linux/fs/file.c
<<
>>
Prefs
   1/*
   2 *  linux/fs/file.c
   3 *
   4 *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
   5 *
   6 *  Manage the dynamic fd arrays in the process files_struct.
   7 */
   8
   9#include <linux/syscalls.h>
  10#include <linux/export.h>
  11#include <linux/fs.h>
  12#include <linux/mm.h>
  13#include <linux/mmzone.h>
  14#include <linux/time.h>
  15#include <linux/sched.h>
  16#include <linux/slab.h>
  17#include <linux/vmalloc.h>
  18#include <linux/file.h>
  19#include <linux/fdtable.h>
  20#include <linux/bitops.h>
  21#include <linux/interrupt.h>
  22#include <linux/spinlock.h>
  23#include <linux/rcupdate.h>
  24#include <linux/workqueue.h>
  25
  26struct fdtable_defer {
  27        spinlock_t lock;
  28        struct work_struct wq;
  29        struct fdtable *next;
  30};
  31
  32int sysctl_nr_open __read_mostly = 1024*1024;
  33int sysctl_nr_open_min = BITS_PER_LONG;
  34int sysctl_nr_open_max = 1024 * 1024; /* raised later */
  35
  36/*
  37 * We use this list to defer free fdtables that have vmalloced
  38 * sets/arrays. By keeping a per-cpu list, we avoid having to embed
  39 * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
  40 * this per-task structure.
  41 */
  42static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
  43
  44static void *alloc_fdmem(size_t size)
  45{
  46        /*
  47         * Very large allocations can stress page reclaim, so fall back to
  48         * vmalloc() if the allocation size will be considered "large" by the VM.
  49         */
  50        if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
  51                void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN);
  52                if (data != NULL)
  53                        return data;
  54        }
  55        return vmalloc(size);
  56}
  57
  58static void free_fdmem(void *ptr)
  59{
  60        is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr);
  61}
  62
  63static void __free_fdtable(struct fdtable *fdt)
  64{
  65        free_fdmem(fdt->fd);
  66        free_fdmem(fdt->open_fds);
  67        kfree(fdt);
  68}
  69
  70static void free_fdtable_work(struct work_struct *work)
  71{
  72        struct fdtable_defer *f =
  73                container_of(work, struct fdtable_defer, wq);
  74        struct fdtable *fdt;
  75
  76        spin_lock_bh(&f->lock);
  77        fdt = f->next;
  78        f->next = NULL;
  79        spin_unlock_bh(&f->lock);
  80        while(fdt) {
  81                struct fdtable *next = fdt->next;
  82
  83                __free_fdtable(fdt);
  84                fdt = next;
  85        }
  86}
  87
  88static void free_fdtable_rcu(struct rcu_head *rcu)
  89{
  90        struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
  91        struct fdtable_defer *fddef;
  92
  93        BUG_ON(!fdt);
  94        BUG_ON(fdt->max_fds <= NR_OPEN_DEFAULT);
  95
  96        if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {
  97                kfree(fdt->fd);
  98                kfree(fdt->open_fds);
  99                kfree(fdt);
 100        } else {
 101                fddef = &get_cpu_var(fdtable_defer_list);
 102                spin_lock(&fddef->lock);
 103                fdt->next = fddef->next;
 104                fddef->next = fdt;
 105                /* vmallocs are handled from the workqueue context */
 106                schedule_work(&fddef->wq);
 107                spin_unlock(&fddef->lock);
 108                put_cpu_var(fdtable_defer_list);
 109        }
 110}
 111
 112/*
 113 * Expand the fdset in the files_struct.  Called with the files spinlock
 114 * held for write.
