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         if (inode->i_op && inode->i_op->permission)
  79                 return inode->i_op->permission(inode, mask);
  80         else if (current->euid == inode->i_uid)
  81                 mode >>= 6;
  82         else if (in_group_p(inode->i_gid))
  83                 mode >>= 3;
  84         if (((mode & mask & 0007) == mask) || suser())
  85                 return 1;
  86         return 0;
  87 }
  88 
  89 /*
  90  * lookup() looks up one part of a pathname, using the fs-dependent
  91  * routines (currently minix_lookup) for it. It also checks for
  92  * fathers (pseudo-roots, mount-points)
  93  */
  94 int lookup(struct inode * dir,const char * name, int len,
     /*  */
  95         struct inode ** result)
  96 {
  97         struct super_block * sb;
  98         int perm;
  99 
 100         *result = NULL;
 101         if (!dir)
 102                 return -ENOENT;
 103 /* check permissions before traversing mount-points */
 104         perm = permission(dir,MAY_EXEC);
 105         if (len==2 && name[0] == '.' && name[1] == '.') {
 106                 if (dir == current->fs->root) {
 107                         *result = dir;
 108                         return 0;
 109                 } else if ((sb = dir->i_sb) && (dir == sb->s_mounted)) {
 110                         sb = dir->i_sb;
 111                         iput(dir);
 112                         dir = sb->s_covered;
 113                         if (!dir)
 114                                 return -ENOENT;
 115                         dir->i_count++;
 116                 }
 117         }
 118         if (!dir->i_op || !dir->i_op->lookup) {
 119                 iput(dir);
 120                 return -ENOTDIR;
 121         }
 122         if (!perm) {
 123                 iput(dir);
 124                 return -EACCES;
 125         }
 126         if (!len) {
 127                 *result = dir;
 128                 return 0;
 129         }
 130         return dir->i_op->lookup(dir,name,len,result);
 131 }
 132 
 133 int follow_link(struct inode * dir, struct inode * inode,
     /*  */
 134         int flag, int mode, struct inode ** res_inode)
 135 {
 136         if (!dir || !inode) {
 137                 iput(dir);
 138                 iput(inode);
 139                 *res_inode = NULL;
 140                 return -ENOENT;
 141         }
 142         if (!inode->i_op || !inode->i_op->follow_link) {
 143                 iput(dir);
 144                 *res_inode = inode;
 145                 return 0;
 146         }
 147         return inode->i_op->follow_link(dir,inode,flag,mode,res_inode);
 148 }
 149 
 150 /*
 151  *      dir_namei()
 152  *
 153  * dir_namei() returns the inode of the directory of the
 154  * specified name, and the name within that directory.
 155  */
 156 static int dir_namei(const char * pathname, int * namelen, const char ** name,
     /*  */
 157         struct inode * base, struct inode ** res_inode)
 158 {
 159         char c;
 160         const char * thisname;
 161         int len,error;
 162         struct inode * inode;
 163 
 164         *res_inode = NULL;
 165         if (!base) {
 166                 base = current->fs->pwd;
 167                 base->i_count++;
 168         }
 169         if ((c = *pathname) == '/') {
 170                 iput(base);
 171                 base = current->fs->root;
 172                 pathname++;
 173                 base->i_count++;
 174         }
 175         while (1) {
 176                 thisname = pathname;
 177                 for(len=0;(c = *(pathname++))&&(c != '/');len++)
 178                         /* nothing */ ;
 179                 if (!c)
 180                         break;
 181                 base->i_count++;
 182                 error = lookup(base,thisname,len,&inode);
 183                 if (error) {
 184                         iput(base);
 185                         return error;
 186                 }
 187                 error = follow_link(base,inode,0,0,&base);
 188                 if (error)
 189                         return error;
 190         }
 191         if (!base->i_op || !base->i_op->lookup) {
 192                 iput(base);
 193                 return -ENOTDIR;
 194         }
 195         *name = thisname;
 196         *namelen = len;
 197         *res_inode = base;
 198         return 0;
 199 }
 200 
 201 static int _namei(const char * pathname, struct inode * base,
     /*  */
 202         int follow_links, struct inode ** res_inode)
 203 {
 204         const char * basename;
 205         int namelen,error;
 206         struct inode * inode;
 207 
 208         *res_inode = NULL;
 209         error = dir_namei(pathname,&namelen,&basename,base,&base);
 210         if (error)
 211                 return error;
 212         base->i_count++;        /* lookup uses up base */
 213         error = lookup(base,basename,namelen,&inode);
 214         if (error) {
 215                 iput(base);
 216                 return error;
 217         }
 218         if (follow_links) {
 219                 error = follow_link(base,inode,0,0,&inode);
 220                 if (error)
 221                         return error;
 222         } else
 223                 iput(base);
 224         *res_inode = inode;
 225         return 0;
 226 }
 227 
 228 int lnamei(const char * pathname, struct inode ** res_inode)
     /*  */
 229 {
 230         int error;
 231         char * tmp;
 232 
 233         error = getname(pathname,&tmp);
 234         if (!error) {
 235                 error = _namei(tmp,NULL,0,res_inode);
 236                 putname(tmp);
 237         }
 238         return error;
 239 }
 240 
 241 /*
 242  *      namei()
 243  *
 244  * is used by most simple commands to get the inode of a specified name.
