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