Eric W. Biederman | 77b14db | 2007-02-14 00:34:12 -0800 | [diff] [blame] | 1 | /* |
| 2 | * /proc/sys support |
| 3 | */ |
| 4 | |
| 5 | #include <linux/sysctl.h> |
| 6 | #include <linux/proc_fs.h> |
| 7 | #include <linux/security.h> |
| 8 | #include "internal.h" |
| 9 | |
| 10 | static struct dentry_operations proc_sys_dentry_operations; |
| 11 | static const struct file_operations proc_sys_file_operations; |
| 12 | static struct inode_operations proc_sys_inode_operations; |
| 13 | |
| 14 | static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table) |
| 15 | { |
| 16 | /* Refresh the cached information bits in the inode */ |
| 17 | if (table) { |
| 18 | inode->i_uid = 0; |
| 19 | inode->i_gid = 0; |
| 20 | inode->i_mode = table->mode; |
| 21 | if (table->proc_handler) { |
| 22 | inode->i_mode |= S_IFREG; |
| 23 | inode->i_nlink = 1; |
| 24 | } else { |
| 25 | inode->i_mode |= S_IFDIR; |
| 26 | inode->i_nlink = 0; /* It is too hard to figure out */ |
| 27 | } |
| 28 | } |
| 29 | } |
| 30 | |
| 31 | static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table) |
| 32 | { |
| 33 | struct inode *inode; |
| 34 | struct proc_inode *dir_ei, *ei; |
| 35 | int depth; |
| 36 | |
| 37 | inode = new_inode(dir->i_sb); |
| 38 | if (!inode) |
| 39 | goto out; |
| 40 | |
| 41 | /* A directory is always one deeper than it's parent */ |
| 42 | dir_ei = PROC_I(dir); |
| 43 | depth = dir_ei->fd + 1; |
| 44 | |
| 45 | ei = PROC_I(inode); |
| 46 | ei->fd = depth; |
| 47 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
| 48 | inode->i_op = &proc_sys_inode_operations; |
| 49 | inode->i_fop = &proc_sys_file_operations; |
Eric W. Biederman | 86a71db | 2007-02-14 00:34:16 -0800 | [diff] [blame] | 50 | inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */ |
Eric W. Biederman | 77b14db | 2007-02-14 00:34:12 -0800 | [diff] [blame] | 51 | proc_sys_refresh_inode(inode, table); |
| 52 | out: |
| 53 | return inode; |
| 54 | } |
| 55 | |
| 56 | static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth) |
| 57 | { |
| 58 | for (;;) { |
| 59 | struct proc_inode *ei; |
| 60 | |
| 61 | ei = PROC_I(dentry->d_inode); |
| 62 | if (ei->fd == depth) |
| 63 | break; /* found */ |
| 64 | |
| 65 | dentry = dentry->d_parent; |
| 66 | } |
| 67 | return dentry; |
| 68 | } |
| 69 | |
| 70 | static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table, |
| 71 | struct qstr *name) |
| 72 | { |
| 73 | int len; |
| 74 | for ( ; table->ctl_name || table->procname; table++) { |
| 75 | |
| 76 | if (!table->procname) |
| 77 | continue; |
| 78 | |
| 79 | len = strlen(table->procname); |
| 80 | if (len != name->len) |
| 81 | continue; |
| 82 | |
| 83 | if (memcmp(table->procname, name->name, len) != 0) |
| 84 | continue; |
| 85 | |
| 86 | /* I have a match */ |
| 87 | return table; |
| 88 | } |
| 89 | return NULL; |
| 90 | } |
| 91 | |
| 92 | static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry, |
| 93 | struct ctl_table *table) |
| 94 | { |
| 95 | struct dentry *ancestor; |
| 96 | struct proc_inode *ei; |
| 97 | int depth, i; |
| 98 | |
| 99 | ei = PROC_I(dentry->d_inode); |
| 100 | depth = ei->fd; |
| 101 | |
| 102 | if (depth == 0) |
| 103 | return table; |
| 104 | |
| 105 | for (i = 1; table && (i <= depth); i++) { |
| 106 | ancestor = proc_sys_ancestor(dentry, i); |
| 107 | table = proc_sys_lookup_table_one(table, &ancestor->d_name); |
| 108 | if (table) |
| 109 | table = table->child; |
| 110 | } |
| 111 | return table; |
| 112 | |
| 113 | } |
| 114 | static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent, |
| 115 | struct qstr *name, |
| 116 | struct ctl_table *table) |
| 117 | { |
| 118 | table = proc_sys_lookup_table(dparent, table); |
| 119 | if (table) |
| 120 | table = proc_sys_lookup_table_one(table, name); |
| 121 | return table; |
| 122 | } |
