fs/namei.c

/* */
This source file includes following definitions.
getname
putname
permission
lookup
follow_link
dir_namei
_namei
lnamei
namei
open_namei
do_mknod
sys_mknod
do_mkdir
sys_mkdir
do_rmdir
sys_rmdir
do_unlink
sys_unlink
do_symlink
sys_symlink
do_link
sys_link
do_rename
sys_rename
   1 /*
   2  *  linux/fs/namei.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6 
   7 /*
   8  * Some corrections by tytso.
   9  */
  10 
  11 #include <asm/segment.h>
  12 
  13 #include <linux/errno.h>
  14 #include <linux/sched.h>
  15 #include <linux/kernel.h>
  16 #include <linux/string.h>
  17 #include <linux/fcntl.h>
  18 #include <linux/stat.h>
  19 
  20 #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
  21 
  22 /*
  23  * In order to reduce some races, while at the same time doing additional
  24  * checking and hopefully speeding things up, we copy filenames to the
  25  * kernel data space before using them..
  26  *
  27  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
  28  */
  29 int getname(const char * filename, char **result)
     /*  */
  30 {
  31         int error;
  32         unsigned long i, page;
  33         char * tmp, c;
  34 
  35         i = (unsigned long) filename;
  36         if (!i || i >= TASK_SIZE)
  37                 return -EFAULT;
  38         i = TASK_SIZE - i;
  39         error = -EFAULT;
  40         if (i > PAGE_SIZE) {
  41                 i = PAGE_SIZE;
  42                 error = -ENAMETOOLONG;
  43         }
  44         c = get_fs_byte(filename++);
  45         if (!c)
  46                 return -ENOENT;
  47         if(!(page = __get_free_page(GFP_KERNEL)))
  48                 return -ENOMEM;
  49         *result = tmp = (char *) page;
  50         while (--i) {
  51                 *(tmp++) = c;
  52                 c = get_fs_byte(filename++);
  53                 if (!c) {
  54                         *tmp = '\0';
  55                         return 0;
  56                 }
  57         }
  58         free_page(page);
  59         return error;
  60 }
  61 
  62 void putname(char * name)
     /*  */
  63 {
  64         free_page((unsigned long) name);
  65 }
  66 
  67 /*
  68  *      permission()
  69  *
  70  * is used to check for read/write/execute permissions on a file.
  71  * I don't know if we should look at just the euid or both euid and
  72  * uid, but that should be easily changed.
  73  */
  74 int permission(struct inode * inode,int mask)
     /*  */
  75 {
  76         int mode = inode->i_mode;
  77 
  78 /* special case: not even root can read/write a deleted file */
  79         if (inode->i_dev && !inode->i_nlink)
  80                 return 0;
  81         else if (inode->i_op && inode->i_op->permission)
  82                 return inode->i_op->permission(inode, mask);
  83         else if (current->euid == inode->i_uid)
  84                 mode >>= 6;
  85         else if (in_group_p(inode->i_gid))
  86                 mode >>= 3;
  87         if (((mode & mask & 0007) == mask) || suser())
  88                 return 1;
  89         return 0;
  90 }
  91 
  92 /*
  93  * lookup() looks up one part of a pathname, using the fs-dependent
  94  * routines (currently minix_lookup) for it. It also checks for
  95  * fathers (pseudo-roots, mount-points)
  96  */
  97 int lookup(struct inode * dir,const char * name, int len,
     /*  */
  98         struct inode ** result)
  99 {
 100         struct super_block * sb;
 101         int perm;
 102 
 103         *result = NULL;
 104         if (!dir)
 105                 return -ENOENT;
 106 /* check permissions before traversing mount-points */
 107         perm = permission(dir,MAY_EXEC);
 108         if (len==2 && name[0] == '.' && name[1] == '.') {
 109                 if (dir == current->root) {
 110                         *result = dir;
 111                         return 0;
 112                 } else if ((sb = dir->i_sb) && (dir == sb->s_mounted)) {
 113                         sb = dir->i_sb;
 114                         iput(dir);
 115                         dir = sb->s_covered;
 116                         if (!dir)
 117                                 return -ENOENT;
 118                         dir->i_count++;
 119                 }
 120         }
 121         if (!dir->i_op || !dir->i_op->lookup) {
 122                 iput(dir);
 123                 return -ENOTDIR;
 124         }
 125         if (!perm) {
 126                 iput(dir);
 127                 return -EACCES;
 128         }
 129         if (!len) {
 130                 *result = dir;
 131                 return 0;
 132         }
 133         return dir->i_op->lookup(dir,name,len,result);
 134 }
 135 
 136 int follow_link(struct inode * dir, struct inode * inode,
     /*  */
 137         int flag, int mode, struct inode ** res_inode)
 138 {
 139         if (!dir || !inode) {
 140                 iput(dir);
 141                 iput(inode);
 142                 *res_inode = NULL;
 143                 return -ENOENT;
 144         }
 145         if (!inode->i_op || !inode->i_op->follow_link) {
 146                 iput(dir);
 147                 *res_inode = inode;
 148                 return 0;
 149         }
 150         return inode->i_op->follow_link(dir,inode,flag,mode,res_inode);
 151 }
 152 
 153 /*
 154  *      dir_namei()
 155  *
 156  * dir_namei() returns the inode of the directory of the
 157  * specified name, and the name within that directory.
