fs/read_write.c

   1 /*
   2  *  linux/fs/read_write.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/slab.h>
   8 #include <linux/stat.h>
   9 #include <linux/fcntl.h>
  10 #include <linux/file.h>
  11 #include <linux/uio.h>
  12 #include <linux/smp_lock.h>
  13 #include <linux/dnotify.h>
  14 #include <linux/security.h>
  15 #include <linux/module.h>
  16 #include <linux/syscalls.h>
  17
  18 #include <asm/uaccess.h>
  19 #include <asm/unistd.h>
  20
  21 struct file_operations generic_ro_fops = {
  22         .llseek         = generic_file_llseek,
  23         .read           = generic_file_read,
  24         .mmap           = generic_file_readonly_mmap,
  25         .sendfile       = generic_file_sendfile,
  26 };
  27
  28 EXPORT_SYMBOL(generic_ro_fops);
  29
  30 loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
  31 {
  32         long long retval;
  33         struct inode *inode = file->f_mapping->host;
  34
  35         down(&inode->i_sem);
  36         switch (origin) {
  37                 case 2:
  38                         offset += inode->i_size;
  39                         break;
  40                 case 1:
  41                         offset += file->f_pos;
  42         }
  43         retval = -EINVAL;
  44         if (offset>=0 && offset<=inode->i_sb->s_maxbytes) {
  45                 if (offset != file->f_pos) {
  46                         file->f_pos = offset;
  47                         file->f_version = 0;
  48                 }
  49                 retval = offset;
  50         }
  51         up(&inode->i_sem);
  52         return retval;
  53 }
  54
  55 EXPORT_SYMBOL(generic_file_llseek);
  56
  57 loff_t remote_llseek(struct file *file, loff_t offset, int origin)
  58 {
  59         long long retval;
  60
  61         lock_kernel();
  62         switch (origin) {
  63                 case 2:
  64                         offset += i_size_read(file->f_dentry->d_inode);
  65                         break;
  66                 case 1:
  67                         offset += file->f_pos;
  68         }
  69         retval = -EINVAL;
  70         if (offset>=0 && offset<=file->f_dentry->d_inode->i_sb->s_maxbytes) {
  71                 if (offset != file->f_pos) {
  72                         file->f_pos = offset;
  73                         file->f_version = 0;
  74                 }
  75                 retval = offset;
  76         }
  77         unlock_kernel();
  78         return retval;
  79 }
  80 EXPORT_SYMBOL(remote_llseek);
  81
  82 loff_t no_llseek(struct file *file, loff_t offset, int origin)
  83 {
  84         return -ESPIPE;
  85 }
  86 EXPORT_SYMBOL(no_llseek);
  87
  88 loff_t default_llseek(struct file *file, loff_t offset, int origin)
  89 {
  90         long long retval;
  91
  92         lock_kernel();
  93         switch (origin) {
  94                 case 2:
  95                         offset += i_size_read(file->f_dentry->d_inode);
  96                         break;
  97                 case 1:
  98                         offset += file->f_pos;
  99         }
 100         retval = -EINVAL;
 101         if (offset >= 0) {
 102                 if (offset != file->f_pos) {
 103                         file->f_pos = offset;
 104                         file->f_version = 0;
 105                 }
 106                 retval = offset;
 107         }
 108         unlock_kernel();
 109         return retval;
 110 }
 111 EXPORT_SYMBOL(default_llseek);
 112
 113 loff_t vfs_llseek(struct file *file, loff_t offset, int origin)
 114 {
 115         loff_t (*fn)(struct file *, loff_t, int);
 116
 117         fn = no_llseek;
 118         if (file->f_mode & FMODE_LSEEK) {
 119                 fn = default_llseek;
 120                 if (file->f_op && file->f_op->llseek)
 121                         fn = file->f_op->llseek;
 122         }
 123         return fn(file, offset, origin);
 124 }
 125 EXPORT_SYMBOL(vfs_llseek);
 126
 127 asmlinkage off_t sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
 128 {
 129         off_t retval;
