fs/file.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
__const_min
free_fdtable_rcu
copy_fd_bitmaps
copy_fdtable
alloc_fdtable
expand_fdtable
expand_files
__set_close_on_exec
__clear_close_on_exec
__set_open_fd
__clear_open_fd
count_open_files
dup_fd
close_files
get_files_struct
put_files_struct
reset_files_struct
exit_files
find_next_fd
__alloc_fd
alloc_fd
get_unused_fd_flags
__put_unused_fd
put_unused_fd
__fd_install
fd_install
__close_fd
__close_fd_get_file
do_close_on_exec
__fget
fget_many
fget
fget_raw
__fget_light
__fdget
__fdget_raw
__fdget_pos
__f_unlock_pos
set_close_on_exec
get_close_on_exec
do_dup2
replace_fd
ksys_dup3
SYSCALL_DEFINE3
SYSCALL_DEFINE2
ksys_dup
SYSCALL_DEFINE1
f_dupfd
iterate_fd
   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/file.c
   4  *
   5  *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
   6  *
   7  *  Manage the dynamic fd arrays in the process files_struct.
   8  */
   9 
  10 #include <linux/syscalls.h>
  11 #include <linux/export.h>
  12 #include <linux/fs.h>
  13 #include <linux/mm.h>
  14 #include <linux/sched/signal.h>
  15 #include <linux/slab.h>
  16 #include <linux/file.h>
  17 #include <linux/fdtable.h>
  18 #include <linux/bitops.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/rcupdate.h>
  21 
  22 unsigned int sysctl_nr_open __read_mostly = 1024*1024;
  23 unsigned int sysctl_nr_open_min = BITS_PER_LONG;
  24 /* our min() is unusable in constant expressions ;-/ */
  25 #define __const_min(x, y) ((x) < (y) ? (x) : (y))
  26 unsigned int sysctl_nr_open_max =
  27         __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
  28 
  29 static void __free_fdtable(struct fdtable *fdt)
  30 {
  31         kvfree(fdt->fd);
  32         kvfree(fdt->open_fds);
  33         kfree(fdt);
  34 }
  35 
  36 static void free_fdtable_rcu(struct rcu_head *rcu)
  37 {
  38         __free_fdtable(container_of(rcu, struct fdtable, rcu));
  39 }
  40 
  41 #define BITBIT_NR(nr)   BITS_TO_LONGS(BITS_TO_LONGS(nr))
  42 #define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
  43 
  44 /*
  45  * Copy 'count' fd bits from the old table to the new table and clear the extra
  46  * space if any.  This does not copy the file pointers.  Called with the files
  47  * spinlock held for write.
  48  */
  49 static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
  50                             unsigned int count)
  51 {
  52         unsigned int cpy, set;
  53 
  54         cpy = count / BITS_PER_BYTE;
  55         set = (nfdt->max_fds - count) / BITS_PER_BYTE;
  56         memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
  57         memset((char *)nfdt->open_fds + cpy, 0, set);
  58         memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
  59         memset((char *)nfdt->close_on_exec + cpy, 0, set);
  60 
  61         cpy = BITBIT_SIZE(count);
  62         set = BITBIT_SIZE(nfdt->max_fds) - cpy;
  63         memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
  64         memset((char *)nfdt->full_fds_bits + cpy, 0, set);
  65 }
  66 
  67 /*
  68  * Copy all file descriptors from the old table to the new, expanded table and
  69  * clear the extra space.  Called with the files spinlock held for write.
  70  */
  71 static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
  72 {
  73         size_t cpy, set;
  74 
  75         BUG_ON(nfdt->max_fds < ofdt->max_fds);
  76 
  77         cpy = ofdt->max_fds * sizeof(struct file *);
  78         set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
  79         memcpy(nfdt->fd, ofdt->fd, cpy);
  80         memset((char *)nfdt->fd + cpy, 0, set);
  81 
  82         copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
  83 }
  84 
  85 static struct fdtable * alloc_fdtable(unsigned int nr)
  86 {
  87         struct fdtable *fdt;
  88         void *data;
  89 
  90         /*
  91          * Figure out how many fds we actually want to support in this fdtable.
  92          * Allocation steps are keyed to the size of the fdarray, since it
  93          * grows far faster than any of the other dynamic data. We try to fit
  94          * the fdarray into comfortable page-tuned chunks: starting at 1024B
  95          * and growing in powers of two from there on.
