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 *table = PROC_I(inode)->sysctl_entry;
 192
 193         if (table->poll)
 194                 filp->private_data = proc_sys_poll_event(table->poll);
 195
 196         return 0;
 197 }
 198
 199 static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
 200 {
 201         struct inode *inode = filp->f_path.dentry->d_inode;
 202         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 203         unsigned long event = (unsigned long)filp->private_data;
 204         unsigned int ret = DEFAULT_POLLMASK;
 205
 206         if (!table->proc_handler)
 207                 goto out;
 208
 209         if (!table->poll)
 210                 goto out;
 211
 212         poll_wait(filp, &table->poll->wait, wait);
 213
 214         if (event != atomic_read(&table->poll->event)) {
 215                 filp->private_data = proc_sys_poll_event(table->poll);
 216                 ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI;
 217         }
 218
 219 out:
 220         return ret;
 221 }
 222
 223 static int proc_sys_fill_cache(struct file *filp, void *dirent,
 224                                 filldir_t filldir,
 225                                 struct ctl_table_header *head,
 226                                 struct ctl_table *table)
 227 {
 228         struct dentry *child, *dir = filp->f_path.dentry;
 229         struct inode *inode;
 230         struct qstr qname;
 231         ino_t ino = 0;
 232         unsigned type = DT_UNKNOWN;
 233
 234         qname.name = table->procname;
 235         qname.len  = strlen(table->procname);
 236         qname.hash = full_name_hash(qname.name, qname.len);
 237
 238         child = d_lookup(dir, &qname);
 239         if (!child) {
 240                 child = d_alloc(dir, &qname);
 241                 if (child) {
 242                         inode = proc_sys_make_inode(dir->d_sb, head, table);
 243                         if (!inode) {
 244                                 dput(child);
 245                                 return -ENOMEM;
 246                         } else {
 247                                 d_set_d_op(child, &proc_sys_dentry_operations);
 248                                 d_add(child, inode);
 249                         }
 250                 } else {
 251                         return -ENOMEM;
 252                 }
 253         }
 254         inode = child->d_inode;
 255         ino  = inode->i_ino;
 256         type = inode->i_mode >> 12;
 257         dput(child);
 258         return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
 259 }
 260
 261 static int scan(struct ctl_table_header *head, ctl_table *table,
 262                 unsigned long *pos, struct file *file,
 263                 void *dirent, filldir_t filldir)
 264 {
 265
 266         for (; table->procname; table++, (*pos)++) {
 267                 int res;
 268
 269                 /* Can't do anything without a proc name */
 270                 if (!table->procname)
 271                         continue;
 272
 273                 if (*pos < file->f_pos)
 274                         continue;
 275
 276                 res = proc_sys_fill_cache(file, dirent, filldir, head, table);
 277                 if (res)
 278                         return res;
 279
 280                 file->f_pos = *pos + 1;
 281         }
 282         return 0;
 283 }
 284
 285 static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
 286 {
 287         struct dentry *dentry = filp->f_path.dentry;
 288         struct inode *inode = dentry->d_inode;
 289         struct ctl_table_header *head = grab_header(inode);
 290         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 291         struct ctl_table_header *h = NULL;
 292         unsigned long pos;
 293         int ret = -EINVAL;
 294
 295         if (IS_ERR(head))
 296                 return PTR_ERR(head);
 297
 298         if (table && !table->child) {
 299                 WARN_ON(1);
 300                 goto out;
 301         }
 302
 303         table = table ? table->child : head->ctl_table;
 304
 305         ret = 0;
 306         /* Avoid a switch here: arm builds fail with missing __cmpdi2 */
 307         if (filp->f_pos == 0) {
 308                 if (filldir(dirent, ".", 1, filp->f_pos,
 309                                 inode->i_ino, DT_DIR) < 0)
 310                         goto out;
 311                 filp->f_pos++;
 312         }
 313         if (filp->f_pos == 1) {
 314                 if (filldir(dirent, "..", 2, filp->f_pos,
 315                                 parent_ino(dentry), DT_DIR) < 0)
 316                         goto out;
 317                 filp->f_pos++;
 318         }
 319         pos = 2;
 320
 321         ret = scan(head, table, &pos, filp, dirent, filldir);
 322         if (ret)
 323                 goto out;
 324
 325         for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 326                 if (h->attached_to != table)
 327                         continue;
 328                 ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
 329                 if (ret) {
 330                         sysctl_head_finish(h);
 331                         break;
 332                 }
 333         }
 334         ret = 1;
 335 out:
 336         sysctl_head_finish(head);
 337         return ret;
 338 }
 339
 340 static int proc_sys_permission(struct inode *inode, int mask)
 341 {
 342         /*
 343          * sysctl entries that are not writeable,
 344          * are _NOT_ writeable, capabilities or not.
