linux/fs/fcntl.c
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   1/*
   2 *  linux/fs/fcntl.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7#include <linux/syscalls.h>
   8#include <linux/init.h>
   9#include <linux/mm.h>
  10#include <linux/fs.h>
  11#include <linux/file.h>
  12#include <linux/fdtable.h>
  13#include <linux/capability.h>
  14#include <linux/dnotify.h>
  15#include <linux/slab.h>
  16#include <linux/module.h>
  17#include <linux/pipe_fs_i.h>
  18#include <linux/security.h>
  19#include <linux/ptrace.h>
  20#include <linux/signal.h>
  21#include <linux/rcupdate.h>
  22#include <linux/pid_namespace.h>
  23
  24#include <asm/poll.h>
  25#include <asm/siginfo.h>
  26#include <asm/uaccess.h>
  27
  28void set_close_on_exec(unsigned int fd, int flag)
  29{
  30        struct files_struct *files = current->files;
  31        struct fdtable *fdt;
  32        spin_lock(&files->file_lock);
  33        fdt = files_fdtable(files);
  34        if (flag)
  35                FD_SET(fd, fdt->close_on_exec);
  36        else
  37                FD_CLR(fd, fdt->close_on_exec);
  38        spin_unlock(&files->file_lock);
  39}
  40
  41static int get_close_on_exec(unsigned int fd)
  42{
  43        struct files_struct *files = current->files;
  44        struct fdtable *fdt;
  45        int res;
  46        rcu_read_lock();
  47        fdt = files_fdtable(files);
  48        res = FD_ISSET(fd, fdt->close_on_exec);
  49        rcu_read_unlock();
  50        return res;
  51}
  52
  53SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
  54{
  55        int err = -EBADF;
  56        struct file * file, *tofree;
  57        struct files_struct * files = current->files;
  58        struct fdtable *fdt;
  59
  60        if ((flags & ~O_CLOEXEC) != 0)
  61                return -EINVAL;
  62
  63        if (unlikely(oldfd == newfd))
  64                return -EINVAL;
  65
  66        spin_lock(&files->file_lock);
  67        err = expand_files(files, newfd);
  68        file = fcheck(oldfd);
  69        if (unlikely(!file))
  70                goto Ebadf;
  71        if (unlikely(err < 0)) {
  72                if (err == -EMFILE)
  73                        goto Ebadf;
  74                goto out_unlock;
  75        }
  76        /*
  77         * We need to detect attempts to do dup2() over allocated but still
  78         * not finished descriptor.  NB: OpenBSD avoids that at the price of
  79         * extra work in their equivalent of fget() - they insert struct
  80         * file immediately after grabbing descriptor, mark it larval if
  81         * more work (e.g. actual opening) is needed and make sure that
  82         * fget() treats larval files as absent.  Potentially interesting,
  83         * but while extra work in fget() is trivial, locking implications
  84         * and amount of surgery on open()-related paths in VFS are not.
  85         * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
  86         * deadlocks in rather amusing ways, AFAICS.  All of that is out of
  87         * scope of POSIX or SUS, since neither considers shared descriptor
  88         * tables and this condition does not arise without those.
  89         */
  90        err = -EBUSY;
  91        fdt = files_fdtable(files);
  92        tofree = fdt->fd[newfd];
  93        if (!tofree && FD_ISSET(newfd, fdt->open_fds))
  94                goto out_unlock;
  95        get_file(file);
  96        rcu_assign_pointer(fdt->fd[newfd], file);
  97        FD_SET(newfd, fdt->open_fds);
  98        if (flags & O_CLOEXEC)
  99                FD_SET(newfd, fdt->close_on_exec);
 100        else
 101                FD_CLR(newfd, fdt->close_on_exec);
 102        spin_unlock(&files->file_lock);
 103
 104        if (tofree)
 105                filp_close(tofree, files);
 106
 107        return newfd;
 108
 109Ebadf:
 110        err = -EBADF;
 111out_unlock:
 112        spin_unlock(&files->file_lock);
 113        return err;
 114}
 115
 116SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 117{
 118        if (unlikely(newfd == oldfd)) { /* corner case */
 119                struct files_struct *files = current->files;
 120                int retval = oldfd;
 121
 122                rcu_read_lock();
 123                if (!fcheck_files(files, oldfd))
 124                        retval = -EBADF;
 125                rcu_read_unlock();
 126                return retval;
 127        }
 128        return sys_dup3(oldfd, newfd, 0);
 129}
 130
 131SYSCALL_DEFINE1(dup, unsigned int, fildes)
 132{
 133        int ret = -EBADF;
 134        struct file *file = fget_raw(fildes);
 135
 136        if (file) {
 137                ret = get_unused_fd();
 138                if (ret >= 0)
 139                        fd_install(ret, file);
 140                else
 141                        fput(file);
 142        }
 143        return ret;
 144}
 145
 146#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
 147
 148static int setfl(int fd, struct file * filp, unsigned long arg)
 149{
 150        struct inode * inode = filp->f_path.dentry->d_inode;
 151        int error = 0;
 152
 153        /*
 154         * O_APPEND cannot be cleared if the file is marked as append-only
 155         * and the file is open for write.