 115 */
 116static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
 117{
 118        unsigned int cpy, set;
 119
 120        BUG_ON(nfdt->max_fds < ofdt->max_fds);
 121
 122        cpy = ofdt->max_fds * sizeof(struct file *);
 123        set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
 124        memcpy(nfdt->fd, ofdt->fd, cpy);
 125        memset((char *)(nfdt->fd) + cpy, 0, set);
 126
 127        cpy = ofdt->max_fds / BITS_PER_BYTE;
 128        set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
 129        memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
 130        memset((char *)(nfdt->open_fds) + cpy, 0, set);
 131        memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
 132        memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
 133}
 134
 135static struct fdtable * alloc_fdtable(unsigned int nr)
 136{
 137        struct fdtable *fdt;
 138        void *data;
 139
 140        /*
 141         * Figure out how many fds we actually want to support in this fdtable.
 142         * Allocation steps are keyed to the size of the fdarray, since it
 143         * grows far faster than any of the other dynamic data. We try to fit
 144         * the fdarray into comfortable page-tuned chunks: starting at 1024B
 145         * and growing in powers of two from there on.
 146         */
 147        nr /= (1024 / sizeof(struct file *));
 148        nr = roundup_pow_of_two(nr + 1);
 149        nr *= (1024 / sizeof(struct file *));
 150        /*
 151         * Note that this can drive nr *below* what we had passed if sysctl_nr_open
 152         * had been set lower between the check in expand_files() and here.  Deal
 153         * with that in caller, it's cheaper that way.
 154         *
 155         * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
 156         * bitmaps handling below becomes unpleasant, to put it mildly...
 157         */
 158        if (unlikely(nr > sysctl_nr_open))
 159                nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
 160
 161        fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
 162        if (!fdt)
 163                goto out;
 164        fdt->max_fds = nr;
 165        data = alloc_fdmem(nr * sizeof(struct file *));
 166        if (!data)
 167                goto out_fdt;
 168        fdt->fd = data;
 169
 170        data = alloc_fdmem(max_t(size_t,
 171                                 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
 172        if (!data)
 173                goto out_arr;
 174        fdt->open_fds = data;
 175        data += nr / BITS_PER_BYTE;
 176        fdt->close_on_exec = data;
 177        fdt->next = NULL;
 178
 179        return fdt;
 180
 181out_arr:
 182        free_fdmem(fdt->fd);
 183out_fdt:
 184        kfree(fdt);
 185out:
 186        return NULL;
 187}
 188
 189/*
 190 * Expand the file descriptor table.
 191 * This function will allocate a new fdtable and both fd array and fdset, of
 192 * the given size.
 193 * Return <0 error code on error; 1 on successful completion.
 194 * The files->file_lock should be held on entry, and will be held on exit.
 195 */
 196static int expand_fdtable(struct files_struct *files, int nr)
 197        __releases(files->file_lock)
 198        __acquires(files->file_lock)
 199{
 200        struct fdtable *new_fdt, *cur_fdt;
 201
 202        spin_unlock(&files->file_lock);
 203        new_fdt = alloc_fdtable(nr);
 204        spin_lock(&files->file_lock);
 205        if (!new_fdt)
 206                return -ENOMEM;
 207        /*
 208         * extremely unlikely race - sysctl_nr_open decreased between the check in
 209         * caller and alloc_fdtable().  Cheaper to catch it here...
 210         */
 211        if (unlikely(new_fdt->max_fds <= nr)) {
 212                __free_fdtable(new_fdt);
 213                return -EMFILE;
 214        }
 215        /*
 216         * Check again since another task may have expanded the fd table while
 217         * we dropped the lock
 218         */
 219        cur_fdt = files_fdtable(files);
 220        if (nr >= cur_fdt->max_fds) {
 221                /* Continue as planned */
 222                copy_fdtable(new_fdt, cur_fdt);
 223                rcu_assign_pointer(files->fdt, new_fdt);
 224                if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
 225                        call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
 226        } else {
 227                /* Somebody else expanded, so undo our attempt */
 228                __free_fdtable(new_fdt);
 229        }
 230        return 1;
 231}
 232
 233/*
 234 * Expand files.
 235 * This function will expand the file structures, if the requested size exceeds
 236 * the current capacity and there is room for expansion.
 237 * Return <0 error code on error; 0 when nothing done; 1 when files were
 238 * expanded and execution may have blocked.
 239 * The files->file_lock should be held on entry, and will be held on exit.