 130         struct file * file;
 131         int fput_needed;
 132
 133         retval = -EBADF;
 134         file = fget_light(fd, &fput_needed);
 135         if (!file)
 136                 goto bad;
 137
 138         retval = -EINVAL;
 139         if (origin <= 2) {
 140                 loff_t res = vfs_llseek(file, offset, origin);
 141                 retval = res;
 142                 if (res != (loff_t)retval)
 143                         retval = -EOVERFLOW;    /* LFS: should only happen on 32 bit platforms */
 144         }
 145         fput_light(file, fput_needed);
 146 bad:
 147         return retval;
 148 }
 149
 150 #ifdef __ARCH_WANT_SYS_LLSEEK
 151 asmlinkage long sys_llseek(unsigned int fd, unsigned long offset_high,
 152                            unsigned long offset_low, loff_t __user * result,
 153                            unsigned int origin)
 154 {
 155         int retval;
 156         struct file * file;
 157         loff_t offset;
 158         int fput_needed;
 159
 160         retval = -EBADF;
 161         file = fget_light(fd, &fput_needed);
 162         if (!file)
 163                 goto bad;
 164
 165         retval = -EINVAL;
 166         if (origin > 2)
 167                 goto out_putf;
 168
 169         offset = vfs_llseek(file, ((loff_t) offset_high << 32) | offset_low,
 170                         origin);
 171
 172         retval = (int)offset;
 173         if (offset >= 0) {
 174                 retval = -EFAULT;
 175                 if (!copy_to_user(result, &offset, sizeof(offset)))
 176                         retval = 0;
 177         }
 178 out_putf:
 179         fput_light(file, fput_needed);
 180 bad:
 181         return retval;
 182 }
 183 #endif
 184
 185
 186 int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count)
 187 {
 188         struct inode *inode;
 189         loff_t pos;
 190
 191         if (unlikely(count > file->f_maxcount))
 192                 goto Einval;
 193         pos = *ppos;
 194         if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))
 195                 goto Einval;
 196
 197         inode = file->f_dentry->d_inode;
 198         if (inode->i_flock && MANDATORY_LOCK(inode))
 199                 return locks_mandatory_area(read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE, inode, file, pos, count);
 200         return 0;
 201
 202 Einval:
 203         return -EINVAL;
 204 }
 205
 206 ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 207 {
 208         struct kiocb kiocb;
 209         ssize_t ret;
 210
 211         init_sync_kiocb(&kiocb, filp);
 212         kiocb.ki_pos = *ppos;
 213         ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos);
 214         if (-EIOCBQUEUED == ret)
 215                 ret = wait_on_sync_kiocb(&kiocb);
 216         *ppos = kiocb.ki_pos;
 217         return ret;
 218 }
 219
 220 EXPORT_SYMBOL(do_sync_read);
 221
 222 ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
 223 {
 224         ssize_t ret;
 225
 226         if (!(file->f_mode & FMODE_READ))
 227                 return -EBADF;
 228         if (!file->f_op || (!file->f_op->read && !file->f_op->aio_read))
 229                 return -EINVAL;
 230         if (unlikely(!access_ok(VERIFY_WRITE, buf, count)))
 231                 return -EFAULT;
 232
 233         ret = rw_verify_area(READ, file, pos, count);
 234         if (!ret) {
 235                 ret = security_file_permission (file, MAY_READ);
 236                 if (!ret) {
 237                         if (file->f_op->read)
 238                                 ret = file->f_op->read(file, buf, count, pos);
 239                         else
 240                                 ret = do_sync_read(file, buf, count, pos);
 241                         if (ret > 0) {
 242                                 dnotify_parent(file->f_dentry, DN_ACCESS);
 243                                 current->rchar += ret;
 244                         }
 245                         current->syscr++;
 246                 }
 247         }
