fs/namei.c

/* */
This source file includes following definitions.
get_max_filename
getname
putname
permission
get_write_access
put_write_access
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 #include <linux/mm.h>
  20 
  21 #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
  22 
  23 /*
  24  * How long a filename can we get from user space?
  25  *  -EFAULT if invalid area
  26  *  0 if ok (ENAMETOOLONG before EFAULT)
  27  *  >0 EFAULT after xx bytes
  28  */
  29 static inline int get_max_filename(unsigned long address)
     /*  */
  30 {
  31         struct vm_area_struct * vma;
  32 
  33         if (get_fs() == KERNEL_DS)
  34                 return 0;
  35         vma = find_vma(current, address);
  36         if (!vma || vma->vm_start > address || !(vma->vm_flags & VM_READ))
  37                 return -EFAULT;
  38         address = vma->vm_end - address;
  39         if (address > PAGE_SIZE)
  40                 return 0;
  41         if (vma->vm_next && vma->vm_next->vm_start == vma->vm_end &&
  42            (vma->vm_next->vm_flags & VM_READ))
  43                 return 0;
  44         return address;
  45 }
  46 
  47 /*
  48  * In order to reduce some races, while at the same time doing additional
  49  * checking and hopefully speeding things up, we copy filenames to the
  50  * kernel data space before using them..
  51  *
  52  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
  53  */
  54 int getname(const char * filename, char **result)
     /*  */
  55 {
  56         int i, error;
  57         unsigned long page;
  58         char * tmp, c;
  59 
  60         i = get_max_filename((unsigned long) filename);
  61         if (i < 0)
  62                 return i;
  63         error = -EFAULT;
  64         if (!i) {
  65                 error = -ENAMETOOLONG;
  66                 i = PAGE_SIZE;
  67         }
  68         c = get_user(filename++);
  69         if (!c)
  70                 return -ENOENT;
  71         if(!(page = __get_free_page(GFP_KERNEL)))
  72                 return -ENOMEM;
  73         *result = tmp = (char *) page;
  74         while (--i) {
  75                 *(tmp++) = c;
  76                 c = get_user(filename++);
  77                 if (!c) {
  78                         *tmp = '\0';
  79                         return 0;
  80                 }
  81         }
  82         free_page(page);
  83         return error;
  84 }
  85 
  86 void putname(char * name)
     /*  */
  87 {
  88         free_page((unsigned long) name);
  89 }
  90 
  91 /*
  92  *      permission()
  93  *
  94  * is used to check for read/write/execute permissions on a file.
  95  * We use "fsuid" for this, letting us set arbitrary permissions
  96  * for filesystem access without changing the "normal" uids which
  97  * are used for other things..
  98  */
  99 int permission(struct inode * inode,int mask)
     /*  */
 100 {
 101         int mode = inode->i_mode;
 102 
 103         if (inode->i_op && inode->i_op->permission)
 104                 return inode->i_op->permission(inode, mask);
 105         else if ((mask & S_IWOTH) && IS_IMMUTABLE(inode))
 106                 return -EACCES; /* Nobody gets write access to an immutable file */
 107         else if (current->fsuid == inode->i_uid)
 108                 mode >>= 6;
 109         else if (in_group_p(inode->i_gid))
 110                 mode >>= 3;
 111         if (((mode & mask & 0007) == mask) || fsuser())
 112                 return 0;
 113         return -EACCES;
 114 }
 115 
 116 /*
 117  * get_write_access() gets write permission for a file.
 118  * put_write_access() releases this write permission.
 119  * This is used for regular files.
 120  * We cannot support write (and maybe mmap read-write shared) accesses and
 121  * MAP_DENYWRITE mmappings simultaneously.
