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/module.h> 11 #include <linux/fs.h> 12 #include <linux/slab.h> 13 #include <linux/file.h> 14 #include <linux/splice.h> 15 #include <linux/xattr.h> 16 #include <linux/security.h> 17 #include <linux/uaccess.h> 18 #include <linux/sched.h> 19 #include <linux/namei.h> 20 #include <linux/fdtable.h> 21 #include <linux/ratelimit.h> 22 #include "overlayfs.h" 23 24 #define OVL_COPY_UP_CHUNK_SIZE (1 << 20) 25 26 static bool __read_mostly ovl_check_copy_up; 27 module_param_named(check_copy_up, ovl_check_copy_up, bool, 28 S_IWUSR | S_IRUGO); 29 MODULE_PARM_DESC(ovl_check_copy_up, 30 "Warn on copy-up when causing process also has a R/O fd open"); 31 32 static int ovl_check_fd(const void *data, struct file *f, unsigned int fd) 33 { 34 const struct dentry *dentry = data; 35 36 if (f->f_inode == d_inode(dentry)) 37 pr_warn_ratelimited("overlayfs: Warning: Copying up %pD, but open R/O on fd %u which will cease to be coherent [pid=%d %s]\n", 38 f, fd, current->pid, current->comm); 39 return 0; 40 } 41 42 /* 43 * Check the fds open by this process and warn if something like the following 44 * scenario is about to occur: 45 * 46 * fd1 = open("foo", O_RDONLY); 47 * fd2 = open("foo", O_RDWR); 48 */ 49 static void ovl_do_check_copy_up(struct dentry *dentry) 50 { 51 if (ovl_check_copy_up) 52 iterate_fd(current->files, 0, ovl_check_fd, dentry); 53 } 54 55 int ovl_copy_xattr(struct dentry *old, struct dentry *new) 56 { 57 ssize_t list_size, size, value_size = 0; 58 char *buf, *name, *value = NULL; 59 int uninitialized_var(error); 60 size_t slen; 61 62 if (!(old->d_inode->i_opflags & IOP_XATTR) || 63 !(new->d_inode->i_opflags & IOP_XATTR)) 64 return 0; 65 66 list_size = vfs_listxattr(old, NULL, 0); 67 if (list_size <= 0) { 68 if (list_size == -EOPNOTSUPP) 69 return 0; 70 return list_size; 71 } 72 73 buf = kzalloc(list_size, GFP_KERNEL); 74 if (!buf) 75 return -ENOMEM; 76 77 list_size = vfs_listxattr(old, buf, list_size); 78 if (list_size <= 0) { 79 error = list_size; 80 goto out; 81 } 82 83 for (name = buf; list_size; name += slen) { 84 slen = strnlen(name, list_size) + 1; 85 86 /* underlying fs providing us with an broken xattr list? */ 87 if (WARN_ON(slen > list_size)) { 88 error = -EIO; 89 break; 90 } 91 list_size -= slen; 92 93 if (ovl_is_private_xattr(name)) 94 continue; 95 retry: 96 size = vfs_getxattr(old, name, value, value_size); 97 if (size == -ERANGE) 98 size = vfs_getxattr(old, name, NULL, 0); 99 100 if (size < 0) { 101 error = size; 102 break; 103 } 104 105 if (size > value_size) { 106 void *new; 107 108 new = krealloc(value, size, GFP_KERNEL); 109 if (!new) { 110 error = -ENOMEM; 111 break; 112 } 113 value = new; 114 value_size = size; 115 goto retry; 116 } 117 118 error = security_inode_copy_up_xattr(name); 119 if (error < 0 && error != -EOPNOTSUPP) 120 break; 121 if (error == 1) { 122 error = 0; 123 continue; /* Discard */ 124 } 125 error = vfs_setxattr(new, name, value, size, 0); 126 if (error) 127 break; 128 } 129 kfree(value); 130 out: 131 kfree(buf); 132 return error; 133 } 134 135 static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len) 136 { 137 struct file *old_file; 138 struct file *new_file; 139 loff_t old_pos = 0; 140 loff_t new_pos = 0; 141 int error = 0; 142 143 if (len == 0) 144 return 0; 145 146 old_file = ovl_path_open(old, O_LARGEFILE | O_RDONLY); 147 if (IS_ERR(old_file)) 148 return PTR_ERR(old_file); 149 150 new_file = ovl_path_open(new, O_LARGEFILE | O_WRONLY); 151 if (IS_ERR(new_file)) { 152 error = PTR_ERR(new_file); 153 goto out_fput; 154 } 155 156 /* FIXME: copy up sparse files efficiently */ 157 while (len) { 158 size_t this_len = OVL_COPY_UP_CHUNK_SIZE; 159 long bytes; 160 161 if (len < this_len) 162 this_len = len; 163 164 if (signal_pending_state(TASK_KILLABLE, current)) { 165 error = -EINTR; 166 break; 167 } 168 169 bytes = do_splice_direct(old_file, &old_pos, 170 new_file, &new_pos, 171 this_len, SPLICE_F_MOVE); 172 if (bytes <= 0) { 173 error = bytes; 174 break; 175 } 176 WARN_ON(old_pos != new_pos); 177 178 len -= bytes; 179 } 180 181 if (!error) 182 error = vfs_fsync(new_file, 0); 183 fput(new_file); 184 out_fput: 185 fput(old_file); 186 return error; 187 } 188 189 static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat) 190 { 191 struct iattr attr = { 192 .ia_valid = 193 ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET, 194 .ia_atime = stat->atime, 195 .ia_mtime = stat->mtime, 196 }; 197 198 return notify_change(upperdentry, &attr, NULL); 199 } 200 201 int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) 202 { 203 int err = 0; 204 205 if (!S_ISLNK(stat->mode)) { 206 struct iattr attr = { 207 .ia_valid = ATTR_MODE, 208 .ia_mode = stat->mode, 209 }; 210 err = notify_change(upperdentry, &attr, NULL); 211 } 212 if (!err) { 213 struct iattr attr = { 214 .ia_valid = ATTR_UID | ATTR_GID, 215 .ia_uid = stat->uid, 216 .ia_gid = stat->gid, 217 }; 218 err = notify_change(upperdentry, &attr, NULL); 219 } 220 if (!err) 221 ovl_set_timestamps(upperdentry, stat); 222 223 return err; 224 } 225 226 static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, 227 struct dentry *dentry, struct path *lowerpath, 228 struct kstat *stat, const char *link) 229 { 230 struct inode *wdir = workdir->d_inode; 231 struct inode *udir = upperdir->d_inode; 232 struct dentry *newdentry = NULL; 233 struct dentry *upper = NULL; 234 umode_t mode = stat->mode; 235 int err; 236 const struct cred *old_creds = NULL; 237 struct cred *new_creds = NULL; 238 239 newdentry = ovl_lookup_temp(workdir, dentry); 240 err = PTR_ERR(newdentry); 241 if (IS_ERR(newdentry)) 242 goto out; 243 244 upper = lookup_one_len(dentry->d_name.name, upperdir, 245 dentry->d_name.len); 246 err = PTR_ERR(upper); 247 if (IS_ERR(upper)) 248 goto out1; 249 250 err = security_inode_copy_up(dentry, &new_creds); 251 if (err < 0) 252 goto out2; 253 254 if (new_creds) 255 old_creds = override_creds(new_creds); 256 257 /* Can't properly set mode on creation because of the umask */ 258 stat->mode &= S_IFMT; 259 err = ovl_create_real(wdir, newdentry, stat, link, NULL, true); 260 stat->mode = mode; 261 262 if (new_creds) { 263 revert_creds(old_creds); 264 put_cred(new_creds); 265 } 266 267 if (err) 268 goto out2; 269 270 if (S_ISREG(stat->mode)) { 271 struct path upperpath; 272 273 ovl_path_upper(dentry, &upperpath); 274 BUG_ON(upperpath.dentry != NULL); 275 upperpath.dentry = newdentry; 276 277 err = ovl_copy_up_data(lowerpath, &upperpath, stat->size); 278 if (err) 279 goto out_cleanup; 280 } 281 282 err = ovl_copy_xattr(lowerpath->dentry, newdentry); 283 if (err) 284 goto out_cleanup; 285 286 inode_lock(newdentry->d_inode); 287 err = ovl_set_attr(newdentry, stat); 288 inode_unlock(newdentry->d_inode); 289 if (err) 290 goto out_cleanup; 291 292 err = ovl_do_rename(wdir, newdentry, udir, upper, 0); 293 if (err) 294 goto out_cleanup; 295 296 ovl_dentry_update(dentry, newdentry); 