 248
 249         return ret;
 250 }
 251
 252 EXPORT_SYMBOL(vfs_read);
 253
 254 ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
 255 {
 256         struct kiocb kiocb;
 257         ssize_t ret;
 258
 259         init_sync_kiocb(&kiocb, filp);
 260         kiocb.ki_pos = *ppos;
 261         ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos);
 262         if (-EIOCBQUEUED == ret)
 263                 ret = wait_on_sync_kiocb(&kiocb);
 264         *ppos = kiocb.ki_pos;
 265         return ret;
 266 }
 267
 268 EXPORT_SYMBOL(do_sync_write);
 269
 270 ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 271 {
 272         ssize_t ret;
 273
 274         if (!(file->f_mode & FMODE_WRITE))
 275                 return -EBADF;
 276         if (!file->f_op || (!file->f_op->write && !file->f_op->aio_write))
 277                 return -EINVAL;
 278         if (unlikely(!access_ok(VERIFY_READ, buf, count)))
 279                 return -EFAULT;
 280
 281         ret = rw_verify_area(WRITE, file, pos, count);
 282         if (!ret) {
 283                 ret = security_file_permission (file, MAY_WRITE);
 284                 if (!ret) {
 285                         if (file->f_op->write)
 286                                 ret = file->f_op->write(file, buf, count, pos);
 287                         else
 288                                 ret = do_sync_write(file, buf, count, pos);
 289                         if (ret > 0) {
 290                                 dnotify_parent(file->f_dentry, DN_MODIFY);
 291                                 current->wchar += ret;
 292                         }
 293                         current->syscw++;
 294                 }
 295         }
 296
 297         return ret;
 298 }
 299
 300 EXPORT_SYMBOL(vfs_write);
 301
 302 static inline loff_t file_pos_read(struct file *file)
 303 {
 304         return file->f_pos;
 305 }
 306
 307 static inline void file_pos_write(struct file *file, loff_t pos)
 308 {
 309         file->f_pos = pos;
 310 }
 311
 312 asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
 313 {
 314         struct file *file;
 315         ssize_t ret = -EBADF;
 316         int fput_needed;
 317
 318         file = fget_light(fd, &fput_needed);
 319         if (file) {
 320                 loff_t pos = file_pos_read(file);
 321                 ret = vfs_read(file, buf, count, &pos);
 322                 file_pos_write(file, pos);
 323                 fput_light(file, fput_needed);
 324         }
 325
 326         return ret;
 327 }
 328 EXPORT_SYMBOL_GPL(sys_read);
 329
 330 asmlinkage ssize_t sys_write(unsigned int fd, const char __user * buf, size_t count)
 331 {
 332         struct file *file;
 333         ssize_t ret = -EBADF;
 334         int fput_needed;
 335
 336         file = fget_light(fd, &fput_needed);
 337         if (file) {
 338                 loff_t pos = file_pos_read(file);
 339                 ret = vfs_write(file, buf, count, &pos);
 340                 file_pos_write(file, pos);
 341                 fput_light(file, fput_needed);
 342         }
 343
 344         return ret;
 345 }
 346
 347 asmlinkage ssize_t sys_pread64(unsigned int fd, char __user *buf,
 348                              size_t count, loff_t pos)
 349 {
 350         struct file *file;
 351         ssize_t ret = -EBADF;
 352         int fput_needed;
 353
 354         if (pos < 0)
 355                 return -EINVAL;
 356
 357         file = fget_light(fd, &fput_needed);
 358         if (file) {
 359                 ret = -ESPIPE;
 360                 if (file->f_mode & FMODE_PREAD)
 361                         ret = vfs_read(file, buf, count, &pos);
 362                 fput_light(file, fput_needed);
 363         }
 364
 365         return ret;
 366 }
 367
 368 asmlinkage ssize_t sys_pwrite64(unsigned int fd, const char __user *buf,
 369                               size_t count, loff_t pos)
 370 {
 371         struct file *file;
 372         ssize_t ret = -EBADF;
 373         int fput_needed;
 374
 375         if (pos < 0)