 122  */
 123 int get_write_access(struct inode * inode)
     /*  */
 124 {
 125         struct task_struct ** p;
 126 
 127         if ((inode->i_count > 1) && S_ISREG(inode->i_mode)) /* shortcut */
 128                 for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
 129                         struct vm_area_struct * mpnt;
 130                         if (!*p)
 131                                 continue;
 132                         for(mpnt = (*p)->mm->mmap; mpnt; mpnt = mpnt->vm_next) {
 133                                 if (inode != mpnt->vm_inode)
 134                                         continue;
 135                                 if (mpnt->vm_flags & VM_DENYWRITE)
 136                                         return -ETXTBSY;
 137                         }
 138                 }
 139         inode->i_wcount++;
 140         return 0;
 141 }
 142 
 143 void put_write_access(struct inode * inode)
     /*  */
 144 {
 145         inode->i_wcount--;
 146 }
 147 
 148 /*
 149  * lookup() looks up one part of a pathname, using the fs-dependent
 150  * routines (currently minix_lookup) for it. It also checks for
 151  * fathers (pseudo-roots, mount-points)
 152  */
 153 int lookup(struct inode * dir,const char * name, int len,
     /*  */
 154         struct inode ** result)
 155 {
 156         struct super_block * sb;
 157         int perm;
 158 
 159         *result = NULL;
 160         if (!dir)
 161                 return -ENOENT;
 162 /* check permissions before traversing mount-points */
 163         perm = permission(dir,MAY_EXEC);
 164         if (len==2 && name[0] == '.' && name[1] == '.') {
 165                 if (dir == current->fs->root) {
 166                         *result = dir;
 167                         return 0;
 168                 } else if ((sb = dir->i_sb) && (dir == sb->s_mounted)) {
 169                         iput(dir);
 170                         dir = sb->s_covered;
 171                         if (!dir)
 172                                 return -ENOENT;
 173                         dir->i_count++;
 174                 }
 175         }
 176         if (!dir->i_op || !dir->i_op->lookup) {
 177                 iput(dir);
 178                 return -ENOTDIR;
 179         }
 180         if (perm != 0) {
 181                 iput(dir);
 182                 return perm;
 183         }
 184         if (!len) {
 185                 *result = dir;
 186                 return 0;
 187         }
 188         return dir->i_op->lookup(dir,name,len,result);
 189 }
 190 
 191 int follow_link(struct inode * dir, struct inode * inode,
     /*  */
 192         int flag, int mode, struct inode ** res_inode)
 193 {
 194         if (!dir || !inode) {
 195                 iput(dir);
 196                 iput(inode);
 197                 *res_inode = NULL;
 198                 return -ENOENT;
 199         }
 200         if (!inode->i_op || !inode->i_op->follow_link) {
 201                 iput(dir);
 202                 *res_inode = inode;
 203                 return 0;
 204         }
 205         return inode->i_op->follow_link(dir,inode,flag,mode,res_inode);
 206 }
 207 
 208 /*
 209  *      dir_namei()
 210  *
 211  * dir_namei() returns the inode of the directory of the
 212  * specified name, and the name within that directory.
 213  */
 214 static int dir_namei(const char * pathname, int * namelen, const char ** name,
     /*  */
 215         struct inode * base, struct inode ** res_inode)
 216 {
 217         char c;
 218         const char * thisname;
 219         int len,error;
 220         struct inode * inode;
 221 
 222         *res_inode = NULL;
 223         if (!base) {
 224                 base = current->fs->pwd;
 225                 base->i_count++;
 226         }
 227         if ((c = *pathname) == '/') {
 228                 iput(base);
 229                 base = current->fs->root;
 230                 pathname++;
 231                 base->i_count++;
 232         }
 233         while (1) {
 234                 thisname = pathname;
 235                 for(len=0;(c = *(pathname++))&&(c != '/');len++)
 236                         /* nothing */ ;
 237                 if (!c)
 238                         break;
 239                 base->i_count++;
 240                 error = lookup(base,thisname,len,&inode);
 241                 if (error) {
 242                         iput(base);
 243                         return error;
 244                 }
 245                 error = follow_link(base,inode,0,0,&base);
 246                 if (error)
 247                         return error;
 248         }
 249         if (!base->i_op || !base->i_op->lookup) {
 250                 iput(base);
 251                 return -ENOTDIR;
 252         }
 253         *name = thisname;
 254         *namelen = len;
 255         *res_inode = base;
 256         return 0;
 257 }
 258 
 259 static int _namei(const char * pathname, struct inode * base,
     /*  */
 260         int follow_links, struct inode ** res_inode)
 261 {
 262         const char * basename;
 263         int namelen,error;
 264         struct inode * inode;
 265 
 266         *res_inode = NULL;
 267         error = dir_namei(pathname,&namelen,&basename,base,&base);
 268         if (error)
 269                 return error;
 270         base->i_count++;        /* lookup uses up base */
 271         error = lookup(base,basename,namelen,&inode);
 272         if (error) {
 273                 iput(base);
 274                 return error;
 275         }
 276         if (follow_links) {
 277                 error = follow_link(base,inode,0,0,&inode);
 278                 if (error)
 279                         return error;
 280         } else
 281                 iput(base);
 282         *res_inode = inode;
 283         return 0;
 284 }
 285 
 286 int lnamei(const char * pathname, struct inode ** res_inode)
     /*  */
 287 {
 288         int error;
 289         char * tmp;
 290 
 291         error = getname(pathname,&tmp);
 292         if (!error) {
 293                 error = _namei(tmp,NULL,0,res_inode);
 294                 putname(tmp);
 295         }
 296         return error;
 297 }
 298 
 299 /*
 300  *      namei()
 301  *
 302  * is used by most simple commands to get the inode of a specified name.
