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 err = ovl_want_write(dentry); 46 if (err) 47 goto out; 48 49 err = ovl_copy_up(dentry); 50 if (!err) { 51 upperdentry = ovl_dentry_upper(dentry); 52 53 mutex_lock(&upperdentry->d_inode->i_mutex); 54 err = notify_change(upperdentry, attr, NULL); 55 mutex_unlock(&upperdentry->d_inode->i_mutex); 56 } 57 ovl_drop_write(dentry); 58 out: 59 return err; 60 } 61 62 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, 63 struct kstat *stat) 64 { 65 struct path realpath; 66 67 ovl_path_real(dentry, &realpath); 68 return vfs_getattr(&realpath, stat); 69 } 70 71 int ovl_permission(struct inode *inode, int mask) 72 { 73 struct ovl_entry *oe; 74 struct dentry *alias = NULL; 75 struct inode *realinode; 76 struct dentry *realdentry; 77 bool is_upper; 78 int err; 79 80 if (S_ISDIR(inode->i_mode)) { 81 oe = inode->i_private; 82 } else if (mask & MAY_NOT_BLOCK) { 83 return -ECHILD; 84 } else { 85 /* 86 * For non-directories find an alias and get the info 87 * from there. 88 */ 89 alias = d_find_any_alias(inode); 90 if (WARN_ON(!alias)) 91 return -ENOENT; 92 93 oe = alias->d_fsdata; 94 } 95 96 realdentry = ovl_entry_real(oe, &is_upper); 97 98 /* Careful in RCU walk mode */ 99 realinode = ACCESS_ONCE(realdentry->d_inode); 100 if (!realinode) { 101 WARN_ON(!(mask & MAY_NOT_BLOCK)); 102 err = -ENOENT; 103 goto out_dput; 104 } 105 106 if (mask & MAY_WRITE) { 107 umode_t mode = realinode->i_mode; 108 109 /* 110 * Writes will always be redirected to upper layer, so 111 * ignore lower layer being read-only. 112 * 113 * If the overlay itself is read-only then proceed 114 * with the permission check, don't return EROFS. 115 * This will only happen if this is the lower layer of 116 * another overlayfs. 117 * 118 * If upper fs becomes read-only after the overlay was 119 * constructed return EROFS to prevent modification of 120 * upper layer. 121 */ 122 err = -EROFS; 123 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && 124 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) 125 goto out_dput; 126 } 127 128 err = __inode_permission(realinode, mask); 129 out_dput: 130 dput(alias); 131 return err; 132 } 133 134 135 struct ovl_link_data { 136 struct dentry *realdentry; 137 void *cookie; 138 }; 139 140 static const char *ovl_follow_link(struct dentry *dentry, void **cookie) 141 { 142 struct dentry *realdentry; 143 struct inode *realinode; 144 struct ovl_link_data *data = NULL; 145 const char *ret; 146 147 realdentry = ovl_dentry_real(dentry); 148 realinode = realdentry->d_inode; 149 150 if (WARN_ON(!realinode->i_op->follow_link)) 151 return ERR_PTR(-EPERM); 152 153 if (realinode->i_op->put_link) { 154 data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); 155 if (!data) 156 return ERR_PTR(-ENOMEM); 157 data->realdentry = realdentry; 158 } 159 160 ret = realinode->i_op->follow_link(realdentry, cookie); 161 if (IS_ERR_OR_NULL(ret)) { 162 kfree(data); 163 return ret; 164 } 165 166 if (data) 167 data->cookie = *cookie; 168 169 *cookie = data; 170 171 return ret; 172 } 173 174 static void ovl_put_link(struct inode *unused, void *c) 175 { 176 struct inode *realinode; 177 struct ovl_link_data *data = c; 178 179 if (!data) 180 return; 181 182 realinode = data->realdentry->d_inode; 183 realinode->i_op->put_link(realinode, data->cookie); 184 kfree(data); 185 } 186 187 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) 188 { 189 struct path realpath; 190 struct inode *realinode; 191 192 ovl_path_real(dentry, &realpath); 193 realinode = realpath.dentry->d_inode; 194 195 if (!realinode->i_op->readlink) 196 return -EINVAL; 197 198 touch_atime(&realpath); 199 200 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); 201 } 202 203 204 static bool ovl_is_private_xattr(const char *name) 205 { 206 return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; 207 } 208 209 int ovl_setxattr(struct dentry *dentry, const char *name, 210 const void *value, size_t size, int flags) 211 { 212 int err; 213 struct dentry *upperdentry; 214 215 err = ovl_want_write(dentry); 216 if (err) 217 goto out; 218 219 err = -EPERM; 220 if (ovl_is_private_xattr(name)) 221 goto out_drop_write; 222 223 err = ovl_copy_up(dentry); 224 if (err) 225 goto out_drop_write; 226 227 upperdentry = ovl_dentry_upper(dentry); 228 err = vfs_setxattr(upperdentry, name, value, size, flags); 229 230 out_drop_write: 231 ovl_drop_write(dentry); 232 out: 233 return err; 234 } 235 236 static bool ovl_need_xattr_filter(struct dentry *dentry, 237 enum ovl_path_type type) 238 { 239 