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 <linux/posix_acl.h> 14 #include "overlayfs.h" 15 16 static int ovl_copy_up_truncate(struct dentry *dentry) 17 { 18 int err; 19 struct dentry *parent; 20 struct kstat stat; 21 struct path lowerpath; 22 const struct cred *old_cred; 23 24 parent = dget_parent(dentry); 25 err = ovl_copy_up(parent); 26 if (err) 27 goto out_dput_parent; 28 29 ovl_path_lower(dentry, &lowerpath); 30 31 old_cred = ovl_override_creds(dentry->d_sb); 32 err = vfs_getattr(&lowerpath, &stat); 33 if (!err) { 34 stat.size = 0; 35 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat); 36 } 37 revert_creds(old_cred); 38 39 out_dput_parent: 40 dput(parent); 41 return err; 42 } 43 44 int ovl_setattr(struct dentry *dentry, struct iattr *attr) 45 { 46 int err; 47 struct dentry *upperdentry; 48 const struct cred *old_cred; 49 50 /* 51 * Check for permissions before trying to copy-up. This is redundant 52 * since it will be rechecked later by ->setattr() on upper dentry. But 53 * without this, copy-up can be triggered by just about anybody. 54 * 55 * We don't initialize inode->size, which just means that 56 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not 57 * check for a swapfile (which this won't be anyway). 58 */ 59 err = setattr_prepare(dentry, attr); 60 if (err) 61 return err; 62 63 err = ovl_want_write(dentry); 64 if (err) 65 goto out; 66 67 if (attr->ia_valid & ATTR_SIZE) { 68 struct inode *realinode = d_inode(ovl_dentry_real(dentry)); 69 70 err = -ETXTBSY; 71 if (atomic_read(&realinode->i_writecount) < 0) 72 goto out_drop_write; 73 } 74 75 err = ovl_copy_up(dentry); 76 if (!err) { 77 struct inode *winode = NULL; 78 79 upperdentry = ovl_dentry_upper(dentry); 80 81 if (attr->ia_valid & ATTR_SIZE) { 82 winode = d_inode(upperdentry); 83 err = get_write_access(winode); 84 if (err) 85 goto out_drop_write; 86 } 87 88 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) 89 attr->ia_valid &= ~ATTR_MODE; 90 91 inode_lock(upperdentry->d_inode); 92 old_cred = ovl_override_creds(dentry->d_sb); 93 err = notify_change(upperdentry, attr, NULL); 94 revert_creds(old_cred); 95 if (!err) 96 ovl_copyattr(upperdentry->d_inode, dentry->d_inode); 97 inode_unlock(upperdentry->d_inode); 98 99 if (winode) 100 put_write_access(winode); 101 } 102 out_drop_write: 103 ovl_drop_write(dentry); 104 out: 105 return err; 106 } 107 108 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, 109 struct kstat *stat) 110 { 111 struct path realpath; 112 const struct cred *old_cred; 113 int err; 114 115 ovl_path_real(dentry, &realpath); 116 old_cred = ovl_override_creds(dentry->d_sb); 117 err = vfs_getattr(&realpath, stat); 118 revert_creds(old_cred); 119 return err; 120 } 121 122 int ovl_permission(struct inode *inode, int mask) 123 { 124 bool is_upper; 125 struct inode *realinode = ovl_inode_real(inode, &is_upper); 126 const struct cred *old_cred; 127 int err; 128 129 /* Careful in RCU walk mode */ 130 if (!realinode) { 131 WARN_ON(!