  96          */
  97         nr /= (1024 / sizeof(struct file *));
  98         nr = roundup_pow_of_two(nr + 1);
  99         nr *= (1024 / sizeof(struct file *));
 100         /*
 101          * Note that this can drive nr *below* what we had passed if sysctl_nr_open
 102          * had been set lower between the check in expand_files() and here.  Deal
 103          * with that in caller, it's cheaper that way.
 104          *
 105          * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
 106          * bitmaps handling below becomes unpleasant, to put it mildly...
 107          */
 108         if (unlikely(nr > sysctl_nr_open))
 109                 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
 110 
 111         fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
 112         if (!fdt)
 113                 goto out;
 114         fdt->max_fds = nr;
 115         data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
 116         if (!data)
 117                 goto out_fdt;
 118         fdt->fd = data;
 119 
 120         data = kvmalloc(max_t(size_t,
 121                                  2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
 122                                  GFP_KERNEL_ACCOUNT);
 123         if (!data)
 124                 goto out_arr;
 125         fdt->open_fds = data;
 126         data += nr / BITS_PER_BYTE;
 127         fdt->close_on_exec = data;
 128         data += nr / BITS_PER_BYTE;
 129         fdt->full_fds_bits = data;
 130 
 131         return fdt;
 132 
 133 out_arr:
 134         kvfree(fdt->fd);
 135 out_fdt:
 136         kfree(fdt);
 137 out:
 138         return NULL;
 139 }
 140 
 141 /*
 142  * Expand the file descriptor table.
 143  * This function will allocate a new fdtable and both fd array and fdset, of
 144  * the given size.
 145  * Return <0 error code on error; 1 on successful completion.
 146  * The files->file_lock should be held on entry, and will be held on exit.
 147  */
 148 static int expand_fdtable(struct files_struct *files, unsigned int nr)
 149         __releases(files->file_lock)
 150         __acquires(files->file_lock)
 151 {
 152         struct fdtable *new_fdt, *cur_fdt;
 153 
 154         spin_unlock(&files->file_lock);
 155         new_fdt = alloc_fdtable(nr);
 156 
 157         /* make sure all __fd_install() have seen resize_in_progress
 158          * or have finished their rcu_read_lock_sched() section.
 159          */
 160         if (atomic_read(&files->count) > 1)
 161                 synchronize_rcu();
 162 
 163         spin_lock(&files->file_lock);
 164         if (!new_fdt)
 165                 return -ENOMEM;
 166         /*
 167          * extremely unlikely race - sysctl_nr_open decreased between the check in
 168          * caller and alloc_fdtable().  Cheaper to catch it here...
 169          */
 170         if (unlikely(new_fdt->max_fds <= nr)) {
 171                 __free_fdtable(new_fdt);
 172                 return -EMFILE;
 173         }
 174         cur_fdt = files_fdtable(files);
 175         BUG_ON(nr < cur_fdt->max_fds);
 176         copy_fdtable(new_fdt, cur_fdt);
 177         rcu_assign_pointer(files->fdt, new_fdt);
 178         if (cur_fdt != &files->fdtab)
 179                 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
 180         /* coupled with smp_rmb() in __fd_install() */
 181         smp_wmb();
 182         return 1;
 183 }
 184 
 185 /*
 186  * Expand files.
 187  * This function will expand the file structures, if the requested size exceeds
 188  * the current capacity and there is room for expansion.
 189  * Return <0 error code on error; 0 when nothing done; 1 when files were
 190  * expanded and execution may have blocked.
 191  * The files->file_lock should be held on entry, and will be held on exit.