 245  * Open, link etc use their own routines, but this is enough for things
 246  * like 'chmod' etc.
 247  */
 248 int namei(const char * pathname, struct inode ** res_inode)
     /*  */
 249 {
 250         int error;
 251         char * tmp;
 252 
 253         error = getname(pathname,&tmp);
 254         if (!error) {
 255                 error = _namei(tmp,NULL,1,res_inode);
 256                 putname(tmp);
 257         }
 258         return error;
 259 }
 260 
 261 /*
 262  *      open_namei()
 263  *
 264  * namei for open - this is in fact almost the whole open-routine.
 265  *
 266  * Note that the low bits of "flag" aren't the same as in the open
 267  * system call - they are 00 - no permissions needed
 268  *                        01 - read permission needed
 269  *                        10 - write permission needed
 270  *                        11 - read/write permissions needed
 271  * which is a lot more logical, and also allows the "no perm" needed
 272  * for symlinks (where the permissions are checked later).
 273  */
 274 int open_namei(const char * pathname, int flag, int mode,
     /*  */
 275         struct inode ** res_inode, struct inode * base)
 276 {
 277         const char * basename;
 278         int namelen,error;
 279         struct inode * dir, *inode;
 280         struct task_struct ** p;
 281 
 282         mode &= S_IALLUGO & ~current->fs->umask;
 283         mode |= S_IFREG;
 284         error = dir_namei(pathname,&namelen,&basename,base,&dir);
 285         if (error)
 286                 return error;
 287         if (!namelen) {                 /* special case: '/usr/' etc */
 288                 if (flag & 2) {
 289                         iput(dir);
 290                         return -EISDIR;
 291                 }
 292                 /* thanks to Paul Pluzhnikov for noticing this was missing.. */
 293                 if (!permission(dir,ACC_MODE(flag))) {
 294                         iput(dir);
 295                         return -EACCES;
 296                 }
 297                 *res_inode=dir;
 298                 return 0;
 299         }
 300         dir->i_count++;         /* lookup eats the dir */
 301         if (flag & O_CREAT) {
 302                 down(&dir->i_sem);
 303                 error = lookup(dir,basename,namelen,&inode);
 304                 if (!error) {
 305                         if (flag & O_EXCL) {
 306                                 iput(inode);
 307                                 error = -EEXIST;
 308                         }
 309                 } else if (!permission(dir,MAY_WRITE | MAY_EXEC))
 310                         error = -EACCES;
 311                 else if (!dir->i_op || !dir->i_op->create)
 312                         error = -EACCES;
 313                 else if (IS_RDONLY(dir))
 314                         error = -EROFS;
 315                 else {
 316                         dir->i_count++;         /* create eats the dir */
 317                         error = dir->i_op->create(dir,basename,namelen,mode,res_inode);
 318                         up(&dir->i_sem);
 319                         iput(dir);
 320                         return error;
 321                 }
 322                 up(&dir->i_sem);
 323         } else
 324                 error = lookup(dir,basename,namelen,&inode);
 325         if (error) {
 326                 iput(dir);
 327                 return error;
 328         }
 329         error = follow_link(dir,inode,flag,mode,&inode);
 330         if (error)
 331                 return error;
 332         if (S_ISDIR(inode->i_mode) && (flag & 2)) {
 333                 iput(inode);
 334                 return -EISDIR;
 335         }
 336         if (!permission(inode,ACC_MODE(flag))) {
 337                 iput(inode);
 338                 return -EACCES;
 339         }
 340         if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
 341                 if (IS_NODEV(inode)) {
 342                         iput(inode);
 343                         return -EACCES;
 344                 }
 345         } else {
 346                 if (IS_RDONLY(inode) && (flag & 2)) {
 347                         iput(inode);
 348                         return -EROFS;
 349                 }
 350         }
 351         if ((inode->i_count > 1) && (flag & 2)) {
 352                 for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
 353                         struct vm_area_struct * mpnt;
