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_writecount++;
 140         return 0;
 141 }
 142 
 143 void put_write_access(struct inode * inode)
     /*  */
 144 {
 145         inode->i_writecount--;
 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                         if (dir->i_sb && dir->i_sb->dq_op)
 375                                 dir->i_sb->dq_op->initialize(dir, -1);
 376                         error = dir->i_op->create(dir, basename, namelen, mode, res_inode);
 377                         up(&dir->i_sem);
 378                         iput(dir);
 379                         return error;
 380                 }
 381                 up(&dir->i_sem);
 382         } else
 383                 error = lookup(dir, basename, namelen, &inode);
 384         if (error) {
 385                 iput(dir);
 386                 return error;
 387         }
 388         error = follow_link(dir,inode,flag,mode,&inode);
 389         if (error)
 390                 return error;
 391         if (S_ISDIR(inode->i_mode) && (flag & 2)) {
 392                 iput(inode);
 393                 return -EISDIR;
 394         }
 395         if ((error = permission(inode,ACC_MODE(flag))) != 0) {
 396                 iput(inode);
 397                 return error;
 398         }
 399         if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
 400                 /*
 401                  * 2-Feb-1995 Bruce Perens <Bruce@Pixar.com>
 402                  * Allow opens of Unix domain sockets and FIFOs for write on
 403                  * read-only filesystems. Their data does not live on the disk.
 404                  *
 405                  * If there was something like IS_NODEV(inode) for
 406                  * pipes and/or sockets I'd check it here.
 407                  */
 408         }
 409         else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
 410                 if (IS_NODEV(inode)) {
 411                         iput(inode);
 412                         return -EACCES;
 413                 }
 414                 flag &= ~O_TRUNC;
 415         } else {
 416                 if (IS_RDONLY(inode) && (flag & 2)) {
 417                         iput(inode);
 418                         return -EROFS;
 419                 }
 420         }
 421         /*
 422          * An append-only file must be opened in append mode for writing
 423          */
 424         if (IS_APPEND(inode) && ((flag & FMODE_WRITE) && !(flag & O_APPEND))) {
 425                 iput(inode);
 426                 return -EPERM;
 427         }
 428         if (flag & O_TRUNC) {
 429                 if ((error = get_write_access(inode))) {
 430                         iput(inode);
 431                         return error;
 432                 }
 433                 /*
 434                  * Refuse to truncate files with mandatory locks held on them
 435                  */
 436                 error = locks_verify_locked(inode);
 437                 if (error) {
 438                         iput(inode);
 439                         return error;
 440                 }
 441                 if (inode->i_sb && inode->i_sb->dq_op)
 442                         inode->i_sb->dq_op->initialize(inode, -1);
 443                         
 444                 error = do_truncate(inode, 0);
 445                 put_write_access(inode);
 446                 if (error) {
 447                         iput(inode);
 448                         return error;
 449                 }
 450         } else
 451                 if (flag & FMODE_WRITE)
 452                         if (inode->i_sb && inode->i_sb->dq_op)
 453                                 inode->i_sb->dq_op->initialize(inode, -1);
 454         *res_inode = inode;
 455         return 0;
 456 }
 457 
 458 int do_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 459 {
 460         const char * basename;
 461         int namelen, error;
 462         struct inode * dir;
 463 
 464         mode &= ~current->fs->umask;
 465         error = dir_namei(filename, &namelen, &basename, NULL, &dir);
 466         if (error)
 467                 return error;
 468         if (!namelen) {
 469                 iput(dir);
 470                 return -ENOENT;
 471         }
 472         if (IS_RDONLY(dir)) {
 473                 iput(dir);
 474                 return -EROFS;
 475         }
 476         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 477                 iput(dir);