 192  */
 193 static int expand_files(struct files_struct *files, unsigned int nr)
 194         __releases(files->file_lock)
 195         __acquires(files->file_lock)
 196 {
 197         struct fdtable *fdt;
 198         int expanded = 0;
 199 
 200 repeat:
 201         fdt = files_fdtable(files);
 202 
 203         /* Do we need to expand? */
 204         if (nr < fdt->max_fds)
 205                 return expanded;
 206 
 207         /* Can we expand? */
 208         if (nr >= sysctl_nr_open)
 209                 return -EMFILE;
 210 
 211         if (unlikely(files->resize_in_progress)) {
 212                 spin_unlock(&files->file_lock);
 213                 expanded = 1;
 214                 wait_event(files->resize_wait, !files->resize_in_progress);
 215                 spin_lock(&files->file_lock);
 216                 goto repeat;
 217         }
 218 
 219         /* All good, so we try */
 220         files->resize_in_progress = true;
 221         expanded = expand_fdtable(files, nr);
 222         files->resize_in_progress = false;
 223 
 224         wake_up_all(&files->resize_wait);
 225         return expanded;
 226 }
 227 
 228 static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
 229 {
 230         __set_bit(fd, fdt->close_on_exec);
 231 }
 232 
 233 static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
 234 {
 235         if (test_bit(fd, fdt->close_on_exec))
 236                 __clear_bit(fd, fdt->close_on_exec);
 237 }
 238 
 239 static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
 240 {
 241         __set_bit(fd, fdt->open_fds);
 242         fd /= BITS_PER_LONG;
 243         if (!~fdt->open_fds[fd])
 244                 __set_bit(fd, fdt->full_fds_bits);
 245 }
 246 
 247 static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
 248 {
 249         __clear_bit(fd, fdt->open_fds);
 250         __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
 251 }
 252 
 253 static unsigned int count_open_files(struct fdtable *fdt)
 254 {
 255         unsigned int size = fdt->max_fds;
 256         unsigned int i;
 257 
 258         /* Find the last open fd */
 259         for (i = size / BITS_PER_LONG; i > 0; ) {
 260                 if (fdt->open_fds[--i])
 261                         break;
 262         }
 263         i = (i + 1) * BITS_PER_LONG;
 264         return i;
 265 }
 266 
 267 /*
 268  * Allocate a new files structure and copy contents from the
 269  * passed in files structure.
 270  * errorp will be valid only when the returned files_struct is NULL.
 271  */
 272 struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 273 {
 274         struct files_struct *newf;
 275         struct file **old_fds, **new_fds;
 276         unsigned int open_files, i;
 277         struct fdtable *old_fdt, *new_fdt;
 278 
 279         *errorp = -ENOMEM;
 280         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 281         if (!newf)
 282                 goto out;
 283 
 284         atomic_set(&newf->count, 1);
 285 
 286         spin_lock_init(&newf->file_lock);
 287         newf->resize_in_progress = false;
 288         init_waitqueue_head(&newf->resize_wait);
 289         newf->next_fd = 0;
 290         new_fdt = &newf->fdtab;
 291         new_fdt->max_fds = NR_OPEN_DEFAULT;
 292         new_fdt->close_on_exec = newf->close_on_exec_init;
 293         new_fdt->open_fds = newf->open_fds_init;
 294         new_fdt->full_fds_bits = newf->full_fds_bits_init;
 295         new_fdt->fd = &newf->fd_array[0];
 296 
 297         spin_lock(&oldf->file_lock);
 298         old_fdt = files_fdtable(oldf);
 299         open_files = count_open_files(old_fdt);
 300 
 301         /*
 302          * Check whether we need to allocate a larger fd array and fd set.
 303          */
 304         while (unlikely(open_files > new_fdt->max_fds)) {
 305                 spin_unlock(&oldf->file_lock);
 306 
 307                 if (new_fdt != &newf->fdtab)
 308                         __free_fdtable(new_fdt);
 309 
 310                 new_fdt = alloc_fdtable(open_files - 1);
 311                 if (!new_fdt) {
 312                         *errorp = -ENOMEM;
 313                         goto out_release;
 314                 }
 315 
 316                 /* beyond sysctl_nr_open; nothing to do */
 317                 if (unlikely(new_fdt->max_fds < open_files)) {
 318                         __free_fdtable(new_fdt);
 319                         *errorp = -EMFILE;
 320                         goto out_release;
 321                 }
 322 
 323                 /*
 324                  * Reacquire the oldf lock and a pointer to its fd table
 325                  * who knows it may have a new bigger fd table. We need
 326                  * the latest pointer.
 327                  */
 328                 spin_lock(&oldf->file_lock);
 329                 old_fdt = files_fdtable(oldf);
 330                 open_files = count_open_files(old_fdt);
 331         }
 332 
 333         copy_fd_bitmaps(new_fdt, old_fdt, open_files);
 334 
 335         old_fds = old_fdt->fd;
 336         new_fds = new_fdt->fd;
 337 
 338         for (i = open_files; i != 0; i--) {
 339                 struct file *f = *old_fds++;
 340                 if (f) {
 341                         get_file(f);
 342                 } else {
 343                         /*
 344                          * The fd may be claimed in the fd bitmap but not yet
 345                          * instantiated in the files array if a sibling thread
 346                          * is partway through open().  So make sure that this
 347                          * fd is available to the new process.
