fs/proc/proc_sysctl.c

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