1 /* 2 * /proc/sys support 3 */ 4 #include <linux/init.h> 5 #include <linux/sysctl.h> 6 #include <linux/poll.h> 7 #include <linux/proc_fs.h> 8 #include <linux/security.h> 9 #include <linux/sched.h> 10 #include <linux/namei.h> 11 #include <linux/mm.h> 12 #include "internal.h" 13 14 static const struct dentry_operations proc_sys_dentry_operations; 15 static const struct file_operations proc_sys_file_operations; 16 static const struct inode_operations proc_sys_inode_operations; 17 static const struct file_operations proc_sys_dir_file_operations; 18 static const struct inode_operations proc_sys_dir_operations; 19 20 void proc_sys_poll_notify(struct ctl_table_poll *poll) 21 { 22 if (!poll) 23 return; 24 25 atomic_inc(&poll->event); 26 wake_up_interruptible(&poll->wait); 27 } 28 29 static struct inode *proc_sys_make_inode(struct super_block *sb, 30 struct ctl_table_header *head, struct ctl_table *table) 31 { 32 struct inode *inode; 33 struct proc_inode *ei; 34 35 inode = new_inode(sb); 36 if (!inode) 37 goto out; 38 39 inode->i_ino = get_next_ino(); 40 41 sysctl_head_get(head); 42 ei = PROC_I(inode); 43 ei->sysctl = head; 44 ei->sysctl_entry = table; 45 46 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 47 inode->i_mode = table->mode; 48 if (!table->child) { 49 inode->i_mode |= S_IFREG; 50 inode->i_op = &proc_sys_inode_operations; 51 inode->i_fop = &proc_sys_file_operations; 52 } else { 53 inode->i_mode |= S_IFDIR; 54 clear_nlink(inode); 55 inode->i_op = &proc_sys_dir_operations; 56 inode->i_fop = &proc_sys_dir_file_operations; 57 } 58 out: 59 return inode; 60 } 61 62 static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name) 63 { 64 int len; 65 for ( ; p->procname; p++) { 66 67 if (!p->procname) 68 continue; 69 70 len = strlen(p->procname); 71 if (len != name->len) 72 continue; 73 74 if (memcmp(p->procname, name->name, len) != 0) 75 continue; 76 77 /* I have a match */ 78 return p; 79 } 80 return NULL; 81 } 82 83 static struct ctl_table_header *grab_header(struct inode *inode) 84 { 85 if (PROC_I(inode)->sysctl) 86 return sysctl_head_grab(PROC_I(inode)->sysctl); 87 else 88 return sysctl_head_next(NULL); 89 } 90 91 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, 92 struct nameidata *nd) 93 { 94 struct ctl_table_header *head = grab_header(dir); 95 struct ctl_table *table = PROC_I(dir)->sysctl_entry; 96 struct ctl_table_header *h = NULL; 97 struct qstr *name = &dentry->d_name; 98 struct ctl_table *p; 99 struct inode *inode; 100 struct dentry *err = ERR_PTR(-ENOENT); 101 102 if (IS_ERR(head)) 103 return ERR_CAST(head); 104 105 if (table && !table->child) { 106 WARN_ON(1); 107 goto out; 108 } 109 110 table = table ? table->child : head->ctl_table; 111 112 p = find_in_table(table, name); 113 if (!p) { 114 for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) { 115 if (h->attached_to != table) 116 continue; 117 p = find_in_table(h->attached_by, name); 118 if (p) 119 break; 120 } 121 } 122 123 if (!p) 124 goto out; 125 126 err = ERR_PTR(-ENOMEM); 127 inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p); 128 if (h) 129 sysctl_head_finish(h); 130 131 if (!inode) 132 goto out; 133 134 err = NULL; 135 d_set_d_op(dentry, &proc_sys_dentry_operations); 136 d_add(dentry, inode); 137 138 out: 139 sysctl_head_finish(head); 140 return err; 141 } 142 143 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, 144 size_t count, loff_t *ppos, int write) 145 { 146 struct inode *inode = filp->f_path.dentry->d_inode; 147 struct ctl_table_header *head = grab_header(inode); 148 struct ctl_table *table = PROC_I(inode)->sysctl_entry; 149 ssize_t error; 150 size_t res; 151 152 if (IS_ERR(head)) 153 return PTR_ERR(head); 154 155 /* 156 * At this point we know that the sysctl was not unregistered 157 * and won't be until we finish. 