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