if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) 240 return S_ISDIR(dentry->d_inode->i_mode); 241 else 242 return false; 243 } 244 245 ssize_t ovl_getxattr(struct dentry *dentry, const char *name, 246 void *value, size_t size) 247 { 248 struct path realpath; 249 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 250 251 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 252 return -ENODATA; 253 254 return vfs_getxattr(realpath.dentry, name, value, size); 255 } 256 257 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 258 { 259 struct path realpath; 260 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 261 ssize_t res; 262 int off; 263 264 res = vfs_listxattr(realpath.dentry, list, size); 265 if (res <= 0 || size == 0) 266 return res; 267 268 if (!ovl_need_xattr_filter(dentry, type)) 269 return res; 270 271 /* filter out private xattrs */ 272 for (off = 0; off < res;) { 273 char *s = list + off; 274 size_t slen = strlen(s) + 1; 275 276 BUG_ON(off + slen > res); 277 278 if (ovl_is_private_xattr(s)) { 279 res -= slen; 280 memmove(s, s + slen, res - off); 281 } else { 282 off += slen; 283 } 284 } 285 286 return res; 287 } 288 289 int ovl_removexattr(struct dentry *dentry, const char *name) 290 { 291 int err; 292 struct path realpath; 293 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 294 295 err = ovl_want_write(dentry); 296 if (err) 297 goto out; 298 299 err = -ENODATA; 300 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 301 goto out_drop_write; 302 303 if (!OVL_TYPE_UPPER(type)) { 304 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 305 if (err < 0) 306 goto out_drop_write; 307 308 err = ovl_copy_up(dentry); 309 if (err) 310 goto out_drop_write; 311 312 ovl_path_upper(dentry, &realpath); 313 } 314 315 err = vfs_removexattr(realpath.dentry, name); 316 out_drop_write: 317 ovl_drop_write(dentry); 318 out: 319 return err; 320 } 321 322 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 323 struct dentry *realdentry) 324 { 325 if (OVL_TYPE_UPPER(type)) 326 return false; 327 328 if (special_file(realdentry->d_inode->i_mode)) 329 return false; 330 331 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 332 return false; 333 334 return true; 335 } 336 337 struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) 338 { 339 int err; 340 struct path realpath; 341 enum ovl_path_type type; 342 343 if (d_is_dir(dentry)) 344 return d_backing_inode(dentry); 345 346 type = ovl_path_real(dentry, &realpath); 347 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { 348 err = ovl_want_write(dentry); 349 if (err) 350 return ERR_PTR(err); 351 352 if (file_flags & O_TRUNC) 353 err = ovl_copy_up_truncate(dentry); 354 else 355 err = ovl_copy_up(dentry); 356 ovl_drop_write(dentry); 357 if (err) 358 return ERR_PTR(err); 359 360 ovl_path_upper(dentry, &realpath); 361 } 362 363 if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE) 364 return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags); 365 366 return d_backing_inode(realpath.dentry); 367 } 368 369 static const struct inode_operations ovl_file_inode_operations = { 370 .setattr = ovl_setattr, 371 .permission = ovl_permission, 372 .getattr = ovl_getattr, 373 .setxattr = ovl_setxattr, 374 .getxattr = ovl_getxattr, 375 .listxattr = ovl_listxattr, 376 .removexattr = ovl_removexattr, 377 }; 378 379 static const struct inode_operations ovl_symlink_inode_operations = { 380 .setattr = ovl_setattr, 381 .follow_link = ovl_follow_link, 382 .put_link = ovl_put_link, 383 .readlink = ovl_readlink, 384 .getattr = ovl_getattr, 385 .setxattr = ovl_setxattr, 386 .getxattr = ovl_getxattr, 387 .listxattr = ovl_listxattr, 388 .removexattr = ovl_removexattr, 389 }; 390 391 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, 392 struct ovl_entry *oe) 393 { 394 struct inode *inode; 395 396 inode = new_inode(sb); 397 if (!inode) 398 return NULL; 399 400 mode &= S_IFMT; 401 402 inode->i_ino = get_next_ino(); 403 inode->i_mode = mode; 404 inode->i_flags |= S_NOATIME | S_NOCMTIME; 405 406 switch (mode) { 407 case S_IFDIR: 408 inode->i_private = oe; 409 inode->i_op = &ovl_dir_inode_operations; 410 inode->i_fop = &ovl_dir_operations; 411 break; 412 413 case S_IFLNK: 414 inode->i_op = &ovl_symlink_inode_operations; 415 break; 416 417 case S_IFREG: 418 case S_IFSOCK: 419 case S_IFBLK: 420 case S_IFCHR: 421 case S_IFIFO: 422 inode->i_op = &ovl_file_inode_operations; 423 break; 424 425 default: 426 WARN(1, "illegal file type: %i\n", mode); 427 iput(inode); 428 inode = NULL; 429 } 430 431 return inode; 432 } 433