fs/proc/proc_sysctl.c

   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/namei.h>
  10 #include "internal.h"
  11
  12 static const struct dentry_operations proc_sys_dentry_operations;
  13 static const struct file_operations proc_sys_file_operations;
  14 static const struct inode_operations proc_sys_inode_operations;
  15 static const struct file_operations proc_sys_dir_file_operations;
  16 static const struct inode_operations proc_sys_dir_operations;
  17
  18 void proc_sys_poll_notify(struct ctl_table_poll *poll)
  19 {
  20         if (!poll)
  21                 return;
  22
  23         atomic_inc(&poll->event);
  24         wake_up_interruptible(&poll->wait);
  25 }
  26
  27 static struct inode *proc_sys_make_inode(struct super_block *sb,
  28                 struct ctl_table_header *head, struct ctl_table *table)
  29 {
  30         struct inode *inode;
  31         struct proc_inode *ei;
  32
  33         inode = new_inode(sb);
  34         if (!inode)
  35                 goto out;
  36
  37         inode->i_ino = get_next_ino();
  38
  39         sysctl_head_get(head);
  40         ei = PROC_I(inode);
  41         ei->sysctl = head;
  42         ei->sysctl_entry = table;
  43
  44         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  45         inode->i_mode = table->mode;
  46         if (!table->child) {
  47                 inode->i_mode |= S_IFREG;
  48                 inode->i_op = &proc_sys_inode_operations;
  49                 inode->i_fop = &proc_sys_file_operations;
  50         } else {
  51                 inode->i_mode |= S_IFDIR;
  52                 clear_nlink(inode);
  53                 inode->i_op = &proc_sys_dir_operations;
  54                 inode->i_fop = &proc_sys_dir_file_operations;
  55         }
  56 out:
  57         return inode;
  58 }
  59
  60 static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
  61 {
  62         int len;
  63         for ( ; p->procname; p++) {
  64
  65                 if (!p->procname)
  66                         continue;
  67
  68                 len = strlen(p->procname);
  69                 if (len != name->len)
  70                         continue;
  71
  72                 if (memcmp(p->procname, name->name, len) != 0)
  73                         continue;
  74
  75                 /* I have a match */
  76                 return p;
  77         }
  78         return NULL;
  79 }
  80
  81 static struct ctl_table_header *grab_header(struct inode *inode)
  82 {
  83         if (PROC_I(inode)->sysctl)
  84                 return sysctl_head_grab(PROC_I(inode)->sysctl);
  85         else
  86                 return sysctl_head_next(NULL);
  87 }
  88
  89 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
  90                                         struct nameidata *nd)
  91 {
  92         struct ctl_table_header *head = grab_header(dir);
  93         struct ctl_table *table = PROC_I(dir)->sysctl_entry;
  94         struct ctl_table_header *h = NULL;
  95         struct qstr *name = &dentry->d_name;
  96         struct ctl_table *p;
  97         struct inode *inode;
  98         struct dentry *err = ERR_PTR(-ENOENT);
  99
 100         if (IS_ERR(head))
 101                 return ERR_CAST(head);
 102
 103         if (table && !table->child) {
 104                 WARN_ON(1);
 105                 goto out;
 106         }
 107
 108         table = table ? table->child : head->ctl_table;
 109
 110         p = find_in_table(table, name);
 111         if (!p) {
 112                 for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 113                         if (h->attached_to != table)
 114                                 continue;
 115                         p = find_in_table(h->attached_by, name);
 116                         if (p)
 117                                 break;
 118                 }
 119         }
 120
 121         if (!p)
 122                 goto out;
 123
 124         err = ERR_PTR(-ENOMEM);
 125         inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
 126         if (h)
 127                 sysctl_head_finish(h);
 128
 129         if (!inode)
 130                 goto out;
 131
 132         err = NULL;
 133         d_set_d_op(dentry, &proc_sys_dentry_operations);
 134         d_add(dentry, inode);
 135
 136 out:
 137         sysctl_head_finish(head);
 138         return err;
 139 }
 140
 141 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
 142                 size_t count, loff_t *ppos, int write)
 143 {
 144         struct inode *inode = filp->f_path.dentry->d_inode;
 145         struct ctl_table_header *head = grab_header(inode);
 146         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 147         ssize_t error;
 148         size_t res;
 149
 150         if (IS_ERR(head))
 151                 return PTR_ERR(head);
 152
 153         /*
 154          * At this point we know that the sysctl was not unregistered
 155          * and won't be until we finish.