 354                         if (!*p)
 355                                 continue;
 356                         if (inode == (*p)->executable) {
 357                                 iput(inode);
 358                                 return -ETXTBSY;
 359                         }
 360                         for(mpnt = (*p)->mm->mmap; mpnt; mpnt = mpnt->vm_next) {
 361                                 if (mpnt->vm_page_prot & PAGE_RW)
 362                                         continue;
 363                                 if (inode == mpnt->vm_inode) {
 364                                         iput(inode);
 365                                         return -ETXTBSY;
 366                                 }
 367                         }
 368                 }
 369         }
 370         if (flag & O_TRUNC) {
 371               inode->i_size = 0;
 372               if (inode->i_op && inode->i_op->truncate)
 373                    inode->i_op->truncate(inode);
 374               if ((error = notify_change(NOTIFY_SIZE, inode))) {
 375                    iput(inode);
 376                    return error;
 377               }
 378               inode->i_dirt = 1;
 379         }
 380         *res_inode = inode;
 381         return 0;
 382 }
 383 
 384 int do_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 385 {
 386         const char * basename;
 387         int namelen, error;
 388         struct inode * dir;
 389 
 390         mode &= ~current->fs->umask;
 391         error = dir_namei(filename,&namelen,&basename, NULL, &dir);
 392         if (error)
 393                 return error;
 394         if (!namelen) {
 395                 iput(dir);
 396                 return -ENOENT;
 397         }
 398         if (IS_RDONLY(dir)) {
 399                 iput(dir);
 400                 return -EROFS;
 401         }
 402         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 403                 iput(dir);
 404                 return -EACCES;
 405         }
 406         if (!dir->i_op || !dir->i_op->mknod) {
 407                 iput(dir);
 408                 return -EPERM;
 409         }
 410         dir->i_count++;
 411         down(&dir->i_sem);
 412         error = dir->i_op->mknod(dir,basename,namelen,mode,dev);
 413         up(&dir->i_sem);
 414         iput(dir);
 415         return error;
 416 }
 417 
 418 asmlinkage int sys_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 419 {
 420         int error;
 421         char * tmp;
 422 
 423         if (S_ISDIR(mode) || (!S_ISFIFO(mode) && !suser()))
 424                 return -EPERM;
 425         switch (mode & S_IFMT) {
 426         case 0:
 427                 mode |= S_IFREG;
 428                 break;
 429         case S_IFREG: case S_IFCHR: case S_IFBLK: case S_IFIFO:
 430                 break;
 431         default:
 432                 return -EINVAL;
 433         }
 434         error = getname(filename,&tmp);
 435         if (!error) {
 436                 error = do_mknod(tmp,mode,dev);
 437                 putname(tmp);
 438         }
 439         return error;
 440 }
 441 
 442 static int do_mkdir(const char * pathname, int mode)
     /*  */
 443 {
 444         const char * basename;
 445         int namelen, error;
 446         struct inode * dir;
 447 
 448         error = dir_namei(pathname,&namelen,&basename,NULL,&dir);
 449         if (error)
 450                 return error;
 451         if (!namelen) {
 452                 iput(dir);
 453                 return -ENOENT;
 454         }
 455         if (IS_RDONLY(dir)) {
 456                 iput(dir);
 457                 return -EROFS;
 458         }
 459         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 460                 iput(dir);
 461                 return -EACCES;
 462         }
 463         if (!dir->i_op || !dir->i_op->mkdir) {
 464                 iput(dir);
 465                 return -EPERM;
 466         }
 467         dir->i_count++;
 468         down(&dir->i_sem);
 469         error = dir->i_op->mkdir(dir,basename,namelen,mode);
 470         up(&dir->i_sem);
 471         iput(dir);
 472         return error;
 473 }
 474 
 475 asmlinkage int sys_mkdir(const char * pathname, int mode)
     /*  */
 476 {
 477         int error;
 478         char * tmp;
 479 
 480         error = getname(pathname,&tmp);
 481         if (!error) {
 482                 error = do_mkdir(tmp,mode);
