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 bool bpf_token_capable(const struct bpf_token *token, int cap) 13 { 14 /* BPF token allows ns_capable() level of capabilities, but only if 15 * token's userns is *exactly* the same as current user's userns 16 */ 17 if (token && current_user_ns() == token->userns) { 18 if (ns_capable(token->userns, cap) || 19 (cap != CAP_SYS_ADMIN && ns_capable(token->userns, CAP_SYS_ADMIN))) 20 return security_bpf_token_capable(token, cap) == 0; 21 } 22 /* otherwise fallback to capable() checks */ 23 return capable(cap) || (cap != CAP_SYS_ADMIN && capable(CAP_SYS_ADMIN)); 24 } 25 26 void bpf_token_inc(struct bpf_token *token) 27 { 28 atomic64_inc(&token->refcnt); 29 } 30 31 static void bpf_token_free(struct bpf_token *token) 32 { 33 security_bpf_token_free(token); 34 put_user_ns(token->userns); 35 kvfree(token); 36 } 37 38 static void bpf_token_put_deferred(struct work_struct *work) 39 { 40 struct bpf_token *token = container_of(work, struct bpf_token, work); 41 42 bpf_token_free(token); 43 } 44 45 void bpf_token_put(struct bpf_token *token) 46 { 47 if (!token) 48 return; 49 50 if (!atomic64_dec_and_test(&token->refcnt)) 51 return; 52 53 INIT_WORK(&token->work, bpf_token_put_deferred); 54 schedule_work(&token->work); 55 } 56 57 static int bpf_token_release(struct inode *inode, struct file *filp) 58 { 59 struct bpf_token *token = filp->private_data; 60 61 bpf_token_put(token); 62 return 0; 63 } 64 65 static void bpf_token_show_fdinfo(struct seq_file *m, struct file *filp) 66 { 67 struct bpf_token *token = filp->private_data; 68 u64 mask; 69 70 BUILD_BUG_ON(__MAX_BPF_CMD >= 64); 71 mask = (1ULL << __MAX_BPF_CMD) - 1; 72 if ((token->allowed_cmds & mask) == mask) 73 seq_printf(m, "allowed_cmds:\tany\n"); 74 else 75 seq_printf(m, "allowed_cmds:\t0x%llx\n", token->allowed_cmds); 76 77 BUILD_BUG_ON(__MAX_BPF_MAP_TYPE >= 64); 78 mask = (1ULL << __MAX_BPF_MAP_TYPE) - 1; 79 if ((token->allowed_maps & mask) == mask) 80 seq_printf(m, "allowed_maps:\tany\n"); 81 else 82 seq_printf(m, "allowed_maps:\t0x%llx\n", token->allowed_maps); 83 84 BUILD_BUG_ON(__MAX_BPF_PROG_TYPE >= 64); 85 mask = (1ULL << __MAX_BPF_PROG_TYPE) - 1; 86 if ((token->allowed_progs & mask) == mask) 87 seq_printf(m, "allowed_progs:\tany\n"); 88 else 89 seq_printf(m, "allowed_progs:\t0x%llx\n", token->allowed_progs); 90 91 BUILD_BUG_ON(__MAX_BPF_ATTACH_TYPE >= 64); 92 mask = (1ULL << __MAX_BPF_ATTACH_TYPE) - 1; 93 if ((token->allowed_attachs & mask) == mask) 94 seq_printf(m, "allowed_attachs:\tany\n"); 95 else 96 seq_printf(m, "allowed_attachs:\t0x%llx\n", token->allowed_attachs); 97 } 98 99 #define BPF_TOKEN_INODE_NAME "bpf-token" 100 101 static const struct inode_operations bpf_token_iops = { }; 102 103 static const struct file_operations bpf_token_fops = { 104 .release = bpf_token_release, 105 .show_fdinfo = bpf_token_show_fdinfo, 106 }; 107 108 int bpf_token_create(union bpf_attr *attr) 109 { 110 struct bpf_mount_opts *mnt_opts; 111 struct bpf_token *token = NULL; 112 struct user_namespace *userns; 113 struct inode *inode; 114 struct file *file; 115 struct path path; 116 struct fd f; 117 umode_t mode; 118 int err, fd; 119 120 f = fdget(attr->token_create.bpffs_fd); 121 if (!f.file) 122 return -EBADF; 123 124 path = f.file->f_path; 125 path_get(&path); 126 fdput(f); 127 128 if (path.dentry != path.mnt->mnt_sb->s_root) { 129 err = -EINVAL; 130 goto out_path; 131 } 132 if (path.mnt->mnt_sb->s_op != &bpf_super_ops) { 133 err = -EINVAL; 134 goto out_path; 135 } 136 err = path_permission(&path, MAY_ACCESS); 137 if (err) 138 goto out_path; 139 140 userns = path.dentry->d_sb->s_user_ns; 141 /* 142 * Enforce that creators of BPF tokens are in the same user 143 * namespace as the BPF FS instance. This makes reasoning about 144 * permissions a lot easier and we can always relax this later. 