 348                          */
 349                         __clear_open_fd(open_files - i, new_fdt);
 350                 }
 351                 rcu_assign_pointer(*new_fds++, f);
 352         }
 353         spin_unlock(&oldf->file_lock);
 354 
 355         /* clear the remainder */
 356         memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
 357 
 358         rcu_assign_pointer(newf->fdt, new_fdt);
 359 
 360         return newf;
 361 
 362 out_release:
 363         kmem_cache_free(files_cachep, newf);
 364 out:
 365         return NULL;
 366 }
 367 
 368 static struct fdtable *close_files(struct files_struct * files)
 369 {
 370         /*
 371          * It is safe to dereference the fd table without RCU or
 372          * ->file_lock because this is the last reference to the
 373          * files structure.
 374          */
 375         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
 376         unsigned int i, j = 0;
 377 
 378         for (;;) {
 379                 unsigned long set;
 380                 i = j * BITS_PER_LONG;
 381                 if (i >= fdt->max_fds)
 382                         break;
 383                 set = fdt->open_fds[j++];
 384                 while (set) {
 385                         if (set & 1) {
 386                                 struct file * file = xchg(&fdt->fd[i], NULL);
 387                                 if (file) {
 388                                         filp_close(file, files);
 389                                         cond_resched();
 390                                 }
 391                         }
 392                         i++;
 393                         set >>= 1;
 394                 }
 395         }
 396 
 397         return fdt;
 398 }
 399 
 400 struct files_struct *get_files_struct(struct task_struct *task)
 401 {
 402         struct files_struct *files;
 403 
 404         task_lock(task);
 405         files = task->files;
 406         if (files)
 407                 atomic_inc(&files->count);
 408         task_unlock(task);
 409 
 410         return files;
 411 }
 412 
 413 void put_files_struct(struct files_struct *files)
 414 {
 415         if (atomic_dec_and_test(&files->count)) {
 416                 struct fdtable *fdt = close_files(files);
 417 
 418                 /* free the arrays if they are not embedded */
 419                 if (fdt != &files->fdtab)
 420                         __free_fdtable(fdt);
 421                 kmem_cache_free(files_cachep, files);
 422         }
 423 }
 424 
 425 void reset_files_struct(struct files_struct *files)
 426 {
 427         struct task_struct *tsk = current;
 428         struct files_struct *old;
 429 
 430         old = tsk->files;
 431         task_lock(tsk);
 432         tsk->files = files;
 433         task_unlock(tsk);
 434         put_files_struct(old);
 435 }
 436 
 437 void exit_files(struct task_struct *tsk)
 438 {
 439         struct files_struct * files = tsk->files;
 440 
 441         if (files) {
 442                 task_lock(tsk);
 443                 tsk->files = NULL;
 444                 task_unlock(tsk);
 445                 put_files_struct(files);
 446         }
 447 }
 448 
 449 struct files_struct init_files = {
 450         .count          = ATOMIC_INIT(1),
 451         .fdt            = &init_files.fdtab,
 452         .fdtab          = {
 453                 .max_fds        = NR_OPEN_DEFAULT,
 454                 .fd             = &init_files.fd_array[0],
 455                 .close_on_exec  = init_files.close_on_exec_init,
 456                 .open_fds       = init_files.open_fds_init,
 457                 .full_fds_bits  = init_files.full_fds_bits_init,
 458         },
 459         .file_lock      = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
 460         .resize_wait    = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
 461 };
 462 
 463 static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
 464 {
 465         unsigned int maxfd = fdt->max_fds;
 466         unsigned int maxbit = maxfd / BITS_PER_LONG;
 467         unsigned int bitbit = start / BITS_PER_LONG;
 468 
 469         bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
 470         if (bitbit > maxfd)
 471                 return maxfd;
 472         if (bitbit > start)
 473                 start = bitbit;
 474         return find_next_zero_bit(fdt->open_fds, maxfd, start);
 475 }
 476 
 477 /*
 478  * allocate a file descriptor, mark it busy.