 156         */
 157        if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
 158                return -EPERM;
 159
 160        /* O_NOATIME can only be set by the owner or superuser */
 161        if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 162                if (!inode_owner_or_capable(inode))
 163                        return -EPERM;
 164
 165        /* required for strict SunOS emulation */
 166        if (O_NONBLOCK != O_NDELAY)
 167               if (arg & O_NDELAY)
 168                   arg |= O_NONBLOCK;
 169
 170        if (arg & O_DIRECT) {
 171                if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 172                        !filp->f_mapping->a_ops->direct_IO)
 173                                return -EINVAL;
 174        }
 175
 176        if (filp->f_op && filp->f_op->check_flags)
 177                error = filp->f_op->check_flags(arg);
 178        if (error)
 179                return error;
 180
 181        /*
 182         * ->fasync() is responsible for setting the FASYNC bit.
 183         */
 184        if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op &&
 185                        filp->f_op->fasync) {
 186                error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 187                if (error < 0)
 188                        goto out;
 189                if (error > 0)
 190                        error = 0;
 191        }
 192        spin_lock(&filp->f_lock);
 193        filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 194        spin_unlock(&filp->f_lock);
 195
 196 out:
 197        return error;
 198}
 199
 200static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
 201                     int force)
 202{
 203        write_lock_irq(&filp->f_owner.lock);
 204        if (force || !filp->f_owner.pid) {
 205                put_pid(filp->f_owner.pid);
 206                filp->f_owner.pid = get_pid(pid);
 207                filp->f_owner.pid_type = type;
 208
 209                if (pid) {
 210                        const struct cred *cred = current_cred();
 211                        filp->f_owner.uid = cred->uid;
 212                        filp->f_owner.euid = cred->euid;
 213                }
 214        }
 215        write_unlock_irq(&filp->f_owner.lock);
 216}
 217
 218int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
 219                int force)
 220{
 221        int err;
 222
 223        err = security_file_set_fowner(filp);
 224        if (err)
 225                return err;
 226
 227        f_modown(filp, pid, type, force);
 228        return 0;
 229}
 230EXPORT_SYMBOL(__f_setown);
 231
 232int f_setown(struct file *filp, unsigned long arg, int force)
 233{
 234        enum pid_type type;
 235        struct pid *pid;
 236        int who = arg;
 237        int result;
 238        type = PIDTYPE_PID;
 239        if (who < 0) {
 240                type = PIDTYPE_PGID;
 241                who = -who;
 242        }
 243        rcu_read_lock();
 244        pid = find_vpid(who);
 245        result = __f_setown(filp, pid, type, force);
 246        rcu_read_unlock();
 247        return result;
 248}
 249EXPORT_SYMBOL(f_setown);
 250
 251void f_delown(struct file *filp)
 252{
 253        f_modown(filp, NULL, PIDTYPE_PID, 1);
 254}
 255
 256pid_t f_getown(struct file *filp)
 257{
 258        pid_t pid;
 259        read_lock(&filp->f_owner.lock);
 260        pid = pid_vnr(filp->f_owner.pid);
 261        if (filp->f_owner.pid_type == PIDTYPE_PGID)
 262                pid = -pid;
 263        read_unlock(&filp->f_owner.lock);
 264        return pid;
 265}
 266
 267static int f_setown_ex(struct file *filp, unsigned long arg)
 268{
 269        struct f_owner_ex * __user owner_p = (void * __user)arg;
 270        struct f_owner_ex owner;
 271        struct pid *pid;
 272        int type;
 273        int ret;
 274
 275        ret = copy_from_user(&owner, owner_p, sizeof(owner));
 276        if (ret)
 277                return -EFAULT;
 278
 279        switch (owner.type) {
 280        case F_OWNER_TID:
 281                type = PIDTYPE_MAX;
 282                break;
 283
 284        case F_OWNER_PID:
 285                type = PIDTYPE_PID;
 286                break;
 287