(mask & MAY_NOT_BLOCK)); 132 return -ECHILD; 133 } 134 135 /* 136 * Check overlay inode with the creds of task and underlying inode 137 * with creds of mounter 138 */ 139 err = generic_permission(inode, mask); 140 if (err) 141 return err; 142 143 old_cred = ovl_override_creds(inode->i_sb); 144 if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) { 145 mask &= ~(MAY_WRITE | MAY_APPEND); 146 /* Make sure mounter can read file for copy up later */ 147 mask |= MAY_READ; 148 } 149 err = inode_permission(realinode, mask); 150 revert_creds(old_cred); 151 152 return err; 153 } 154 155 static const char *ovl_get_link(struct dentry *dentry, 156 struct inode *inode, 157 struct delayed_call *done) 158 { 159 const struct cred *old_cred; 160 const char *p; 161 162 if (!dentry) 163 return ERR_PTR(-ECHILD); 164 165 old_cred = ovl_override_creds(dentry->d_sb); 166 p = vfs_get_link(ovl_dentry_real(dentry), done); 167 revert_creds(old_cred); 168 return p; 169 } 170 171 bool ovl_is_private_xattr(const char *name) 172 { 173 return strncmp(name, OVL_XATTR_PREFIX, 174 sizeof(OVL_XATTR_PREFIX) - 1) == 0; 175 } 176 177 int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value, 178 size_t size, int flags) 179 { 180 int err; 181 struct path realpath; 182 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 183 const struct cred *old_cred; 184 185 err = ovl_want_write(dentry); 186 if (err) 187 goto out; 188 189 if (!value && !OVL_TYPE_UPPER(type)) { 190 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 191 if (err < 0) 192 goto out_drop_write; 193 } 194 195 err = ovl_copy_up(dentry); 196 if (err) 197 goto out_drop_write; 198 199 if (!OVL_TYPE_UPPER(type)) 200 ovl_path_upper(dentry, &realpath); 201 202 old_cred = ovl_override_creds(dentry->d_sb); 203 if (value) 204 err = vfs_setxattr(realpath.dentry, name, value, size, flags); 205 else { 206 WARN_ON(flags != XATTR_REPLACE); 207 err = vfs_removexattr(realpath.dentry, name); 208 } 209 revert_creds(old_cred); 210 211 out_drop_write: 212 ovl_drop_write(dentry); 213 out: 214 return err; 215 } 216 217 int ovl_xattr_get(struct dentry *dentry, const char *name, 218 void *value, size_t size) 219 { 220 struct dentry *realdentry = ovl_dentry_real(dentry); 221 ssize_t res; 222 const struct cred *old_cred; 223 224 old_cred = ovl_override_creds(dentry->d_sb); 225 res = vfs_getxattr(realdentry, name, value, size); 226 revert_creds(old_cred); 227 return res; 228 } 229 230 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 231 { 232 struct dentry *realdentry = ovl_dentry_real(dentry); 233 ssize_t res; 234 size_t len; 235 char *s; 236 const struct cred *old_cred; 237 238 old_cred = ovl_override_creds(dentry->d_sb); 239 res = vfs_listxattr(realdentry, list, size); 240 revert_creds(old_cred); 241 if (res <= 0 || size == 0) 242 return res; 243 244 /* filter out private xattrs */ 245 for (s = list, len = res; len;) { 246 size_t slen = strnlen(s, len) + 1; 247 248 /* underlying fs providing us with an broken xattr list? */ 249 if (WARN_ON(slen > len)) 250 return -EIO; 251 252 len -= slen; 253 if (ovl_is_private_xattr(s)) { 254 res -= slen; 255 memmove(s, s + slen, len); 256 } else { 257 s += slen; 258 } 259 } 260 261 return res; 262 } 263 264 struct posix_acl *ovl_get_acl(struct inode *inode, int type) 265 { 266 struct inode *realinode = ovl_inode_real(inode, NULL); 267 const struct cred *old_cred; 268 struct posix_acl *acl; 269 270 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode)) 271 return NULL; 272 273 if (!realinode->i_op->get_acl) 274 return NULL; 275 276 old_cred = ovl_override_creds(inode->i_sb); 277 acl = get_acl(realinode, type); 278 revert_creds(old_cred); 279 280 return acl; 281 } 282 283 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 284 struct dentry *realdentry) 