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