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