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