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/cred.h> 13 #include <linux/xattr.h> 14 #include <linux/posix_acl.h> 15 #include "overlayfs.h" 16 17 int ovl_setattr(struct dentry *dentry, struct iattr *attr) 18 { 19 int err; 20 struct dentry *upperdentry; 21 const struct cred *old_cred; 22 23 /* 24 * Check for permissions before trying to copy-up. This is redundant 25 * since it will be rechecked later by ->setattr() on upper dentry. But 26 * without this, copy-up can be triggered by just about anybody. 27 * 28 * We don't initialize inode->size, which just means that 29 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not 30 * check for a swapfile (which this won't be anyway). 31 */ 32 err = setattr_prepare(dentry, attr); 33 if (err) 34 return err; 35 36 err = ovl_want_write(dentry); 37 if (err) 38 goto out; 39 40 err = ovl_copy_up(dentry); 41 if (!err) { 42 upperdentry = ovl_dentry_upper(dentry); 43 44 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) 45 attr->ia_valid &= ~ATTR_MODE; 46 47 inode_lock(upperdentry->d_inode); 48 old_cred = ovl_override_creds(dentry->d_sb); 49 err = notify_change(upperdentry, attr, NULL); 50 revert_creds(old_cred); 51 if (!err) 52 ovl_copyattr(upperdentry->d_inode, dentry->d_inode); 53 inode_unlock(upperdentry->d_inode); 54 } 55 ovl_drop_write(dentry); 56 out: 57 return err; 58 } 59 60 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, 61 struct kstat *stat) 62 { 63 struct path realpath; 64 const struct cred *old_cred; 65 int err; 66 67 ovl_path_real(dentry, &realpath); 68 old_cred = ovl_override_creds(dentry->d_sb); 69 err = vfs_getattr(&realpath, stat); 70 revert_creds(old_cred); 71 return err; 72 } 73 74 int ovl_permission(struct inode *inode, int mask) 75 { 76 bool is_upper; 77 struct inode *realinode = ovl_inode_real(inode, &is_upper); 78 const struct cred *old_cred; 79 int err; 80 81 /* Careful in RCU walk mode */ 82 if (!realinode) { 83 WARN_ON(!(mask & MAY_NOT_BLOCK)); 84 return -ECHILD; 85 } 86 87 /* 88 * Check overlay inode with the creds of task and underlying inode 89 * with creds of mounter 90 */ 91 err = generic_permission(inode, mask); 92 if (err) 93 return err; 94 95 old_cred = ovl_override_creds(inode->i_sb); 96 if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) { 97 mask &= ~(MAY_WRITE | MAY_APPEND); 98 /* Make sure mounter can read file for copy up later */ 99 mask |= MAY_READ; 100 } 101 err = inode_permission(realinode, mask); 102 revert_creds(old_cred); 103 104 return err; 105 } 106 107 static const char *ovl_get_link(struct dentry *dentry, 108 struct inode *inode, 109 struct delayed_call *done) 110 { 111 const struct cred *old_cred; 112 const char *p; 113 114 if (!dentry) 115 return ERR_PTR(-ECHILD); 116 117 old_cred = ovl_override_creds(dentry->d_sb); 118 p = vfs_get_link(ovl_dentry_real(dentry), done); 119 revert_creds(old_cred); 120 return p; 121 } 122 123 bool ovl_is_private_xattr(const char *name) 124 { 125 return strncmp(name, OVL_XATTR_PREFIX, 126 sizeof(OVL_XATTR_PREFIX) - 1) == 0; 127 } 128 129 int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value, 130 size_t size, int flags) 131 { 132 int err; 133 struct path realpath; 134 enum ovl_path_type type = ovl_path_real(dentry, &realpath); 135 const struct cred *old_cred; 136 137 err = ovl_want_write(dentry); 138 if (err) 139 goto out; 140 141 if (!value && !OVL_TYPE_UPPER(type)) { 142 err = vfs_getxattr(realpath.dentry, name, NULL, 0); 143 if (err < 0) 144 goto out_drop_write; 145 } 146 147 err = ovl_copy_up(dentry); 148 if (err) 149 goto out_drop_write; 150 151 if (!OVL_TYPE_UPPER(type)) 152 ovl_path_upper(dentry, &realpath); 153 154 old_cred = ovl_override_creds(dentry->d_sb); 155 if (value) 156 err = vfs_setxattr(realpath.dentry, name, value, size, flags); 157 else { 158 WARN_ON(flags != XATTR_REPLACE); 159 err = vfs_removexattr(realpath.dentry, name); 160 } 161 revert_creds(old_cred); 162 163 out_drop_write: 164 ovl_drop_write(dentry); 165 out: 166 return err; 167 } 168 169 int ovl_xattr_get(struct dentry *dentry, const char *name, 170 void *value, size_t size) 171 { 172 struct dentry *realdentry = ovl_dentry_real(dentry); 173 ssize_t res; 174 const struct cred *old_cred; 175 176 old_cred = ovl_override_creds(dentry->d_sb); 177 res = vfs_getxattr(realdentry, name, value, size); 178 revert_creds(old_cred); 179 return res; 180 } 181 182 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) 183 { 184 struct dentry *realdentry = ovl_dentry_real(dentry); 185 ssize_t res; 186 size_t len; 187 char *s; 188 const struct cred *old_cred; 189 190 old_cred = ovl_override_creds(dentry->d_sb); 191 res = vfs_listxattr(realdentry, list, size); 192 revert_creds(old_cred); 193 if (res <= 0 || size == 0) 194 return res; 195 196 /* filter out private xattrs */ 197 for (s = list, len = res; len;) { 198 size_t slen = strnlen(s, len) + 1; 199 200 /* underlying fs providing us with an broken xattr list? */ 201 if (WARN_ON(slen > len)) 202 return -EIO; 203 204 len -= slen; 205 if (ovl_is_private_xattr(s)) { 206 res -= slen; 207 memmove(s, s + slen, len); 208 } else { 209 s += slen; 210 } 211 } 212 213 return res; 214 } 215 216 struct posix_acl *ovl_get_acl(struct inode *inode, int type) 217 { 218 struct inode *realinode = ovl_inode_real(inode, NULL); 219 const struct cred *old_cred; 220 struct posix_acl *acl; 221 222 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode)) 223 return NULL; 224 225 old_cred = ovl_override_creds(inode->i_sb); 226 acl = get_acl(realinode, type); 227 revert_creds(old_cred); 228 229 return acl; 230 } 231 232 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, 233 struct dentry *realdentry) 234 { 235 if (OVL_TYPE_UPPER(type)) 236 return false; 237 238 if (special_file(realdentry->d_inode->i_mode)) 239 return false; 240 241 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) 242 return false; 243 244 return true; 245 } 246 247 int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags) 248 { 249 int err = 0; 250 struct path realpath; 251 enum ovl_path_type type; 252 253 type = ovl_path_real(dentry, &realpath); 254 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { 255 err = ovl_want_write(dentry); 256 if (!err) { 257 err = ovl_copy_up_flags(dentry, file_flags); 258 ovl_drop_write(dentry); 259 } 260 } 261 262 return err; 263 } 264 265 int ovl_update_time(struct inode *inode, struct timespec *ts, int flags) 266 { 267 struct dentry *alias; 268 struct path upperpath; 269 270 if (!(flags & S_ATIME)) 271 return 0; 272 273 alias = d_find_any_alias(inode); 274 if (!alias) 275 return 0; 276 277 ovl_path_upper(alias, &upperpath); 278 if (upperpath.dentry) { 279 touch_atime(&upperpath); 280 inode->i_atime = d_inode(upperpath.dentry)->i_atime; 281 } 282 283 dput(alias); 284 285 return 0; 286 } 287 288 static const struct inode_operations ovl_file_inode_operations = { 289 .setattr = ovl_setattr, 290 .permission = ovl_permission, 291 .getattr = ovl_getattr, 292 .listxattr = ovl_listxattr, 293 .get_acl = ovl_get_acl, 294 .update_time = ovl_update_time, 295 }; 296 297 static const struct inode_operations ovl_symlink_inode_operations = { 298 .setattr = ovl_setattr, 299 .get_link = ovl_get_link, 300 .getattr = ovl_getattr, 301 .listxattr = ovl_listxattr, 302 .update_time = ovl_update_time, 303 }; 304 305 static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev) 306 { 307 inode->i_ino = get_next_ino(); 308 inode->i_mode = mode; 309 inode->i_flags |= S_NOCMTIME; 310 #ifdef CONFIG_FS_POSIX_ACL 311 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE; 312 #endif 313 314 switch (mode & S_IFMT) { 315 case S_IFREG: 316 inode->i_op = &ovl_file_inode_operations; 317 break; 318 319 case S_IFDIR: 320 inode->i_op = &ovl_dir_inode_operations; 321 inode->i_fop = &ovl_dir_operations; 322 break; 323 324 case S_IFLNK: 325 inode->i_op = &ovl_symlink_inode_operations; 326 break; 327 328 default: 329 inode->i_op = &ovl_file_inode_operations; 330 init_special_inode(inode, mode, rdev); 331 break; 332 } 333 } 334 335 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev) 336 { 337 struct inode *inode; 338 339 inode = new_inode(sb); 340 if (inode) 341 ovl_fill_inode(inode, mode, rdev); 342 343 return inode; 344 } 345 346 static int ovl_inode_test(struct inode *inode, void *data) 347 { 348 return ovl_inode_real(inode, NULL) == data; 349 } 350 351 static int ovl_inode_set(struct inode *inode, void *data) 352 { 353 inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK); 354 return 0; 355 } 356 357 struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode) 358 359 { 360 struct inode *inode; 361 362 inode = iget5_locked(sb, (unsigned long) realinode, 363 ovl_inode_test, ovl_inode_set, realinode); 364 if (inode && inode->i_state & I_NEW) { 365 ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev); 366 set_nlink(inode, realinode->i_nlink); 367 unlock_new_inode(inode); 368 } 369 370 return inode; 371 } 372