 303  * Open, link etc use their own routines, but this is enough for things
 304  * like 'chmod' etc.
 305  */
 306 int namei(const char * pathname, struct inode ** res_inode)
     /*  */
 307 {
 308         int error;
 309         char * tmp;
 310 
 311         error = getname(pathname,&tmp);
 312         if (!error) {
 313                 error = _namei(tmp,NULL,1,res_inode);
 314                 putname(tmp);
 315         }
 316         return error;
 317 }
 318 
 319 /*
 320  *      open_namei()
 321  *
 322  * namei for open - this is in fact almost the whole open-routine.
 323  *
 324  * Note that the low bits of "flag" aren't the same as in the open
 325  * system call - they are 00 - no permissions needed
 326  *                        01 - read permission needed
 327  *                        10 - write permission needed
 328  *                        11 - read/write permissions needed
 329  * which is a lot more logical, and also allows the "no perm" needed
 330  * for symlinks (where the permissions are checked later).
 331  */
 332 int open_namei(const char * pathname, int flag, int mode,
     /*  */
 333         struct inode ** res_inode, struct inode * base)
 334 {
 335         const char * basename;
 336         int namelen,error;
 337         struct inode * dir, *inode;
 338 
 339         mode &= S_IALLUGO & ~current->fs->umask;
 340         mode |= S_IFREG;
 341         error = dir_namei(pathname,&namelen,&basename,base,&dir);
 342         if (error)
 343                 return error;
 344         if (!namelen) {                 /* special case: '/usr/' etc */
 345                 if (flag & 2) {
 346                         iput(dir);
 347                         return -EISDIR;
 348                 }
 349                 /* thanks to Paul Pluzhnikov for noticing this was missing.. */
 350                 if ((error = permission(dir,ACC_MODE(flag))) != 0) {
 351                         iput(dir);
 352                         return error;
 353                 }
 354                 *res_inode=dir;
 355                 return 0;
 356         }
 357         dir->i_count++;         /* lookup eats the dir */
 358         if (flag & O_CREAT) {
 359                 down(&dir->i_sem);
 360                 error = lookup(dir,basename,namelen,&inode);
 361                 if (!error) {
 362                         if (flag & O_EXCL) {
 363                                 iput(inode);
 364                                 error = -EEXIST;
 365                         }
 366                 } else if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0)
 367                         ;       /* error is already set! */
 368                 else if (!dir->i_op || !dir->i_op->create)
 369                         error = -EACCES;
 370                 else if (IS_RDONLY(dir))
 371                         error = -EROFS;
 372                 else {
 373                         dir->i_count++;         /* create eats the dir */
 374                         error = dir->i_op->create(dir,basename,namelen,mode,res_inode);
 375                         up(&dir->i_sem);
 376                         iput(dir);
 377                         return error;
 378                 }
 379                 up(&dir->i_sem);
 380         } else
 381                 error = lookup(dir,basename,namelen,&inode);
 382         if (error) {
 383                 iput(dir);
 384                 return error;
 385         }
 386         error = follow_link(dir,inode,flag,mode,&inode);
 387         if (error)
 388                 return error;
 389         if (S_ISDIR(inode->i_mode) && (flag & 2)) {
 390                 iput(inode);
 391                 return -EISDIR;
 392         }
 393         if ((error = permission(inode,ACC_MODE(flag))) != 0) {
 394                 iput(inode);
 395                 return error;
 396         }
 397         if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
 398                 if (IS_NODEV(inode)) {
 399                         iput(inode);
 400                         return -EACCES;
 401                 }
 402                 flag &= ~O_TRUNC;
 403         } else {
 404                 if (IS_RDONLY(inode) && (flag & 2)) {
 405                         iput(inode);
 406                         return -EROFS;
 407                 }
 408         }
 409         /*
 410          * An append-only file must be opened in append mode for writing
 411          */
 412         if (IS_APPEND(inode) && ((flag & 2) && !(flag & O_APPEND))) {
 413                 iput(inode);
 414                 return -EPERM;
 415         }
 416         if (flag & O_TRUNC) {