 483                 putname(tmp);
 484         }
 485         return error;
 486 }
 487 
 488 static int do_rmdir(const char * name)
     /*  */
 489 {
 490         const char * basename;
 491         int namelen, error;
 492         struct inode * dir;
 493 
 494         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 495         if (error)
 496                 return error;
 497         if (!namelen) {
 498                 iput(dir);
 499                 return -ENOENT;
 500         }
 501         if (IS_RDONLY(dir)) {
 502                 iput(dir);
 503                 return -EROFS;
 504         }
 505         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 506                 iput(dir);
 507                 return -EACCES;
 508         }
 509         if (!dir->i_op || !dir->i_op->rmdir) {
 510                 iput(dir);
 511                 return -EPERM;
 512         }
 513         return dir->i_op->rmdir(dir,basename,namelen);
 514 }
 515 
 516 asmlinkage int sys_rmdir(const char * pathname)
     /*  */
 517 {
 518         int error;
 519         char * tmp;
 520 
 521         error = getname(pathname,&tmp);
 522         if (!error) {
 523                 error = do_rmdir(tmp);
 524                 putname(tmp);
 525         }
 526         return error;
 527 }
 528 
 529 static int do_unlink(const char * name)
     /*  */
 530 {
 531         const char * basename;
 532         int namelen, error;
 533         struct inode * dir;
 534 
 535         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 536         if (error)
 537                 return error;
 538         if (!namelen) {
 539                 iput(dir);
 540                 return -EPERM;
 541         }
 542         if (IS_RDONLY(dir)) {
 543                 iput(dir);
 544                 return -EROFS;
 545         }
 546         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 547                 iput(dir);
 548                 return -EACCES;
 549         }
 550         if (!dir->i_op || !dir->i_op->unlink) {
 551                 iput(dir);
 552                 return -EPERM;
 553         }
 554         return dir->i_op->unlink(dir,basename,namelen);
 555 }
 556 
 557 asmlinkage int sys_unlink(const char * pathname)
     /*  */
 558 {
 559         int error;
 560         char * tmp;
 561 
 562         error = getname(pathname,&tmp);
 563         if (!error) {
 564                 error = do_unlink(tmp);
 565                 putname(tmp);
 566         }
 567         return error;
 568 }
 569 
 570 static int do_symlink(const char * oldname, const char * newname)
     /*  */
 571 {
 572         struct inode * dir;
 573         const char * basename;
 574         int namelen, error;
 575 
 576         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 577         if (error)
 578                 return error;
 579         if (!namelen) {
 580                 iput(dir);
 581                 return -ENOENT;
 582         }
 583         if (IS_RDONLY(dir)) {
 584                 iput(dir);
 585                 return -EROFS;
 586         }
 587         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 588                 iput(dir);
 589                 return -EACCES;
 590         }
 591         if (!dir->i_op || !dir->i_op->symlink) {
 592                 iput(dir);
 593                 return -EPERM;
 594         }
 595         dir->i_count++;
 596         down(&dir->i_sem);
 597         error = dir->i_op->symlink(dir,basename,namelen,oldname);
 598         up(&dir->i_sem);
 599         iput(dir);
 600         return error;
 601 }
 602 
 603 asmlinkage int sys_symlink(const char * oldname, const char * newname)
     /*  */
 604 {
 605         int error;
 606         char * from, * to;
 607 
 608         error = getname(oldname,&from);
 609         if (!error) {
 610                 error = getname(newname,&to);
 611                 if (!error) {
 612                         error = do_symlink(from,to);
 613                         putname(to);
 614                 }
 615                 putname(from);
 616         }
 617         return error;
 618 }
 619 
 620 static int do_link(struct inode * oldinode, const char * newname)
     /*  */
 621 {
 622         struct inode * dir;
 623         const char * basename;
 624         int namelen, error;
 625 
 626         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 627         if (error) {
 628                 iput(oldinode);