 345          */
 346         struct ctl_table_header *head;
 347         struct ctl_table *table;
 348         int error;
 349
 350         /* Executable files are not allowed under /proc/sys/ */
 351         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 352                 return -EACCES;
 353
 354         head = grab_header(inode);
 355         if (IS_ERR(head))
 356                 return PTR_ERR(head);
 357
 358         table = PROC_I(inode)->sysctl_entry;
 359         if (!table) /* global root - r-xr-xr-x */
 360                 error = mask & MAY_WRITE ? -EACCES : 0;
 361         else /* Use the permissions on the sysctl table entry */
 362                 error = sysctl_perm(head->root, table, mask & ~MAY_NOT_BLOCK);
 363
 364         sysctl_head_finish(head);
 365         return error;
 366 }
 367
 368 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
 369 {
 370         struct inode *inode = dentry->d_inode;
 371         int error;
 372
 373         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
 374                 return -EPERM;
 375
 376         error = inode_change_ok(inode, attr);
 377         if (error)
 378                 return error;
 379
 380         if ((attr->ia_valid & ATTR_SIZE) &&
 381             attr->ia_size != i_size_read(inode)) {
 382                 error = vmtruncate(inode, attr->ia_size);
 383                 if (error)
 384                         return error;
 385         }
 386
 387         setattr_copy(inode, attr);
 388         mark_inode_dirty(inode);
 389         return 0;
 390 }
 391
 392 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 393 {
 394         struct inode *inode = dentry->d_inode;
 395         struct ctl_table_header *head = grab_header(inode);
 396         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 397
 398         if (IS_ERR(head))
 399                 return PTR_ERR(head);
 400
 401         generic_fillattr(inode, stat);
 402         if (table)
 403                 stat->mode = (stat->mode & S_IFMT) | table->mode;
 404
 405         sysctl_head_finish(head);
 406         return 0;
 407 }
 408
 409 static const struct file_operations proc_sys_file_operations = {
 410         .open           = proc_sys_open,
 411         .poll           = proc_sys_poll,
 412         .read           = proc_sys_read,
 413         .write          = proc_sys_write,
 414         .llseek         = default_llseek,
 415 };
 416
 417 static const struct file_operations proc_sys_dir_file_operations = {
 418         .read           = generic_read_dir,
 419         .readdir        = proc_sys_readdir,
 420         .llseek         = generic_file_llseek,
 421 };
 422
 423 static const struct inode_operations proc_sys_inode_operations = {
 424         .permission     = proc_sys_permission,
 425         .setattr        = proc_sys_setattr,
 426         .getattr        = proc_sys_getattr,
 427 };
 428
 429 static const struct inode_operations proc_sys_dir_operations = {
 430         .lookup         = proc_sys_lookup,
 431         .permission     = proc_sys_permission,
 432         .setattr        = proc_sys_setattr,
 433         .getattr        = proc_sys_getattr,
 434 };
 435
 436 static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
 437 {
 438         if (nd->flags & LOOKUP_RCU)
 439                 return -ECHILD;
 440         return !PROC_I(dentry->d_inode)->sysctl->unregistering;
 441 }
 442
 443 static int proc_sys_delete(const struct dentry *dentry)
 444 {
 445         return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
 446 }
 447
 448 static int proc_sys_compare(const struct dentry *parent,
 449                 const struct inode *pinode,
 450                 const struct dentry *dentry, const struct inode *inode,
 451                 unsigned int len, const char *str, const struct qstr *name)
 452 {
 453         struct ctl_table_header *head;
 454         /* Although proc doesn't have negative dentries, rcu-walk means
 455          * that inode here can be NULL */
 456         /* AV: can it, indeed? */
 457         if (!inode)
 458                 return 1;
 459         if (name->len != len)
 460                 return 1;
 461         if (memcmp(name->name, str, len))
 462                 return 1;
 463         head = rcu_dereference(PROC_I(inode)->sysctl);
 464         return !head || !sysctl_is_seen(head);
 465 }
 466
 467 static const struct dentry_operations proc_sys_dentry_operations = {
 468         .d_revalidate   = proc_sys_revalidate,
 469         .d_delete       = proc_sys_delete,
 470         .d_compare      = proc_sys_compare,
 471 };
 472
 473 int __init proc_sys_init(void)
 474 {
 475         struct proc_dir_entry *proc_sys_root;
 476
 477         proc_sys_root = proc_mkdir("sys", NULL);
 478         proc_sys_root->proc_iops = &proc_sys_dir_operations;
 479         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
 480         proc_sys_root->nlink = 0;
 481         return 0;
 482 }