 240 */
 241static int expand_files(struct files_struct *files, int nr)
 242{
 243        struct fdtable *fdt;
 244
 245        fdt = files_fdtable(files);
 246
 247        /* Do we need to expand? */
 248        if (nr < fdt->max_fds)
 249                return 0;
 250
 251        /* Can we expand? */
 252        if (nr >= sysctl_nr_open)
 253                return -EMFILE;
 254
 255        /* All good, so we try */
 256        return expand_fdtable(files, nr);
 257}
 258
 259static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
 260{
 261        __set_bit(fd, fdt->close_on_exec);
 262}
 263
 264static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
 265{
 266        __clear_bit(fd, fdt->close_on_exec);
 267}
 268
 269static inline void __set_open_fd(int fd, struct fdtable *fdt)
 270{
 271        __set_bit(fd, fdt->open_fds);
 272}
 273
 274static inline void __clear_open_fd(int fd, struct fdtable *fdt)
 275{
 276        __clear_bit(fd, fdt->open_fds);
 277}
 278
 279static int count_open_files(struct fdtable *fdt)
 280{
 281        int size = fdt->max_fds;
 282        int i;
 283
 284        /* Find the last open fd */
 285        for (i = size / BITS_PER_LONG; i > 0; ) {
 286                if (fdt->open_fds[--i])
 287                        break;
 288        }
 289        i = (i + 1) * BITS_PER_LONG;
 290        return i;
 291}
 292
 293/*
 294 * Allocate a new files structure and copy contents from the
 295 * passed in files structure.
 296 * errorp will be valid only when the returned files_struct is NULL.
 297 */
 298struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 299{
 300        struct files_struct *newf;
 301        struct file **old_fds, **new_fds;
 302        int open_files, size, i;
 303        struct fdtable *old_fdt, *new_fdt;
 304
 305        *errorp = -ENOMEM;
 306        newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 307        if (!newf)
 308                goto out;
 309
 310        atomic_set(&newf->count, 1);
 311
 312        spin_lock_init(&newf->file_lock);
 313        newf->next_fd = 0;
 314        new_fdt = &newf->fdtab;
 315        new_fdt->max_fds = NR_OPEN_DEFAULT;
 316        new_fdt->close_on_exec = newf->close_on_exec_init;
 317        new_fdt->open_fds = newf->open_fds_init;
 318        new_fdt->fd = &newf->fd_array[0];
 319        new_fdt->next = NULL;
 320
 321        spin_lock(&oldf->file_lock);
 322        old_fdt = files_fdtable(oldf);
 323        open_files = count_open_files(old_fdt);
 324
 325        /*
 326         * Check whether we need to allocate a larger fd array and fd set.
 327         */
 328        while (unlikely(open_files > new_fdt->max_fds)) {
 329                spin_unlock(&oldf->file_lock);
 330
 331                if (new_fdt != &newf->fdtab)
 332                        __free_fdtable(new_fdt);
 333
 334                new_fdt = alloc_fdtable(open_files - 1);
 335                if (!new_fdt) {
 336                        *errorp = -ENOMEM;
 337                        goto out_release;
 338                }
 339
 340                /* beyond sysctl_nr_open; nothing to do */
 341                if (unlikely(new_fdt->max_fds < open_files)) {
 342                        __free_fdtable(new_fdt);
 343                        *errorp = -EMFILE;
 344                        goto out_release;
 345                }
 346
 347                /*
 348                 * Reacquire the oldf lock and a pointer to its fd table
 349                 * who knows it may have a new bigger fd table. We need
 350                 * the latest pointer.
 351                 */
 352                spin_lock(&oldf->file_lock);
 353                old_fdt = files_fdtable(oldf);
 354                open_files = count_open_files(old_fdt);
 355        }
 356
 357        old_fds = old_fdt->fd;
 358        new_fds = new_fdt->fd;
 359
 360        memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8);
 361        memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8);
 362
 363        for (i = open_files; i != 0; i--) {
 364                struct file *f = *old_fds++;
 365                if (f) {
 366                        get_file(f);
 367                } else {
 368                        /*
 369                         * The fd may be claimed in the fd bitmap but not yet
 370                         * instantiated in the files array if a sibling thread
 371                         * is partway through open().  So make sure that this
 372                         * fd is available to the new process.