 478                 return error;
 479         }
 480         if (!dir->i_op || !dir->i_op->mknod) {
 481                 iput(dir);
 482                 return -EPERM;
 483         }
 484         dir->i_count++;
 485         if (dir->i_sb && dir->i_sb->dq_op)
 486                 dir->i_sb->dq_op->initialize(dir, -1);
 487         down(&dir->i_sem);
 488         error = dir->i_op->mknod(dir,basename,namelen,mode,dev);
 489         up(&dir->i_sem);
 490         iput(dir);
 491         return error;
 492 }
 493 
 494 asmlinkage int sys_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 495 {
 496         int error;
 497         char * tmp;
 498 
 499         if (S_ISDIR(mode) || (!S_ISFIFO(mode) && !fsuser()))
 500                 return -EPERM;
 501         switch (mode & S_IFMT) {
 502         case 0:
 503                 mode |= S_IFREG;
 504                 break;
 505         case S_IFREG: case S_IFCHR: case S_IFBLK: case S_IFIFO: case S_IFSOCK:
 506                 break;
 507         default:
 508                 return -EINVAL;
 509         }
 510         error = getname(filename,&tmp);
 511         if (!error) {
 512                 error = do_mknod(tmp,mode,dev);
 513                 putname(tmp);
 514         }
 515         return error;
 516 }
 517 
 518 static int do_mkdir(const char * pathname, int mode)
     /*  */
 519 {
 520         const char * basename;
 521         int namelen, error;
 522         struct inode * dir;
 523 
 524         error = dir_namei(pathname, &namelen, &basename, NULL, &dir);
 525         if (error)
 526                 return error;
 527         if (!namelen) {
 528                 iput(dir);
 529                 return -ENOENT;
 530         }
 531         if (IS_RDONLY(dir)) {
 532                 iput(dir);
 533                 return -EROFS;
 534         }
 535         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 536                 iput(dir);
 537                 return error;
 538         }
 539         if (!dir->i_op || !dir->i_op->mkdir) {
 540                 iput(dir);
 541                 return -EPERM;
 542         }
 543         dir->i_count++;
 544         if (dir->i_sb && dir->i_sb->dq_op)
 545                 dir->i_sb->dq_op->initialize(dir, -1);
 546         down(&dir->i_sem);
 547         error = dir->i_op->mkdir(dir, basename, namelen, mode & 0777 & ~current->fs->umask);
 548         up(&dir->i_sem);
 549         iput(dir);
 550         return error;
 551 }
 552 
 553 asmlinkage int sys_mkdir(const char * pathname, int mode)
     /*  */
 554 {
 555         int error;
 556         char * tmp;
 557 
 558         error = getname(pathname,&tmp);
 559         if (!error) {
 560                 error = do_mkdir(tmp,mode);
 561                 putname(tmp);
 562         }
 563         return error;
 564 }
 565 
 566 static int do_rmdir(const char * name)
     /*  */
 567 {
 568         const char * basename;
 569         int namelen, error;
 570         struct inode * dir;
 571 
 572         error = dir_namei(name, &namelen, &basename, NULL, &dir);
 573         if (error)
 574                 return error;
 575         if (!namelen) {
 576                 iput(dir);
 577                 return -ENOENT;
 578         }
 579         if (IS_RDONLY(dir)) {
 580                 iput(dir);
 581                 return -EROFS;
 582         }
 583         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 584                 iput(dir);
 585                 return error;
 586         }
 587         /*
 588          * A subdirectory cannot be removed from an append-only directory
 589          */
 590         if (IS_APPEND(dir)) {
 591                 iput(dir);
 592                 return -EPERM;
 593         }
 594         if (!dir->i_op || !dir->i_op->rmdir) {
 595                 iput(dir);
 596                 return -EPERM;
 597         }
 598         if (dir->i_sb && dir->i_sb->dq_op)
 599                 dir->i_sb->dq_op->initialize(dir, -1);
 600         return dir->i_op->rmdir(dir,basename,namelen);
 601 }
 602 
 603 asmlinkage int sys_rmdir(const char * pathname)
     /*  */
 604 {
 605         int error;
 606         char * tmp;
 607 
 608         error = getname(pathname,&tmp);
 609         if (!error) {
 610                 error = do_rmdir(tmp);
 611                 putname(tmp);
 612         }
 613         return error;
 614 }
 615 
