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