 376                 return -EINVAL;
 377
 378         file = fget_light(fd, &fput_needed);
 379         if (file) {
 380                 ret = -ESPIPE;
 381                 if (file->f_mode & FMODE_PWRITE)
 382                         ret = vfs_write(file, buf, count, &pos);
 383                 fput_light(file, fput_needed);
 384         }
 385
 386         return ret;
 387 }
 388
 389 /*
 390  * Reduce an iovec's length in-place.  Return the resulting number of segments
 391  */
 392 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to)
 393 {
 394         unsigned long seg = 0;
 395         size_t len = 0;
 396
 397         while (seg < nr_segs) {
 398                 seg++;
 399                 if (len + iov->iov_len >= to) {
 400                         iov->iov_len = to - len;
 401                         break;
 402                 }
 403                 len += iov->iov_len;
 404                 iov++;
 405         }
 406         return seg;
 407 }
 408
 409 EXPORT_SYMBOL(iov_shorten);
 410
 411 /* A write operation does a read from user space and vice versa */
 412 #define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)
 413
 414 static ssize_t do_readv_writev(int type, struct file *file,
 415                                const struct iovec __user * uvector,
 416                                unsigned long nr_segs, loff_t *pos)
 417 {
 418         typedef ssize_t (*io_fn_t)(struct file *, char __user *, size_t, loff_t *);
 419         typedef ssize_t (*iov_fn_t)(struct file *, const struct iovec *, unsigned long, loff_t *);
 420
 421         size_t tot_len;
 422         struct iovec iovstack[UIO_FASTIOV];
 423         struct iovec *iov=iovstack, *vector;
 424         ssize_t ret;
 425         int seg;
 426         io_fn_t fn;
 427         iov_fn_t fnv;
 428
 429         /*
 430          * SuS says "The readv() function *may* fail if the iovcnt argument
 431          * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
 432          * traditionally returned zero for zero segments, so...
 433          */
 434         ret = 0;
 435         if (nr_segs == 0)
 436                 goto out;
 437
 438         /*
 439          * First get the "struct iovec" from user memory and
 440          * verify all the pointers
 441          */
 442         ret = -EINVAL;
 443         if ((nr_segs > UIO_MAXIOV) || (nr_segs <= 0))
 444                 goto out;
 445         if (!file->f_op)
 446                 goto out;
 447         if (nr_segs > UIO_FASTIOV) {
 448                 ret = -ENOMEM;
 449                 iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
 450                 if (!iov)
 451                         goto out;
 452         }
 453         ret = -EFAULT;
 454         if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector)))
 455                 goto out;
 456
 457         /*
 458          * Single unix specification:
 459          * We should -EINVAL if an element length is not >= 0 and fitting an
 460          * ssize_t.  The total length is fitting an ssize_t
 461          *
 462          * Be careful here because iov_len is a size_t not an ssize_t
 463          */
 464         tot_len = 0;
 465         ret = -EINVAL;
 466         for (seg = 0; seg < nr_segs; seg++) {
 467                 void __user *buf = iov[seg].iov_base;
 468                 ssize_t len = (ssize_t)iov[seg].iov_len;
 469
 470                 if (unlikely(!access_ok(vrfy_dir(type), buf, len)))
 471                         goto Efault;
 472                 if (len < 0)    /* size_t not fitting an ssize_t .. */
 473                         goto out;
 474                 tot_len += len;
 475                 if ((ssize_t)tot_len < 0) /* maths overflow on the ssize_t */
 476                         goto out;
 477         }
 478         if (tot_len == 0) {
 479                 ret = 0;
 480                 goto out;
 481         }
 482
 483         ret = rw_verify_area(type, file, pos, tot_len);
 484         if (ret)
 485                 goto out;
 486
 487         fnv = NULL;