 373                         */
 374                        __clear_open_fd(open_files - i, new_fdt);
 375                }
 376                rcu_assign_pointer(*new_fds++, f);
 377        }
 378        spin_unlock(&oldf->file_lock);
 379
 380        /* compute the remainder to be cleared */
 381        size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 382
 383        /* This is long word aligned thus could use a optimized version */
 384        memset(new_fds, 0, size);
 385
 386        if (new_fdt->max_fds > open_files) {
 387                int left = (new_fdt->max_fds - open_files) / 8;
 388                int start = open_files / BITS_PER_LONG;
 389
 390                memset(&new_fdt->open_fds[start], 0, left);
 391                memset(&new_fdt->close_on_exec[start], 0, left);
 392        }
 393
 394        rcu_assign_pointer(newf->fdt, new_fdt);
 395
 396        return newf;
 397
 398out_release:
 399        kmem_cache_free(files_cachep, newf);
 400out:
 401        return NULL;
 402}
 403
 404static void close_files(struct files_struct * files)
 405{
 406        int i, j;
 407        struct fdtable *fdt;
 408
 409        j = 0;
 410
 411        /*
 412         * It is safe to dereference the fd table without RCU or
 413         * ->file_lock because this is the last reference to the
 414         * files structure.  But use RCU to shut RCU-lockdep up.
 415         */
 416        rcu_read_lock();
 417        fdt = files_fdtable(files);
 418        rcu_read_unlock();
 419        for (;;) {
 420                unsigned long set;
 421                i = j * BITS_PER_LONG;
 422                if (i >= fdt->max_fds)
 423                        break;
 424                set = fdt->open_fds[j++];
 425                while (set) {
 426                        if (set & 1) {
 427                                struct file * file = xchg(&fdt->fd[i], NULL);
 428                                if (file) {
 429                                        filp_close(file, files);
 430                                        cond_resched();
 431                                }
 432                        }
 433                        i++;
 434                        set >>= 1;
 435                }
 436        }
 437}
 438
 439struct files_struct *get_files_struct(struct task_struct *task)
 440{
 441        struct files_struct *files;
 442
 443        task_lock(task);
 444        files = task->files;
 445        if (files)
 446                atomic_inc(&files->count);
 447        task_unlock(task);
 448
 449        return files;
 450}
 451
 452void put_files_struct(struct files_struct *files)
 453{
 454        struct fdtable *fdt;
 455
 456        if (atomic_dec_and_test(&files->count)) {
 457                close_files(files);
 458                /* not really needed, since nobody can see us */
 459                rcu_read_lock();
 460                fdt = files_fdtable(files);
 461                rcu_read_unlock();
 462                /* free the arrays if they are not embedded */
 463                if (fdt != &files->fdtab)
 464                        __free_fdtable(fdt);
 465                kmem_cache_free(files_cachep, files);
 466        }
 467}
 468
 469void reset_files_struct(struct files_struct *files)
 470{
 471        struct task_struct *tsk = current;
 472        struct files_struct *old;
 473
 474        old = tsk->files;
 475        task_lock(tsk);
 476        tsk->files = files;
 477        task_unlock(tsk);
 478        put_files_struct(old);
 479}
 480
 481void exit_files(struct task_struct *tsk)
 482{
 483        struct files_struct * files = tsk->files;
 484
 485        if (files) {
 486                task_lock(tsk);
 487                tsk->files = NULL;
 488                task_unlock(tsk);
 489                put_files_struct(files);
 490        }
 491}
 492
 493static void __devinit fdtable_defer_list_init(int cpu)
 494{
 495        struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
 496        spin_lock_init(&fddef->lock);
 497        INIT_WORK(&fddef->wq, free_fdtable_work);
 498        fddef->next = NULL;
 499}
 500
 501void __init files_defer_init(void)
 502{
 503        int i;
 504        for_each_possible_cpu(i)
 505                fdtable_defer_list_init(i);
 506        sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
 507                             -BITS_PER_LONG;
 508}
 509
 510struct files_struct init_files = {
 511        .count          = ATOMIC_INIT(1),
 512        .fdt            = &init_files.fdtab,
 513        .fdtab          = {
 514                .max_fds        = NR_OPEN_DEFAULT,
 515                .fd             = &init_files.fd_array[0],
 516                .close_on_exec  = init_files.close_on_exec_init,
 517                .open_fds       = init_files.open_fds_init,
 518        },
 519        .file_lock      = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
 520};
 521
 522void daemonize_descriptors(void)
 523{
 524        atomic_inc(&init_files.count);
 525        reset_files_struct(&init_files);
 526}
 527
 528/*
 529 * allocate a file descriptor, mark it busy.
