fs/xattr.c

   1 /*
   2   File: fs/xattr.c
   3
   4   Extended attribute handling.
   5
   6   Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
   7   Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
   8   Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
   9  */
  10 #include <linux/fs.h>
  11 #include <linux/slab.h>
  12 #include <linux/smp_lock.h>
  13 #include <linux/file.h>
  14 #include <linux/xattr.h>
  15 #include <linux/namei.h>
  16 #include <linux/security.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/module.h>
  19 #include <asm/uaccess.h>
  20
  21 /*
  22  * Extended attribute SET operations
  23  */
  24 static long
  25 setxattr(struct dentry *d, char __user *name, void __user *value,
  26          size_t size, int flags)
  27 {
  28         int error;
  29         void *kvalue = NULL;
  30         char kname[XATTR_NAME_MAX + 1];
  31
  32         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
  33                 return -EINVAL;
  34
  35         error = strncpy_from_user(kname, name, sizeof(kname));
  36         if (error == 0 || error == sizeof(kname))
  37                 error = -ERANGE;
  38         if (error < 0)
  39                 return error;
  40
  41         if (size) {
  42                 if (size > XATTR_SIZE_MAX)
  43                         return -E2BIG;
  44                 kvalue = kmalloc(size, GFP_KERNEL);
  45                 if (!kvalue)
  46                         return -ENOMEM;
  47                 if (copy_from_user(kvalue, value, size)) {
  48                         kfree(kvalue);
  49                         return -EFAULT;
  50                 }
  51         }
  52
  53         error = -EOPNOTSUPP;
  54         if (d->d_inode->i_op && d->d_inode->i_op->setxattr) {
  55                 down(&d->d_inode->i_sem);
  56                 error = security_inode_setxattr(d, kname, kvalue, size, flags);
  57                 if (error)
  58                         goto out;
  59                 error = d->d_inode->i_op->setxattr(d, kname, kvalue, size, flags);
  60                 if (!error)
  61                         security_inode_post_setxattr(d, kname, kvalue, size, flags);
  62 out:
  63                 up(&d->d_inode->i_sem);
  64         }
  65         if (kvalue)
  66                 kfree(kvalue);
  67         return error;
  68 }
  69
  70 asmlinkage long
  71 sys_setxattr(char __user *path, char __user *name, void __user *value,
  72              size_t size, int flags)
  73 {
  74         struct nameidata nd;
  75         int error;
  76
  77         error = user_path_walk(path, &nd);
  78         if (error)
  79                 return error;
  80         error = setxattr(nd.dentry, name, value, size, flags);
  81         path_release(&nd);
  82         return error;
  83 }
  84
  85 asmlinkage long
  86 sys_lsetxattr(char __user *path, char __user *name, void __user *value,
  87               size_t size, int flags)
  88 {
  89         struct nameidata nd;
  90         int error;
  91
  92         error = user_path_walk_link(path, &nd);
  93         if (error)
  94                 return error;
  95         error = setxattr(nd.dentry, name, value, size, flags);
  96         path_release(&nd);
  97         return error;
  98 }
  99
 100 asmlinkage long
 101 sys_fsetxattr(int fd, char __user *name, void __user *value,
 102               size_t size, int flags)
 103 {
 104         struct file *f;
 105         int error = -EBADF;
 106
 107         f = fget(fd);
 108         if (!f)
 109                 return error;
 110         error = setxattr(f->f_dentry, name, value, size, flags);
 111         fput(f);
 112         return error;
 113 }
 114
 115 /*
 116  * Extended attribute GET operations
 117  */
 118 static ssize_t
 119 getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
 120 {
 121         ssize_t error;
 122         void *kvalue = NULL;
 123         char kname[XATTR_NAME_MAX + 1];
 124
 125         error = strncpy_from_user(kname, name, sizeof(kname));
 126         if (error == 0 || error == sizeof(kname))
 127                 error = -ERANGE;
 128         if (error < 0)
 129                 return error;
 130
 131         if (size) {
 132                 if (size > XATTR_SIZE_MAX)
 133                         size = XATTR_SIZE_MAX;
 134                 kvalue = kmalloc(size, GFP_KERNEL);
 135                 if (!kvalue)
 136                         return -ENOMEM;
 137         }
 138
 139         error = -EOPNOTSUPP;
 140         if (d->d_inode->i_op && d->d_inode->i_op->getxattr) {
 141                 error = security_inode_getxattr(d, kname);
 142                 if (error)
 143                         goto out;
 144                 error = d->d_inode->i_op->getxattr(d, kname, kvalue, size);
 145                 if (error > 0) {
 146                         if (size && copy_to_user(value, kvalue, error))
 147                                 error = -EFAULT;
 148                 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 149                         /* The file system tried to returned a value bigger
 150                            than XATTR_SIZE_MAX bytes. Not possible. */
 151                         error = -E2BIG;
