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 static const char *ovl_get_link(struct dentry *dentry, 135 struct inode *inode, 136 struct delayed_call *done) 137 { 138 struct dentry *realdentry; 139 struct inode *realinode; 140 141 if (!dentry) 142 return ERR_PTR(-ECHILD); 143 144 realdentry = ovl_dentry_real(dentry); 145 realinode = realdentry->d_inode; 146 147 if (WARN_ON(!realinode->i_op->get_link)) 148 return ERR_PTR(-EPERM); 149 150 return realinode->i_op->get_link(realdentry, realinode, done); 151 } 152 153 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) 154 { 155 struct path realpath; 156 struct inode *realinode; 157 158 ovl_path_real(dentry, &realpath); 159 realinode = realpath.dentry->d_inode; 160 161 if (!realinode->i_op->readlink) 162 return -EINVAL; 163 164 touch_atime(&realpath); 165 166 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); 167 } 168 169 170 static bool ovl_is_private_xattr(const char *name) 171 { 172 return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; 173 } 174 175 int ovl_setxattr(struct dentry *dentry, const char *name, 176 const void *value, size_t size, int flags) 177 { 178 int err; 179 struct dentry *upperdentry; 180 181 err = ovl_want_write(dentry); 182 if (err) 183 goto out; 184 185 err = -EPERM; 186 if (ovl_is_private_xattr(name)) 187 goto out_drop_write; 188 189 err = ovl_copy_up(dentry); 190 if (err) 191 goto out_drop_write; 192 193 upperdentry = ovl_dentry_upper(dentry); 194 err = vfs_setxattr(upperdentry, name, value, size, flags); 195 196 out_drop_write: 197 ovl_drop_write(dentry); 198 out: 199 return err; 200 } 201 202 static bool ovl_need_xattr_filter(struct dentry *dentry, 203 enum ovl_path_type type) 204 { 205 if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) 206 return S_ISDIR(dentry->d_inode->i_mode); 207 else 208 return false; 209 } 210 211 ssize_t ovl_getxattr(struct dentry *dentry, const char *name, 212 void *value, size_t size) 213 { 214 struct path realpath; 215 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 216 217 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 218 return -ENODATA; 219 220 return vfs_getxattr(realpath.dentry, name, value, size); 221 } 222 223 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 224 { 225 struct path realpath; 226 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 227 ssize_t res; 228 int off; 229 230 res = vfs_listxattr(realpath.dentry, list, size); 231 if (res <= 0 || size == 0) 232 return res; 233 234 if (!ovl_need_xattr_filter(dentry, type)) 235 return res; 236 237 /* filter out private xattrs */ 238 for (off = 0; off < res;) { 239 char *s = list + off; 240 size_t slen = strlen(s) + 1; 241 242 BUG_ON(off + slen > res); 243 244 if (ovl_is_private_xattr(s)) { 245 res -= slen; 246 memmove(s, s + slen, res - off); 247 } else { 248 off += slen; 249 } 250 } 251 252 return res; 253 } 254 255 int ovl_removexattr(struct dentry *dentry, const char *name) 256 { 257 int err; 258 struct path realpath; 259 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 260 261 err = ovl_want_write(dentry); 262 if (err) 263 goto out; 264 265 err = -ENODATA; 266 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) 267 goto out_drop_write; 268 269 if (!OVL_TYPE_UPPER(type)) { 270 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 271 if (err < 0) 272 goto out_drop_write; 273 274 err = ovl_copy_up(dentry); 275 if (err) 276 goto out_drop_write; 277 278 ovl_path_upper(dentry, &realpath); 279 } 280 281 err = vfs_removexattr(realpath.dentry, name); 282 out_drop_write: 283 ovl_drop_write(dentry); 284 out: 285 return err; 286 } 287 288 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 289 struct dentry *realdentry) 290 { 291 if (OVL_TYPE_UPPER(type)) 292 return false; 293 294 if (special_file(realdentry->d_inode->i_mode)) 295 return false; 296 297 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 298 return false; 299 300 return true; 301 } 302 303 struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) 304 { 305 int err; 306 struct path realpath; 307 enum ovl_path_type type; 308 309 if (d_is_dir(dentry)) 310 return d_backing_inode(dentry); 311 312 type = ovl_path_real(dentry, &realpath); 313 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { 314 err = ovl_want_write(dentry); 315 if (err) 316 return ERR_PTR(err); 317 318 if (file_flags & O_TRUNC) 319 err = ovl_copy_up_truncate(dentry); 320 else 321 err = ovl_copy_up(dentry); 322 ovl_drop_write(dentry); 323 if (err) 324 return ERR_PTR(err); 325 326 ovl_path_upper(dentry, &realpath); 327 } 328 329 if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE) 330 return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags); 331 332 return d_backing_inode(realpath.dentry); 333 } 334 335 static const struct inode_operations ovl_file_inode_operations = { 336 .setattr = ovl_setattr, 337 .permission = ovl_permission, 338 .getattr = ovl_getattr, 339 .setxattr = ovl_setxattr, 340 .getxattr = ovl_getxattr, 341 .listxattr = ovl_listxattr, 342 .removexattr = ovl_removexattr, 343 }; 344 345 static const struct inode_operations ovl_symlink_inode_operations = { 346 .setattr = ovl_setattr, 347 .get_link = ovl_get_link, 348 .readlink = ovl_readlink, 349 .getattr = ovl_getattr, 350 .setxattr = ovl_setxattr, 351 .getxattr = ovl_getxattr, 352 .listxattr = ovl_listxattr, 353 .removexattr = ovl_removexattr, 354 }; 355 356 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, 357 struct ovl_entry *oe) 358 { 359 struct inode *inode; 360 361 inode = new_inode(sb); 362 if (!inode) 363 return NULL; 364 365 mode &= S_IFMT; 366 367 inode->i_ino = get_next_ino(); 368 inode->i_mode = mode; 369 inode->i_flags |= S_NOATIME | S_NOCMTIME; 370 371 switch (mode) { 372 case S_IFDIR: 373 inode->i_private = oe; 374 inode->i_op = &ovl_dir_inode_operations; 375 inode->i_fop = &ovl_dir_operations; 376 break; 377 378 case S_IFLNK: 379 inode->i_op = &ovl_symlink_inode_operations; 380 break; 381 382 case S_IFREG: 383 case S_IFSOCK: 384 case S_IFBLK: 385 case S_IFCHR: 386 case S_IFIFO: 387 inode->i_op = &ovl_file_inode_operations; 388 break; 389 390 default: 391 WARN(1, "illegal file type: %i\n", mode); 392 iput(inode); 393 inode = NULL; 394 } 395 396 return inode; 397 } 398