 530 */
 531int __alloc_fd(struct files_struct *files,
 532               unsigned start, unsigned end, unsigned flags)
 533{
 534        unsigned int fd;
 535        int error;
 536        struct fdtable *fdt;
 537
 538        spin_lock(&files->file_lock);
 539repeat:
 540        fdt = files_fdtable(files);
 541        fd = start;
 542        if (fd < files->next_fd)
 543                fd = files->next_fd;
 544
 545        if (fd < fdt->max_fds)
 546                fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd);
 547
 548        /*
 549         * N.B. For clone tasks sharing a files structure, this test
 550         * will limit the total number of files that can be opened.
 551         */
 552        error = -EMFILE;
 553        if (fd >= end)
 554                goto out;
 555
 556        error = expand_files(files, fd);
 557        if (error < 0)
 558                goto out;
 559
 560        /*
 561         * If we needed to expand the fs array we
 562         * might have blocked - try again.
 563         */
 564        if (error)
 565                goto repeat;
 566
 567        if (start <= files->next_fd)
 568                files->next_fd = fd + 1;
 569
 570        __set_open_fd(fd, fdt);
 571        if (flags & O_CLOEXEC)
 572                __set_close_on_exec(fd, fdt);
 573        else
 574                __clear_close_on_exec(fd, fdt);
 575        error = fd;
 576#if 1
 577        /* Sanity check */
 578        if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
 579                printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
 580                rcu_assign_pointer(fdt->fd[fd], NULL);
 581        }
 582#endif
 583
 584out:
 585        spin_unlock(&files->file_lock);
 586        return error;
 587}
 588
 589static int alloc_fd(unsigned start, unsigned flags)
 590{
 591        return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
 592}
 593
 594int get_unused_fd_flags(unsigned flags)
 595{
 596        return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
 597}
 598EXPORT_SYMBOL(get_unused_fd_flags);
 599
 600static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 601{
 602        struct fdtable *fdt = files_fdtable(files);
 603        __clear_open_fd(fd, fdt);
 604        if (fd < files->next_fd)
 605                files->next_fd = fd;
 606}
 607
 608void put_unused_fd(unsigned int fd)
 609{
 610        struct files_struct *files = current->files;
 611        spin_lock(&files->file_lock);
 612        __put_unused_fd(files, fd);
 613        spin_unlock(&files->file_lock);
 614}
 615
 616EXPORT_SYMBOL(put_unused_fd);
 617
 618/*
 619 * Install a file pointer in the fd array.
 620 *
 621 * The VFS is full of places where we drop the files lock between
 622 * setting the open_fds bitmap and installing the file in the file
 623 * array.  At any such point, we are vulnerable to a dup2() race
 624 * installing a file in the array before us.  We need to detect this and
 625 * fput() the struct file we are about to overwrite in this case.
 626 *
 627 * It should never happen - if we allow dup2() do it, _really_ bad things
 628 * will follow.
 629 *
 630 * NOTE: __fd_install() variant is really, really low-level; don't
 631 * use it unless you are forced to by truly lousy API shoved down
 632 * your throat.  'files' *MUST* be either current->files or obtained
 633 * by get_files_struct(current) done by whoever had given it to you,
 634 * or really bad things will happen.  Normally you want to use
 635 * fd_install() instead.