 152                 }
 153         }
 154 out:
 155         if (kvalue)
 156                 kfree(kvalue);
 157         return error;
 158 }
 159
 160 asmlinkage ssize_t
 161 sys_getxattr(char __user *path, char __user *name, void __user *value,
 162              size_t size)
 163 {
 164         struct nameidata nd;
 165         ssize_t error;
 166
 167         error = user_path_walk(path, &nd);
 168         if (error)
 169                 return error;
 170         error = getxattr(nd.dentry, name, value, size);
 171         path_release(&nd);
 172         return error;
 173 }
 174
 175 asmlinkage ssize_t
 176 sys_lgetxattr(char __user *path, char __user *name, void __user *value,
 177               size_t size)
 178 {
 179         struct nameidata nd;
 180         ssize_t error;
 181
 182         error = user_path_walk_link(path, &nd);
 183         if (error)
 184                 return error;
 185         error = getxattr(nd.dentry, name, value, size);
 186         path_release(&nd);
 187         return error;
 188 }
 189
 190 asmlinkage ssize_t
 191 sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
 192 {
 193         struct file *f;
 194         ssize_t error = -EBADF;
 195
 196         f = fget(fd);
 197         if (!f)
 198                 return error;
 199         error = getxattr(f->f_dentry, name, value, size);
 200         fput(f);
 201         return error;
 202 }
 203
 204 /*
 205  * Extended attribute LIST operations
 206  */
 207 static ssize_t
 208 listxattr(struct dentry *d, char __user *list, size_t size)
 209 {
 210         ssize_t error;
 211         char *klist = NULL;
 212
 213         if (size) {
 214                 if (size > XATTR_LIST_MAX)
 215                         size = XATTR_LIST_MAX;
 216                 klist = kmalloc(size, GFP_KERNEL);
 217                 if (!klist)
 218                         return -ENOMEM;
 219         }
 220
 221         error = -EOPNOTSUPP;
 222         if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
 223                 error = security_inode_listxattr(d);
 224                 if (error)
 225                         goto out;
 226                 error = d->d_inode->i_op->listxattr(d, klist, size);
 227                 if (error > 0) {
 228                         if (size && copy_to_user(list, klist, error))
 229                                 error = -EFAULT;
 230                 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 231                         /* The file system tried to returned a list bigger
 232                            than XATTR_LIST_MAX bytes. Not possible. */
 233                         error = -E2BIG;
 234                 }
 235         }
 236 out:
 237         if (klist)
 238                 kfree(klist);
 239         return error;
 240 }
 241
 242 asmlinkage ssize_t
 243 sys_listxattr(char __user *path, char __user *list, size_t size)
 244 {
 245         struct nameidata nd;
 246         ssize_t error;
 247
 248         error = user_path_walk(path, &nd);
 249         if (error)
 250                 return error;
 251         error = listxattr(nd.dentry, list, size);
 252         path_release(&nd);
 253         return error;
 254 }
 255
 256 asmlinkage ssize_t
 257 sys_llistxattr(char __user *path, char __user *list, size_t size)
 258 {
 259         struct nameidata nd;
 260         ssize_t error;
 261
 262         error = user_path_walk_link(path, &nd);
 263         if (error)
 264                 return error;
 265         error = listxattr(nd.dentry, list, size);
 266         path_release(&nd);
 267         return error;
 268 }
 269
 270 asmlinkage ssize_t
 271 sys_flistxattr(int fd, char __user *list, size_t size)
 272 {
 273         struct file *f;
 274         ssize_t error = -EBADF;
 275
 276         f = fget(fd);
 277         if (!f)
 278                 return error;
 279         error = listxattr(f->f_dentry, list, size);
 280         fput(f);
 281         return error;
 282 }
 283
 284 /*
 285  * Extended attribute REMOVE operations
 286  */
 287 static long
 288 removexattr(struct dentry *d, char __user *name)
 289 {
 290         int error;
 291         char kname[XATTR_NAME_MAX + 1];
 292
 293         error = strncpy_from_user(kname, name, sizeof(kname));
 294         if (error == 0 || error == sizeof(kname))
 295                 error = -ERANGE;
 296         if (error < 0)
 297                 return error;
 298
 299         error = -EOPNOTSUPP;
 300         if (d->d_inode->i_op && d->d_inode->i_op->removexattr) {
 301                 error = security_inode_removexattr(d, kname);
 302                 if (error)
 303                         goto out;
 304                 down(&d->d_inode->i_sem);
 305                 error = d->d_inode->i_op->removexattr(d, kname);
 306                 up(&d->d_inode->i_sem);
 307         }
 308 out:
 309         return error;
 310 }
 311
 312 asmlinkage long
 313 sys_removexattr(char __user *path, char __user *name)
 314 {
 315         struct nameidata nd;
 316         int error;
 317
 318         error = user_path_walk(path, &nd);
 319         if (error)
 320                 return error;
 321         error = removexattr(nd.dentry, name);
 322         path_release(&nd);
