 1; 83 if ((token->allowed_maps & mask) == mask) 84 seq_printf(m, "allowed_maps:\tany\n"); 85 else 86 seq_printf(m, "allowed_maps:\t0x%llx\n", token->allowed_maps); 87 88 BUILD_BUG_ON(__MAX_BPF_PROG_TYPE >= 64); 89 mask = (1ULL << __MAX_BPF_PROG_TYPE) - 1; 90 if ((token->allowed_progs & mask) == mask) 91 seq_printf(m, "allowed_progs:\tany\n"); 92 else 93 seq_printf(m, "allowed_progs:\t0x%llx\n", token->allowed_progs); 94 95 BUILD_BUG_ON(__MAX_BPF_ATTACH_TYPE >= 64); 96 mask = (1ULL << __MAX_BPF_ATTACH_TYPE) - 1; 97 if ((token->allowed_attachs & mask) == mask) 98 seq_printf(m, "allowed_attachs:\tany\n"); 99 else 100 seq_printf(m, "allowed_attachs:\t0x%llx\n", token->allowed_attachs); 101 } 102 103 #define BPF_TOKEN_INODE_NAME "bpf-token" 104 105 static const struct inode_operations bpf_token_iops = { }; 106 107 static const struct file_operations bpf_token_fops = { 108 .release = bpf_token_release, 109 .show_fdinfo = bpf_token_show_fdinfo, 110 }; 111 112 int bpf_token_create(union bpf_attr *attr) 113 { 114 struct bpf_mount_opts *mnt_opts; 115 struct bpf_token *token = NULL; 116 struct user_namespace *userns; 117 struct inode *inode; 118 struct file *file; 119 struct path path; 120 struct fd f; 121 umode_t mode; 122 int err, fd; 123 124 f = fdget(attr->token_create.bpffs_fd); 125 if (!f.file) 126 return -EBADF; 127 128 path = f.file->f_path; 129 path_get(&path); 130 fdput(f); 131 132 if (path.dentry != path.mnt->mnt_sb->s_root) { 133 err = -EINVAL; 134 goto out_path; 135 } 136 if (path.mnt->mnt_sb->s_op != &bpf_super_ops) { 137 err = -EINVAL; 138 goto out_path; 139 } 140 err = path_permission(&path, MAY_ACCESS); 141 if (err) 142 goto out_path; 143 144 userns = path.dentry->d_sb->s_user_ns; 145 /* 146 * Enforce that creators of BPF tokens are in the same user 147 * namespace as the BPF FS instance. This makes reasoning about 148 * permissions a lot easier and we can always relax this later. 149 */ 150 if (current_user_ns() != userns) { 151 err = -EPERM; 152 goto out_path; 153 } 154 if (!ns_capable(userns, CAP_BPF)) { 155 err = -EPERM; 156 goto out_path; 157 } 158 159 /* Creating BPF token in init_user_ns doesn't make much sense. */ 160 if (current_user_ns() == &init_user_ns) { 161 err = -EOPNOTSUPP; 162 goto out_path; 163 } 164 165 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 166 inode = bpf_get_inode(path.mnt->mnt_sb, NULL, mode); 167 if (IS_ERR(inode)) { 168 err = PTR_ERR(inode); 169 goto out_path; 170 } 171 172 inode->i_op = &bpf_token_iops; 173 inode->i_fop = &bpf_token_fops; 174 clear_nlink(inode); /* make sure it is unlinked */ 175 176 file = alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, O_RDWR, &bpf_token_fops); 177 if (IS_ERR(file)) { 178 iput(inode); 179 err = PTR_ERR(file); 180 goto out_path; 181 } 182 183 token = kzalloc(sizeof(*token), GFP_USER); 184 if (!token) { 185 err = -ENOMEM; 186 goto out_file; 187 } 188 189 atomic64_set(&token->refcnt, 1); 190 191 /* remember bpffs owning userns for future ns_capable() checks */ 192 token->userns = get_user_ns(userns); 193 194 mnt_opts = path.dentry->d_sb->s_fs_info; 195 token->allowed_cmds = mnt_opts->delegate_cmds; 196 token->allowed_maps = mnt_opts->delegate_maps; 197 token->allowed_progs = mnt_opts->delegate_progs; 198 token->allowed_attachs = mnt_opts->delegate_attachs; 199 200 err = security_bpf_token_create(token, attr, &path); 201 if (err) 202 goto out_token; 203 204 fd = get_unused_fd_flags(O_CLOEXEC); 205 if (fd < 0) { 206 err = fd; 207 goto out_token; 208 } 209 210 file->private_data = token; 211 fd_install(fd, file); 212 213 path_put(&path); 214 return fd; 215 216 out_token: 217 bpf_token_free(token); 218 out_file: 219 fput(file); 220 out_path: 221 path_put(&path); 222 return err; 223 } 224 225 struct bpf_token *bpf_token_get_from_fd(u32 ufd) 226 { 227 struct fd f = fdget(ufd); 228 struct bpf_token *token; 229 230 if (!f.file) 231 return ERR_PTR(-EBADF); 232 if (f.file->f_op != &bpf_token_fops) { 233 fdput(f); 234 return ERR_PTR(-EINVAL); 235 } 236 237 token = f.file->private_data; 238 bpf_token_inc(token); 239 fdput(f); 240 241 return token; 242 } 243 244 bool bpf_token_allow_cmd(const struct bpf_token *token, enum bpf_cmd cmd) 245 { 246 if (!token) 247 return false; 248 if (!(token->allowed_cmds & (1ULL << cmd))) 249 return false; 250 return security_bpf_token_cmd(token, cmd) == 0; 251 } 252 253 bool bpf_token_allow_map_type(const struct bpf_token *token, enum bpf_map_type type) 254 { 255 if (!token || type >= __MAX_BPF_MAP_TYPE) 256 return false; 257 258 return token->allowed_maps & (1ULL << type); 259 } 260 261 bool bpf_token_allow_prog_type(const struct bpf_token *token, 262 enum bpf_prog_type prog_type, 263 enum bpf_attach_type attach_type) 264 { 265 if (!token || prog_type >= __MAX_BPF_PROG_TYPE || attach_type >= __MAX_BPF_ATTACH_TYPE) 266 return false; 267 268 return (token->allowed_progs & (1ULL << prog_type)) && 269 (token->allowed_attachs & (1ULL << attach_type)); 270 } 271