 636 */
 637
 638void __fd_install(struct files_struct *files, unsigned int fd,
 639                struct file *file)
 640{
 641        struct fdtable *fdt;
 642        spin_lock(&files->file_lock);
 643        fdt = files_fdtable(files);
 644        BUG_ON(fdt->fd[fd] != NULL);
 645        rcu_assign_pointer(fdt->fd[fd], file);
 646        spin_unlock(&files->file_lock);
 647}
 648
 649void fd_install(unsigned int fd, struct file *file)
 650{
 651        __fd_install(current->files, fd, file);
 652}
 653
 654EXPORT_SYMBOL(fd_install);
 655
 656/*
 657 * The same warnings as for __alloc_fd()/__fd_install() apply here...
 658 */
 659int __close_fd(struct files_struct *files, unsigned fd)
 660{
 661        struct file *file;
 662        struct fdtable *fdt;
 663
 664        spin_lock(&files->file_lock);
 665        fdt = files_fdtable(files);
 666        if (fd >= fdt->max_fds)
 667                goto out_unlock;
 668        file = fdt->fd[fd];
 669        if (!file)
 670                goto out_unlock;
 671        rcu_assign_pointer(fdt->fd[fd], NULL);
 672        __clear_close_on_exec(fd, fdt);
 673        __put_unused_fd(files, fd);
 674        spin_unlock(&files->file_lock);
 675        return filp_close(file, files);
 676
 677out_unlock:
 678        spin_unlock(&files->file_lock);
 679        return -EBADF;
 680}
 681
 682void do_close_on_exec(struct files_struct *files)
 683{
 684        unsigned i;
 685        struct fdtable *fdt;
 686
 687        /* exec unshares first */
 688        spin_lock(&files->file_lock);
 689        for (i = 0; ; i++) {
 690                unsigned long set;
 691                unsigned fd = i * BITS_PER_LONG;
 692                fdt = files_fdtable(files);
 693                if (fd >= fdt->max_fds)
 694                        break;
 695                set = fdt->close_on_exec[i];
 696                if (!set)
 697                        continue;
 698                fdt->close_on_exec[i] = 0;
 699                for ( ; set ; fd++, set >>= 1) {
 700                        struct file *file;
 701                        if (!(set & 1))
 702                                continue;
 703                        file = fdt->fd[fd];
 704                        if (!file)
 705                                continue;
 706                        rcu_assign_pointer(fdt->fd[fd], NULL);
 707                        __put_unused_fd(files, fd);
 708                        spin_unlock(&files->file_lock);
 709                        filp_close(file, files);
 710                        cond_resched();
 711                        spin_lock(&files->file_lock);
 712                }
 713
 714        }
 715        spin_unlock(&files->file_lock);
 716}
 717
 718struct file *fget(unsigned int fd)
 719{
 720        struct file *file;
 721        struct files_struct *files = current->files;
 722
 723        rcu_read_lock();
 724        file = fcheck_files(files, fd);
 725        if (file) {
 726                /* File object ref couldn't be taken */
 727                if (file->f_mode & FMODE_PATH ||
 728                    !atomic_long_inc_not_zero(&file->f_count))
 729                        file = NULL;
 730        }
 731        rcu_read_unlock();
 732
 733        return file;
 734}
 735
 736EXPORT_SYMBOL(fget);
 737
 738struct file *fget_raw(unsigned int fd)
 739{
 740        struct file *file;
 741        struct files_struct *files = current->files;
 742
 743        rcu_read_lock();
 744        file = fcheck_files(files, fd);
 745        if (file) {
 746                /* File object ref couldn't be taken */
 747                if (!atomic_long_inc_not_zero(&file->f_count))
 748                        file = NULL;
 749        }
 750        rcu_read_unlock();
 751
 752        return file;
 753}
 754
 755EXPORT_SYMBOL(fget_raw);
 756
 757/*
 758 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
 759 *
 760 * You can use this instead of fget if you satisfy all of the following
 761 * conditions:
 762 * 1) You must call fput_light before exiting the syscall and returning control
 763 *    to userspace (i.e. you cannot remember the returned struct file * after
 764 *    returning to userspace).