 158  */
 159 static int dir_namei(const char * pathname, int * namelen, const char ** name,
     /*  */
 160         struct inode * base, struct inode ** res_inode)
 161 {
 162         char c;
 163         const char * thisname;
 164         int len,error;
 165         struct inode * inode;
 166 
 167         *res_inode = NULL;
 168         if (!base) {
 169                 base = current->pwd;
 170                 base->i_count++;
 171         }
 172         if ((c = *pathname) == '/') {
 173                 iput(base);
 174                 base = current->root;
 175                 pathname++;
 176                 base->i_count++;
 177         }
 178         while (1) {
 179                 thisname = pathname;
 180                 for(len=0;(c = *(pathname++))&&(c != '/');len++)
 181                         /* nothing */ ;
 182                 if (!c)
 183                         break;
 184                 base->i_count++;
 185                 error = lookup(base,thisname,len,&inode);
 186                 if (error) {
 187                         iput(base);
 188                         return error;
 189                 }
 190                 error = follow_link(base,inode,0,0,&base);
 191                 if (error)
 192                         return error;
 193         }
 194         if (!base->i_op || !base->i_op->lookup) {
 195                 iput(base);
 196                 return -ENOTDIR;
 197         }
 198         *name = thisname;
 199         *namelen = len;
 200         *res_inode = base;
 201         return 0;
 202 }
 203 
 204 static int _namei(const char * pathname, struct inode * base,
     /*  */
 205         int follow_links, struct inode ** res_inode)
 206 {
 207         const char * basename;
 208         int namelen,error;
 209         struct inode * inode;
 210 
 211         *res_inode = NULL;
 212         error = dir_namei(pathname,&namelen,&basename,base,&base);
 213         if (error)
 214                 return error;
 215         base->i_count++;        /* lookup uses up base */
 216         error = lookup(base,basename,namelen,&inode);
 217         if (error) {
 218                 iput(base);
 219                 return error;
 220         }
 221         if (follow_links) {
 222                 error = follow_link(base,inode,0,0,&inode);
 223                 if (error)
 224                         return error;
 225         } else
 226                 iput(base);
 227         *res_inode = inode;
 228         return 0;
 229 }
 230 
 231 int lnamei(const char * pathname, struct inode ** res_inode)
     /*  */
 232 {
 233         int error;
 234         char * tmp;
 235 
 236         error = getname(pathname,&tmp);
 237         if (!error) {
 238                 error = _namei(tmp,NULL,0,res_inode);
 239                 putname(tmp);
 240         }
 241         return error;
 242 }
 243 
 244 /*
 245  *      namei()
 246  *
 247  * is used by most simple commands to get the inode of a specified name.
 248  * Open, link etc use their own routines, but this is enough for things
 249  * like 'chmod' etc.
 250  */
 251 int namei(const char * pathname, struct inode ** res_inode)
     /*  */
 252 {
 253         int error;
 254         char * tmp;
 255 
 256         error = getname(pathname,&tmp);
 257         if (!error) {
 258                 error = _namei(tmp,NULL,1,res_inode);
 259                 putname(tmp);
 260         }
 261         return error;
 262 }
 263 
 264 /*
 265  *      open_namei()
 266  *
 267  * namei for open - this is in fact almost the whole open-routine.
 268  *
 269  * Note that the low bits of "flag" aren't the same asin the open
 270  * system call - they are 00 - no permissions needed
 271  *                        01 - read permission needed
 272  *                        10 - write permission needed
 273  *                        11 - read/write permissions needed
 274  * which is a lot more logical, and also allows the "no perm" needed
 275  * for symlinks (where the permissions are checked later).
