1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/bpf.h> 3 #include <linux/vmalloc.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 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_token *token __free(kfree) = NULL; 115 struct bpf_mount_opts *mnt_opts; 116 struct user_namespace *userns; 117 struct inode *inode; 118 CLASS(fd, f)(attr->token_create.bpffs_fd); 119 struct path path; 120 struct super_block *sb; 121 umode_t mode; 122 int err; 123 124 if (fd_empty(f)) 125 return -EBADF; 126 127 path = fd_file(f)->f_path; 128 sb = path.dentry->d_sb; 129 130 if (path.dentry != sb->s_root) 131 return -EINVAL; 132 if (sb->s_op != &bpf_super_ops) 133 return -EINVAL; 134 err = path_permission(&path, MAY_ACCESS); 135 if (err) 136 return err; 137 138 userns = sb->s_user_ns; 139 /* 140 * Enforce that creators of BPF tokens are in the same user 141 * namespace as the BPF FS instance. This makes reasoning about 142 * permissions a lot easier and we can always relax this later. 143 */ 144 if (current_user_ns() != userns) 145 return -EPERM; 146 if (!ns_capable(userns, CAP_BPF)) 147 return -EPERM; 148 149 /* Creating BPF token in init_user_ns doesn't make much sense. */ 150 if (current_user_ns() == &init_user_ns) 151 return -EOPNOTSUPP; 152 153 mnt_opts = sb->s_fs_info; 154 if (mnt_opts->delegate_cmds == 0 && 155 mnt_opts->delegate_maps == 0 && 156 mnt_opts->delegate_progs == 0 && 157 mnt_opts->delegate_attachs == 0) 158 return -ENOENT; /* no BPF token delegation is set up */ 159 160 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 161 inode = bpf_get_inode(sb, NULL, mode); 162 if (IS_ERR(inode)) 163 return PTR_ERR(inode); 164 165 inode->i_op = &bpf_token_iops; 166 inode->i_fop = &bpf_token_fops; 167 clear_nlink(inode); /* make sure it is unlinked */ 168 169 FD_PREPARE(fdf, O_CLOEXEC, 170 alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, 171 O_RDWR, &bpf_token_fops)); 172 if (fdf.err) 173 return fdf.err; 174 175 token = kzalloc(sizeof(*token), GFP_USER); 176 if (!token) 177 return -ENOMEM; 178 179 atomic64_set(&token->refcnt, 1); 180 181 /* remember bpffs owning userns for future ns_capable() checks. */ 182 token->userns = userns; 183 token->allowed_cmds = mnt_opts->delegate_cmds; 184 token->allowed_maps = mnt_opts->delegate_maps; 185 token->allowed_progs = mnt_opts->delegate_progs; 186 token->allowed_attachs = mnt_opts->delegate_attachs; 187 188 err = security_bpf_token_create(token, attr, &path); 189 if (err) 190 return err; 191 192 get_user_ns(token->userns); 193 fd_prepare_file(fdf)->private_data = no_free_ptr(token); 194 return fd_publish(fdf); 195 } 196 197 int bpf_token_get_info_by_fd(struct bpf_token *token, 198 const union bpf_attr *attr, 199 union bpf_attr __user *uattr) 200 { 201 struct bpf_token_info __user *uinfo = u64_to_user_ptr(attr->info.info); 202 struct bpf_token_info info; 203 u32 info_len = attr->info.info_len; 204 205 info_len = min_t(u32, info_len, sizeof(info)); 206 memset(&info, 0, sizeof(info)); 207 208 info.allowed_cmds = token->allowed_cmds; 209 info.allowed_maps = token->allowed_maps; 210 info.allowed_progs = token->allowed_progs; 211 info.allowed_attachs = token->allowed_attachs; 212 213 if (copy_to_user(uinfo, &info, info_len) || 214 put_user(info_len, &uattr->info.info_len)) 215 return -EFAULT; 216 217 return 0; 218 } 219 220 struct bpf_token *bpf_token_get_from_fd(u32 ufd) 221 { 222 CLASS(fd, f)(ufd); 223 struct bpf_token *token; 224 225 if (fd_empty(f)) 226 return ERR_PTR(-EBADF); 227 if (fd_file(f)->f_op != &bpf_token_fops) 228 return ERR_PTR(-EINVAL); 229 230 token = fd_file(f)->private_data; 231 bpf_token_inc(token); 232 233 return token; 234 } 235 236 bool bpf_token_allow_cmd(const struct bpf_token *token, enum bpf_cmd cmd) 237 { 238 if (!token) 239 return false; 240 if (!(token->allowed_cmds & BIT_ULL(cmd))) 241 return false; 242 return security_bpf_token_cmd(token, cmd) == 0; 243 } 244 245 bool bpf_token_allow_map_type(const struct bpf_token *token, enum bpf_map_type type) 246 { 247 if (!token || type >= __MAX_BPF_MAP_TYPE) 248 return false; 249 250 return token->allowed_maps & BIT_ULL(type); 251 } 252 253 bool bpf_token_allow_prog_type(const struct bpf_token *token, 254 enum bpf_prog_type prog_type, 255 enum bpf_attach_type attach_type) 256 { 257 if (!token || prog_type >= __MAX_BPF_PROG_TYPE || attach_type >= __MAX_BPF_ATTACH_TYPE) 258 return false; 259 260 return (token->allowed_progs & BIT_ULL(prog_type)) && 261 (token->allowed_attachs & BIT_ULL(attach_type)); 262 } 263