145 */ 146 if (current_user_ns() != userns) { 147 err = -EPERM; 148 goto out_path; 149 } 150 if (!ns_capable(userns, CAP_BPF)) { 151 err = -EPERM; 152 goto out_path; 153 } 154 155 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 156 inode = bpf_get_inode(path.mnt->mnt_sb, NULL, mode); 157 if (IS_ERR(inode)) { 158 err = PTR_ERR(inode); 159 goto out_path; 160 } 161 162 inode->i_op = &bpf_token_iops; 163 inode->i_fop = &bpf_token_fops; 164 clear_nlink(inode); /* make sure it is unlinked */ 165 166 file = alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, O_RDWR, &bpf_token_fops); 167 if (IS_ERR(file)) { 168 iput(inode); 169 err = PTR_ERR(file); 170 goto out_path; 171 } 172 173 token = kvzalloc(sizeof(*token), GFP_USER); 174 if (!token) { 175 err = -ENOMEM; 176 goto out_file; 177 } 178 179 atomic64_set(&token->refcnt, 1); 180 181 /* remember bpffs owning userns for future ns_capable() checks */ 182 token->userns = get_user_ns(userns); 183 184 mnt_opts = path.dentry->d_sb->s_fs_info; 185 token->allowed_cmds = mnt_opts->delegate_cmds; 186 token->allowed_maps = mnt_opts->delegate_maps; 187 token->allowed_progs = mnt_opts->delegate_progs; 188 token->allowed_attachs = mnt_opts->delegate_attachs; 189 190 err = security_bpf_token_create(token, attr, &path); 191 if (err) 192 goto out_token; 193 194 fd = get_unused_fd_flags(O_CLOEXEC); 195 if (fd < 0) { 196 err = fd; 197 goto out_token; 198 } 199 200 file->private_data = token; 201 fd_install(fd, file); 202 203 path_put(&path); 204 return fd; 205 206 out_token: 207 bpf_token_free(token); 208 out_file: 209 fput(file); 210 out_path: 211 path_put(&path); 212 return err; 213 } 214 215 struct bpf_token *bpf_token_get_from_fd(u32 ufd) 216 { 217 struct fd f = fdget(ufd); 218 struct bpf_token *token; 219 220 if (!f.file) 221 return ERR_PTR(-EBADF); 222 if (f.file->f_op != &bpf_token_fops) { 223 fdput(f); 224 return ERR_PTR(-EINVAL); 225 } 226 227 token = f.file->private_data; 228 bpf_token_inc(token); 229 fdput(f); 230 231 return token; 232 } 233 234 bool bpf_token_allow_cmd(const struct bpf_token *token, enum bpf_cmd cmd) 235 { 236 /* BPF token can be used only within exactly the same userns in which 237 * it was created 238 */ 239 if (!token || current_user_ns() != token->userns) 240 return false; 241 if (!(token->allowed_cmds & (1ULL << cmd))) 242 return false; 243 return security_bpf_token_cmd(token, cmd) == 0; 244 } 245 246 bool bpf_token_allow_map_type(const struct bpf_token *token, enum bpf_map_type type) 247 { 248 if (!token || type >= __MAX_BPF_MAP_TYPE) 249 return false; 250 251 return token->allowed_maps & (1ULL << type); 252 } 253 254 bool bpf_token_allow_prog_type(const struct bpf_token *token, 255 enum bpf_prog_type prog_type, 256 enum bpf_attach_type attach_type) 257 { 258 if (!token || prog_type >= __MAX_BPF_PROG_TYPE || attach_type >= __MAX_BPF_ATTACH_TYPE) 259 return false; 260 261 return (token->allowed_progs & (1ULL << prog_type)) && 262 (token->allowed_attachs & (1ULL << attach_type)); 263 } 264