 288        case F_OWNER_PGRP:
 289                type = PIDTYPE_PGID;
 290                break;
 291
 292        default:
 293                return -EINVAL;
 294        }
 295
 296        rcu_read_lock();
 297        pid = find_vpid(owner.pid);
 298        if (owner.pid && !pid)
 299                ret = -ESRCH;
 300        else
 301                ret = __f_setown(filp, pid, type, 1);
 302        rcu_read_unlock();
 303
 304        return ret;
 305}
 306
 307static int f_getown_ex(struct file *filp, unsigned long arg)
 308{
 309        struct f_owner_ex * __user owner_p = (void * __user)arg;
 310        struct f_owner_ex owner;
 311        int ret = 0;
 312
 313        read_lock(&filp->f_owner.lock);
 314        owner.pid = pid_vnr(filp->f_owner.pid);
 315        switch (filp->f_owner.pid_type) {
 316        case PIDTYPE_MAX:
 317                owner.type = F_OWNER_TID;
 318                break;
 319
 320        case PIDTYPE_PID:
 321                owner.type = F_OWNER_PID;
 322                break;
 323
 324        case PIDTYPE_PGID:
 325                owner.type = F_OWNER_PGRP;
 326                break;
 327
 328        default:
 329                WARN_ON(1);
 330                ret = -EINVAL;
 331                break;
 332        }
 333        read_unlock(&filp->f_owner.lock);
 334
 335        if (!ret) {
 336                ret = copy_to_user(owner_p, &owner, sizeof(owner));
 337                if (ret)
 338                        ret = -EFAULT;
 339        }
 340        return ret;
 341}
 342
 343static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 344                struct file *filp)
 345{
 346        long err = -EINVAL;
 347
 348        switch (cmd) {
 349        case F_DUPFD:
 350        case F_DUPFD_CLOEXEC:
 351                if (arg >= rlimit(RLIMIT_NOFILE))
 352                        break;
 353                err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
 354                if (err >= 0) {
 355                        get_file(filp);
 356                        fd_install(err, filp);
 357                }
 358                break;
 359        case F_GETFD:
 360                err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 361                break;
 362        case F_SETFD:
 363                err = 0;
 364                set_close_on_exec(fd, arg & FD_CLOEXEC);
 365                break;
 366        case F_GETFL:
 367                err = filp->f_flags;
 368                break;
 369        case F_SETFL:
 370                err = setfl(fd, filp, arg);
 371                break;
 372        case F_GETLK:
 373                err = fcntl_getlk(filp, (struct flock __user *) arg);
 374                break;
 375        case F_SETLK:
 376        case F_SETLKW:
 377                err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 378                break;
 379        case F_GETOWN:
 380                /*
 381                 * XXX If f_owner is a process group, the
 382                 * negative return value will get converted
 383                 * into an error.  Oops.  If we keep the
 384                 * current syscall conventions, the only way
 385                 * to fix this will be in libc.
 386                 */
 387                err = f_getown(filp);
 388                force_successful_syscall_return();
 389                break;
 390        case F_SETOWN:
 391                err = f_setown(filp, arg, 1);
 392                break;
 393        case F_GETOWN_EX:
 394                err = f_getown_ex(filp, arg);
 395                break;
 396        case F_SETOWN_EX:
 397                err = f_setown_ex(filp, arg);
 398                break;
 399        case F_GETSIG:
 400                err = filp->f_owner.signum;
 401                break;
 402        case F_SETSIG:
 403                /* arg == 0 restores default behaviour. */
 404                if (!valid_signal(arg)) {
 405                        break;
 406                }
 407                err = 0;
 408                filp->f_owner.signum = arg;
 409                break;
 410        case F_GETLEASE:
 411                err = fcntl_getlease(filp);
 412                break;
 413        case F_SETLEASE:
 414                err = fcntl_setlease(fd, filp, arg);