| 123 | |
| 124 | static struct ctl_table *do_proc_sys_lookup(struct dentry *parent, |
| 125 | struct qstr *name, |
| 126 | struct ctl_table_header **ptr) |
| 127 | { |
| 128 | struct ctl_table_header *head; |
| 129 | struct ctl_table *table = NULL; |
| 130 | |
| 131 | for (head = sysctl_head_next(NULL); head; |
| 132 | head = sysctl_head_next(head)) { |
| 133 | table = proc_sys_lookup_entry(parent, name, head->ctl_table); |
| 134 | if (table) |
| 135 | break; |
| 136 | } |
| 137 | *ptr = head; |
| 138 | return table; |
| 139 | } |
| 140 | |
| 141 | static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, |
| 142 | struct nameidata *nd) |
| 143 | { |
| 144 | struct ctl_table_header *head; |
| 145 | struct inode *inode; |
| 146 | struct dentry *err; |
| 147 | struct ctl_table *table; |
| 148 | |
| 149 | err = ERR_PTR(-ENOENT); |
| 150 | table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); |
| 151 | if (!table) |
| 152 | goto out; |
| 153 | |
| 154 | err = ERR_PTR(-ENOMEM); |
| 155 | inode = proc_sys_make_inode(dir, table); |
| 156 | if (!inode) |
| 157 | goto out; |
| 158 | |
| 159 | err = NULL; |
| 160 | dentry->d_op = &proc_sys_dentry_operations; |
| 161 | d_add(dentry, inode); |
| 162 | |
| 163 | out: |
| 164 | sysctl_head_finish(head); |
| 165 | return err; |
| 166 | } |
| 167 | |
| 168 | static ssize_t proc_sys_read(struct file *filp, char __user *buf, |
| 169 | size_t count, loff_t *ppos) |
| 170 | { |
| 171 | struct dentry *dentry = filp->f_dentry; |
| 172 | struct ctl_table_header *head; |
| 173 | struct ctl_table *table; |
| 174 | ssize_t error, res; |
| 175 | |
| 176 | table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); |
| 177 | /* Has the sysctl entry disappeared on us? */ |
| 178 | error = -ENOENT; |
| 179 | if (!table) |
| 180 | goto out; |
| 181 | |
| 182 | /* Has the sysctl entry been replaced by a directory? */ |
| 183 | error = -EISDIR; |
| 184 | if (!table->proc_handler) |
| 185 | goto out; |
| 186 | |
| 187 | /* |
| 188 | * At this point we know that the sysctl was not unregistered |
| 189 | * and won't be until we finish. |
| 190 | */ |
| 191 | error = -EPERM; |
| 192 | if (sysctl_perm(table, MAY_READ)) |
| 193 | goto out; |
| 194 | |
| 195 | /* careful: calling conventions are nasty here */ |
| 196 | res = count; |
| 197 | error = table->proc_handler(table, 0, filp, buf, &res, ppos); |
| 198 | if (!error) |
| 199 | error = res; |
| 200 | out: |
| 201 | sysctl_head_finish(head); |
| 202 | |
| 203 | return error; |
| 204 | } |
| 205 | |
| 206 | static ssize_t proc_sys_write(struct file *filp, const char __user *buf, |
| 207 | size_t count, loff_t *ppos) |
| 208 | { |
| 209 | struct dentry *dentry = filp->f_dentry; |
| 210 | struct ctl_table_header *head; |
| 211 | struct ctl_table *table; |
| 212 | ssize_t error, res; |
| 213 | |
| 214 | table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); |
| 215 | /* Has the sysctl entry disappeared on us? */ |
| 216 | error = -ENOENT; |
| 217 | if (!table) |
| 218 | goto out; |
| 219 | |
| 220 | /* Has the sysctl entry been replaced by a directory? */ |
| 221 | error = -EISDIR; |
| 222 | if (!table->proc_handler) |
| 223 | goto out; |
| 224 | |
| 225 | /* |
| 226 | * At this point we know that the sysctl was not unregistered |
| 227 | * and won't be until we finish. |
| 228 | */ |
| 229 | error = -EPERM; |
| 230 | if (sysctl_perm(table, MAY_WRITE)) |
| 231 | goto out; |
| 232 | |
| 233 | /* careful: calling conventions are nasty here */ |
| 234 | res = count; |
| 235 | error = table->proc_handler(table, 1, filp, (char __user *)buf, |
| 236 | &res, ppos); |
| 237 | if (!error) |
| 238 | error = res; |
| 239 | out: |
| 240 | sysctl_head_finish(head); |
| 241 | |
| 242 | return error; |
| 243 | } |
| 244 | |
| 245 | |
| 246 | static int proc_sys_fill_cache(struct file *filp, void *dirent, |
