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->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->pwd;
 167                 base->i_count++;
 168         }
 169         if ((c = *pathname) == '/') {
 170                 iput(base);
 171                 base = current->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,i;
 279         struct inode * dir, *inode;
 280         struct task_struct ** p;
 281 
 282         mode &= S_IALLUGO & ~current->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         for (i = 0; i < 5; i++) {       /* races... */
 301                 dir->i_count++;         /* lookup eats the dir */
 302                 error = lookup(dir,basename,namelen,&inode);
 303                 if (!error)
 304                         break;
 305                 if (!(flag & O_CREAT)) {
 306                         iput(dir);
 307                         return error;
 308                 }
 309                 if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 310                         iput(dir);
 311                         return -EACCES;
 312                 }
 313                 if (!dir->i_op || !dir->i_op->create) {
 314                         iput(dir);
 315                         return -EACCES;
 316                 }
 317                 if (IS_RDONLY(dir)) {
 318                         iput(dir);
 319                         return -EROFS;
 320                 }
 321                 dir->i_count++;         /* create eats the dir */
 322                 error = dir->i_op->create(dir,basename,namelen,mode,res_inode);
 323                 if (error != -EEXIST) {
 324                         iput(dir);
 325                         return error;
 326                 }
 327         }
 328         if (error) {
 329                 iput(dir);
 330                 return error;
 331         }
 332         if ((flag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) {
 333                 iput(dir);
 334                 iput(inode);
 335                 return -EEXIST;
 336         }
 337         error = follow_link(dir,inode,flag,mode,&inode);
 338         if (error)
 339                 return error;
 340         if (S_ISDIR(inode->i_mode) && (flag & 2)) {
 341                 iput(inode);
 342                 return -EISDIR;
 343         }
 344         if (!permission(inode,ACC_MODE(flag))) {
 345                 iput(inode);
 346                 return -EACCES;
 347         }
 348         if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
 349                 if (IS_NODEV(inode)) {
 350                         iput(inode);
 351                         return -EACCES;
 352                 }
 353         } else {
 354                 if (IS_RDONLY(inode) && (flag & 2)) {
 355                         iput(inode);
 356                         return -EROFS;
 357                 }
 358         }
 359         if ((inode->i_count > 1) && (flag & 2)) {
 360                 for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
 361                         struct vm_area_struct * mpnt;
 362                         if (!*p)
 363                                 continue;
 364                         if (inode == (*p)->executable) {
 365                                 iput(inode);
 366                                 return -ETXTBSY;
 367                         }
 368                         for(mpnt = (*p)->mmap; mpnt; mpnt = mpnt->vm_next) {
 369                                 if (mpnt->vm_page_prot & PAGE_RW)
 370                                         continue;
 371                                 if (inode == mpnt->vm_inode) {
 372                                         iput(inode);
 373                                         return -ETXTBSY;
 374                                 }
 375                         }
 376                 }
 377         }
 378         if (flag & O_TRUNC) {
 379               inode->i_size = 0;
 380               if (inode->i_op && inode->i_op->truncate)
 381                    inode->i_op->truncate(inode);
 382               if ((error = notify_change(NOTIFY_SIZE, inode))) {
 383                    iput(inode);
 384                    return error;
 385               }
 386               inode->i_dirt = 1;
 387         }
 388         *res_inode = inode;
 389         return 0;
 390 }
 391 
 392 int do_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 393 {
 394         const char * basename;
 395         int namelen, error;
 396         struct inode * dir;
 397 
 398         mode &= ~current->umask;
 399         error = dir_namei(filename,&namelen,&basename, NULL, &dir);
 400         if (error)
 401                 return error;
 402         if (!namelen) {
 403                 iput(dir);
 404                 return -ENOENT;
 405         }
 406         if (IS_RDONLY(dir)) {
 407                 iput(dir);
 408                 return -EROFS;
 409         }
 410         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 411                 iput(dir);
 412                 return -EACCES;
 413         }
 414         if (!dir->i_op || !dir->i_op->mknod) {
 415                 iput(dir);
 416                 return -EPERM;
 417         }