 415                break;
 416        case F_NOTIFY:
 417                err = fcntl_dirnotify(fd, filp, arg);
 418                break;
 419        case F_SETPIPE_SZ:
 420        case F_GETPIPE_SZ:
 421                err = pipe_fcntl(filp, cmd, arg);
 422                break;
 423        default:
 424                break;
 425        }
 426        return err;
 427}
 428
 429static int check_fcntl_cmd(unsigned cmd)
 430{
 431        switch (cmd) {
 432        case F_DUPFD:
 433        case F_DUPFD_CLOEXEC:
 434        case F_GETFD:
 435        case F_SETFD:
 436        case F_GETFL:
 437                return 1;
 438        }
 439        return 0;
 440}
 441
 442SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
 443{       
 444        struct file *filp;
 445        long err = -EBADF;
 446
 447        filp = fget_raw(fd);
 448        if (!filp)
 449                goto out;
 450
 451        if (unlikely(filp->f_mode & FMODE_PATH)) {
 452                if (!check_fcntl_cmd(cmd)) {
 453                        fput(filp);
 454                        goto out;
 455                }
 456        }
 457
 458        err = security_file_fcntl(filp, cmd, arg);
 459        if (err) {
 460                fput(filp);
 461                return err;
 462        }
 463
 464        err = do_fcntl(fd, cmd, arg, filp);
 465
 466        fput(filp);
 467out:
 468        return err;
 469}
 470
 471#if BITS_PER_LONG == 32
 472SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 473                unsigned long, arg)
 474{       
 475        struct file * filp;
 476        long err;
 477
 478        err = -EBADF;
 479        filp = fget_raw(fd);
 480        if (!filp)
 481                goto out;
 482
 483        if (unlikely(filp->f_mode & FMODE_PATH)) {
 484                if (!check_fcntl_cmd(cmd)) {
 485                        fput(filp);
 486                        goto out;
 487                }
 488        }
 489
 490        err = security_file_fcntl(filp, cmd, arg);
 491        if (err) {
 492                fput(filp);
 493                return err;
 494        }
 495        err = -EBADF;
 496        
 497        switch (cmd) {
 498                case F_GETLK64:
 499                        err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 500                        break;
 501                case F_SETLK64:
 502                case F_SETLKW64:
 503                        err = fcntl_setlk64(fd, filp, cmd,
 504                                        (struct flock64 __user *) arg);
 505                        break;
 506                default:
 507                        err = do_fcntl(fd, cmd, arg, filp);
 508                        break;
 509        }
 510        fput(filp);
 511out:
 512        return err;
 513}
 514#endif
 515
 516/* Table to convert sigio signal codes into poll band bitmaps */
 517
 518static const long band_table[NSIGPOLL] = {
 519        POLLIN | POLLRDNORM,                    /* POLL_IN */
 520        POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 521        POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 522        POLLERR,                                /* POLL_ERR */
 523        POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 524        POLLHUP | POLLERR                       /* POLL_HUP */
 525};
 526
 527static inline int sigio_perm(struct task_struct *p,
 528                             struct fown_struct *fown, int sig)
 529{
 530        const struct cred *cred;
 531        int ret;
 532
 533        rcu_read_lock();
 534        cred = __task_cred(p);
 535        ret = ((fown->euid == 0 ||
 536                fown->euid == cred->suid || fown->euid == cred->uid ||
 537                fown->uid  == cred->suid || fown->uid  == cred->uid) &&
 538               !security_file_send_sigiotask(p, fown, sig));
 539        rcu_read_unlock();
 540        return ret;
 541}
 542
 543static void send_sigio_to_task(struct task_struct *p,
 544                               struct fown_struct *fown,
 545                               int fd, int reason, int group)
 546{
 547        /*
 548         * F_SETSIG can change ->signum lockless in parallel, make
 549         * sure we read it once and use the same value throughout.