| 247 | filldir_t filldir, struct ctl_table *table) |
| 248 | { |
| 249 | struct ctl_table_header *head; |
| 250 | struct ctl_table *child_table = NULL; |
| 251 | struct dentry *child, *dir = filp->f_path.dentry; |
| 252 | struct inode *inode; |
| 253 | struct qstr qname; |
| 254 | ino_t ino = 0; |
| 255 | unsigned type = DT_UNKNOWN; |
| 256 | int ret; |
| 257 | |
| 258 | qname.name = table->procname; |
| 259 | qname.len = strlen(table->procname); |
| 260 | qname.hash = full_name_hash(qname.name, qname.len); |
| 261 | |
| 262 | /* Suppress duplicates. |
| 263 | * Only fill a directory entry if it is the value that |
| 264 | * an ordinary lookup of that name returns. Hide all |
| 265 | * others. |
| 266 | * |
| 267 | * If we ever cache this translation in the dcache |
| 268 | * I should do a dcache lookup first. But for now |
| 269 | * it is just simpler not to. |
| 270 | */ |
| 271 | ret = 0; |
| 272 | child_table = do_proc_sys_lookup(dir, &qname, &head); |
| 273 | sysctl_head_finish(head); |
| 274 | if (child_table != table) |
| 275 | return 0; |
| 276 | |
| 277 | child = d_lookup(dir, &qname); |
| 278 | if (!child) { |
| 279 | struct dentry *new; |
| 280 | new = d_alloc(dir, &qname); |
| 281 | if (new) { |
| 282 | inode = proc_sys_make_inode(dir->d_inode, table); |
| 283 | if (!inode) |
| 284 | child = ERR_PTR(-ENOMEM); |
| 285 | else { |
| 286 | new->d_op = &proc_sys_dentry_operations; |
| 287 | d_add(new, inode); |
| 288 | } |
| 289 | if (child) |
| 290 | dput(new); |
| 291 | else |
| 292 | child = new; |
| 293 | } |
| 294 | } |
| 295 | if (!child || IS_ERR(child) || !child->d_inode) |
| 296 | goto end_instantiate; |
| 297 | inode = child->d_inode; |
| 298 | if (inode) { |
| 299 | ino = inode->i_ino; |
| 300 | type = inode->i_mode >> 12; |
| 301 | } |
| 302 | dput(child); |
| 303 | end_instantiate: |
| 304 | if (!ino) |
| 305 | ino= find_inode_number(dir, &qname); |
| 306 | if (!ino) |
| 307 | ino = 1; |
| 308 | return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type); |
| 309 | } |
| 310 | |
| 311 | static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) |
| 312 | { |
| 313 | struct dentry *dentry = filp->f_dentry; |
| 314 | struct inode *inode = dentry->d_inode; |
| 315 | struct ctl_table_header *head = NULL; |
| 316 | struct ctl_table *table; |
| 317 | unsigned long pos; |
| 318 | int ret; |
| 319 | |
| 320 | ret = -ENOTDIR; |
| 321 | if (!S_ISDIR(inode->i_mode)) |
| 322 | goto out; |
| 323 | |
| 324 | ret = 0; |
| 325 | /* Avoid a switch here: arm builds fail with missing __cmpdi2 */ |
| 326 | if (filp->f_pos == 0) { |
| 327 | if (filldir(dirent, ".", 1, filp->f_pos, |
| 328 | inode->i_ino, DT_DIR) < 0) |
| 329 | goto out; |
| 330 | filp->f_pos++; |
| 331 | } |
| 332 | if (filp->f_pos == 1) { |
| 333 | if (filldir(dirent, "..", 2, filp->f_pos, |
| 334 | parent_ino(dentry), DT_DIR) < 0) |
| 335 | goto out; |
| 336 | filp->f_pos++; |
| 337 | } |
| 338 | pos = 2; |
| 339 | |
| 340 | /* - Find each instance of the directory |
| 341 | * - Read all entries in each instance |
| 342 | * - Before returning an entry to user space lookup the entry |
| 343 | * by name and if I find a different entry don't return |
| 344 | * this one because it means it is a buried dup. |
| 345 | * For sysctl this should only happen for directory entries. |
| 346 | */ |
| 347 | for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) { |
| 348 | table = proc_sys_lookup_table(dentry, head->ctl_table); |
| 349 | |
| 350 | if (!table) |
| 351 | continue; |
| 352 | |
| 353 | for (; table->ctl_name || table->procname; table++, pos++) { |
| 354 | /* Can't do anything without a proc name */ |
| 355 | if (!table->procname) |
| 356 | continue; |
| 357 | |
| 358 | if (pos < filp->f_pos) |
| 359 | continue; |
| 360 | |