 616 static int do_unlink(const char * name)
     /*  */
 617 {
 618         const char * basename;
 619         int namelen, error;
 620         struct inode * dir;
 621 
 622         error = dir_namei(name, &namelen, &basename, NULL, &dir);
 623         if (error)
 624                 return error;
 625         if (!namelen) {
 626                 iput(dir);
 627                 return -EPERM;
 628         }
 629         if (IS_RDONLY(dir)) {
 630                 iput(dir);
 631                 return -EROFS;
 632         }
 633         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 634                 iput(dir);
 635                 return error;
 636         }
 637         /*
 638          * A file cannot be removed from an append-only directory
 639          */
 640         if (IS_APPEND(dir)) {
 641                 iput(dir);
 642                 return -EPERM;
 643         }
 644         if (!dir->i_op || !dir->i_op->unlink) {
 645                 iput(dir);
 646                 return -EPERM;
 647         }
 648         if (dir->i_sb && dir->i_sb->dq_op)
 649                 dir->i_sb->dq_op->initialize(dir, -1);
 650         return dir->i_op->unlink(dir,basename,namelen);
 651 }
 652 
 653 asmlinkage int sys_unlink(const char * pathname)
     /*  */
 654 {
 655         int error;
 656         char * tmp;
 657 
 658         error = getname(pathname,&tmp);
 659         if (!error) {
 660                 error = do_unlink(tmp);
 661                 putname(tmp);
 662         }
 663         return error;
 664 }
 665 
 666 static int do_symlink(const char * oldname, const char * newname)
     /*  */
 667 {
 668         struct inode * dir;
 669         const char * basename;
 670         int namelen, error;
 671 
 672         error = dir_namei(newname, &namelen, &basename, NULL, &dir);
 673         if (error)
 674                 return error;
 675         if (!namelen) {
 676                 iput(dir);
 677                 return -ENOENT;
 678         }
 679         if (IS_RDONLY(dir)) {
 680                 iput(dir);
 681                 return -EROFS;
 682         }
 683         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 684                 iput(dir);
 685                 return error;
 686         }
 687         if (!dir->i_op || !dir->i_op->symlink) {
 688                 iput(dir);
 689                 return -EPERM;
 690         }
 691         dir->i_count++;
 692         if (dir->i_sb && dir->i_sb->dq_op)
 693                 dir->i_sb->dq_op->initialize(dir, -1);
 694         down(&dir->i_sem);
 695         error = dir->i_op->symlink(dir,basename,namelen,oldname);
 696         up(&dir->i_sem);
 697         iput(dir);
 698         return error;
 699 }
 700 
 701 asmlinkage int sys_symlink(const char * oldname, const char * newname)
     /*  */
 702 {
 703         int error;
 704         char * from, * to;
 705 
 706         error = getname(oldname,&from);
 707         if (!error) {
 708                 error = getname(newname,&to);
 709                 if (!error) {
 710                         error = do_symlink(from,to);
 711                         putname(to);
 712                 }
 713                 putname(from);
 714         }
 715         return error;
 716 }
 717 
 718 static int do_link(struct inode * oldinode, const char * newname)
     /*  */
 719 {
 720         struct inode * dir;
 721         const char * basename;
 722         int namelen, error;
 723 
 724         error = dir_namei(newname, &namelen, &basename, NULL, &dir);
 725         if (error) {
 726                 iput(oldinode);
 727                 return error;
 728         }
 729         if (!namelen) {
 730                 iput(oldinode);
 731                 iput(dir);
 732                 return -EPERM;
 733         }
 734         if (IS_RDONLY(dir)) {
 735                 iput(oldinode);
 736                 iput(dir);
 737                 return -EROFS;
 738         }
 739         if (dir->i_dev != oldinode->i_dev) {
 740                 iput(dir);
 741                 iput(oldinode);
 742                 return -EXDEV;
 743         }
 744         if ((error = permission(dir,MAY_WRITE | MAY_EXEC)) != 0) {
 745                 iput(dir);
 746                 iput(oldinode);
 747                 return error;
 748         }
 749         /*
 750          * A link to an append-only or immutable file cannot be created
 751          */