 488         if (type == READ) {
 489                 fn = file->f_op->read;
 490                 fnv = file->f_op->readv;
 491         } else {
 492                 fn = (io_fn_t)file->f_op->write;
 493                 fnv = file->f_op->writev;
 494         }
 495         if (fnv) {
 496                 ret = fnv(file, iov, nr_segs, pos);
 497                 goto out;
 498         }
 499
 500         /* Do it by hand, with file-ops */
 501         ret = 0;
 502         vector = iov;
 503         while (nr_segs > 0) {
 504                 void __user * base;
 505                 size_t len;
 506                 ssize_t nr;
 507
 508                 base = vector->iov_base;
 509                 len = vector->iov_len;
 510                 vector++;
 511                 nr_segs--;
 512
 513                 nr = fn(file, base, len, pos);
 514
 515                 if (nr < 0) {
 516                         if (!ret) ret = nr;
 517                         break;
 518                 }
 519                 ret += nr;
 520                 if (nr != len)
 521                         break;
 522         }
 523 out:
 524         if (iov != iovstack)
 525                 kfree(iov);
 526         if ((ret + (type == READ)) > 0)
 527                 dnotify_parent(file->f_dentry,
 528                                 (type == READ) ? DN_ACCESS : DN_MODIFY);
 529         return ret;
 530 Efault:
 531         ret = -EFAULT;
 532         goto out;
 533 }
 534
 535 ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
 536                   unsigned long vlen, loff_t *pos)
 537 {
 538         if (!(file->f_mode & FMODE_READ))
 539                 return -EBADF;
 540         if (!file->f_op || (!file->f_op->readv && !file->f_op->read))
 541                 return -EINVAL;
 542
 543         return do_readv_writev(READ, file, vec, vlen, pos);
 544 }
 545
 546 EXPORT_SYMBOL(vfs_readv);
 547
 548 ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
 549                    unsigned long vlen, loff_t *pos)
 550 {
 551         if (!(file->f_mode & FMODE_WRITE))
 552                 return -EBADF;
 553         if (!file->f_op || (!file->f_op->writev && !file->f_op->write))
 554                 return -EINVAL;
 555
 556         return do_readv_writev(WRITE, file, vec, vlen, pos);
 557 }
 558
 559 EXPORT_SYMBOL(vfs_writev);
 560
 561 asmlinkage ssize_t
 562 sys_readv(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
 563 {
 564         struct file *file;
 565         ssize_t ret = -EBADF;
 566         int fput_needed;
 567
 568         file = fget_light(fd, &fput_needed);
 569         if (file) {
 570                 loff_t pos = file_pos_read(file);
 571                 ret = vfs_readv(file, vec, vlen, &pos);
 572                 file_pos_write(file, pos);
 573                 fput_light(file, fput_needed);
 574         }
 575
 576         if (ret > 0)
 577                 current->rchar += ret;
 578         current->syscr++;
 579         return ret;
 580 }
 581
 582 asmlinkage ssize_t
 583 sys_writev(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
 584 {
 585         struct file *file;
 586         ssize_t ret = -EBADF;
 587         int fput_needed;
 588
 589         file = fget_light(fd, &fput_needed);
 590         if (file) {
 591                 loff_t pos = file_pos_read(file);
 592                 ret = vfs_writev(file, vec, vlen, &pos);
 593                 file_pos_write(file, pos);
 594                 fput_light(file, fput_needed);
 595         }
 596
 597         if (ret > 0)
 598                 current->wchar += ret;
 599         current->syscw++;
 600         return ret;
 601 }
 602
 603 static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 604                            size_t count, loff_t max)
 605 {
 606         struct file * in_file, * out_file;
 607         struct inode * in_inode, * out_inode;
 608         loff_t pos;
 609         ssize_t retval;
 610         int fput_needed_in, fput_needed_out;
 611
 612         /*
 613          * Get input file, and verify that it is ok..