158 */ 159 error = -EPERM; 160 if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ)) 161 goto out; 162 163 /* if that can happen at all, it should be -EINVAL, not -EISDIR */ 164 error = -EINVAL; 165 if (!table->proc_handler) 166 goto out; 167 168 /* careful: calling conventions are nasty here */ 169 res = count; 170 error = table->proc_handler(table, write, buf, &res, ppos); 171 if (!error) 172 error = res; 173 out: 174 sysctl_head_finish(head); 175 176 return error; 177 } 178 179 static ssize_t proc_sys_read(struct file *filp, char __user *buf, 180 size_t count, loff_t *ppos) 181 { 182 return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0); 183 } 184 185 static ssize_t proc_sys_write(struct file *filp, const char __user *buf, 186 size_t count, loff_t *ppos) 187 { 188 return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1); 189 } 190 191 static int proc_sys_open(struct inode *inode, struct file *filp) 192 { 193 struct ctl_table *table = PROC_I(inode)->sysctl_entry; 194 195 if (table->poll) 196 filp->private_data = proc_sys_poll_event(table->poll); 197 198 return 0; 199 } 200 201 static unsigned int proc_sys_poll(struct file *filp, poll_table *wait) 202 { 203 struct inode *inode = filp->f_path.dentry->d_inode; 204 struct ctl_table *table = PROC_I(inode)->sysctl_entry; 205 unsigned long event = (unsigned long)filp->private_data; 206 unsigned int ret = DEFAULT_POLLMASK; 207 208 if (!table->proc_handler) 209 goto out; 210 211 if (!table->poll) 212 goto out; 213 214 poll_wait(filp, &table->poll->wait, wait); 215 216 if (event != atomic_read(&table->poll->event)) { 217 filp->private_data = proc_sys_poll_event(table->poll); 218 ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI; 219 } 220 221 out: 222 return ret; 223 } 224 225 static int proc_sys_fill_cache(struct file *filp, void *dirent, 226 filldir_t filldir, 227 struct ctl_table_header *head, 228 struct ctl_table *table) 229 { 230 struct dentry *child, *dir = filp->f_path.dentry; 231 struct inode *inode; 232 struct qstr qname; 233 ino_t ino = 0; 234 unsigned type = DT_UNKNOWN; 235 236 qname.name = table->procname; 237 qname.len = strlen(table->procname); 238 qname.hash = full_name_hash(qname.name, qname.len); 239 240 child = d_lookup(dir, &qname); 241 if (!child) { 242 child = d_alloc(dir, &qname); 243 if (child) { 244 inode = proc_sys_make_inode(dir->d_sb, head, table); 245 if (!inode) { 246 dput(child); 247 return -ENOMEM; 248 } else { 249 d_set_d_op(child, &proc_sys_dentry_operations); 250 d_add(child, inode); 251 } 252 } else { 253 return -ENOMEM; 254 } 255 } 256 inode = child->d_inode; 257 ino = inode->i_ino; 258 type = inode->i_mode >> 12; 259 dput(child); 260 return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type); 261 } 262 263 static int scan(struct ctl_table_header *head, ctl_table *table, 264 unsigned long *pos, struct file *file, 265 void *dirent, filldir_t filldir) 266 { 267 268 for (; table->procname; table++, (*pos)++) { 269 int res; 270 271 /* Can't do anything without a proc name */ 272 if (!table->procname) 273 continue; 274 275 if (*pos < file->f_pos) 276 continue; 277 278 res = proc_sys_fill_cache(file, dirent, filldir, head, table); 279 if (res) 280 return res; 281 282 file->f_pos = *pos + 1; 283 } 284 return 0; 285 } 286 287 static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) 288 { 289 struct dentry *dentry = filp->f_path.dentry; 290 struct inode *inode = dentry->d_inode; 291 struct ctl_table_header *head = grab_header(inode); 292 struct ctl_table *table = PROC_I(inode)->sysctl_entry; 293 struct ctl_table_header *h = NULL; 294 unsigned long pos; 295 int ret = -EINVAL; 296 297 if (IS_ERR(head)) 298 return PTR_ERR(head); 299 300 if (table && !table->child) { 301 WARN_ON(1); 302 goto out; 303 } 304 305 table = table ? table->child : head->ctl_table; 306 307 ret = 0; 308 /* Avoid a switch here: arm builds fail with missing __cmpdi2 */ 309 if (filp->f_pos == 0) { 310 if (filldir(dirent, ".", 1, filp->f_pos, 311 inode->i_ino, DT_DIR) < 0) 312 goto out; 313 filp->f_pos++; 314 } 315 if (filp->f_pos == 1) { 316 if (filldir(dirent, "..", 2, filp->f_pos, 317 parent_ino(dentry), DT_DIR) < 0) 318 goto out; 319 filp->f_pos++; 320 } 321 pos = 2; 322 323 ret = scan(head, table, &pos, filp, dirent, filldir); 324 if (ret) 325 goto out; 326 327 for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) { 328 if (h->attached_to != table) 329 continue; 330 ret = scan(h, h->attached_by, &pos, filp, dirent, filldir); 331 if (ret) { 332 sysctl_head_finish(h); 