 629                 return error;
 630         }
 631         if (!namelen) {
 632                 iput(oldinode);
 633                 iput(dir);
 634                 return -EPERM;
 635         }
 636         if (IS_RDONLY(dir)) {
 637                 iput(oldinode);
 638                 iput(dir);
 639                 return -EROFS;
 640         }
 641         if (dir->i_dev != oldinode->i_dev) {
 642                 iput(dir);
 643                 iput(oldinode);
 644                 return -EXDEV;
 645         }
 646         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 647                 iput(dir);
 648                 iput(oldinode);
 649                 return -EACCES;
 650         }
 651         if (!dir->i_op || !dir->i_op->link) {
 652                 iput(dir);
 653                 iput(oldinode);
 654                 return -EPERM;
 655         }
 656         dir->i_count++;
 657         down(&dir->i_sem);
 658         error = dir->i_op->link(oldinode, dir, basename, namelen);
 659         up(&dir->i_sem);
 660         iput(dir);
 661         return error;
 662 }
 663 
 664 asmlinkage int sys_link(const char * oldname, const char * newname)
     /*  */
 665 {
 666         int error;
 667         char * to;
 668         struct inode * oldinode;
 669 
 670         error = namei(oldname, &oldinode);
 671         if (error)
 672                 return error;
 673         error = getname(newname,&to);
 674         if (error) {
 675                 iput(oldinode);
 676                 return error;
 677         }
 678         error = do_link(oldinode,to);
 679         putname(to);
 680         return error;
 681 }
 682 
 683 static int do_rename(const char * oldname, const char * newname)
     /*  */
 684 {
 685         struct inode * old_dir, * new_dir;
 686         const char * old_base, * new_base;
 687         int old_len, new_len, error;
 688 
 689         error = dir_namei(oldname,&old_len,&old_base,NULL,&old_dir);
 690         if (error)
 691                 return error;
 692         if (!permission(old_dir,MAY_WRITE | MAY_EXEC)) {
 693                 iput(old_dir);
 694                 return -EACCES;
 695         }
 696         if (!old_len || (old_base[0] == '.' &&
 697             (old_len == 1 || (old_base[1] == '.' &&
 698              old_len == 2)))) {
 699                 iput(old_dir);
 700                 return -EPERM;
 701         }
 702         error = dir_namei(newname,&new_len,&new_base,NULL,&new_dir);
 703         if (error) {
 704                 iput(old_dir);
 705                 return error;
 706         }
 707         if (!permission(new_dir,MAY_WRITE | MAY_EXEC)) {
 708                 iput(old_dir);
 709                 iput(new_dir);
 710                 return -EACCES;
 711         }
 712         if (!new_len || (new_base[0] == '.' &&
 713             (new_len == 1 || (new_base[1] == '.' &&
 714              new_len == 2)))) {
 715                 iput(old_dir);
 716                 iput(new_dir);
 717                 return -EPERM;
 718         }
 719         if (new_dir->i_dev != old_dir->i_dev) {
 720                 iput(old_dir);
 721                 iput(new_dir);
 722                 return -EXDEV;
 723         }
 724         if (IS_RDONLY(new_dir) || IS_RDONLY(old_dir)) {
 725                 iput(old_dir);
 726                 iput(new_dir);
 727                 return -EROFS;
 728         }
 729         if (!old_dir->i_op || !old_dir->i_op->rename) {
 730                 iput(old_dir);
 731                 iput(new_dir);
 732                 return -EPERM;
 733         }
 734         new_dir->i_count++;
 735         down(&new_dir->i_sem);
 736         error = old_dir->i_op->rename(old_dir, old_base, old_len, 
 737                 new_dir, new_base, new_len);
 738         up(&new_dir->i_sem);
 739         iput(new_dir);
 740         return error;
 741 }
 742 
 743 asmlinkage int sys_rename(const char * oldname, const char * newname)
     /*  */
 744 {
 745         int error;
 746         char * from, * to;
 747 
 748         error = getname(oldname,&from);
 749         if (!error) {
 750                 error = getname(newname,&to);
 751                 if (!error) {
 752                         error = do_rename(from,to);
 753                         putname(to);
 754                 }
 755                 putname(from);
 756         }
 757         return error;
 758 }
/* */
root/fs/namei.c

DEFINITIONS