 479  */
 480 int __alloc_fd(struct files_struct *files,
 481                unsigned start, unsigned end, unsigned flags)
 482 {
 483         unsigned int fd;
 484         int error;
 485         struct fdtable *fdt;
 486 
 487         spin_lock(&files->file_lock);
 488 repeat:
 489         fdt = files_fdtable(files);
 490         fd = start;
 491         if (fd < files->next_fd)
 492                 fd = files->next_fd;
 493 
 494         if (fd < fdt->max_fds)
 495                 fd = find_next_fd(fdt, fd);
 496 
 497         /*
 498          * N.B. For clone tasks sharing a files structure, this test
 499          * will limit the total number of files that can be opened.
 500          */
 501         error = -EMFILE;
 502         if (fd >= end)
 503                 goto out;
 504 
 505         error = expand_files(files, fd);
 506         if (error < 0)
 507                 goto out;
 508 
 509         /*
 510          * If we needed to expand the fs array we
 511          * might have blocked - try again.
 512          */
 513         if (error)
 514                 goto repeat;
 515 
 516         if (start <= files->next_fd)
 517                 files->next_fd = fd + 1;
 518 
 519         __set_open_fd(fd, fdt);
 520         if (flags & O_CLOEXEC)
 521                 __set_close_on_exec(fd, fdt);
 522         else
 523                 __clear_close_on_exec(fd, fdt);
 524         error = fd;
 525 #if 1
 526         /* Sanity check */
 527         if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
 528                 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
 529                 rcu_assign_pointer(fdt->fd[fd], NULL);
 530         }
 531 #endif
 532 
 533 out:
 534         spin_unlock(&files->file_lock);
 535         return error;
 536 }
 537 
 538 static int alloc_fd(unsigned start, unsigned flags)
 539 {
 540         return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
 541 }
 542 
 543 int get_unused_fd_flags(unsigned flags)
 544 {
 545         return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
 546 }
 547 EXPORT_SYMBOL(get_unused_fd_flags);
 548 
 549 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 550 {
 551         struct fdtable *fdt = files_fdtable(files);
 552         __clear_open_fd(fd, fdt);
 553         if (fd < files->next_fd)
 554                 files->next_fd = fd;
 555 }
 556 
 557 void put_unused_fd(unsigned int fd)
 558 {
 559         struct files_struct *files = current->files;
 560         spin_lock(&files->file_lock);
 561         __put_unused_fd(files, fd);
 562         spin_unlock(&files->file_lock);
 563 }
 564 
 565 EXPORT_SYMBOL(put_unused_fd);
 566 
 567 /*
 568  * Install a file pointer in the fd array.
 569  *
 570  * The VFS is full of places where we drop the files lock between
 571  * setting the open_fds bitmap and installing the file in the file
 572  * array.  At any such point, we are vulnerable to a dup2() race
 573  * installing a file in the array before us.  We need to detect this and
 574  * fput() the struct file we are about to overwrite in this case.
 575  *
 576  * It should never happen - if we allow dup2() do it, _really_ bad things
 577  * will follow.
 578  *
 579  * NOTE: __fd_install() variant is really, really low-level; don't
 580  * use it unless you are forced to by truly lousy API shoved down
 581  * your throat.  'files' *MUST* be either current->files or obtained
 582  * by get_files_struct(current) done by whoever had given it to you,
 583  * or really bad things will happen.  Normally you want to use
 584  * fd_install() instead.
 585  */
 586 
 587 void __fd_install(struct files_struct *files, unsigned int fd,
 588                 struct file *file)
 589 {
 590         struct fdtable *fdt;
 591 
 592         rcu_read_lock_sched();
 593 
 594         if (unlikely(files->resize_in_progress)) {
 595                 rcu_read_unlock_sched();
 596                 spin_lock(&files->file_lock);
 597                 fdt = files_fdtable(files);
 598                 BUG_ON(fdt->fd[fd] != NULL);
 599                 rcu_assign_pointer(fdt->fd[fd], file);
 600                 spin_unlock(&files->file_lock);
 601                 return;
 602         }
 603         /* coupled with smp_wmb() in expand_fdtable() */
 604         smp_rmb();
 605         fdt = rcu_dereference_sched(files->fdt);
 606         BUG_ON(fdt->fd[fd] != NULL);
 607         rcu_assign_pointer(fdt->fd[fd], file);
 608         rcu_read_unlock_sched();
 609 }
 610 
 611 void fd_install(unsigned int fd, struct file *file)
 612 {
 613         __fd_install(current->files, fd, file);
 614 }
 615 
 616 EXPORT_SYMBOL(fd_install);
 617 
 618 /*
 619  * The same warnings as for __alloc_fd()/__fd_install() apply here...