 550         */
 551        int signum = ACCESS_ONCE(fown->signum);
 552
 553        if (!sigio_perm(p, fown, signum))
 554                return;
 555
 556        switch (signum) {
 557                siginfo_t si;
 558                default:
 559                        /* Queue a rt signal with the appropriate fd as its
 560                           value.  We use SI_SIGIO as the source, not 
 561                           SI_KERNEL, since kernel signals always get 
 562                           delivered even if we can't queue.  Failure to
 563                           queue in this case _should_ be reported; we fall
 564                           back to SIGIO in that case. --sct */
 565                        si.si_signo = signum;
 566                        si.si_errno = 0;
 567                        si.si_code  = reason;
 568                        /* Make sure we are called with one of the POLL_*
 569                           reasons, otherwise we could leak kernel stack into
 570                           userspace.  */
 571                        BUG_ON((reason & __SI_MASK) != __SI_POLL);
 572                        if (reason - POLL_IN >= NSIGPOLL)
 573                                si.si_band  = ~0L;
 574                        else
 575                                si.si_band = band_table[reason - POLL_IN];
 576                        si.si_fd    = fd;
 577                        if (!do_send_sig_info(signum, &si, p, group))
 578                                break;
 579                /* fall-through: fall back on the old plain SIGIO signal */
 580                case 0:
 581                        do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group);
 582        }
 583}
 584
 585void send_sigio(struct fown_struct *fown, int fd, int band)
 586{
 587        struct task_struct *p;
 588        enum pid_type type;
 589        struct pid *pid;
 590        int group = 1;
 591        
 592        read_lock(&fown->lock);
 593
 594        type = fown->pid_type;
 595        if (type == PIDTYPE_MAX) {
 596                group = 0;
 597                type = PIDTYPE_PID;
 598        }
 599
 600        pid = fown->pid;
 601        if (!pid)
 602                goto out_unlock_fown;
 603        
 604        read_lock(&tasklist_lock);
 605        do_each_pid_task(pid, type, p) {
 606                send_sigio_to_task(p, fown, fd, band, group);
 607        } while_each_pid_task(pid, type, p);
 608        read_unlock(&tasklist_lock);
 609 out_unlock_fown:
 610        read_unlock(&fown->lock);
 611}
 612
 613static void send_sigurg_to_task(struct task_struct *p,
 614                                struct fown_struct *fown, int group)
 615{
 616        if (sigio_perm(p, fown, SIGURG))
 617                do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group);
 618}
 619
 620int send_sigurg(struct fown_struct *fown)
 621{
 622        struct task_struct *p;
 623        enum pid_type type;
 624        struct pid *pid;
 625        int group = 1;
 626        int ret = 0;
 627        
 628        read_lock(&fown->lock);
 629
 630        type = fown->pid_type;
 631        if (type == PIDTYPE_MAX) {
 632                group = 0;
 633                type = PIDTYPE_PID;
 634        }
 635
 636        pid = fown->pid;
 637        if (!pid)
 638                goto out_unlock_fown;
 639
 640        ret = 1;
 641        
 642        read_lock(&tasklist_lock);
 643        do_each_pid_task(pid, type, p) {
 644                send_sigurg_to_task(p, fown, group);
 645        } while_each_pid_task(pid, type, p);
 646        read_unlock(&tasklist_lock);
 647 out_unlock_fown:
 648        read_unlock(&fown->lock);
 649        return ret;
 650}
 651
 652static DEFINE_SPINLOCK(fasync_lock);
 653static struct kmem_cache *fasync_cache __read_mostly;
 654
 655static void fasync_free_rcu(struct rcu_head *head)
 656{
 657        kmem_cache_free(fasync_cache,
 658                        container_of(head, struct fasync_struct, fa_rcu));
 659}
 660
 661/*
 662 * Remove a fasync entry. If successfully removed, return
 663 * positive and clear the FASYNC flag. If no entry exists,
 664 * do nothing and return 0.
 665 *
 666 * NOTE! It is very important that the FASYNC flag always
 667 * match the state "is the filp on a fasync list".
 668 *
 669 */
 670int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
 671{
 672        struct fasync_struct *fa, **fp;
 673        int result = 0;
 674
 675        spin_lock(&filp->f_lock);
 676        spin_lock(&fasync_lock);
 677        for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 678                if (fa->fa_file != filp)
 679                        continue;
 680
 681                spin_lock_irq(&fa->fa_lock);
 682                fa->fa_file = NULL;
 683                spin_unlock_irq(&fa->fa_lock);
 684
 685                *fp = fa->fa_next;
 686                call_rcu(&fa->fa_rcu, fasync_free_rcu);
 687                filp->f_flags &= ~FASYNC;
 688                result = 1;
 689                break;
 690        }
 691        spin_unlock(&fasync_lock);
 692        spin_unlock(&filp->f_lock);
 693        return result;
 694}
 695
 696struct fasync_struct *fasync_alloc(void)
 697{
 698        return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 699}
 700
 701/*
 702 * NOTE! This can be used only for unused fasync entries:
 703 * entries that actually got inserted on the fasync list
 704 * need to be released by rcu - see fasync_remove_entry.
 705 */
 706void fasync_free(struct fasync_struct *new)
 707{
 708        kmem_cache_free(fasync_cache, new);
 709}
 710
 711/*
 712 * Insert a new entry into the fasync list.  Return the pointer to the
 713 * old one if we didn't use the new one.
 714 *
 715 * NOTE! It is very important that the FASYNC flag always
 716 * match the state "is the filp on a fasync list".