 418         return dir->i_op->mknod(dir,basename,namelen,mode,dev);
 419 }
 420 
 421 asmlinkage int sys_mknod(const char * filename, int mode, dev_t dev)
     /*  */
 422 {
 423         int error;
 424         char * tmp;
 425 
 426         if (S_ISDIR(mode) || (!S_ISFIFO(mode) && !suser()))
 427                 return -EPERM;
 428         switch (mode & S_IFMT) {
 429         case 0:
 430                 mode |= S_IFREG;
 431                 break;
 432         case S_IFREG: case S_IFCHR: case S_IFBLK: case S_IFIFO:
 433                 break;
 434         default:
 435                 return -EINVAL;
 436         }
 437         error = getname(filename,&tmp);
 438         if (!error) {
 439                 error = do_mknod(tmp,mode,dev);
 440                 putname(tmp);
 441         }
 442         return error;
 443 }
 444 
 445 static int do_mkdir(const char * pathname, int mode)
     /*  */
 446 {
 447         const char * basename;
 448         int namelen, error;
 449         struct inode * dir;
 450 
 451         error = dir_namei(pathname,&namelen,&basename,NULL,&dir);
 452         if (error)
 453                 return error;
 454         if (!namelen) {
 455                 iput(dir);
 456                 return -ENOENT;
 457         }
 458         if (IS_RDONLY(dir)) {
 459                 iput(dir);
 460                 return -EROFS;
 461         }
 462         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 463                 iput(dir);
 464                 return -EACCES;
 465         }
 466         if (!dir->i_op || !dir->i_op->mkdir) {
 467                 iput(dir);
 468                 return -EPERM;
 469         }
 470         return dir->i_op->mkdir(dir,basename,namelen,mode);
 471 }
 472 
 473 asmlinkage int sys_mkdir(const char * pathname, int mode)
     /*  */
 474 {
 475         int error;
 476         char * tmp;
 477 
 478         error = getname(pathname,&tmp);
 479         if (!error) {
 480                 error = do_mkdir(tmp,mode);
 481                 putname(tmp);
 482         }
 483         return error;
 484 }
 485 
 486 static int do_rmdir(const char * name)
     /*  */
 487 {
 488         const char * basename;
 489         int namelen, error;
 490         struct inode * dir;
 491 
 492         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 493         if (error)
 494                 return error;
 495         if (!namelen) {
 496                 iput(dir);
 497                 return -ENOENT;
 498         }
 499         if (IS_RDONLY(dir)) {
 500                 iput(dir);
 501                 return -EROFS;
 502         }
 503         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 504                 iput(dir);
 505                 return -EACCES;
 506         }
 507         if (!dir->i_op || !dir->i_op->rmdir) {
 508                 iput(dir);
 509                 return -EPERM;
 510         }
 511         return dir->i_op->rmdir(dir,basename,namelen);
 512 }
 513 
 514 asmlinkage int sys_rmdir(const char * pathname)
     /*  */
 515 {
 516         int error;
 517         char * tmp;
 518 
 519         error = getname(pathname,&tmp);
 520         if (!error) {
 521                 error = do_rmdir(tmp);
 522                 putname(tmp);
 523         }
 524         return error;
 525 }
 526 
 527 static int do_unlink(const char * name)
     /*  */
 528 {
 529         const char * basename;
 530         int namelen, error;
 531         struct inode * dir;
 532 
 533         error = dir_namei(name,&namelen,&basename,NULL,&dir);
 534         if (error)
 535                 return error;
 536         if (!namelen) {
 537                 iput(dir);
 538                 return -EPERM;
 539         }
 540         if (IS_RDONLY(dir)) {
 541                 iput(dir);
 542                 return -EROFS;
 543         }
 544         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 545                 iput(dir);
 546                 return -EACCES;
 547         }
 548         if (!dir->i_op || !dir->i_op->unlink) {
 549                 iput(dir);
 550                 return -EPERM;
 551         }
 552         return dir->i_op->unlink(dir,basename,namelen);
 553 }
 554 
 555 asmlinkage int sys_unlink(const char * pathname)
     /*  */
 556 {
 557         int error;
 558         char * tmp;
 559 
 560         error = getname(pathname,&tmp);
 561         if (!error) {
 562                 error = do_unlink(tmp);
 563                 putname(tmp);
 564         }
 565         return error;
 566 }
 567 
 568 static int do_symlink(const char * oldname, const char * newname)
     /*  */
 569 {
 570         struct inode * dir;
 571         const char * basename;
 572         int namelen, error;
 573 
 574         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 575         if (error)
 576                 return error;
 577         if (!namelen) {
 578                 iput(dir);
 579                 return -ENOENT;
 580         }
 581         if (IS_RDONLY(dir)) {
 582                 iput(dir);
 583                 return -EROFS;
 584         }
 585         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 586                 iput(dir);
 587                 return -EACCES;