 620  */
 621 int __close_fd(struct files_struct *files, unsigned fd)
 622 {
 623         struct file *file;
 624         struct fdtable *fdt;
 625 
 626         spin_lock(&files->file_lock);
 627         fdt = files_fdtable(files);
 628         if (fd >= fdt->max_fds)
 629                 goto out_unlock;
 630         file = fdt->fd[fd];
 631         if (!file)
 632                 goto out_unlock;
 633         rcu_assign_pointer(fdt->fd[fd], NULL);
 634         __put_unused_fd(files, fd);
 635         spin_unlock(&files->file_lock);
 636         return filp_close(file, files);
 637 
 638 out_unlock:
 639         spin_unlock(&files->file_lock);
 640         return -EBADF;
 641 }
 642 EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
 643 
 644 /*
 645  * variant of __close_fd that gets a ref on the file for later fput
 646  */
 647 int __close_fd_get_file(unsigned int fd, struct file **res)
 648 {
 649         struct files_struct *files = current->files;
 650         struct file *file;
 651         struct fdtable *fdt;
 652 
 653         spin_lock(&files->file_lock);
 654         fdt = files_fdtable(files);
 655         if (fd >= fdt->max_fds)
 656                 goto out_unlock;
 657         file = fdt->fd[fd];
 658         if (!file)
 659                 goto out_unlock;
 660         rcu_assign_pointer(fdt->fd[fd], NULL);
 661         __put_unused_fd(files, fd);
 662         spin_unlock(&files->file_lock);
 663         get_file(file);
 664         *res = file;
 665         return filp_close(file, files);
 666 
 667 out_unlock:
 668         spin_unlock(&files->file_lock);
 669         *res = NULL;
 670         return -ENOENT;
 671 }
 672 
 673 void do_close_on_exec(struct files_struct *files)
 674 {
 675         unsigned i;
 676         struct fdtable *fdt;
 677 
 678         /* exec unshares first */
 679         spin_lock(&files->file_lock);
 680         for (i = 0; ; i++) {
 681                 unsigned long set;
 682                 unsigned fd = i * BITS_PER_LONG;
 683                 fdt = files_fdtable(files);
 684                 if (fd >= fdt->max_fds)
 685                         break;
 686                 set = fdt->close_on_exec[i];
 687                 if (!set)
 688                         continue;
 689                 fdt->close_on_exec[i] = 0;
 690                 for ( ; set ; fd++, set >>= 1) {
 691                         struct file *file;
 692                         if (!(set & 1))
 693                                 continue;
 694                         file = fdt->fd[fd];
 695                         if (!file)
 696                                 continue;
 697                         rcu_assign_pointer(fdt->fd[fd], NULL);
 698                         __put_unused_fd(files, fd);
 699                         spin_unlock(&files->file_lock);
 700                         filp_close(file, files);
 701                         cond_resched();
 702                         spin_lock(&files->file_lock);
 703                 }
 704 
 705         }
 706         spin_unlock(&files->file_lock);
 707 }
 708 
 709 static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
 710 {
 711         struct files_struct *files = current->files;
 712         struct file *file;
 713 
 714         rcu_read_lock();
 715 loop:
 716         file = fcheck_files(files, fd);
 717         if (file) {
 718                 /* File object ref couldn't be taken.
 719                  * dup2() atomicity guarantee is the reason
 720                  * we loop to catch the new file (or NULL pointer)
 721                  */
 722                 if (file->f_mode & mask)
 723                         file = NULL;
 724                 else if (!get_file_rcu_many(file, refs))
 725                         goto loop;
 726         }
 727         rcu_read_unlock();
 728 
 729         return file;
 730 }
 731 
 732 struct file *fget_many(unsigned int fd, unsigned int refs)
 733 {
 734         return __fget(fd, FMODE_PATH, refs);
 735 }
 736 
 737 struct file *fget(unsigned int fd)
 738 {
 739         return __fget(fd, FMODE_PATH, 1);
 740 }
 741 EXPORT_SYMBOL(fget);
 742 
 743 struct file *fget_raw(unsigned int fd)
 744 {
 745         return __fget(fd, 0, 1);
 746 }
 747 EXPORT_SYMBOL(fget_raw);
 748 
 749 /*
 750  * Lightweight file lookup - no refcnt increment if fd table isn't shared.
