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 = BIT_ULL(__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 = BIT_ULL(__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 = BIT_ULL(__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 = BIT_ULL(__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 CLASS(fd, f)(attr->token_create.bpffs_fd); 120 struct path path; 121 struct super_block *sb; 122 umode_t mode; 123 int err, fd; 124 125 if (fd_empty(f)) 126 return -EBADF; 127 128 path = fd_file(f)->f_path; 129 sb = path.dentry->d_sb; 130 131 if (path.dentry != sb->s_root) 132 return -EINVAL; 133 if (sb->s_op != &bpf_super_ops) 134 return -EINVAL; 135 err = path_permission(&path, MAY_ACCESS); 136 if (err) 137 return err; 138 139 userns = sb->s_user_ns; 140 /* 141 * Enforce that creators of BPF tokens are in the same user 142 * namespace as the BPF FS instance. This makes reasoning about 143 * permissions a lot easier and we can always relax this later. 144 */ 145 if (current_user_ns() != userns) 146 return -EPERM; 147 if (!ns_capable(userns, CAP_BPF)) 148 return -EPERM; 149 150 /* Creating BPF token in init_user_ns doesn't make much sense. */ 151 if (current_user_ns() == &init_user_ns) 152 return -EOPNOTSUPP; 153 154 mnt_opts = sb->s_fs_info; 155 if (mnt_opts->delegate_cmds == 0 && 156 mnt_opts->delegate_maps == 0 && 157 mnt_opts->delegate_progs == 0 && 158 mnt_opts->delegate_attachs == 0) 159 return -ENOENT; /* no BPF token delegation is set up */ 160 161 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 162 inode = bpf_get_inode(sb, NULL, mode); 163 if (IS_ERR(inode)) 164 return PTR_ERR(inode); 165 166 inode->i_op = &bpf_token_iops; 167 inode->i_fop = &bpf_token_fops; 168 clear_nlink(inode); /* make sure it is unlinked */ 169 170 file = alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, O_RDWR, &bpf_token_fops); 171 if (IS_ERR(file)) { 172 iput(inode); 173 return PTR_ERR(file); 174 } 175 176 token = kzalloc(sizeof(*token), GFP_USER); 177 if (!token) { 178 err = -ENOMEM; 179 goto out_file; 180 } 181 182 atomic64_set(&token->refcnt, 1); 183 184 /* remember bpffs owning userns for future ns_capable() checks */ 185 token->userns = get_user_ns(userns); 186 187 token->allowed_cmds = mnt_opts->delegate_cmds; 188 token->allowed_maps = mnt_opts->delegate_maps; 189 token->allowed_progs = mnt_opts->delegate_progs; 190 token->allowed_attachs = mnt_opts->delegate_attachs; 191 192 err = security_bpf_token_create(token, attr, &path); 193 if (err) 194 goto out_token; 195 196 fd = get_unused_fd_flags(O_CLOEXEC); 197 if (fd < 0) { 198 err = fd; 199 goto out_token; 200 } 201 202 file->private_data = token; 203 fd_install(fd, file); 204 205 return fd; 206 207 out_token: 208 bpf_token_free(token); 209 out_file: 210 fput(file); 211 return err; 212 } 213 214 struct bpf_token *bpf_token_get_from_fd(u32 ufd) 215 { 216 CLASS(fd, f)(ufd); 217 struct bpf_token *token; 218 219 if (fd_empty(f)) 220 return ERR_PTR(-EBADF); 221 if (fd_file(f)->f_op != &bpf_token_fops) 222 return ERR_PTR(-EINVAL); 223 224 token = fd_file(f)->private_data; 225 bpf_token_inc(token); 226 227 return token; 228 } 229 230 bool bpf_token_allow_cmd(const struct bpf_token *token, enum bpf_cmd cmd) 231 { 232 if (!token) 233 return false; 234 if (!(token->allowed_cmds & BIT_ULL(cmd))) 235 return false; 236 return security_bpf_token_cmd(token, cmd) == 0; 237 } 238 239 bool bpf_token_allow_map_type(const struct bpf_token *token, enum bpf_map_type type) 240 { 241 if (!token || type >= __MAX_BPF_MAP_TYPE) 242 return false; 243 244 return token->allowed_maps & BIT_ULL(type); 245 } 246 247 bool bpf_token_allow_prog_type(const struct bpf_token *token, 248 enum bpf_prog_type prog_type, 249 enum bpf_attach_type attach_type) 250 { 251 if (!token || prog_type >= __MAX_BPF_PROG_TYPE || attach_type >= __MAX_BPF_ATTACH_TYPE) 252 return false; 253 254 return (token->allowed_progs & BIT_ULL(prog_type)) && 255 (token->allowed_attachs & BIT_ULL(attach_type)); 256 } 257