 156          */
 157         error = -EPERM;
 158         if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
 159                 goto out;
 160
 161         /* if that can happen at all, it should be -EINVAL, not -EISDIR */
 162         error = -EINVAL;
 163         if (!table->proc_handler)
 164                 goto out;
 165
 166         /* careful: calling conventions are nasty here */
 167         res = count;
 168         error = table->proc_handler(table, write, buf, &res, ppos);
 169         if (!error)
 170                 error = res;
 171 out:
 172         sysctl_head_finish(head);
 173
 174         return error;
 175 }
 176
 177 static ssize_t proc_sys_read(struct file *filp, char __user *buf,
 178                                 size_t count, loff_t *ppos)
 179 {
 180         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
 181 }
 182
 183 static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
 184                                 size_t count, loff_t *ppos)
 185 {
 186         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
 187 }
 188
 189 static int proc_sys_open(struct inode *inode, struct file *filp)
 190 {
 191         struct ctl_table_header *head = grab_header(inode);
 192         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 193
 194         /* sysctl was unregistered */
 195         if (IS_ERR(head))
 196                 return PTR_ERR(head);
 197
 198         if (table->poll)
 199                 filp->private_data = proc_sys_poll_event(table->poll);
 200
 201         sysctl_head_finish(head);
 202
 203         return 0;
 204 }
 205
 206 static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
 207 {
 208         struct inode *inode = filp->f_path.dentry->d_inode;
 209         struct ctl_table_header *head = grab_header(inode);
 210         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 211         unsigned int ret = DEFAULT_POLLMASK;
 212         unsigned long event;
 213
 214         /* sysctl was unregistered */
 215         if (IS_ERR(head))
 216                 return POLLERR | POLLHUP;
 217
 218         if (!table->proc_handler)
 219                 goto out;
 220
 221         if (!table->poll)
 222                 goto out;
 223
 224         event = (unsigned long)filp->private_data;
 225         poll_wait(filp, &table->poll->wait, wait);
 226
 227         if (event != atomic_read(&table->poll->event)) {
 228                 filp->private_data = proc_sys_poll_event(table->poll);
 229                 ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI;
 230         }
 231
 232 out:
 233         sysctl_head_finish(head);
 234
 235         return ret;
 236 }
 237
 238 static int proc_sys_fill_cache(struct file *filp, void *dirent,
 239                                 filldir_t filldir,
 240                                 struct ctl_table_header *head,
 241                                 struct ctl_table *table)
 242 {
 243         struct dentry *child, *dir = filp->f_path.dentry;
 244         struct inode *inode;
 245         struct qstr qname;
 246         ino_t ino = 0;
 247         unsigned type = DT_UNKNOWN;
 248
 249         qname.name = table->procname;
 250         qname.len  = strlen(table->procname);
 251         qname.hash = full_name_hash(qname.name, qname.len);
 252
 253         child = d_lookup(dir, &qname);
 254         if (!child) {
 255                 child = d_alloc(dir, &qname);
 256                 if (child) {
 257                         inode = proc_sys_make_inode(dir->d_sb, head, table);
 258                         if (!inode) {
 259                                 dput(child);
 260                                 return -ENOMEM;
 261                         } else {
 262                                 d_set_d_op(child, &proc_sys_dentry_operations);
 263                                 d_add(child, inode);
 264                         }
 265                 } else {
 266                         return -ENOMEM;
 267                 }
 268         }
 269         inode = child->d_inode;
 270         ino  = inode->i_ino;
 271         type = inode->i_mode >> 12;
 272         dput(child);
 273         return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
 274 }
 275
 276 static int scan(struct ctl_table_header *head, ctl_table *table,
 277                 unsigned long *pos, struct file *file,
 278                 void *dirent, filldir_t filldir)
 279 {
 280
 281         for (; table->procname; table++, (*pos)++) {
 282                 int res;
 283
 284                 /* Can't do anything without a proc name */
 285                 if (!table->procname)
 286                         continue;
 287
 288                 if (*pos < file->f_pos)
 289                         continue;
 290
 291                 res = proc_sys_fill_cache(file, dirent, filldir, head, table);
 292                 if (res)
 293                         return res;
 294
 295                 file->f_pos = *pos + 1;
 296         }
 297         return 0;
 298 }
 299
 300 static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
 301 {
 302         struct dentry *dentry = filp->f_path.dentry;
 303         struct inode *inode = dentry->d_inode;
 304         struct ctl_table_header *head = grab_header(inode);
 305         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 306         struct ctl_table_header *h = NULL;
 307         unsigned long pos;
 308         int ret = -EINVAL;
 309
 310         if (IS_ERR(head))
 311                 return PTR_ERR(head);
 312
 313         if (table && !table->child) {
 314                 WARN_ON(1);
 315                 goto out;
 316         }
 317
 318         table = table ? table->child : head->ctl_table;
 319
 320         ret = 0;
 321         /* Avoid a switch here: arm builds fail with missing __cmpdi2 */
 322         if (filp->f_pos == 0) {
 323                 if (filldir(dirent, ".", 1, filp->f_pos,
 324                                 inode->i_ino, DT_DIR) < 0)
 325                         goto out;
 326                 filp->f_pos++;
 327         }
 328         if (filp->f_pos == 1) {
 329                 if (filldir(dirent, "..", 2, filp->f_pos,
 330                                 parent_ino(dentry), DT_DIR) < 0)
 331                         goto out;
 332                 filp->f_pos++;
 333         }
 334         pos = 2;
 335
 336         ret = scan(head, table, &pos, filp, dirent, filldir);
 337         if (ret)
 338                 goto out;
 339
 340         for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 341                 if (h->attached_to != table)
 342                         continue;
 343                 ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
 344                 if (ret) {
 345                         sysctl_head_finish(h);
 346                         break;
 347                 }
 348         }
 349         ret = 1;
 350 out:
 351         sysctl_head_finish(head);
 352         return ret;
 353 }
 354
 355 static int proc_sys_permission(struct inode *inode, int mask)
 356 {
 357         /*
 358          * sysctl entries that are not writeable,
 359          * are _NOT_ writeable, capabilities or not.