 751  *
 752  * You can use this instead of fget if you satisfy all of the following
 753  * conditions:
 754  * 1) You must call fput_light before exiting the syscall and returning control
 755  *    to userspace (i.e. you cannot remember the returned struct file * after
 756  *    returning to userspace).
 757  * 2) You must not call filp_close on the returned struct file * in between
 758  *    calls to fget_light and fput_light.
 759  * 3) You must not clone the current task in between the calls to fget_light
 760  *    and fput_light.
 761  *
 762  * The fput_needed flag returned by fget_light should be passed to the
 763  * corresponding fput_light.
 764  */
 765 static unsigned long __fget_light(unsigned int fd, fmode_t mask)
 766 {
 767         struct files_struct *files = current->files;
 768         struct file *file;
 769 
 770         if (atomic_read(&files->count) == 1) {
 771                 file = __fcheck_files(files, fd);
 772                 if (!file || unlikely(file->f_mode & mask))
 773                         return 0;
 774                 return (unsigned long)file;
 775         } else {
 776                 file = __fget(fd, mask, 1);
 777                 if (!file)
 778                         return 0;
 779                 return FDPUT_FPUT | (unsigned long)file;
 780         }
 781 }
 782 unsigned long __fdget(unsigned int fd)
 783 {
 784         return __fget_light(fd, FMODE_PATH);
 785 }
 786 EXPORT_SYMBOL(__fdget);
 787 
 788 unsigned long __fdget_raw(unsigned int fd)
 789 {
 790         return __fget_light(fd, 0);
 791 }
 792 
 793 unsigned long __fdget_pos(unsigned int fd)
 794 {
 795         unsigned long v = __fdget(fd);
 796         struct file *file = (struct file *)(v & ~3);
 797 
 798         if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
 799                 if (file_count(file) > 1) {
 800                         v |= FDPUT_POS_UNLOCK;
 801                         mutex_lock(&file->f_pos_lock);
 802                 }
 803         }
 804         return v;
 805 }
 806 
 807 void __f_unlock_pos(struct file *f)
 808 {
 809         mutex_unlock(&f->f_pos_lock);
 810 }
 811 
 812 /*
 813  * We only lock f_pos if we have threads or if the file might be
 814  * shared with another process. In both cases we'll have an elevated
 815  * file count (done either by fdget() or by fork()).
 816  */
 817 
 818 void set_close_on_exec(unsigned int fd, int flag)
 819 {
 820         struct files_struct *files = current->files;
 821         struct fdtable *fdt;
 822         spin_lock(&files->file_lock);
 823         fdt = files_fdtable(files);
 824         if (flag)
 825                 __set_close_on_exec(fd, fdt);
 826         else
 827                 __clear_close_on_exec(fd, fdt);
 828         spin_unlock(&files->file_lock);
 829 }
 830 
 831 bool get_close_on_exec(unsigned int fd)
 832 {
 833         struct files_struct *files = current->files;
 834         struct fdtable *fdt;
 835         bool res;
 836         rcu_read_lock();
 837         fdt = files_fdtable(files);
 838         res = close_on_exec(fd, fdt);
 839         rcu_read_unlock();
 840         return res;
 841 }
 842 
 843 static int do_dup2(struct files_struct *files,
 844         struct file *file, unsigned fd, unsigned flags)
 845 __releases(&files->file_lock)
 846 {
 847         struct file *tofree;
 848         struct fdtable *fdt;
 849 
 850         /*
 851          * We need to detect attempts to do dup2() over allocated but still
 852          * not finished descriptor.  NB: OpenBSD avoids that at the price of
 853          * extra work in their equivalent of fget() - they insert struct
 854          * file immediately after grabbing descriptor, mark it larval if
 855          * more work (e.g. actual opening) is needed and make sure that
 856          * fget() treats larval files as absent.  Potentially interesting,
 857          * but while extra work in fget() is trivial, locking implications
 858          * and amount of surgery on open()-related paths in VFS are not.
 859          * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
 860          * deadlocks in rather amusing ways, AFAICS.  All of that is out of
 861          * scope of POSIX or SUS, since neither considers shared descriptor
 862          * tables and this condition does not arise without those.