 323         return error;
 324 }
 325
 326 asmlinkage long
 327 sys_lremovexattr(char __user *path, char __user *name)
 328 {
 329         struct nameidata nd;
 330         int error;
 331
 332         error = user_path_walk_link(path, &nd);
 333         if (error)
 334                 return error;
 335         error = removexattr(nd.dentry, name);
 336         path_release(&nd);
 337         return error;
 338 }
 339
 340 asmlinkage long
 341 sys_fremovexattr(int fd, char __user *name)
 342 {
 343         struct file *f;
 344         int error = -EBADF;
 345
 346         f = fget(fd);
 347         if (!f)
 348                 return error;
 349         error = removexattr(f->f_dentry, name);
 350         fput(f);
 351         return error;
 352 }
 353
 354
 355 static const char *
 356 strcmp_prefix(const char *a, const char *a_prefix)
 357 {
 358         while (*a_prefix && *a == *a_prefix) {
 359                 a++;
 360                 a_prefix++;
 361         }
 362         return *a_prefix ? NULL : a;
 363 }
 364
 365 /*
 366  * In order to implement different sets of xattr operations for each xattr
 367  * prefix with the generic xattr API, a filesystem should create a
 368  * null-terminated array of struct xattr_handler (one for each prefix) and
 369  * hang a pointer to it off of the s_xattr field of the superblock.
 370  *
 371  * The generic_fooxattr() functions will use this list to dispatch xattr
 372  * operations to the correct xattr_handler.
 373  */
 374 #define for_each_xattr_handler(handlers, handler)               \
 375                 for ((handler) = *(handlers)++;                 \
 376                         (handler) != NULL;                      \
 377                         (handler) = *(handlers)++)
 378
 379 /*
 380  * Find the xattr_handler with the matching prefix.
 381  */
 382 static struct xattr_handler *
 383 xattr_resolve_name(struct xattr_handler **handlers, const char **name)
 384 {
 385         struct xattr_handler *handler;
 386
 387         if (!*name)
 388                 return NULL;
 389
 390         for_each_xattr_handler(handlers, handler) {
 391                 const char *n = strcmp_prefix(*name, handler->prefix);
 392                 if (n) {
 393                         *name = n;
 394                         break;
 395                 }
 396         }
 397         return handler;
 398 }
 399
 400 /*
 401  * Find the handler for the prefix and dispatch its get() operation.
 402  */
 403 ssize_t
 404 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 405 {
 406         struct xattr_handler *handler;
 407         struct inode *inode = dentry->d_inode;
 408
 409         handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
 410         if (!handler)
 411                 return -EOPNOTSUPP;
 412         return handler->get(inode, name, buffer, size);
 413 }
 414
 415 /*
 416  * Combine the results of the list() operation from every xattr_handler in the
 417  * list.
 418  */
 419 ssize_t
 420 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 421 {
 422         struct inode *inode = dentry->d_inode;
 423         struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;
 424         unsigned int size = 0;
 425
 426         if (!buffer) {
 427                 for_each_xattr_handler(handlers, handler)
 428                         size += handler->list(inode, NULL, 0, NULL, 0);
 429         } else {
 430                 char *buf = buffer;
 431
 432                 for_each_xattr_handler(handlers, handler) {
 433                         size = handler->list(inode, buf, buffer_size, NULL, 0);
 434                         if (size > buffer_size)
 435                                 return -ERANGE;
 436                         buf += size;
 437                         buffer_size -= size;
 438                 }
 439                 size = buf - buffer;
 440         }
 441         return size;
 442 }
 443
 444 /*
 445  * Find the handler for the prefix and dispatch its set() operation.
 446  */
 447 int
 448 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 449 {
 450         struct xattr_handler *handler;
 451         struct inode *inode = dentry->d_inode;
 452
 453         if (size == 0)
 454                 value = "";  /* empty EA, do not remove */
 455         handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
 456         if (!handler)
 457                 return -EOPNOTSUPP;
 458         return handler->set(inode, name, value, size, flags);
 459 }
 460
 461 /*
 462  * Find the handler for the prefix and dispatch its set() operation to remove
 463  * any associated extended attribute.
 464  */
 465 int
 466 generic_removexattr(struct dentry *dentry, const char *name)
 467 {
 468         struct xattr_handler *handler;
 469         struct inode *inode = dentry->d_inode;
 470
 471         handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
 472         if (!handler)
 473                 return -EOPNOTSUPP;
 474         return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
 475 }
 476
 477 EXPORT_SYMBOL(generic_getxattr);
 478 EXPORT_SYMBOL(generic_listxattr);
 479 EXPORT_SYMBOL(generic_setxattr);
 480 EXPORT_SYMBOL(generic_removexattr);