 360          */
 361         struct ctl_table_header *head;
 362         struct ctl_table *table;
 363         int error;
 364
 365         /* Executable files are not allowed under /proc/sys/ */
 366         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 367                 return -EACCES;
 368
 369         head = grab_header(inode);
 370         if (IS_ERR(head))
 371                 return PTR_ERR(head);
 372
 373         table = PROC_I(inode)->sysctl_entry;
 374         if (!table) /* global root - r-xr-xr-x */
 375                 error = mask & MAY_WRITE ? -EACCES : 0;
 376         else /* Use the permissions on the sysctl table entry */
 377                 error = sysctl_perm(head->root, table, mask & ~MAY_NOT_BLOCK);
 378
 379         sysctl_head_finish(head);
 380         return error;
 381 }
 382
 383 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
 384 {
 385         struct inode *inode = dentry->d_inode;
 386         int error;
 387
 388         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
 389                 return -EPERM;
 390
 391         error = inode_change_ok(inode, attr);
 392         if (error)
 393                 return error;
 394
 395         if ((attr->ia_valid & ATTR_SIZE) &&
 396             attr->ia_size != i_size_read(inode)) {
 397                 error = vmtruncate(inode, attr->ia_size);
 398                 if (error)
 399                         return error;
 400         }
 401
 402         setattr_copy(inode, attr);
 403         mark_inode_dirty(inode);
 404         return 0;
 405 }
 406
 407 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 408 {
 409         struct inode *inode = dentry->d_inode;
 410         struct ctl_table_header *head = grab_header(inode);
 411         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 412
 413         if (IS_ERR(head))
 414                 return PTR_ERR(head);
 415
 416         generic_fillattr(inode, stat);
 417         if (table)
 418                 stat->mode = (stat->mode & S_IFMT) | table->mode;
 419
 420         sysctl_head_finish(head);
 421         return 0;
 422 }
 423
 424 static const struct file_operations proc_sys_file_operations = {
 425         .open           = proc_sys_open,
 426         .poll           = proc_sys_poll,
 427         .read           = proc_sys_read,
 428         .write          = proc_sys_write,
 429         .llseek         = default_llseek,
 430 };
 431
 432 static const struct file_operations proc_sys_dir_file_operations = {
 433         .read           = generic_read_dir,
 434         .readdir        = proc_sys_readdir,
 435         .llseek         = generic_file_llseek,
 436 };
 437
 438 static const struct inode_operations proc_sys_inode_operations = {
 439         .permission     = proc_sys_permission,
 440         .setattr        = proc_sys_setattr,
 441         .getattr        = proc_sys_getattr,
 442 };
 443
 444 static const struct inode_operations proc_sys_dir_operations = {
 445         .lookup         = proc_sys_lookup,
 446         .permission     = proc_sys_permission,
 447         .setattr        = proc_sys_setattr,
 448         .getattr        = proc_sys_getattr,
 449 };
 450
 451 static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
 452 {
 453         if (nd->flags & LOOKUP_RCU)
 454                 return -ECHILD;
 455         return !PROC_I(dentry->d_inode)->sysctl->unregistering;
 456 }
 457
 458 static int proc_sys_delete(const struct dentry *dentry)
 459 {
 460         return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
 461 }
 462
 463 static int proc_sys_compare(const struct dentry *parent,
 464                 const struct inode *pinode,
 465                 const struct dentry *dentry, const struct inode *inode,
 466                 unsigned int len, const char *str, const struct qstr *name)
 467 {
 468         struct ctl_table_header *head;
 469         /* Although proc doesn't have negative dentries, rcu-walk means
 470          * that inode here can be NULL */
 471         /* AV: can it, indeed? */
 472         if (!inode)
 473                 return 1;
 474         if (name->len != len)
 475                 return 1;
 476         if (memcmp(name->name, str, len))
 477                 return 1;
 478         head = rcu_dereference(PROC_I(inode)->sysctl);
 479         return !head || !sysctl_is_seen(head);
 480 }
 481
 482 static const struct dentry_operations proc_sys_dentry_operations = {
 483         .d_revalidate   = proc_sys_revalidate,
 484         .d_delete       = proc_sys_delete,
 485         .d_compare      = proc_sys_compare,
 486 };
 487
 488 int __init proc_sys_init(void)
 489 {
 490         struct proc_dir_entry *proc_sys_root;
 491
 492         proc_sys_root = proc_mkdir("sys", NULL);
 493         proc_sys_root->proc_iops = &proc_sys_dir_operations;
 494         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
 495         proc_sys_root->nlink = 0;
 496         return 0;
 497 }