 863          */
 864         fdt = files_fdtable(files);
 865         tofree = fdt->fd[fd];
 866         if (!tofree && fd_is_open(fd, fdt))
 867                 goto Ebusy;
 868         get_file(file);
 869         rcu_assign_pointer(fdt->fd[fd], file);
 870         __set_open_fd(fd, fdt);
 871         if (flags & O_CLOEXEC)
 872                 __set_close_on_exec(fd, fdt);
 873         else
 874                 __clear_close_on_exec(fd, fdt);
 875         spin_unlock(&files->file_lock);
 876 
 877         if (tofree)
 878                 filp_close(tofree, files);
 879 
 880         return fd;
 881 
 882 Ebusy:
 883         spin_unlock(&files->file_lock);
 884         return -EBUSY;
 885 }
 886 
 887 int replace_fd(unsigned fd, struct file *file, unsigned flags)
 888 {
 889         int err;
 890         struct files_struct *files = current->files;
 891 
 892         if (!file)
 893                 return __close_fd(files, fd);
 894 
 895         if (fd >= rlimit(RLIMIT_NOFILE))
 896                 return -EBADF;
 897 
 898         spin_lock(&files->file_lock);
 899         err = expand_files(files, fd);
 900         if (unlikely(err < 0))
 901                 goto out_unlock;
 902         return do_dup2(files, file, fd, flags);
 903 
 904 out_unlock:
 905         spin_unlock(&files->file_lock);
 906         return err;
 907 }
 908 
 909 static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 910 {
 911         int err = -EBADF;
 912         struct file *file;
 913         struct files_struct *files = current->files;
 914 
 915         if ((flags & ~O_CLOEXEC) != 0)
 916                 return -EINVAL;
 917 
 918         if (unlikely(oldfd == newfd))
 919                 return -EINVAL;
 920 
 921         if (newfd >= rlimit(RLIMIT_NOFILE))
 922                 return -EBADF;
 923 
 924         spin_lock(&files->file_lock);
 925         err = expand_files(files, newfd);
 926         file = fcheck(oldfd);
 927         if (unlikely(!file))
 928                 goto Ebadf;
 929         if (unlikely(err < 0)) {
 930                 if (err == -EMFILE)
 931                         goto Ebadf;
 932                 goto out_unlock;
 933         }
 934         return do_dup2(files, file, newfd, flags);
 935 
 936 Ebadf:
 937         err = -EBADF;
 938 out_unlock:
 939         spin_unlock(&files->file_lock);
 940         return err;
 941 }
 942 
 943 SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
 944 {
 945         return ksys_dup3(oldfd, newfd, flags);
 946 }
 947 
 948 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 949 {
 950         if (unlikely(newfd == oldfd)) { /* corner case */
 951                 struct files_struct *files = current->files;
 952                 int retval = oldfd;
 953 
 954                 rcu_read_lock();
 955                 if (!fcheck_files(files, oldfd))
 956                         retval = -EBADF;
 957                 rcu_read_unlock();
 958                 return retval;
 959         }
 960         return ksys_dup3(oldfd, newfd, 0);
 961 }
 962 
 963 int ksys_dup(unsigned int fildes)
 964 {
 965         int ret = -EBADF;
 966         struct file *file = fget_raw(fildes);
 967 
 968         if (file) {
 969                 ret = get_unused_fd_flags(0);
 970                 if (ret >= 0)
 971                         fd_install(ret, file);
 972                 else
 973                         fput(file);
 974         }
 975         return ret;
 976 }
 977 
 978 SYSCALL_DEFINE1(dup, unsigned int, fildes)
 979 {
 980         return ksys_dup(fildes);
 981 }
 982 
 983 int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 984 {
 985         int err;
 986         if (from >= rlimit(RLIMIT_NOFILE))
 987                 return -EINVAL;
 988         err = alloc_fd(from, flags);
 989         if (err >= 0) {
 990                 get_file(file);
 991                 fd_install(err, file);
 992         }
 993         return err;
 994 }
 995 
 996 int iterate_fd(struct files_struct *files, unsigned n,
 997                 int (*f)(const void *, struct file *, unsigned),
 998                 const void *p)
 999 {
1000         struct fdtable *fdt;
1001         int res = 0;
1002         if (!files)
1003                 return 0;
1004         spin_lock(&files->file_lock);
1005         for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1006                 struct file *file;
1007                 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1008                 if (!file)
1009                         continue;
1010                 res = f(p, file, n);
1011                 if (res)
1012                         break;
1013         }
1014         spin_unlock(&files->file_lock);
1015         return res;
1016 }
1017 EXPORT_SYMBOL(iterate_fd);
/* [<][>][^][v][top][bottom][index][help] */
root/fs/file.c

DEFINITIONS
