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_last(struct dentry *dentry, struct iattr *attr, 16 bool no_data) 17 { 18 int err; 19 struct dentry *parent; 20 struct kstat stat; 21 struct path lowerpath; 22 23 parent = dget_parent(dentry); 24 err = ovl_copy_up(parent); 25 if (err) 26 goto out_dput_parent; 27 28 ovl_path_lower(dentry, &lowerpath); 29 err = vfs_getattr(&lowerpath, &stat); 30 if (err) 31 goto out_dput_parent; 32 33 if (no_data) 34 stat.size = 0; 35 36 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr); 37 38 out_dput_parent: 39 dput(parent); 40 return err; 41 } 42 43 int ovl_setattr(struct dentry *dentry, struct iattr *attr) 44 { 45 int err; 46 struct dentry *upperdentry; 47 48 err = ovl_want_write(dentry); 49 if (err) 50 goto out; 51 52 upperdentry = ovl_dentry_upper(dentry); 53 if (upperdentry) { 54 mutex_lock(&upperdentry->d_inode->i_mutex); 55 err = notify_change(upperdentry, attr, NULL); 56 mutex_unlock(&upperdentry->d_inode->i_mutex); 57 } else { 58 err = ovl_copy_up_last(dentry, attr, false); 59 } 60 ovl_drop_write(dentry); 61 out: 62 return err; 63 } 64 65 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, 66 struct kstat *stat) 67 { 68 struct path realpath; 69 70 ovl_path_real(dentry, &realpath); 71 return vfs_getattr(&realpath, stat); 72 } 73 74 int ovl_permission(struct inode *inode, int mask) 75 { 76 struct ovl_entry *oe; 77 struct dentry *alias = NULL; 78 struct inode *realinode; 79 struct dentry *realdentry; 80 bool is_upper; 81 int err; 82 83 if (S_ISDIR(inode->i_mode)) { 84 oe = inode->i_private; 85 } else if (mask & MAY_NOT_BLOCK) { 86 return -ECHILD; 87 } else { 88 /* 89 * For non-directories find an alias and get the info 90 * from there. 91 */ 92 alias = d_find_any_alias(inode); 93 if (WARN_ON(!alias)) 94 return -ENOENT; 95 96 oe = alias->d_fsdata; 97 } 98 99 realdentry = ovl_entry_real(oe, &is_upper); 100 101 /* Careful in RCU walk mode */ 102 realinode = ACCESS_ONCE(realdentry->d_inode); 103 if (!realinode) { 104 WARN_ON(!(mask & MAY_NOT_BLOCK)); 105 err = -ENOENT; 106 goto out_dput; 107 } 108 109 if (mask & MAY_WRITE) { 110 umode_t mode = realinode->i_mode; 111 112 /* 113 * Writes will always be redirected to upper layer, so 114 * ignore lower layer being read-only. 115 * 116 * If the overlay itself is read-only then proceed 117 * with the permission check, don't return EROFS. 118 * This will only happen if this is the lower layer of 119 * another overlayfs. 120 * 121 * If upper fs becomes read-only after the overlay was 122 * constructed return EROFS to prevent modification of 123 * upper layer. 124 */ 125 err = -EROFS; 126 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && 127 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) 128 goto out_dput; 129 } 130 131 err = __inode_permission(realinode, mask); 132 out_dput: 133 dput(alias); 134 return err; 135 } 136 137 138 struct ovl_link_data { 139 struct dentry *realdentry; 140 void *cookie; 141 }; 142 143 static const char *ovl_follow_link(struct dentry *dentry, void **cookie) 144 { 145 struct dentry *realdentry; 146 struct inode *realinode; 147 struct ovl_link_data *data = NULL; 148 const char *ret; 149 150 realdentry = ovl_dentry_real(dentry); 151 realinode = realdentry->d_inode; 152 153 if (WARN_ON(!realinode->i_op->follow_link)) 154 return ERR_PTR(-EPERM); 155 156 if (realinode->i_op->put_link) { 157 data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); 158 if (!data) 159 return ERR_PTR(-ENOMEM); 160 data->realdentry = realdentry; 161 } 162 163 ret = realinode->i_op->follow_link(realdentry, cookie); 164 if (IS_ERR_OR_NULL(ret)) { 165 kfree(data); 166 return ret; 167 } 168 169 if (data) 170 data->cookie = *cookie; 171 172 *cookie = data; 173 174 return ret; 175 } 176 177 static void ovl_put_link(struct inode *unused, void *c) 178 { 179 struct inode *realinode; 180 struct ovl_link_data *data = c; 181 182 if (!data) 183 return; 184 185 realinode = data->realdentry->d_inode; 186 realinode->i_op->put_link(realinode, data->cookie); 187 kfree(data); 188 } 189 190 