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_each_task(p) {
 129                         struct vm_area_struct * mpnt;
 130                         if (!p->mm)
 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                 down(&inode->i_sem);
 431                 inode->i_size = 0;
 432                 if (inode->i_op && inode->i_op->truncate)
 433                         inode->i_op->truncate(inode);
 434                 up(&inode->i_sem);
 435                 inode->i_dirt = 1;
 436                 put_write_access(inode);
 437         }
 438         *res_inode = inode;
 439         return 0;
 440 }
 441 
 442 int do_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 443 {
 444         const char * basename;
 445         int namelen, error;
 446         struct inode * dir;
 447 
 448         mode &= ~current->fs->umask;
 449         error = dir_namei(filename,&namelen,&basename, NULL, &dir);
 450         if (error)
 451                 return error;
 452         if (!namelen) {
 453                 iput(dir);
 454                 return -ENOENT;
 455         }
 456         if (IS_RDONLY(dir)) {
 457                 iput(dir);
 458                 return -EROFS;
 459         }
 460         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 461                 iput(dir);
 462                 return error;
 463         }
 464         if (!dir->i_op || !dir->i_op->mknod) {
 465                 iput(dir);
 466                 return -EPERM;
 467         }
 468         dir->i_count++;
 469         down(&dir->i_sem);
 470         error = dir->i_op->mknod(dir,basename,namelen,mode,dev);
 471         up(&dir->i_sem);
 472         iput(dir);
 473         return error;
 474 }
 475 
 476 asmlinkage int sys_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 477 {
 478         int error;
 479         char * tmp;
 480 
 481         if (S_ISDIR(mode) || (!S_ISFIFO(mode) && !fsuser()))
 482                 return -EPERM;
 483         switch (mode & S_IFMT) {
 484         case 0:
 485                 mode |= S_IFREG;
 486                 break;
 487         case S_IFREG: case S_IFCHR: case S_IFBLK: case S_IFIFO: case S_IFSOCK:
 488                 break;
 489         default:
 490                 return -EINVAL;
 491         }
 492         error = getname(filename,&tmp);
 493         if (!error) {
 494                 error = do_mknod(tmp,mode,dev);
 495                 putname(tmp);
 496         }
 497         return error;
 498 }
 499 
 500 static int do_mkdir(const char * pathname, int mode)
     /*  */
 501 {
 502         const char * basename;
 503         int namelen, error;
 504         struct inode * dir;
 505 
 506         error = dir_namei(pathname,&namelen,&basename,NULL,&dir);
 507         if (error)
 508                 return error;
 509         if (!namelen) {
 510                 iput(dir);
 511                 return -ENOENT;
 512         }
 513         if (IS_RDONLY(dir)) {
 514                 iput(dir);
 515                 return -EROFS;
 516         }
 517         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 518                 iput(dir);
 519                 return error;
 520         }
 521         if (!dir->i_op || !dir->i_op->mkdir) {
 522                 iput(dir);
 523                 return -EPERM;
 524         }
 525         dir->i_count++;
 526         down(&dir->i_sem);
 527         error = dir->i_op->mkdir(dir, basename, namelen, mode & 0777 & ~current->fs->umask);
 528         up(&dir->i_sem);
 529         iput(dir);
 530         return error;
 531 }
 532 
 533 asmlinkage int sys_mkdir(const char * pathname, int mode)
     /*  */
 534 {
 535         int error;
 536         char * tmp;
 537 
 538         error = getname(pathname,&tmp);
 539         if (!error) {
 540                 error = do_mkdir(tmp,mode);
 541                 putname(tmp);
 542         }
 543         return error;
 544 }
 545 
 546 static int do_rmdir(const char * name)
     /*  */
 547 {
 548         const char * basename;
 549         int namelen, error;
 550         struct inode * dir;
 551 
 552         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 553         if (error)
 554                 return error;
 555         if (!namelen) {
 556                 iput(dir);
 557                 return -ENOENT;
 558         }
 559         if (IS_RDONLY(dir)) {
 560                 iput(dir);
 561                 return -EROFS;
 562         }
 563         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 564                 iput(dir);
 565                 return error;
