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