 276  */
 277 int open_namei(const char * pathname, int flag, int mode,
     /*  */
 278         struct inode ** res_inode, struct inode * base)
 279 {
 280         const char * basename;
 281         int namelen,error,i;
 282         struct inode * dir, *inode;
 283         struct task_struct ** p;
 284 
 285         mode &= S_IALLUGO & ~current->umask;
 286         mode |= S_IFREG;
 287         error = dir_namei(pathname,&namelen,&basename,base,&dir);
 288         if (error)
 289                 return error;
 290         if (!namelen) {                 /* special case: '/usr/' etc */
 291                 if (flag & 2) {
 292                         iput(dir);
 293                         return -EISDIR;
 294                 }
 295                 /* thanks to Paul Pluzhnikov for noticing this was missing.. */
 296                 if (!permission(dir,ACC_MODE(flag))) {
 297                         iput(dir);
 298                         return -EACCES;
 299                 }
 300                 *res_inode=dir;
 301                 return 0;
 302         }
 303         for (i = 0; i < 5; i++) {       /* races... */
 304                 dir->i_count++;         /* lookup eats the dir */
 305                 error = lookup(dir,basename,namelen,&inode);
 306                 if (!error)
 307                         break;
 308                 if (!(flag & O_CREAT)) {
 309                         iput(dir);
 310                         return error;
 311                 }
 312                 if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 313                         iput(dir);
 314                         return -EACCES;
 315                 }
 316                 if (!dir->i_op || !dir->i_op->create) {
 317                         iput(dir);
 318                         return -EACCES;
 319                 }
 320                 if (IS_RDONLY(dir)) {
 321                         iput(dir);
 322                         return -EROFS;
 323                 }
 324                 dir->i_count++;         /* create eats the dir */
 325                 error = dir->i_op->create(dir,basename,namelen,mode,res_inode);
 326                 if (error != -EEXIST) {
 327                         iput(dir);
 328                         return error;
 329                 }
 330         }
 331         if (error) {
 332                 iput(dir);
 333                 return error;
 334         }
 335         if ((flag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) {
 336                 iput(dir);
 337                 iput(inode);
 338                 return -EEXIST;
 339         }
 340         error = follow_link(dir,inode,flag,mode,&inode);
 341         if (error)
 342                 return error;
 343         if (S_ISDIR(inode->i_mode) && (flag & 2)) {
 344                 iput(inode);
 345                 return -EISDIR;
 346         }
 347         if (!permission(inode,ACC_MODE(flag))) {
 348                 iput(inode);
 349                 return -EACCES;
 350         }
 351         if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
 352                 if (IS_NODEV(inode)) {
 353                         iput(inode);
 354                         return -EACCES;
 355                 }
 356         } else {
 357                 if (IS_RDONLY(inode) && (flag & 2)) {
 358                         iput(inode);
 359                         return -EROFS;
 360                 }
 361         }
 362         if ((inode->i_count > 1) && (flag & 2)) {
 363                 for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
 364                         struct vm_area_struct * mpnt;
 365                         if (!*p)
 366                                 continue;
 367                         if (inode == (*p)->executable) {
 368                                 iput(inode);
 369                                 return -ETXTBSY;
 370                         }
 371                         for(mpnt = (*p)->mmap; mpnt; mpnt = mpnt->vm_next) {
 372                                 if (inode == mpnt->vm_inode) {
 373                                         iput(inode);
 374                                         return -ETXTBSY;
 375                                 }
 376                         }
 377                 }
 378         }
 379         *res_inode = inode;
 380         return 0;
 381 }
 382 
 383 int do_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 384 {
 385         const char * basename;
 386         int namelen, error;
 387         struct inode * dir;
 388 
 389         mode &= ~current->umask;
 390         error = dir_namei(filename,&namelen,&basename, NULL, &dir);
 391         if (error)
 392                 return error;
 393         if (!namelen) {
 394                 iput(dir);
 395                 return -ENOENT;
 396         }
 397         if (IS_RDONLY(dir)) {
 398                 iput(dir);
 399                 return -EROFS;
 400         }
 401         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 402                 iput(dir);
 403                 return -EACCES;
 404         }