 566         }
 567         /*
 568          * A subdirectory cannot be removed from an append-only directory
 569          */
 570         if (IS_APPEND(dir)) {
 571                 iput(dir);
 572                 return -EPERM;
 573         }
 574         if (!dir->i_op || !dir->i_op->rmdir) {
 575                 iput(dir);
 576                 return -EPERM;
 577         }
 578         return dir->i_op->rmdir(dir,basename,namelen);
 579 }
 580 
 581 asmlinkage int sys_rmdir(const char * pathname)
     /*  */
 582 {
 583         int error;
 584         char * tmp;
 585 
 586         error = getname(pathname,&tmp);
 587         if (!error) {
 588                 error = do_rmdir(tmp);
 589                 putname(tmp);
 590         }
 591         return error;
 592 }
 593 
 594 static int do_unlink(const char * name)
     /*  */
 595 {
 596         const char * basename;
 597         int namelen, error;
 598         struct inode * dir;
 599 
 600         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 601         if (error)
 602                 return error;
 603         if (!namelen) {
 604                 iput(dir);
 605                 return -EPERM;
 606         }
 607         if (IS_RDONLY(dir)) {
 608                 iput(dir);
 609                 return -EROFS;
 610         }
 611         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 612                 iput(dir);
 613                 return error;
 614         }
 615         /*
 616          * A file cannot be removed from an append-only directory
 617          */
 618         if (IS_APPEND(dir)) {
 619                 iput(dir);
 620                 return -EPERM;
 621         }
 622         if (!dir->i_op || !dir->i_op->unlink) {
 623                 iput(dir);
 624                 return -EPERM;
 625         }
 626         return dir->i_op->unlink(dir,basename,namelen);
 627 }
 628 
 629 asmlinkage int sys_unlink(const char * pathname)
     /*  */
 630 {
 631         int error;
 632         char * tmp;
 633 
 634         error = getname(pathname,&tmp);
 635         if (!error) {
 636                 error = do_unlink(tmp);
 637                 putname(tmp);
 638         }
 639         return error;
 640 }
 641 
 642 static int do_symlink(const char * oldname, const char * newname)
     /*  */
 643 {
 644         struct inode * dir;
 645         const char * basename;
 646         int namelen, error;
 647 
 648         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 649         if (error)
 650                 return error;
 651         if (!namelen) {
 652                 iput(dir);
 653                 return -ENOENT;
 654         }
 655         if (IS_RDONLY(dir)) {
 656                 iput(dir);
 657                 return -EROFS;
 658         }
 659         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 660                 iput(dir);
 661                 return error;
 662         }
 663         if (!dir->i_op || !dir->i_op->symlink) {
 664                 iput(dir);
 665                 return -EPERM;
 666         }
 667         dir->i_count++;
 668         down(&dir->i_sem);
 669         error = dir->i_op->symlink(dir,basename,namelen,oldname);
 670         up(&dir->i_sem);
 671         iput(dir);
 672         return error;
 673 }
 674 
 675 asmlinkage int sys_symlink(const char * oldname, const char * newname)
     /*  */
 676 {
 677         int error;
 678         char * from, * to;
 679 
 680         error = getname(oldname,&from);
 681         if (!error) {
 682                 error = getname(newname,&to);
 683                 if (!error) {
 684                         error = do_symlink(from,to);
 685                         putname(to);
 686                 }
 687                 putname(from);
 688         }
 689         return error;
 690 }
 691 
 692 static int do_link(struct inode * oldinode, const char * newname)
     /*  */
 693 {
 694         struct inode * dir;
 695         const char * basename;
 696         int namelen, error;
 697 
 698         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 699         if (error) {
 700                 iput(oldinode);
 701                 return error;
 702         }
 703         if (!namelen) {
 704                 iput(oldinode);
 705                 iput(dir);
 706                 return -EPERM;
 707         }
 708         if (IS_RDONLY(dir)) {
 709                 iput(oldinode);
 710                 iput(dir);
 711                 return -EROFS;
 712         }
 713         if (dir->i_dev != oldinode->i_dev) {
 714                 iput(dir);