 614          */
 615         retval = -EBADF;
 616         in_file = fget_light(in_fd, &fput_needed_in);
 617         if (!in_file)
 618                 goto out;
 619         if (!(in_file->f_mode & FMODE_READ))
 620                 goto fput_in;
 621         retval = -EINVAL;
 622         in_inode = in_file->f_dentry->d_inode;
 623         if (!in_inode)
 624                 goto fput_in;
 625         if (!in_file->f_op || !in_file->f_op->sendfile)
 626                 goto fput_in;
 627         retval = -ESPIPE;
 628         if (!ppos)
 629                 ppos = &in_file->f_pos;
 630         else
 631                 if (!(in_file->f_mode & FMODE_PREAD))
 632                         goto fput_in;
 633         retval = rw_verify_area(READ, in_file, ppos, count);
 634         if (retval)
 635                 goto fput_in;
 636
 637         retval = security_file_permission (in_file, MAY_READ);
 638         if (retval)
 639                 goto fput_in;
 640
 641         /*
 642          * Get output file, and verify that it is ok..
 643          */
 644         retval = -EBADF;
 645         out_file = fget_light(out_fd, &fput_needed_out);
 646         if (!out_file)
 647                 goto fput_in;
 648         if (!(out_file->f_mode & FMODE_WRITE))
 649                 goto fput_out;
 650         retval = -EINVAL;
 651         if (!out_file->f_op || !out_file->f_op->sendpage)
 652                 goto fput_out;
 653         out_inode = out_file->f_dentry->d_inode;
 654         retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count);
 655         if (retval)
 656                 goto fput_out;
 657
 658         retval = security_file_permission (out_file, MAY_WRITE);
 659         if (retval)
 660                 goto fput_out;
 661
 662         if (!max)
 663                 max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);
 664
 665         pos = *ppos;
 666         retval = -EINVAL;
 667         if (unlikely(pos < 0))
 668                 goto fput_out;
 669         if (unlikely(pos + count > max)) {
 670                 retval = -EOVERFLOW;
 671                 if (pos >= max)
 672                         goto fput_out;
 673                 count = max - pos;
 674         }
 675
 676         retval = in_file->f_op->sendfile(in_file, ppos, count, file_send_actor, out_file);
 677
 678         if (retval > 0) {
 679                 current->rchar += retval;
 680                 current->wchar += retval;
 681         }
 682         current->syscr++;
 683         current->syscw++;
 684
 685         if (*ppos > max)
 686                 retval = -EOVERFLOW;
 687
 688 fput_out:
 689         fput_light(out_file, fput_needed_out);
 690 fput_in:
 691         fput_light(in_file, fput_needed_in);
 692 out:
 693         return retval;
 694 }
 695
 696 asmlinkage ssize_t sys_sendfile(int out_fd, int in_fd, off_t __user *offset, size_t count)
 697 {
 698         loff_t pos;
 699         off_t off;
 700         ssize_t ret;
 701
 702         if (offset) {
 703                 if (unlikely(get_user(off, offset)))
 704                         return -EFAULT;
 705                 pos = off;
 706                 ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
 707                 if (unlikely(put_user(pos, offset)))
 708                         return -EFAULT;
 709                 return ret;
 710         }
 711
 712         return do_sendfile(out_fd, in_fd, NULL, count, 0);
 713 }
 714
 715 asmlinkage ssize_t sys_sendfile64(int out_fd, int in_fd, loff_t __user *offset, size_t count)
 716 {
 717         loff_t pos;
 718         ssize_t ret;
 719
 720         if (offset) {
 721                 if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
 722                         return -EFAULT;
 723                 ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
 724                 if (unlikely(put_user(pos, offset)))
 725                         return -EFAULT;
 726                 return ret;
 727         }
 728
 729         return do_sendfile(out_fd, in_fd, NULL, count, 0);
 730 }