 417                 struct iattr newattrs;
 418 
 419                 if ((error = get_write_access(inode))) {
 420                         iput(inode);
 421                         return error;
 422                 }
 423                 newattrs.ia_size = 0;
 424                 newattrs.ia_valid = ATTR_SIZE;
 425                 if ((error = notify_change(inode, &newattrs))) {
 426                         put_write_access(inode);
 427                         iput(inode);
 428                         return error;
 429                 }
 430                 inode->i_size = 0;
 431                 if (inode->i_op && inode->i_op->truncate)
 432                         inode->i_op->truncate(inode);
 433                 inode->i_dirt = 1;
 434                 put_write_access(inode);
 435         }
 436         *res_inode = inode;
 437         return 0;
 438 }
 439 
 440 int do_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 441 {
 442         const char * basename;
 443         int namelen, error;
 444         struct inode * dir;
 445 
 446         mode &= ~current->fs->umask;
 447         error = dir_namei(filename,&namelen,&basename, NULL, &dir);
 448         if (error)
 449                 return error;
 450         if (!namelen) {
 451                 iput(dir);
 452                 return -ENOENT;
 453         }
 454         if (IS_RDONLY(dir)) {
 455                 iput(dir);
 456                 return -EROFS;
 457         }
 458         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 459                 iput(dir);
 460                 return error;
 461         }
 462         if (!dir->i_op || !dir->i_op->mknod) {
 463                 iput(dir);
 464                 return -EPERM;
 465         }
 466         dir->i_count++;
 467         down(&dir->i_sem);
 468         error = dir->i_op->mknod(dir,basename,namelen,mode,dev);
 469         up(&dir->i_sem);
 470         iput(dir);
 471         return error;
 472 }
 473 
 474 asmlinkage int sys_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 475 {
 476         int error;
 477         char * tmp;
 478 
 479         if (S_ISDIR(mode) || (!S_ISFIFO(mode) && !fsuser()))
 480                 return -EPERM;
 481         switch (mode & S_IFMT) {
 482         case 0:
 483                 mode |= S_IFREG;
 484                 break;
 485         case S_IFREG: case S_IFCHR: case S_IFBLK: case S_IFIFO: case S_IFSOCK:
 486                 break;
 487         default:
 488                 return -EINVAL;
 489         }
 490         error = getname(filename,&tmp);
 491         if (!error) {
 492                 error = do_mknod(tmp,mode,dev);
 493                 putname(tmp);
 494         }
 495         return error;
 496 }
 497 
 498 static int do_mkdir(const char * pathname, int mode)
     /*  */
 499 {
 500         const char * basename;
 501         int namelen, error;
 502         struct inode * dir;
 503 
 504         error = dir_namei(pathname,&namelen,&basename,NULL,&dir);
 505         if (error)
 506                 return error;
 507         if (!namelen) {
 508                 iput(dir);
 509                 return -ENOENT;
 510         }
 511         if (IS_RDONLY(dir)) {
 512                 iput(dir);
 513                 return -EROFS;
 514         }
 515         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 516                 iput(dir);
 517                 return error;
 518         }
 519         if (!dir->i_op || !dir->i_op->mkdir) {
 520                 iput(dir);
 521                 return -EPERM;
 522         }
 523         dir->i_count++;
 524         down(&dir->i_sem);
 525         error = dir->i_op->mkdir(dir, basename, namelen, mode & 0777 & ~current->fs->umask);
 526         up(&dir->i_sem);
 527         iput(dir);
 528         return error;
 529 }
 530 
 531 asmlinkage int sys_mkdir(const char * pathname, int mode)
     /*  */
 532 {
 533         int error;
 534         char * tmp;
 535 
 536         error = getname(pathname,&tmp);
 537         if (!error) {
 538                 error = do_mkdir(tmp,mode);
 539                 putname(tmp);
 540         }
 541         return error;
 542 }
 543 
 544 static int do_rmdir(const char * name)
     /*  */
 545 {
 546         const char * basename;
 547         int namelen, error;
 548         struct inode * dir;
 549 
 550         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 551         if (error)
 552                 return error;
 553         if (!namelen) {
 554                 iput(dir);
 555                 return -ENOENT;
 556         }
 557         if (IS_RDONLY(dir)) {
 558                 iput(dir);
 559                 return -EROFS;