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) 191 { 192 struct path realpath; 193 struct inode *realinode; 194 195 ovl_path_real(dentry, &realpath); 196 realinode = realpath.dentry->d_inode; 197 198 if (!realinode->i_op->readlink) 199 return -EINVAL; 200 201 touch_atime(&realpath); 202 203 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); 204 } 205 206 207 static bool ovl_is_private_xattr(const char *name) 208 { 209 return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; 210 } 211 212 int ovl_setxattr(struct dentry *dentry, const char *name, 213 const void *value, size_t size, int flags) 214 { 215 int err; 216 struct dentry *upperdentry; 217 218 err = ovl_want_write(dentry); 219 if (err) 220 goto out; 221 222 err = -EPERM; 223 if (ovl_is_private_xattr(name)) 224 goto out_drop_write; 225 226 err = ovl_copy_up(dentry); 227 if (err) 228 goto out_drop_write; 229 230 upperdentry = ovl_dentry_upper(dentry); 231 err = vfs_setxattr(upperdentry, name, value, size, flags); 232 233 out_drop_write: 234 ovl_drop_write(dentry); 235 out: 236 return err; 237 } 238 239 static bool ovl_need_xattr_filter(struct dentry *dentry, 240 enum ovl_path_type type) 241 { 242 if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) 243 return S_ISDIR(dentry->d_inode->i_mode); 244 else 245 return false; 246 } 247 248 ssize_t ovl_getxattr(struct dentry *dentry, const char *name, 249 void *value, size_t size) 250 { 251 struct path realpath; 252 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 253 254 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 255 return -ENODATA; 256 257 return vfs_getxattr(realpath.dentry, name, value, size); 258 } 259 260 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 261 { 262 struct path realpath; 263 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 264 ssize_t res; 265 int off; 266 267 res = vfs_listxattr(realpath.dentry, list, size); 268 if (res <= 0 || size == 0) 269 return res; 270 271 if (!ovl_need_xattr_filter(dentry, type)) 272 return res; 273 274 /* filter out private xattrs */ 275 for (off = 0; off < res;) { 276 char *s = list + off; 277 size_t slen = strlen(s) + 1; 278 279 BUG_ON(off + slen > res); 280 281 if (ovl_is_private_xattr(s)) { 282 res -= slen; 283 memmove(s, s + slen, res - off); 284 } else { 285 off += slen; 286 } 287 } 288 289 return res; 290 } 291 292 int ovl_removexattr(struct dentry *dentry, const char *name) 293 { 294 int err; 295 struct path realpath; 296 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 297 298 err = ovl_want_write(dentry); 299 if (err) 300 goto out; 301 302 err = -ENODATA; 303 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 304 goto out_drop_write; 305 306 if (!OVL_TYPE_UPPER(type)) { 307 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 308 if (err < 0) 309 goto out_drop_write; 310 311 err = ovl_copy_up(dentry); 312 if (err) 313 goto out_drop_write; 314 315 ovl_path_upper(dentry, &realpath); 316 } 317 318 err = vfs_removexattr(realpath.dentry, name); 319 out_drop_write: 320 ovl_drop_write(dentry); 321 out: 322 return err; 323 } 324 325 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 326 struct dentry *realdentry) 327 { 328 if (OVL_TYPE_UPPER(type)) 329 return false; 330 331 if (special_file(realdentry->d_inode->i_mode)) 332 return false; 333 334 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 335 return false; 336 337 return true; 338 } 339 340 struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) 341 { 342 int err; 343 struct path realpath; 344 enum ovl_path_type type; 345 346 if (d_is_dir(dentry)) 347 return d_backing_inode(dentry); 348 349 type = ovl_path_real(dentry, &realpath); 350 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { 351 err = ovl_want_write(dentry); 352 if (err) 353 return ERR_PTR(err); 354 355 if (file_flags & O_TRUNC) 356 err = ovl_copy_up_last(dentry, NULL, true); 357 else 358 err = ovl_copy_up(dentry); 359 ovl_drop_write(dentry); 360 if (err) 361 return ERR_PTR(err); 362 363 ovl_path_upper(dentry, &realpath); 364 } 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