 765 * 2) You must not call filp_close on the returned struct file * in between
 766 *    calls to fget_light and fput_light.
 767 * 3) You must not clone the current task in between the calls to fget_light
 768 *    and fput_light.
 769 *
 770 * The fput_needed flag returned by fget_light should be passed to the
 771 * corresponding fput_light.
 772 */
 773struct file *fget_light(unsigned int fd, int *fput_needed)
 774{
 775        struct file *file;
 776        struct files_struct *files = current->files;
 777
 778        *fput_needed = 0;
 779        if (atomic_read(&files->count) == 1) {
 780                file = fcheck_files(files, fd);
 781                if (file && (file->f_mode & FMODE_PATH))
 782                        file = NULL;
 783        } else {
 784                rcu_read_lock();
 785                file = fcheck_files(files, fd);
 786                if (file) {
 787                        if (!(file->f_mode & FMODE_PATH) &&
 788                            atomic_long_inc_not_zero(&file->f_count))
 789                                *fput_needed = 1;
 790                        else
 791                                /* Didn't get the reference, someone's freed */
 792                                file = NULL;
 793                }
 794                rcu_read_unlock();
 795        }
 796
 797        return file;
 798}
 799EXPORT_SYMBOL(fget_light);
 800
 801struct file *fget_raw_light(unsigned int fd, int *fput_needed)
 802{
 803        struct file *file;
 804        struct files_struct *files = current->files;
 805
 806        *fput_needed = 0;
 807        if (atomic_read(&files->count) == 1) {
 808                file = fcheck_files(files, fd);
 809        } else {
 810                rcu_read_lock();
 811                file = fcheck_files(files, fd);
 812                if (file) {
 813                        if (atomic_long_inc_not_zero(&file->f_count))
 814                                *fput_needed = 1;
 815                        else
 816                                /* Didn't get the reference, someone's freed */
 817                                file = NULL;
 818                }
 819                rcu_read_unlock();
 820        }
 821
 822        return file;
 823}
 824
 825void set_close_on_exec(unsigned int fd, int flag)
 826{
 827        struct files_struct *files = current->files;
 828        struct fdtable *fdt;
 829        spin_lock(&files->file_lock);
 830        fdt = files_fdtable(files);
 831        if (flag)
 832                __set_close_on_exec(fd, fdt);
 833        else
 834                __clear_close_on_exec(fd, fdt);
 835        spin_unlock(&files->file_lock);
 836}
 837
 838bool get_close_on_exec(unsigned int fd)
 839{
 840        struct files_struct *files = current->files;
 841        struct fdtable *fdt;
 842        bool res;
 843        rcu_read_lock();
 844        fdt = files_fdtable(files);
 845        res = close_on_exec(fd, fdt);
 846        rcu_read_unlock();
 847        return res;
 848}
 849
 850static int do_dup2(struct files_struct *files,
 851        struct file *file, unsigned fd, unsigned flags)
 852{
 853        struct file *tofree;
 854        struct fdtable *fdt;
 855
 856        /*
 857         * We need to detect attempts to do dup2() over allocated but still
 858         * not finished descriptor.  NB: OpenBSD avoids that at the price of
 859         * extra work in their equivalent of fget() - they insert struct
 860         * file immediately after grabbing descriptor, mark it larval if
 861         * more work (e.g. actual opening) is needed and make sure that
 862         * fget() treats larval files as absent.  Potentially interesting,
 863         * but while extra work in fget() is trivial, locking implications
 864         * and amount of surgery on open()-related paths in VFS are not.
 865         * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
 866         * deadlocks in rather amusing ways, AFAICS.  All of that is out of
 867         * scope of POSIX or SUS, since neither considers shared descriptor
 868         * tables and this condition does not arise without those.