 715                 iput(oldinode);
 716                 return -EXDEV;
 717         }
 718         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 719                 iput(dir);
 720                 iput(oldinode);
 721                 return error;
 722         }
 723         /*
 724          * A link to an append-only or immutable file cannot be created
 725          */
 726         if (IS_APPEND(oldinode) || IS_IMMUTABLE(oldinode)) {
 727                 iput(dir);
 728                 iput(oldinode);
 729                 return -EPERM;
 730         }
 731         if (!dir->i_op || !dir->i_op->link) {
 732                 iput(dir);
 733                 iput(oldinode);
 734                 return -EPERM;
 735         }
 736         dir->i_count++;
 737         down(&dir->i_sem);
 738         error = dir->i_op->link(oldinode, dir, basename, namelen);
 739         up(&dir->i_sem);
 740         iput(dir);
 741         return error;
 742 }
 743 
 744 asmlinkage int sys_link(const char * oldname, const char * newname)
     /*  */
 745 {
 746         int error;
 747         char * to;
 748         struct inode * oldinode;
 749 
 750         error = namei(oldname, &oldinode);
 751         if (error)
 752                 return error;
 753         error = getname(newname,&to);
 754         if (error) {
 755                 iput(oldinode);
 756                 return error;
 757         }
 758         error = do_link(oldinode,to);
 759         putname(to);
 760         return error;
 761 }
 762 
 763 static int do_rename(const char * oldname, const char * newname)
     /*  */
 764 {
 765         struct inode * old_dir, * new_dir;
 766         const char * old_base, * new_base;
 767         int old_len, new_len, error;
 768 
 769         error = dir_namei(oldname,&old_len,&old_base,NULL,&old_dir);
 770         if (error)
 771                 return error;
 772         if ((error = permission(old_dir,MAY_WRITE | MAY_EXEC)) != 0) {
 773                 iput(old_dir);
 774                 return error;
 775         }
 776         if (!old_len || (old_base[0] == '.' &&
 777             (old_len == 1 || (old_base[1] == '.' &&
 778              old_len == 2)))) {
 779                 iput(old_dir);
 780                 return -EPERM;
 781         }
 782         error = dir_namei(newname,&new_len,&new_base,NULL,&new_dir);
 783         if (error) {
 784                 iput(old_dir);
 785                 return error;
 786         }
 787         if ((error = permission(new_dir,MAY_WRITE | MAY_EXEC)) != 0){
 788                 iput(old_dir);
 789                 iput(new_dir);
 790                 return error;
 791         }
 792         if (!new_len || (new_base[0] == '.' &&
 793             (new_len == 1 || (new_base[1] == '.' &&
 794              new_len == 2)))) {
 795                 iput(old_dir);
 796                 iput(new_dir);
 797                 return -EPERM;
 798         }
 799         if (new_dir->i_dev != old_dir->i_dev) {
 800                 iput(old_dir);
 801                 iput(new_dir);
 802                 return -EXDEV;
 803         }
 804         if (IS_RDONLY(new_dir) || IS_RDONLY(old_dir)) {
 805                 iput(old_dir);
 806                 iput(new_dir);
 807                 return -EROFS;
 808         }
 809         /*
 810          * A file cannot be removed from an append-only directory
 811          */
 812         if (IS_APPEND(old_dir)) {
 813                 iput(old_dir);
 814                 iput(new_dir);
 815                 return -EPERM;
 816         }
 817         if (!old_dir->i_op || !old_dir->i_op->rename) {
 818                 iput(old_dir);
 819                 iput(new_dir);
 820                 return -EPERM;
 821         }
 822         new_dir->i_count++;
 823         down(&new_dir->i_sem);
 824         error = old_dir->i_op->rename(old_dir, old_base, old_len, 
 825                 new_dir, new_base, new_len);
 826         up(&new_dir->i_sem);
 827         iput(new_dir);
 828         return error;
 829 }
 830 
 831 asmlinkage int sys_rename(const char * oldname, const char * newname)
     /*  */
 832 {
 833         int error;
 834         char * from, * to;
 835 
 836         error = getname(oldname,&from);
 837         if (!error) {
 838                 error = getname(newname,&to);
 839                 if (!error) {
 840                         error = do_rename(from,to);
 841                         putname(to);
 842                 }
 843                 putname(from);
 844         }
 845         return error;
 846 }
/* */
root/fs/namei.c

DEFINITIONS
