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 void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) 144 { 145 void *ret; 146 struct dentry *realdentry; 147 struct inode *realinode; 148 149 realdentry = ovl_dentry_real(dentry); 150 realinode = realdentry->d_inode; 151 152 if (WARN_ON(!realinode->i_op->follow_link)) 153 return ERR_PTR(-EPERM); 154 155 ret = realinode->i_op->follow_link(realdentry, nd); 156 if (IS_ERR(ret)) 157 return ret; 158 159 if (realinode->i_op->put_link) { 160 struct ovl_link_data *data; 161 162 data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); 163 if (!data) { 164 realinode->i_op->put_link(realdentry, nd, ret); 165 return ERR_PTR(-ENOMEM); 166 } 167 data->realdentry = realdentry; 168 data->cookie = ret; 169 170 return data; 171 } else { 172 return NULL; 173 } 174 } 175 176 static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c) 177 { 178 struct inode *realinode; 179 struct ovl_link_data *data = c; 180 181 if (!data) 182 return; 183 184 realinode = data->realdentry->d_inode; 185 realinode->i_op->put_link(data->realdentry, nd, data->cookie); 186 kfree(data); 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, "trusted.overlay.", 14) == 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 return type == OVL_PATH_UPPER && S_ISDIR(dentry->d_inode->i_mode); 242 } 243 244 ssize_t ovl_getxattr(struct dentry *dentry, const char *name, 245 void *value, size_t size) 246 { 247 struct path realpath; 248 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 249 250 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 251 return -ENODATA; 252 253 return vfs_getxattr(realpath.dentry, name, value, size); 254 } 255 256 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 257 { 258 struct path realpath; 259 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 260 ssize_t res; 261 int off; 262 263 res = vfs_listxattr(realpath.dentry, list, size); 264 if (res <= 0 || size == 0) 265 return res; 266 267 if (!ovl_need_xattr_filter(dentry, type)) 268 return res; 269 270 /* filter out private xattrs */ 271 for (off = 0; off < res;) { 272 char *s = list + off; 273 size_t slen = strlen(s) + 1; 274 275 BUG_ON(off + slen > res); 276 277 if (ovl_is_private_xattr(s)) { 278 res -= slen; 279 memmove(s, s + slen, res - off); 280 } else { 281 off += slen; 282 } 283 } 284 285 return res; 286 } 287 288 int ovl_removexattr(struct dentry *dentry, const char *name) 289 { 290 int err; 291 struct path realpath; 292 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 293 294 err = ovl_want_write(dentry); 295 if (err) 296 goto out; 297 298 err = -ENODATA; 299 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 300 goto out_drop_write; 301 302 if (type == OVL_PATH_LOWER) { 303 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 304 if (err < 0) 305 goto out_drop_write; 306 307 err = ovl_copy_up(dentry); 308 if (err) 309 goto out_drop_write; 310 311 ovl_path_upper(dentry, &realpath); 312 } 313 314 err = vfs_removexattr(realpath.dentry, name); 315 out_drop_write: 316 ovl_drop_write(dentry); 317 out: 318 return err; 319 } 320 321 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 322 struct dentry *realdentry) 323 { 324 if (type != OVL_PATH_LOWER) 325 return false; 326 327 if (special_file(realdentry->d_inode->i_mode)) 328 return false; 329 330 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 331 return false; 332 333 return true; 334 } 335 336 static int ovl_dentry_open(struct dentry *dentry, struct file *file, 337 const struct cred *cred) 338 { 339 int err; 340 struct path realpath; 341 enum ovl_path_type type; 342 bool want_write = false; 343 344 type = ovl_path_real(dentry, &realpath); 345 if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) { 346 want_write = true; 347 err = ovl_want_write(dentry); 348 if (err) 349 goto out; 350 351 if (file->f_flags & O_TRUNC) 352 err = ovl_copy_up_last(dentry, NULL, true); 353 else 354 err = ovl_copy_up(dentry); 355 if (err) 356 goto out_drop_write; 357 358 ovl_path_upper(dentry, &realpath); 359 } 360 361 err = vfs_open(&realpath, file, cred); 362 out_drop_write: 363 if (want_write) 364 ovl_drop_write(dentry); 365 out: 366 return err; 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 .dentry_open = ovl_dentry_open, 378 }; 379 380 static const struct inode_operations ovl_symlink_inode_operations = { 381 .setattr = ovl_setattr, 382 .follow_link = ovl_follow_link, 383 .put_link = ovl_put_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 } 435