 405         if (!dir->i_op || !dir->i_op->mknod) {
 406                 iput(dir);
 407                 return -EPERM;
 408         }
 409         return dir->i_op->mknod(dir,basename,namelen,mode,dev);
 410 }
 411 
 412 extern "C" int sys_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 413 {
 414         int error;
 415         char * tmp;
 416 
 417         if (S_ISDIR(mode)  || (!S_ISFIFO(mode) && !suser()))
 418                 return -EPERM;
 419         error = getname(filename,&tmp);
 420         if (!error) {
 421                 error = do_mknod(tmp,mode,dev);
 422                 putname(tmp);
 423         }
 424         return error;
 425 }
 426 
 427 static int do_mkdir(const char * pathname, int mode)
     /*  */
 428 {
 429         const char * basename;
 430         int namelen, error;
 431         struct inode * dir;
 432 
 433         error = dir_namei(pathname,&namelen,&basename,NULL,&dir);
 434         if (error)
 435                 return error;
 436         if (!namelen) {
 437                 iput(dir);
 438                 return -ENOENT;
 439         }
 440         if (IS_RDONLY(dir)) {
 441                 iput(dir);
 442                 return -EROFS;
 443         }
 444         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 445                 iput(dir);
 446                 return -EACCES;
 447         }
 448         if (!dir->i_op || !dir->i_op->mkdir) {
 449                 iput(dir);
 450                 return -EPERM;
 451         }
 452         return dir->i_op->mkdir(dir,basename,namelen,mode);
 453 }
 454 
 455 extern "C" int sys_mkdir(const char * pathname, int mode)
     /*  */
 456 {
 457         int error;
 458         char * tmp;
 459 
 460         error = getname(pathname,&tmp);
 461         if (!error) {
 462                 error = do_mkdir(tmp,mode);
 463                 putname(tmp);
 464         }
 465         return error;
 466 }
 467 
 468 static int do_rmdir(const char * name)
     /*  */
 469 {
 470         const char * basename;
 471         int namelen, error;
 472         struct inode * dir;
 473 
 474         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 475         if (error)
 476                 return error;
 477         if (!namelen) {
 478                 iput(dir);
 479                 return -ENOENT;
 480         }
 481         if (IS_RDONLY(dir)) {
 482                 iput(dir);
 483                 return -EROFS;
 484         }
 485         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 486                 iput(dir);
 487                 return -EACCES;
 488         }
 489         if (!dir->i_op || !dir->i_op->rmdir) {
 490                 iput(dir);
 491                 return -EPERM;
 492         }
 493         return dir->i_op->rmdir(dir,basename,namelen);
 494 }
 495 
 496 extern "C" int sys_rmdir(const char * pathname)
     /*  */
 497 {
 498         int error;
 499         char * tmp;
 500 
 501         error = getname(pathname,&tmp);
 502         if (!error) {
 503                 error = do_rmdir(tmp);
 504                 putname(tmp);
 505         }
 506         return error;
 507 }
 508 
 509 static int do_unlink(const char * name)
     /*  */
 510 {
 511         const char * basename;
 512         int namelen, error;
 513         struct inode * dir;
 514 
 515         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 516         if (error)
 517                 return error;
 518         if (!namelen) {
 519                 iput(dir);
 520                 return -EPERM;
 521         }
 522         if (IS_RDONLY(dir)) {
 523                 iput(dir);
 524                 return -EROFS;
 525         }
 526         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 527                 iput(dir);
 528                 return -EACCES;
 529         }
 530         if (!dir->i_op || !dir->i_op->unlink) {
 531                 iput(dir);
 532                 return -EPERM;
 533         }
 534         return dir->i_op->unlink(dir,basename,namelen);
 535 }
 536 
 537 extern "C" int sys_unlink(const char * pathname)
     /*  */
 538 {
 539         int error;
 540         char * tmp;
 541 
 542         error = getname(pathname,&tmp);
 543         if (!error) {
 544                 error = do_unlink(tmp);
 545                 putname(tmp);
 546         }
 547         return error;
 548 }
 549 
 550 static int do_symlink(const char * oldname, const char * newname)
     /*  */
 551 {
 552         struct inode * dir;
 553         const char * basename;
 554         int namelen, error;
 555 
 556         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 557         if (error)
 558                 return error;
 559         if (!namelen) {
 560                 iput(dir);
 561                 return -ENOENT;
 562         }
 563         if (IS_RDONLY(dir)) {
 564                 iput(dir);
 565                 return -EROFS;
 566         }
 567         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 568                 iput(dir);
 569                 return -EACCES;
 570         }
 571         if (!dir->i_op || !dir->i_op->symlink) {
