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 ssize_t ovl_getxattr(struct dentry *dentry, const char *name, 239 void *value, size_t size) 240 { 241 if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE && 242 ovl_is_private_xattr(name)) 243 return -ENODATA; 244 245 return vfs_getxattr(ovl_dentry_real(dentry), name, value, size); 246 } 247 248 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 249 { 250 ssize_t res; 251 int off; 252 253 res = vfs_listxattr(ovl_dentry_real(dentry), list, size); 254 if (res <= 0 || size == 0) 255 return res; 256 257 if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE) 258 return res; 259 260 /* filter out private xattrs */ 261 for (off = 0; off < res;) { 262 char *s = list + off; 263 size_t slen = strlen(s) + 1; 264 265 BUG_ON(off + slen > res); 266 267 if (ovl_is_private_xattr(s)) { 268 res -= slen; 269 memmove(s, s + slen, res - off); 270 } else { 271 off += slen; 272 } 273 } 274 275 return res; 276 } 277 278 int ovl_removexattr(struct dentry *dentry, const char *name) 279 { 280 int err; 281 struct path realpath; 282 enum ovl_path_type type; 283 284 err = ovl_want_write(dentry); 285 if (err) 286 goto out; 287 288 if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE && 289 ovl_is_private_xattr(name)) 290 goto out_drop_write; 291 292 type = ovl_path_real(dentry, &realpath); 293 if (type == OVL_PATH_LOWER) { 294 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 295 if (err < 0) 296 goto out_drop_write; 297 298 err = ovl_copy_up(dentry); 299 if (err) 300 goto out_drop_write; 301 302 ovl_path_upper(dentry, &realpath); 303 } 304 305 err = vfs_removexattr(realpath.dentry, name); 306 out_drop_write: 307 ovl_drop_write(dentry); 308 out: 309 return err; 310 } 311 312 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 313 struct dentry *realdentry) 314 { 315 if (type != OVL_PATH_LOWER) 316 return false; 317 318 if (special_file(realdentry->d_inode->i_mode)) 319 return false; 320 321 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 322 return false; 323 324 return true; 325 } 326 327 static int ovl_dentry_open(struct dentry *dentry, struct file *file, 328 const struct cred *cred) 329 { 330 int err; 331 struct path realpath; 332 enum ovl_path_type type; 333 bool want_write = false; 334 335 type = ovl_path_real(dentry, &realpath); 336 if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) { 337 want_write = true; 338 err = ovl_want_write(dentry); 339 if (err) 340 goto out; 341 342 if (file->f_flags & O_TRUNC) 343 err = ovl_copy_up_last(dentry, NULL, true); 344 else 345 err = ovl_copy_up(dentry); 346 if (err) 347 goto out_drop_write; 348 349 ovl_path_upper(dentry, &realpath); 350 } 351 352 err = vfs_open(&realpath, file, cred); 353 out_drop_write: 354 if (want_write) 355 ovl_drop_write(dentry); 356 out: 357 return err; 358 } 359 360 static const struct inode_operations ovl_file_inode_operations = { 361 .setattr = ovl_setattr, 362 .permission = ovl_permission, 363 .getattr = ovl_getattr, 364 .setxattr = ovl_setxattr, 365 .getxattr = ovl_getxattr, 366 .listxattr = ovl_listxattr, 367 .removexattr = ovl_removexattr, 368 .dentry_open = ovl_dentry_open, 369 }; 370 371 static const struct inode_operations ovl_symlink_inode_operations = { 372 .setattr = ovl_setattr, 373 .follow_link = ovl_follow_link, 374 .put_link = ovl_put_link, 375 .readlink = ovl_readlink, 376 .getattr = ovl_getattr, 377 .setxattr = ovl_setxattr, 378 .getxattr = ovl_getxattr, 379 .listxattr = ovl_listxattr, 380 .removexattr = ovl_removexattr, 381 }; 382 383 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, 384 struct ovl_entry *oe) 385 { 386 struct inode *inode; 387 388 inode = new_inode(sb); 389 if (!inode) 390 return NULL; 391 392 mode &= S_IFMT; 393 394 inode->i_ino = get_next_ino(); 395 inode->i_mode = mode; 396 inode->i_flags |= S_NOATIME | S_NOCMTIME; 397 398 switch (mode) { 399 case S_IFDIR: 400 inode->i_private = oe; 401 inode->i_op = &ovl_dir_inode_operations; 402 inode->i_fop = &ovl_dir_operations; 403 break; 404 405 case S_IFLNK: 406 inode->i_op = &ovl_symlink_inode_operations; 407 break; 408 409 case S_IFREG: 410 case S_IFSOCK: 411 case S_IFBLK: 412 case S_IFCHR: 413 case S_IFIFO: 414 inode->i_op = &ovl_file_inode_operations; 415 break; 416 417 default: 418 WARN(1, "illegal file type: %i\n", mode); 419 iput(inode); 420 inode = NULL; 421 } 422 423 return inode; 424 425 } 426