 717 */
 718struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
 719{
 720        struct fasync_struct *fa, **fp;
 721
 722        spin_lock(&filp->f_lock);
 723        spin_lock(&fasync_lock);
 724        for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 725                if (fa->fa_file != filp)
 726                        continue;
 727
 728                spin_lock_irq(&fa->fa_lock);
 729                fa->fa_fd = fd;
 730                spin_unlock_irq(&fa->fa_lock);
 731                goto out;
 732        }
 733
 734        spin_lock_init(&new->fa_lock);
 735        new->magic = FASYNC_MAGIC;
 736        new->fa_file = filp;
 737        new->fa_fd = fd;
 738        new->fa_next = *fapp;
 739        rcu_assign_pointer(*fapp, new);
 740        filp->f_flags |= FASYNC;
 741
 742out:
 743        spin_unlock(&fasync_lock);
 744        spin_unlock(&filp->f_lock);
 745        return fa;
 746}
 747
 748/*
 749 * Add a fasync entry. Return negative on error, positive if
 750 * added, and zero if did nothing but change an existing one.
 751 */
 752static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
 753{
 754        struct fasync_struct *new;
 755
 756        new = fasync_alloc();
 757        if (!new)
 758                return -ENOMEM;
 759
 760        /*
 761         * fasync_insert_entry() returns the old (update) entry if
 762         * it existed.
 763         *
 764         * So free the (unused) new entry and return 0 to let the
 765         * caller know that we didn't add any new fasync entries.
 766         */
 767        if (fasync_insert_entry(fd, filp, fapp, new)) {
 768                fasync_free(new);
 769                return 0;
 770        }
 771
 772        return 1;
 773}
 774
 775/*
 776 * fasync_helper() is used by almost all character device drivers
 777 * to set up the fasync queue, and for regular files by the file
 778 * lease code. It returns negative on error, 0 if it did no changes
 779 * and positive if it added/deleted the entry.
 780 */
 781int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 782{
 783        if (!on)
 784                return fasync_remove_entry(filp, fapp);
 785        return fasync_add_entry(fd, filp, fapp);
 786}
 787
 788EXPORT_SYMBOL(fasync_helper);
 789
 790/*
 791 * rcu_read_lock() is held
 792 */
 793static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
 794{
 795        while (fa) {
 796                struct fown_struct *fown;
 797                unsigned long flags;
 798
 799                if (fa->magic != FASYNC_MAGIC) {
 800                        printk(KERN_ERR "kill_fasync: bad magic number in "
 801                               "fasync_struct!\n");
 802                        return;
 803                }
 804                spin_lock_irqsave(&fa->fa_lock, flags);
 805                if (fa->fa_file) {
 806                        fown = &fa->fa_file->f_owner;
 807                        /* Don't send SIGURG to processes which have not set a
 808                           queued signum: SIGURG has its own default signalling
 809                           mechanism. */
 810                        if (!(sig == SIGURG && fown->signum == 0))
 811                                send_sigio(fown, fa->fa_fd, band);
 812                }
 813                spin_unlock_irqrestore(&fa->fa_lock, flags);
 814                fa = rcu_dereference(fa->fa_next);
 815        }
 816}
 817
 818void kill_fasync(struct fasync_struct **fp, int sig, int band)
 819{
 820        /* First a quick test without locking: usually
 821         * the list is empty.
 822         */
 823        if (*fp) {
 824                rcu_read_lock();
 825                kill_fasync_rcu(rcu_dereference(*fp), sig, band);
 826                rcu_read_unlock();
 827        }
 828}
 829EXPORT_SYMBOL(kill_fasync);
 830
 831static int __init fcntl_init(void)
 832{
 833        /*
 834         * Please add new bits here to ensure allocation uniqueness.
 835         * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
 836         * is defined as O_NONBLOCK on some platforms and not on others.
 837         */
 838        BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
 839                O_RDONLY        | O_WRONLY      | O_RDWR        |
 840                O_CREAT         | O_EXCL        | O_NOCTTY      |
 841                O_TRUNC         | O_APPEND      | /* O_NONBLOCK | */
 842                __O_SYNC        | O_DSYNC       | FASYNC        |
 843                O_DIRECT        | O_LARGEFILE   | O_DIRECTORY   |
 844                O_NOFOLLOW      | O_NOATIME     | O_CLOEXEC     |
 845                __FMODE_EXEC    | O_PATH
 846                ));
 847
 848        fasync_cache = kmem_cache_create("fasync_cache",
 849                sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 850        return 0;
 851}
 852
 853module_init(fcntl_init)
 854
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