297 ovl_inode_update(d_inode(dentry), d_inode(newdentry)); 298 newdentry = NULL; 299 300 /* 301 * Non-directores become opaque when copied up. 302 */ 303 if (!S_ISDIR(stat->mode)) 304 ovl_dentry_set_opaque(dentry, true); 305 out2: 306 dput(upper); 307 out1: 308 dput(newdentry); 309 out: 310 return err; 311 312 out_cleanup: 313 ovl_cleanup(wdir, newdentry); 314 goto out2; 315 } 316 317 /* 318 * Copy up a single dentry 319 * 320 * Directory renames only allowed on "pure upper" (already created on 321 * upper filesystem, never copied up). Directories which are on lower or 322 * are merged may not be renamed. For these -EXDEV is returned and 323 * userspace has to deal with it. This means, when copying up a 324 * directory we can rely on it and ancestors being stable. 325 * 326 * Non-directory renames start with copy up of source if necessary. The 327 * actual rename will only proceed once the copy up was successful. Copy 328 * up uses upper parent i_mutex for exclusion. Since rename can change 329 * d_parent it is possible that the copy up will lock the old parent. At 330 * that point the file will have already been copied up anyway. 331 */ 332 int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry, 333 struct path *lowerpath, struct kstat *stat) 334 { 335 DEFINE_DELAYED_CALL(done); 336 struct dentry *workdir = ovl_workdir(dentry); 337 int err; 338 struct kstat pstat; 339 struct path parentpath; 340 struct dentry *lowerdentry = lowerpath->dentry; 341 struct dentry *upperdir; 342 struct dentry *upperdentry; 343 const char *link = NULL; 344 345 if (WARN_ON(!workdir)) 346 return -EROFS; 347 348 ovl_do_check_copy_up(lowerdentry); 349 350 ovl_path_upper(parent, &parentpath); 351 upperdir = parentpath.dentry; 352 353 err = vfs_getattr(&parentpath, &pstat); 354 if (err) 355 return err; 356 357 if (S_ISLNK(stat->mode)) { 358 link = vfs_get_link(lowerdentry, &done); 359 if (IS_ERR(link)) 360 return PTR_ERR(link); 361 } 362 363 err = -EIO; 364 if (lock_rename(workdir, upperdir) != NULL) { 365 pr_err("overlayfs: failed to lock workdir+upperdir\n"); 366 goto out_unlock; 367 } 368 upperdentry = ovl_dentry_upper(dentry); 369 if (upperdentry) { 370 /* Raced with another copy-up? Nothing to do, then... */ 371 err = 0; 372 goto out_unlock; 373 } 374 375 err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath, 376 stat, link); 377 if (!err) { 378 /* Restore timestamps on parent (best effort) */ 379 ovl_set_timestamps(upperdir, &pstat); 380 } 381 out_unlock: 382 unlock_rename(workdir, upperdir); 383 do_delayed_call(&done); 384 385 return err; 386 } 387 388 int ovl_copy_up(struct dentry *dentry) 389 { 390 int err = 0; 391 const struct cred *old_cred = ovl_override_creds(dentry->d_sb); 392 393 while (!err) { 394 struct dentry *next; 395 struct dentry *parent; 396 struct path lowerpath; 397 struct kstat stat; 398 enum ovl_path_type type = ovl_path_type(dentry); 399 400 if (OVL_TYPE_UPPER(type)) 401 break; 402 403 next = dget(dentry); 404 /* find the topmost dentry not yet copied up */ 405 for (;;) { 406 parent = dget_parent(next); 407 408 type = ovl_path_type(parent); 409 if (OVL_TYPE_UPPER(type)) 410 break; 411 412 dput(next); 413 next = parent; 414 } 415 416 ovl_path_lower(next, &lowerpath); 417 err = vfs_getattr(&lowerpath, &stat); 418 if (!err) 419 err = ovl_copy_up_one(parent, next, &lowerpath, &stat); 420 421 dput(parent); 422 dput(next); 423 } 424 revert_creds(old_cred); 425 426 return err; 427 } 428