| 361 | if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0) |
| 362 | goto out; |
| 363 | filp->f_pos = pos + 1; |
| 364 | } |
| 365 | } |
| 366 | ret = 1; |
| 367 | out: |
| 368 | sysctl_head_finish(head); |
| 369 | return ret; |
| 370 | } |
| 371 | |
| 372 | static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd) |
| 373 | { |
| 374 | /* |
| 375 | * sysctl entries that are not writeable, |
| 376 | * are _NOT_ writeable, capabilities or not. |
| 377 | */ |
| 378 | struct ctl_table_header *head; |
| 379 | struct ctl_table *table; |
| 380 | struct dentry *dentry; |
| 381 | int mode; |
| 382 | int depth; |
| 383 | int error; |
| 384 | |
| 385 | head = NULL; |
| 386 | depth = PROC_I(inode)->fd; |
| 387 | |
| 388 | /* First check the cached permissions, in case we don't have |
| 389 | * enough information to lookup the sysctl table entry. |
| 390 | */ |
| 391 | error = -EACCES; |
| 392 | mode = inode->i_mode; |
| 393 | |
| 394 | if (current->euid == 0) |
| 395 | mode >>= 6; |
| 396 | else if (in_group_p(0)) |
| 397 | mode >>= 3; |
| 398 | |
| 399 | if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask) |
| 400 | error = 0; |
| 401 | |
| 402 | /* If we can't get a sysctl table entry the permission |
| 403 | * checks on the cached mode will have to be enough. |
| 404 | */ |
| 405 | if (!nd || !depth) |
| 406 | goto out; |
| 407 | |
| 408 | dentry = nd->dentry; |
| 409 | table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); |
| 410 | |
| 411 | /* If the entry does not exist deny permission */ |
| 412 | error = -EACCES; |
| 413 | if (!table) |
| 414 | goto out; |
| 415 | |
| 416 | /* Use the permissions on the sysctl table entry */ |
| 417 | error = sysctl_perm(table, mask); |
| 418 | out: |
| 419 | sysctl_head_finish(head); |
| 420 | return error; |
| 421 | } |
| 422 | |
| 423 | static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr) |
| 424 | { |
| 425 | struct inode *inode = dentry->d_inode; |
| 426 | int error; |
| 427 | |
| 428 | if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) |
| 429 | return -EPERM; |
| 430 | |
| 431 | error = inode_change_ok(inode, attr); |
John Johansen | 9d0633c | 2007-05-08 00:29:44 -0700 | [diff] [blame] | 432 | if (!error) |
| 433 | error = inode_setattr(inode, attr); |
Eric W. Biederman | 77b14db | 2007-02-14 00:34:12 -0800 | [diff] [blame] | 434 | |
| 435 | return error; |
| 436 | } |
| 437 | |
| 438 | /* I'm lazy and don't distinguish between files and directories, |
| 439 | * until access time. |
| 440 | */ |
| 441 | static const struct file_operations proc_sys_file_operations = { |
| 442 | .read = proc_sys_read, |
| 443 | .write = proc_sys_write, |
| 444 | .readdir = proc_sys_readdir, |
| 445 | }; |
| 446 | |
| 447 | static struct inode_operations proc_sys_inode_operations = { |
| 448 | .lookup = proc_sys_lookup, |
| 449 | .permission = proc_sys_permission, |
| 450 | .setattr = proc_sys_setattr, |
| 451 | }; |
| 452 | |
| 453 | static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd) |
| 454 | { |
| 455 | struct ctl_table_header *head; |
| 456 | struct ctl_table *table; |
| 457 | table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); |
| 458 | proc_sys_refresh_inode(dentry->d_inode, table); |
| 459 | sysctl_head_finish(head); |
| 460 | return !!table; |
| 461 | } |
| 462 | |
| 463 | static struct dentry_operations proc_sys_dentry_operations = { |
| 464 | .d_revalidate = proc_sys_revalidate, |
| 465 | }; |
| 466 | |
| 467 | static struct proc_dir_entry *proc_sys_root; |
| 468 | |
| 469 | int proc_sys_init(void) |
| 470 | { |
| 471 | proc_sys_root = proc_mkdir("sys", NULL); |
| 472 | proc_sys_root->proc_iops = &proc_sys_inode_operations; |
| 473 | proc_sys_root->proc_fops = &proc_sys_file_operations; |
| 474 | proc_sys_root->nlink = 0; |
| 475 | return 0; |
| 476 | } |