 752         if (IS_APPEND(oldinode) || IS_IMMUTABLE(oldinode)) {
 753                 iput(dir);
 754                 iput(oldinode);
 755                 return -EPERM;
 756         }
 757         if (!dir->i_op || !dir->i_op->link) {
 758                 iput(dir);
 759                 iput(oldinode);
 760                 return -EPERM;
 761         }
 762         dir->i_count++;
 763         if (dir->i_sb && dir->i_sb->dq_op)
 764                 dir->i_sb->dq_op->initialize(dir, -1);
 765         down(&dir->i_sem);
 766         error = dir->i_op->link(oldinode, dir, basename, namelen);
 767         up(&dir->i_sem);
 768         iput(dir);
 769         return error;
 770 }
 771 
 772 asmlinkage int sys_link(const char * oldname, const char * newname)
     /*  */
 773 {
 774         int error;
 775         char * to;
 776         struct inode * oldinode;
 777 
 778         error = lnamei(oldname, &oldinode);
 779         if (error)
 780                 return error;
 781         error = getname(newname,&to);
 782         if (error) {
 783                 iput(oldinode);
 784                 return error;
 785         }
 786         error = do_link(oldinode,to);
 787         putname(to);
 788         return error;
 789 }
 790 
 791 static int do_rename(const char * oldname, const char * newname)
     /*  */
 792 {
 793         struct inode * old_dir, * new_dir;
 794         const char * old_base, * new_base;
 795         int old_len, new_len, error;
 796 
 797         error = dir_namei(oldname, &old_len, &old_base, NULL, &old_dir);
 798         if (error)
 799                 return error;
 800         if ((error = permission(old_dir,MAY_WRITE | MAY_EXEC)) != 0) {
 801                 iput(old_dir);
 802                 return error;
 803         }
 804         if (!old_len || (old_base[0] == '.' &&
 805             (old_len == 1 || (old_base[1] == '.' &&
 806              old_len == 2)))) {
 807                 iput(old_dir);
 808                 return -EPERM;
 809         }
 810         error = dir_namei(newname, &new_len, &new_base, NULL, &new_dir);
 811         if (error) {
 812                 iput(old_dir);
 813                 return error;
 814         }
 815         if ((error = permission(new_dir,MAY_WRITE | MAY_EXEC)) != 0){
 816                 iput(old_dir);
 817                 iput(new_dir);
 818                 return error;
 819         }
 820         if (!new_len || (new_base[0] == '.' &&
 821             (new_len == 1 || (new_base[1] == '.' &&
 822              new_len == 2)))) {
 823                 iput(old_dir);
 824                 iput(new_dir);
 825                 return -EPERM;
 826         }
 827         if (new_dir->i_dev != old_dir->i_dev) {
 828                 iput(old_dir);
 829                 iput(new_dir);
 830                 return -EXDEV;
 831         }
 832         if (IS_RDONLY(new_dir) || IS_RDONLY(old_dir)) {
 833                 iput(old_dir);
 834                 iput(new_dir);
 835                 return -EROFS;
 836         }
 837         /*
 838          * A file cannot be removed from an append-only directory
 839          */
 840         if (IS_APPEND(old_dir)) {
 841                 iput(old_dir);
 842                 iput(new_dir);
 843                 return -EPERM;
 844         }
 845         if (!old_dir->i_op || !old_dir->i_op->rename) {
 846                 iput(old_dir);
 847                 iput(new_dir);
 848                 return -EPERM;
 849         }
 850         new_dir->i_count++;
 851         if (new_dir->i_sb && new_dir->i_sb->dq_op)
 852                 new_dir->i_sb->dq_op->initialize(new_dir, -1);
 853         down(&new_dir->i_sem);
 854         error = old_dir->i_op->rename(old_dir, old_base, old_len, 
 855                 new_dir, new_base, new_len);
 856         up(&new_dir->i_sem);
 857         iput(new_dir);
 858         return error;
 859 }
 860 
 861 asmlinkage int sys_rename(const char * oldname, const char * newname)
     /*  */
 862 {
 863         int error;
 864         char * from, * to;
 865 
 866         error = getname(oldname,&from);
 867         if (!error) {
 868                 error = getname(newname,&to);
 869                 if (!error) {
 870                         error = do_rename(from,to);
 871                         putname(to);
 872                 }
 873                 putname(from);
 874         }
 875         return error;
 876 }
/* */
root/fs/namei.c

DEFINITIONS