 560         }
 561         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 562                 iput(dir);
 563                 return error;
 564         }
 565         /*
 566          * A subdirectory cannot be removed from an append-only directory
 567          */
 568         if (IS_APPEND(dir)) {
 569                 iput(dir);
 570                 return -EPERM;
 571         }
 572         if (!dir->i_op || !dir->i_op->rmdir) {
 573                 iput(dir);
 574                 return -EPERM;
 575         }
 576         return dir->i_op->rmdir(dir,basename,namelen);
 577 }
 578 
 579 asmlinkage int sys_rmdir(const char * pathname)
     /*  */
 580 {
 581         int error;
 582         char * tmp;
 583 
 584         error = getname(pathname,&tmp);
 585         if (!error) {
 586                 error = do_rmdir(tmp);
 587                 putname(tmp);
 588         }
 589         return error;
 590 }
 591 
 592 static int do_unlink(const char * name)
     /*  */
 593 {
 594         const char * basename;
 595         int namelen, error;
 596         struct inode * dir;
 597 
 598         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 599         if (error)
 600                 return error;
 601         if (!namelen) {
 602                 iput(dir);
 603                 return -EPERM;
 604         }
 605         if (IS_RDONLY(dir)) {
 606                 iput(dir);
 607                 return -EROFS;
 608         }
 609         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 610                 iput(dir);
 611                 return error;
 612         }
 613         /*
 614          * A file cannot be removed from an append-only directory
 615          */
 616         if (IS_APPEND(dir)) {
 617                 iput(dir);
 618                 return -EPERM;
 619         }
 620         if (!dir->i_op || !dir->i_op->unlink) {
 621                 iput(dir);
 622                 return -EPERM;
 623         }
 624         return dir->i_op->unlink(dir,basename,namelen);
 625 }
 626 
 627 asmlinkage int sys_unlink(const char * pathname)
     /*  */
 628 {
 629         int error;
 630         char * tmp;
 631 
 632         error = getname(pathname,&tmp);
 633         if (!error) {
 634                 error = do_unlink(tmp);
 635                 putname(tmp);
 636         }
 637         return error;
 638 }
 639 
 640 static int do_symlink(const char * oldname, const char * newname)
     /*  */
 641 {
 642         struct inode * dir;
 643         const char * basename;
 644         int namelen, error;
 645 
 646         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 647         if (error)
 648                 return error;
 649         if (!namelen) {
 650                 iput(dir);
 651                 return -ENOENT;
 652         }
 653         if (IS_RDONLY(dir)) {
 654                 iput(dir);
 655                 return -EROFS;
 656         }
 657         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 658                 iput(dir);
 659                 return error;
 660         }
 661         if (!dir->i_op || !dir->i_op->symlink) {
 662                 iput(dir);
 663                 return -EPERM;
 664         }
 665         dir->i_count++;
 666         down(&dir->i_sem);
 667         error = dir->i_op->symlink(dir,basename,namelen,oldname);
 668         up(&dir->i_sem);
 669         iput(dir);
 670         return error;
 671 }
 672 
 673 asmlinkage int sys_symlink(const char * oldname, const char * newname)
     /*  */
 674 {
 675         int error;
 676         char * from, * to;
 677 
 678         error = getname(oldname,&from);
 679         if (!error) {
 680                 error = getname(newname,&to);
 681                 if (!error) {
 682                         error = do_symlink(from,to);
 683                         putname(to);
 684                 }
 685                 putname(from);
 686         }
 687         return error;
 688 }
 689 
 690 static int do_link(struct inode * oldinode, const char * newname)
     /*  */
 691 {
 692         struct inode * dir;
 693         const char * basename;
 694         int namelen, error;
 695 
 696         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 697         if (error) {
 698                 iput(oldinode);
 699                 return error;
 700         }
 701         if (!namelen) {
 702                 iput(oldinode);
 703                 iput(dir);
 704                 return -EPERM;
 705         }
 706         if (IS_RDONLY(dir)) {
 707                 iput(oldinode);
 708                 iput(dir);
 709                 return -EROFS;
 710         }