 588         }
 589         if (!dir->i_op || !dir->i_op->symlink) {
 590                 iput(dir);
 591                 return -EPERM;
 592         }
 593         return dir->i_op->symlink(dir,basename,namelen,oldname);
 594 }
 595 
 596 asmlinkage int sys_symlink(const char * oldname, const char * newname)
     /*  */
 597 {
 598         int error;
 599         char * from, * to;
 600 
 601         error = getname(oldname,&from);
 602         if (!error) {
 603                 error = getname(newname,&to);
 604                 if (!error) {
 605                         error = do_symlink(from,to);
 606                         putname(to);
 607                 }
 608                 putname(from);
 609         }
 610         return error;
 611 }
 612 
 613 static int do_link(struct inode * oldinode, const char * newname)
     /*  */
 614 {
 615         struct inode * dir;
 616         const char * basename;
 617         int namelen, error;
 618 
 619         error = dir_namei(newname,&namelen,&basename,NULL,&dir);
 620         if (error) {
 621                 iput(oldinode);
 622                 return error;
 623         }
 624         if (!namelen) {
 625                 iput(oldinode);
 626                 iput(dir);
 627                 return -EPERM;
 628         }
 629         if (IS_RDONLY(dir)) {
 630                 iput(oldinode);
 631                 iput(dir);
 632                 return -EROFS;
 633         }
 634         if (dir->i_dev != oldinode->i_dev) {
 635                 iput(dir);
 636                 iput(oldinode);
 637                 return -EXDEV;
 638         }
 639         if (!permission(dir,MAY_WRITE | MAY_EXEC)) {
 640                 iput(dir);
 641                 iput(oldinode);
 642                 return -EACCES;
 643         }
 644         if (!dir->i_op || !dir->i_op->link) {
 645                 iput(dir);
 646                 iput(oldinode);
 647                 return -EPERM;
 648         }
 649         return dir->i_op->link(oldinode, dir, basename, namelen);
 650 }
 651 
 652 asmlinkage int sys_link(const char * oldname, const char * newname)
     /*  */
 653 {
 654         int error;
 655         char * to;
 656         struct inode * oldinode;
 657 
 658         error = namei(oldname, &oldinode);
 659         if (error)
 660                 return error;
 661         error = getname(newname,&to);
 662         if (error) {
 663                 iput(oldinode);
 664                 return error;
 665         }
 666         error = do_link(oldinode,to);
 667         putname(to);
 668         return error;
 669 }
 670 
 671 static int do_rename(const char * oldname, const char * newname)
     /*  */
 672 {
 673         struct inode * old_dir, * new_dir;
 674         const char * old_base, * new_base;
 675         int old_len, new_len, error;
 676 
 677         error = dir_namei(oldname,&old_len,&old_base,NULL,&old_dir);
 678         if (error)
 679                 return error;
 680         if (!permission(old_dir,MAY_WRITE | MAY_EXEC)) {
 681                 iput(old_dir);
 682                 return -EACCES;
 683         }
 684         if (!old_len || (old_base[0] == '.' &&
 685             (old_len == 1 || (old_base[1] == '.' &&
 686              old_len == 2)))) {
 687                 iput(old_dir);
 688                 return -EPERM;
 689         }
 690         error = dir_namei(newname,&new_len,&new_base,NULL,&new_dir);
 691         if (error) {
 692                 iput(old_dir);
 693                 return error;
 694         }
 695         if (!permission(new_dir,MAY_WRITE | MAY_EXEC)) {
 696                 iput(old_dir);
 697                 iput(new_dir);
 698                 return -EACCES;
 699         }
 700         if (!new_len || (new_base[0] == '.' &&
 701             (new_len == 1 || (new_base[1] == '.' &&
 702              new_len == 2)))) {
 703                 iput(old_dir);
 704                 iput(new_dir);
 705                 return -EPERM;
 706         }
 707         if (new_dir->i_dev != old_dir->i_dev) {
 708                 iput(old_dir);
 709                 iput(new_dir);
 710                 return -EXDEV;
 711         }
 712         if (IS_RDONLY(new_dir) || IS_RDONLY(old_dir)) {
 713                 iput(old_dir);
 714                 iput(new_dir);
 715                 return -EROFS;
 716         }
 717         if (!old_dir->i_op || !old_dir->i_op->rename) {
 718                 iput(old_dir);
 719                 iput(new_dir);
 720                 return -EPERM;
 721         }
 722         return old_dir->i_op->rename(old_dir, old_base, old_len, 
 723                 new_dir, new_base, new_len);
 724 }
 725 
 726 asmlinkage int sys_rename(const char * oldname, const char * newname)
     /*  */
 727 {
 728         int error;
 729         char * from, * to;
 730 
 731         error = getname(oldname,&from);
 732         if (!error) {
 733                 error = getname(newname,&to);
 734                 if (!error) {
 735                         error = do_rename(from,to);
 736                         putname(to);
 737                 }
 738                 putname(from);
 739         }
 740         return error;
 741 }
/* */
root/fs/namei.c

DEFINITIONS
