1 /* 2 * 3 * Copyright (C) 2011 Novell Inc. 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 as published by 7 * the Free Software Foundation. 8 */ 9 10 #include <linux/fs.h> 11 #include <linux/slab.h> 12 #include <linux/xattr.h> 13 #include "overlayfs.h" 14 15 static int ovl_copy_up_truncate(struct dentry *dentry) 16 { 17 int err; 18 struct dentry *parent; 19 struct kstat stat; 20 struct path lowerpath; 21 22 parent = dget_parent(dentry); 23 err = ovl_copy_up(parent); 24 if (err) 25 goto out_dput_parent; 26 27 ovl_path_lower(dentry, &lowerpath); 28 err = vfs_getattr(&lowerpath, &stat); 29 if (err) 30 goto out_dput_parent; 31 32 stat.size = 0; 33 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat); 34 35 out_dput_parent: 36 dput(parent); 37 return err; 38 } 39 40 int ovl_setattr(struct dentry *dentry, struct iattr *attr) 41 { 42 int err; 43 struct dentry *upperdentry; 44 45 /* 46 * Check for permissions before trying to copy-up. This is redundant 47 * since it will be rechecked later by ->setattr() on upper dentry. But 48 * without this, copy-up can be triggered by just about anybody. 49 * 50 * We don't initialize inode->size, which just means that 51 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not 52 * check for a swapfile (which this won't be anyway). 53 */ 54 err = inode_change_ok(dentry->d_inode, attr); 55 if (err) 56 return err; 57 58 err = ovl_want_write(dentry); 59 if (err) 60 goto out; 61 62 err = ovl_copy_up(dentry); 63 if (!err) { 64 upperdentry = ovl_dentry_upper(dentry); 65 66 inode_lock(upperdentry->d_inode); 67 err = notify_change(upperdentry, attr, NULL); 68 inode_unlock(upperdentry->d_inode); 69 } 70 ovl_drop_write(dentry); 71 out: 72 return err; 73 } 74 75 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, 76 struct kstat *stat) 77 { 78 struct path realpath; 79 80 ovl_path_real(dentry, &realpath); 81 return vfs_getattr(&realpath, stat); 82 } 83 84 int ovl_permission(struct inode *inode, int mask) 85 { 86 struct ovl_entry *oe; 87 struct dentry *alias = NULL; 88 struct inode *realinode; 89 struct dentry *realdentry; 90 bool is_upper; 91 int err; 92 93 if (S_ISDIR(inode->i_mode)) { 94 oe = inode->i_private; 95 } else if (mask & MAY_NOT_BLOCK) { 96 return -ECHILD; 97 } else { 98 /* 99 * For non-directories find an alias and get the info 100 * from there. 101 */ 102 alias = d_find_any_alias(inode); 103 if (WARN_ON(!alias)) 104 return -ENOENT; 105 106 oe = alias->d_fsdata; 107 } 108 109 realdentry = ovl_entry_real(oe, &is_upper); 110 111 if (ovl_is_default_permissions(inode)) { 112 struct kstat stat; 113 struct path realpath = { .dentry = realdentry }; 114 115 if (mask & MAY_NOT_BLOCK) 116 return -ECHILD; 117 118 realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper); 119 120 err = vfs_getattr(&realpath, &stat); 121 if (err) 122 return err; 123 124 if ((stat.mode ^ inode->i_mode) & S_IFMT) 125 return -ESTALE; 126 127 inode->i_mode = stat.mode; 128 inode->i_uid = stat.uid; 129 inode->i_gid = stat.gid; 130 131 return generic_permission(inode, mask); 132 } 133 134 /* Careful in RCU walk mode */ 135 realinode = ACCESS_ONCE(realdentry->d_inode); 136 if (!realinode) { 137 WARN_ON(!(mask & MAY_NOT_BLOCK)); 138 err = -ENOENT; 139 goto out_dput; 140 } 141 142 if (mask & MAY_WRITE) { 143 umode_t mode = realinode->i_mode; 144 145 /* 146 * Writes will always be redirected to upper layer, so 147 * ignore lower layer being read-only. 148 * 149 * If the overlay itself is read-only then proceed 150 * with the permission check, don't return EROFS. 151 * This will only happen if this is the lower layer of 152 * another overlayfs. 153 * 154 * If upper fs becomes read-only after the overlay was 155 * constructed return EROFS to prevent modification of 156 * upper layer. 157 */ 158 err = -EROFS; 159 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && 160 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) 161 goto out_dput; 162 } 163 164 err = __inode_permission(realinode, mask); 165 out_dput: 166 dput(alias); 167 return err; 168 } 169 170 static const char *ovl_get_link(struct dentry *dentry, 171 struct inode *inode, 172 struct delayed_call *done) 173 { 174 struct dentry *realdentry; 175 struct inode *realinode; 176 177 if (!dentry) 178 return ERR_PTR(-ECHILD); 179 180 realdentry = ovl_dentry_real(dentry); 181 realinode = realdentry->d_inode; 182 183 if (WARN_ON(!realinode->i_op->get_link)) 184 return ERR_PTR(-EPERM); 185 186 return realinode->i_op->get_link(realdentry, realinode, done); 187 } 188 189 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) 190 { 191 struct path realpath; 192 struct inode *realinode; 193 194 ovl_path_real(dentry, &realpath); 195 realinode = realpath.dentry->d_inode; 196 197 if (!realinode->i_op->readlink) 198 return -EINVAL; 199 200 touch_atime(&realpath); 201 202 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); 203 } 204 205 206 static bool ovl_is_private_xattr(const char *name) 207 { 208 return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; 209 } 210 211 int ovl_setxattr(struct dentry *dentry, const char *name, 212 const void *value, size_t size, int flags) 213 { 214 int err; 215 struct dentry *upperdentry; 216 217 err = ovl_want_write(dentry); 218 if (err) 219 goto out; 220 221 err = -EPERM; 222 if (ovl_is_private_xattr(name)) 223 goto out_drop_write; 224 225 err = ovl_copy_up(dentry); 226 if (err) 227 goto out_drop_write; 228 229 upperdentry = ovl_dentry_upper(dentry); 230 err = vfs_setxattr(upperdentry, name, value, size, flags); 231 232 out_drop_write: 233 ovl_drop_write(dentry); 234 out: 235 return err; 236 } 237 238 static bool ovl_need_xattr_filter(struct dentry *dentry, 239 enum ovl_path_type type) 240 { 241 if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) 242 return S_ISDIR(dentry->d_inode->i_mode); 243 else 244 return false; 245 } 246 247 ssize_t ovl_getxattr(struct dentry *dentry, const char *name, 248 void *value, size_t size) 249 { 250 struct path realpath; 251 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 252 253 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 254 return -ENODATA; 255 256 return vfs_getxattr(realpath.dentry, name, value, size); 257 } 258 259 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 260 { 261 struct path realpath; 262 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 263 ssize_t res; 264 int off; 265 266 res = vfs_listxattr(realpath.dentry, list, size); 267 if (res <= 0 || size == 0) 268 return res; 269 270 if (!ovl_need_xattr_filter(dentry, type)) 271 return res; 272 273 /* filter out private xattrs */ 274 for (off = 0; off < res;) { 275 char *s = list + off; 276 size_t slen = strlen(s) + 1; 277 278 BUG_ON(off + slen > res); 279 280 if (ovl_is_private_xattr(s)) { 281 res -= slen; 282 memmove(s, s + slen, res - off); 283 } else { 284 off += slen; 285 } 286 } 287 288 return res; 289 } 290 291 int ovl_removexattr(struct dentry *dentry, const char *name) 292 { 293 int err; 294 struct path realpath; 295 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 296 297 err = ovl_want_write(dentry); 298 if (err) 299 goto out; 300 301 err = -ENODATA; 302 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 303 goto out_drop_write; 304 305 if (!OVL_TYPE_UPPER(type)) { 306 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 307 if (err < 0) 308 goto out_drop_write; 309 310 err = ovl_copy_up(dentry); 311 if (err) 312 goto out_drop_write; 313 314 ovl_path_upper(dentry, &realpath); 315 } 316 317 err = vfs_removexattr(realpath.dentry, name); 318 out_drop_write: 319 ovl_drop_write(dentry); 320 out: 321 return err; 322 } 323 324 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 325 struct dentry *realdentry) 326 { 327 if (OVL_TYPE_UPPER(type)) 328 return false; 329 330 if (special_file(realdentry->d_inode->i_mode)) 331 return false; 332 333 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 334 return false; 335 336 return true; 337 } 338 339 struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) 340 { 341 int err; 342 struct path realpath; 343 enum ovl_path_type type; 344 345 if (d_is_dir(dentry)) 346 return d_backing_inode(dentry); 347 348 type = ovl_path_real(dentry, &realpath); 349 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { 350 err = ovl_want_write(dentry); 351 if (err) 352 return ERR_PTR(err); 353 354 if (file_flags & O_TRUNC) 355 err = ovl_copy_up_truncate(dentry); 356 else 357 err = ovl_copy_up(dentry); 358 ovl_drop_write(dentry); 359 if (err) 360 return ERR_PTR(err); 361 362 ovl_path_upper(dentry, &realpath); 363 } 364 365 if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE) 366 return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags); 367 368 return d_backing_inode(realpath.dentry); 369 } 370 371 static const struct inode_operations ovl_file_inode_operations = { 372 .setattr = ovl_setattr, 373 .permission = ovl_permission, 374 .getattr = ovl_getattr, 375 .setxattr = ovl_setxattr, 376 .getxattr = ovl_getxattr, 377 .listxattr = ovl_listxattr, 378 .removexattr = ovl_removexattr, 379 }; 380 381 static const struct inode_operations ovl_symlink_inode_operations = { 382 .setattr = ovl_setattr, 383 .get_link = ovl_get_link, 384 .readlink = ovl_readlink, 385 .getattr = ovl_getattr, 386 .setxattr = ovl_setxattr, 387 .getxattr = ovl_getxattr, 388 .listxattr = ovl_listxattr, 389 .removexattr = ovl_removexattr, 390 }; 391 392 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, 393 struct ovl_entry *oe) 394 { 395 struct inode *inode; 396 397 inode = new_inode(sb); 398 if (!inode) 399 return NULL; 400 401 mode &= S_IFMT; 402 403 inode->i_ino = get_next_ino(); 404 inode->i_mode = mode; 405 inode->i_flags |= S_NOATIME | S_NOCMTIME; 406 407 switch (mode) { 408 case S_IFDIR: 409 inode->i_private = oe; 410 inode->i_op = &ovl_dir_inode_operations; 411 inode->i_fop = &ovl_dir_operations; 412 break; 413 414 case S_IFLNK: 415 inode->i_op = &ovl_symlink_inode_operations; 416 break; 417 418 case S_IFREG: 419 case S_IFSOCK: 420 case S_IFBLK: 421 case S_IFCHR: 422 case S_IFIFO: 423 inode->i_op = &ovl_file_inode_operations; 424 break; 425 426 default: 427 WARN(1, "illegal file type: %i\n", mode); 428 iput(inode); 429 inode = NULL; 430 } 431 432 return inode; 433 } 434