 572                 iput(dir);
 573                 return -EPERM;
 574         }
 575         return dir->i_op->symlink(dir,basename,namelen,oldname);
 576 }
 577 
 578 extern "C" int sys_symlink(const char * oldname, const char * newname)
     /*  */
 579 {
 580         int error;
 581         char * from, * to;
 582 
 583         error = getname(oldname,&from);
 584         if (!error) {
 585                 error = getname(newname,&to);
 586                 if (!error) {
 587                         error = do_symlink(from,to);
 588                         putname(to);
 589                 }
 590                 putname(from);
 591         }
 592         return error;
 593 }
 594 
 595 static int do_link(struct inode * oldinode, const char * newname)
     /*  */
 596 {
 597         struct inode * dir;
 598         const char * basename;
 599         int namelen, error;
 600 
 601         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 602         if (error) {
 603                 iput(oldinode);
 604                 return error;
 605         }
 606         if (!namelen) {
 607                 iput(oldinode);
 608                 iput(dir);
 609                 return -EPERM;
 610         }
 611         if (IS_RDONLY(dir)) {
 612                 iput(oldinode);
 613                 iput(dir);
 614                 return -EROFS;
 615         }
 616         if (dir->i_dev != oldinode->i_dev) {
 617                 iput(dir);
 618                 iput(oldinode);
 619                 return -EXDEV;
 620         }
 621         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 622                 iput(dir);
 623                 iput(oldinode);
 624                 return -EACCES;
 625         }
 626         if (!dir->i_op || !dir->i_op->link) {
 627                 iput(dir);
 628                 iput(oldinode);
 629                 return -EPERM;
 630         }
 631         return dir->i_op->link(oldinode, dir, basename, namelen);
 632 }
 633 
 634 extern "C" int sys_link(const char * oldname, const char * newname)
     /*  */
 635 {
 636         int error;
 637         char * to;
 638         struct inode * oldinode;
 639 
 640         error = namei(oldname, &oldinode);
 641         if (error)
 642                 return error;
 643         error = getname(newname,&to);
 644         if (!error) {
 645                 error = do_link(oldinode,to);
 646                 putname(to);
 647         }
 648         return error;
 649 }
 650 
 651 static int do_rename(const char * oldname, const char * newname)
     /*  */
 652 {
 653         struct inode * old_dir, * new_dir;
 654         const char * old_base, * new_base;
 655         int old_len, new_len, error;
 656 
 657         error = dir_namei(oldname,&old_len,&old_base,NULL,&old_dir);
 658         if (error)
 659                 return error;
 660         if (!permission(old_dir,MAY_WRITE | MAY_EXEC)) {
 661                 iput(old_dir);
 662                 return -EACCES;
 663         }
 664         if (!old_len || (old_base[0] == '.' &&
 665             (old_len == 1 || (old_base[1] == '.' &&
 666              old_len == 2)))) {
 667                 iput(old_dir);
 668                 return -EPERM;
 669         }
 670         error = dir_namei(newname,&new_len,&new_base,NULL,&new_dir);
 671         if (error) {
 672                 iput(old_dir);
 673                 return error;
 674         }
 675         if (!permission(new_dir,MAY_WRITE | MAY_EXEC)) {
 676                 iput(old_dir);
 677                 iput(new_dir);
 678                 return -EACCES;
 679         }
 680         if (!new_len || (new_base[0] == '.' &&
 681             (new_len == 1 || (new_base[1] == '.' &&
 682              new_len == 2)))) {
 683                 iput(old_dir);
 684                 iput(new_dir);
 685                 return -EPERM;
 686         }
 687         if (new_dir->i_dev != old_dir->i_dev) {
 688                 iput(old_dir);
 689                 iput(new_dir);
 690                 return -EXDEV;
 691         }
 692         if (IS_RDONLY(new_dir) || IS_RDONLY(old_dir)) {
 693                 iput(old_dir);
 694                 iput(new_dir);
 695                 return -EROFS;
 696         }
 697         if (!old_dir->i_op || !old_dir->i_op->rename) {
 698                 iput(old_dir);
 699                 iput(new_dir);
 700                 return -EPERM;
 701         }
 702         return old_dir->i_op->rename(old_dir, old_base, old_len, 
 703                 new_dir, new_base, new_len);
 704 }
 705 
 706 extern "C" int sys_rename(const char * oldname, const char * newname)
     /*  */
 707 {
 708         int error;
 709         char * from, * to;
 710 
 711         error = getname(oldname,&from);
 712         if (!error) {
 713                 error = getname(newname,&to);
 714                 if (!error) {
 715                         error = do_rename(from,to);
 716                         putname(to);
 717                 }
 718                 putname(from);
 719         }
 720         return error;
 721 }
/* */
root/fs/namei.c

DEFINITIONS