333 break; 334 } 335 } 336 ret = 1; 337 out: 338 sysctl_head_finish(head); 339 return ret; 340 } 341 342 static int proc_sys_permission(struct inode *inode, int mask) 343 { 344 /* 345 * sysctl entries that are not writeable, 346 * are _NOT_ writeable, capabilities or not. 347 */ 348 struct ctl_table_header *head; 349 struct ctl_table *table; 350 int error; 351 352 /* Executable files are not allowed under /proc/sys/ */ 353 if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) 354 return -EACCES; 355 356 head = grab_header(inode); 357 if (IS_ERR(head)) 358 return PTR_ERR(head); 359 360 table = PROC_I(inode)->sysctl_entry; 361 if (!table) /* global root - r-xr-xr-x */ 362 error = mask & MAY_WRITE ? -EACCES : 0; 363 else /* Use the permissions on the sysctl table entry */ 364 error = sysctl_perm(head->root, table, mask & ~MAY_NOT_BLOCK); 365 366 sysctl_head_finish(head); 367 return error; 368 } 369 370 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr) 371 { 372 struct inode *inode = dentry->d_inode; 373 int error; 374 375 if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) 376 return -EPERM; 377 378 error = inode_change_ok(inode, attr); 379 if (error) 380 return error; 381 382 if ((attr->ia_valid & ATTR_SIZE) && 383 attr->ia_size != i_size_read(inode)) { 384 error = vmtruncate(inode, attr->ia_size); 385 if (error) 386 return error; 387 } 388 389 setattr_copy(inode, attr); 390 mark_inode_dirty(inode); 391 return 0; 392 } 393 394 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) 395 { 396 struct inode *inode = dentry->d_inode; 397 struct ctl_table_header *head = grab_header(inode); 398 struct ctl_table *table = PROC_I(inode)->sysctl_entry; 399 400 if (IS_ERR(head)) 401 return PTR_ERR(head); 402 403 generic_fillattr(inode, stat); 404 if (table) 405 stat->mode = (stat->mode & S_IFMT) | table->mode; 406 407 sysctl_head_finish(head); 408 return 0; 409 } 410 411 static const struct file_operations proc_sys_file_operations = { 412 .open = proc_sys_open, 413 .poll = proc_sys_poll, 414 .read = proc_sys_read, 415 .write = proc_sys_write, 416 .llseek = default_llseek, 417 }; 418 419 static const struct file_operations proc_sys_dir_file_operations = { 420 .read = generic_read_dir, 421 .readdir = proc_sys_readdir, 422 .llseek = generic_file_llseek, 423 }; 424 425 static const struct inode_operations proc_sys_inode_operations = { 426 .permission = proc_sys_permission, 427 .setattr = proc_sys_setattr, 428 .getattr = proc_sys_getattr, 429 }; 430 431 static const struct inode_operations proc_sys_dir_operations = { 432 .lookup = proc_sys_lookup, 433 .permission = proc_sys_permission, 434 .setattr = proc_sys_setattr, 435 .getattr = proc_sys_getattr, 436 }; 437 438 static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd) 439 { 440 if (nd->flags & LOOKUP_RCU) 441 return -ECHILD; 442 return !PROC_I(dentry->d_inode)->sysctl->unregistering; 443 } 444 445 static int proc_sys_delete(const struct dentry *dentry) 446 { 447 return !!PROC_I(dentry->d_inode)->sysctl->unregistering; 448 } 449 450 static int proc_sys_compare(const struct dentry *parent, 451 const struct inode *pinode, 452 const struct dentry *dentry, const struct inode *inode, 453 unsigned int len, const char *str, const struct qstr *name) 454 { 455 struct ctl_table_header *head; 456 /* Although proc doesn't have negative dentries, rcu-walk means 457 * that inode here can be NULL */ 458 /* AV: can it, indeed? */ 459 if (!inode) 460 return 1; 461 if (name->len != len) 462 return 1; 463 if (memcmp(name->name, str, len)) 464 return 1; 465 head = rcu_dereference(PROC_I(inode)->sysctl); 466 return !head || !sysctl_is_seen(head); 467 } 468 469 static const struct dentry_operations proc_sys_dentry_operations = { 470 .d_revalidate = proc_sys_revalidate, 471 .d_delete = proc_sys_delete, 472 .d_compare = proc_sys_compare, 473 }; 474 475 int __init proc_sys_init(void) 476 { 477 struct proc_dir_entry *proc_sys_root; 478 479 proc_sys_root = proc_mkdir("sys", NULL); 480 proc_sys_root->proc_iops = &proc_sys_dir_operations; 481 proc_sys_root->proc_fops = &proc_sys_dir_file_operations; 482 proc_sys_root->nlink = 0; 483 return 0; 484 } 485