285 { 286 if (OVL_TYPE_UPPER(type)) 287 return false; 288 289 if (special_file(realdentry->d_inode->i_mode)) 290 return false; 291 292 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 293 return false; 294 295 return true; 296 } 297 298 int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags) 299 { 300 int err = 0; 301 struct path realpath; 302 enum ovl_path_type type; 303 304 type = ovl_path_real(dentry, &realpath); 305 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { 306 err = ovl_want_write(dentry); 307 if (!err) { 308 if (file_flags & O_TRUNC) 309 err = ovl_copy_up_truncate(dentry); 310 else 311 err = ovl_copy_up(dentry); 312 ovl_drop_write(dentry); 313 } 314 } 315 316 return err; 317 } 318 319 int ovl_update_time(struct inode *inode, struct timespec *ts, int flags) 320 { 321 struct dentry *alias; 322 struct path upperpath; 323 324 if (!(flags & S_ATIME)) 325 return 0; 326 327 alias = d_find_any_alias(inode); 328 if (!alias) 329 return 0; 330 331 ovl_path_upper(alias, &upperpath); 332 if (upperpath.dentry) { 333 touch_atime(&upperpath); 334 inode->i_atime = d_inode(upperpath.dentry)->i_atime; 335 } 336 337 dput(alias); 338 339 return 0; 340 } 341 342 static const struct inode_operations ovl_file_inode_operations = { 343 .setattr = ovl_setattr, 344 .permission = ovl_permission, 345 .getattr = ovl_getattr, 346 .listxattr = ovl_listxattr, 347 .get_acl = ovl_get_acl, 348 .update_time = ovl_update_time, 349 }; 350 351 static const struct inode_operations ovl_symlink_inode_operations = { 352 .setattr = ovl_setattr, 353 .get_link = ovl_get_link, 354 .readlink = generic_readlink, 355 .getattr = ovl_getattr, 356 .listxattr = ovl_listxattr, 357 .update_time = ovl_update_time, 358 }; 359 360 static void ovl_fill_inode(struct inode *inode, umode_t mode) 361 { 362 inode->i_ino = get_next_ino(); 363 inode->i_mode = mode; 364 inode->i_flags |= S_NOCMTIME; 365 #ifdef CONFIG_FS_POSIX_ACL 366 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE; 367 #endif 368 369 mode &= S_IFMT; 370 switch (mode) { 371 case S_IFDIR: 372 inode->i_op = &ovl_dir_inode_operations; 373 inode->i_fop = &ovl_dir_operations; 374 break; 375 376 case S_IFLNK: 377 inode->i_op = &ovl_symlink_inode_operations; 378 break; 379 380 default: 381 WARN(1, "illegal file type: %i\n", mode); 382 /* Fall through */ 383 384 case S_IFREG: 385 case S_IFSOCK: 386 case S_IFBLK: 387 case S_IFCHR: 388 case S_IFIFO: 389 inode->i_op = &ovl_file_inode_operations; 390 break; 391 } 392 } 393 394 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode) 395 { 396 struct inode *inode; 397 398 inode = new_inode(sb); 399 if (inode) 400 ovl_fill_inode(inode, mode); 401 402 return inode; 403 } 404 405 static int ovl_inode_test(struct inode *inode, void *data) 406 { 407 return ovl_inode_real(inode, NULL) == data; 408 } 409 410 static int ovl_inode_set(struct inode *inode, void *data) 411 { 412 inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK); 413 return 0; 414 } 415 416 struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode) 417 418 { 419 struct inode *inode; 420 421 inode = iget5_locked(sb, (unsigned long) realinode, 422 ovl_inode_test, ovl_inode_set, realinode); 423 if (inode && inode->i_state & I_NEW) { 424 ovl_fill_inode(inode, realinode->i_mode); 425 set_nlink(inode, realinode->i_nlink); 426 unlock_new_inode(inode); 427 } 428 429 return inode; 430 } 431