 711         if (dir->i_dev != oldinode->i_dev) {
 712                 iput(dir);
 713                 iput(oldinode);
 714                 return -EXDEV;
 715         }
 716         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 717                 iput(dir);
 718                 iput(oldinode);
 719                 return error;
 720         }
 721         /*
 722          * A link to an append-only or immutable file cannot be created
 723          */
 724         if (IS_APPEND(oldinode) || IS_IMMUTABLE(oldinode)) {
 725                 iput(dir);
 726                 iput(oldinode);
 727                 return -EPERM;
 728         }
 729         if (!dir->i_op || !dir->i_op->link) {
 730                 iput(dir);
 731                 iput(oldinode);
 732                 return -EPERM;
 733         }
 734         dir->i_count++;
 735         down(&dir->i_sem);
 736         error = dir->i_op->link(oldinode, dir, basename, namelen);
 737         up(&dir->i_sem);
 738         iput(dir);
 739         return error;
 740 }
 741 
 742 asmlinkage int sys_link(const char * oldname, const char * newname)
     /*  */
 743 {
 744         int error;
 745         char * to;
 746         struct inode * oldinode;
 747 
 748         error = namei(oldname, &oldinode);
 749         if (error)
 750                 return error;
 751         error = getname(newname,&to);
 752         if (error) {
 753                 iput(oldinode);
 754                 return error;
 755         }
 756         error = do_link(oldinode,to);
 757         putname(to);
 758         return error;
 759 }
 760 
 761 static int do_rename(const char * oldname, const char * newname)
     /*  */
 762 {
 763         struct inode * old_dir, * new_dir;
 764         const char * old_base, * new_base;
 765         int old_len, new_len, error;
 766 
 767         error = dir_namei(oldname,&old_len,&old_base,NULL,&old_dir);
 768         if (error)
 769                 return error;
 770         if ((error = permission(old_dir,MAY_WRITE | MAY_EXEC)) != 0) {
 771                 iput(old_dir);
 772                 return error;
 773         }
 774         if (!old_len || (old_base[0] == '.' &&
 775             (old_len == 1 || (old_base[1] == '.' &&
 776              old_len == 2)))) {
 777                 iput(old_dir);
 778                 return -EPERM;
 779         }
 780         error = dir_namei(newname,&new_len,&new_base,NULL,&new_dir);
 781         if (error) {
 782                 iput(old_dir);
 783                 return error;
 784         }
 785         if ((error = permission(new_dir,MAY_WRITE | MAY_EXEC)) != 0){
 786                 iput(old_dir);
 787                 iput(new_dir);
 788                 return error;
 789         }
 790         if (!new_len || (new_base[0] == '.' &&
 791             (new_len == 1 || (new_base[1] == '.' &&
 792              new_len == 2)))) {
 793                 iput(old_dir);
 794                 iput(new_dir);
 795                 return -EPERM;
 796         }
 797         if (new_dir->i_dev != old_dir->i_dev) {
 798                 iput(old_dir);
 799                 iput(new_dir);
 800                 return -EXDEV;
 801         }
 802         if (IS_RDONLY(new_dir) || IS_RDONLY(old_dir)) {
 803                 iput(old_dir);
 804                 iput(new_dir);
 805                 return -EROFS;
 806         }
 807         /*
 808          * A file cannot be removed from an append-only directory
 809          */
 810         if (IS_APPEND(old_dir)) {
 811                 iput(old_dir);
 812                 iput(new_dir);
 813                 return -EPERM;
 814         }
 815         if (!old_dir->i_op || !old_dir->i_op->rename) {
 816                 iput(old_dir);
 817                 iput(new_dir);
 818                 return -EPERM;
 819         }
 820         new_dir->i_count++;
 821         down(&new_dir->i_sem);
 822         error = old_dir->i_op->rename(old_dir, old_base, old_len, 
 823                 new_dir, new_base, new_len);
 824         up(&new_dir->i_sem);
 825         iput(new_dir);
 826         return error;
 827 }
 828 
 829 asmlinkage int sys_rename(const char * oldname, const char * newname)
     /*  */
 830 {
 831         int error;
 832         char * from, * to;
 833 
 834         error = getname(oldname,&from);
 835         if (!error) {
 836                 error = getname(newname,&to);
 837                 if (!error) {
 838                         error = do_rename(from,to);
 839                         putname(to);
 840                 }
 841                 putname(from);
 842         }
 843         return error;
 844 }
/* */
root/fs/namei.c

DEFINITIONS