 869         */
 870        fdt = files_fdtable(files);
 871        tofree = fdt->fd[fd];
 872        if (!tofree && fd_is_open(fd, fdt))
 873                goto Ebusy;
 874        get_file(file);
 875        rcu_assign_pointer(fdt->fd[fd], file);
 876        __set_open_fd(fd, fdt);
 877        if (flags & O_CLOEXEC)
 878                __set_close_on_exec(fd, fdt);
 879        else
 880                __clear_close_on_exec(fd, fdt);
 881        spin_unlock(&files->file_lock);
 882
 883        if (tofree)
 884                filp_close(tofree, files);
 885
 886        return fd;
 887
 888Ebusy:
 889        spin_unlock(&files->file_lock);
 890        return -EBUSY;
 891}
 892
 893int replace_fd(unsigned fd, struct file *file, unsigned flags)
 894{
 895        int err;
 896        struct files_struct *files = current->files;
 897
 898        if (!file)
 899                return __close_fd(files, fd);
 900
 901        if (fd >= rlimit(RLIMIT_NOFILE))
 902                return -EBADF;
 903
 904        spin_lock(&files->file_lock);
 905        err = expand_files(files, fd);
 906        if (unlikely(err < 0))
 907                goto out_unlock;
 908        return do_dup2(files, file, fd, flags);
 909
 910out_unlock:
 911        spin_unlock(&files->file_lock);
 912        return err;
 913}
 914
 915SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
 916{
 917        int err = -EBADF;
 918        struct file *file;
 919        struct files_struct *files = current->files;
 920
 921        if ((flags & ~O_CLOEXEC) != 0)
 922                return -EINVAL;
 923
 924        if (unlikely(oldfd == newfd))
 925                return -EINVAL;
 926
 927        if (newfd >= rlimit(RLIMIT_NOFILE))
 928                return -EBADF;
 929
 930        spin_lock(&files->file_lock);
 931        err = expand_files(files, newfd);
 932        file = fcheck(oldfd);
 933        if (unlikely(!file))
 934                goto Ebadf;
 935        if (unlikely(err < 0)) {
 936                if (err == -EMFILE)
 937                        goto Ebadf;
 938                goto out_unlock;
 939        }
 940        return do_dup2(files, file, newfd, flags);
 941
 942Ebadf:
 943        err = -EBADF;
 944out_unlock:
 945        spin_unlock(&files->file_lock);
 946        return err;
 947}
 948
 949SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 950{
 951        if (unlikely(newfd == oldfd)) { /* corner case */
 952                struct files_struct *files = current->files;
 953                int retval = oldfd;
 954
 955                rcu_read_lock();
 956                if (!fcheck_files(files, oldfd))
 957                        retval = -EBADF;
 958                rcu_read_unlock();
 959                return retval;
 960        }
 961        return sys_dup3(oldfd, newfd, 0);
 962}
 963
 964SYSCALL_DEFINE1(dup, unsigned int, fildes)
 965{
 966        int ret = -EBADF;
 967        struct file *file = fget_raw(fildes);
 968
 969        if (file) {
 970                ret = get_unused_fd();
 971                if (ret >= 0)
 972                        fd_install(ret, file);
 973                else
 974                        fput(file);
 975        }
 976        return ret;
 977}
 978
 979int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 980{
 981        int err;
 982        if (from >= rlimit(RLIMIT_NOFILE))
 983                return -EINVAL;
 984        err = alloc_fd(from, flags);
 985        if (err >= 0) {
 986                get_file(file);
 987                fd_install(err, file);
 988        }
 989        return err;
 990}
 991
 992int iterate_fd(struct files_struct *files, unsigned n,
 993                int (*f)(const void *, struct file *, unsigned),
 994                const void *p)
 995{
 996        struct fdtable *fdt;
 997        int res = 0;
 998        if (!files)
 999                return 0;
1000        spin_lock(&files->file_lock);
1001        for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1002                struct file *file;
1003                file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1004                if (!file)
1005                        continue;
1006                res = f(p, file, n);
1007                if (res)
1008                        break;
1009        }
1010        spin_unlock(&files->file_lock);
1011        return res;
1012}
1013EXPORT_SYMBOL(iterate_fd);
1014
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.