fs/fcntl.c

   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
  28 void 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
  41 static 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
  53 SYSCALL_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
 109 Ebadf:
 110         err = -EBADF;
 111 out_unlock:
 112         spin_unlock(&files->file_lock);
 113         return err;
 114 }
 115
 116 SYSCALL_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
 131 SYSCALL_DEFINE1(dup, unsigned int, fildes)
 132 {
 133         int ret = -EBADF;
 134         struct file *file = fget(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
 148 static 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 (!is_owner_or_cap(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
 200 static 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
 218 int __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 }
 230 EXPORT_SYMBOL(__f_setown);
 231
 232 int 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 }
 249 EXPORT_SYMBOL(f_setown);
 250
 251 void f_delown(struct file *filp)
 252 {
 253         f_modown(filp, NULL, PIDTYPE_PID, 1);
 254 }
 255
 256 pid_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
 267 static 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
 307 static 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
 343 static 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
 429 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
 430 {
 431         struct file *filp;
 432         long err = -EBADF;
 433
 434         filp = fget(fd);
 435         if (!filp)
 436                 goto out;
 437
 438         err = security_file_fcntl(filp, cmd, arg);
 439         if (err) {
 440                 fput(filp);
 441                 return err;
 442         }
 443
 444         err = do_fcntl(fd, cmd, arg, filp);
 445
 446         fput(filp);
 447 out:
 448         return err;
 449 }
 450
 451 #if BITS_PER_LONG == 32
 452 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 453                 unsigned long, arg)
 454 {
 455         struct file * filp;
 456         long err;
 457
 458         err = -EBADF;
 459         filp = fget(fd);
 460         if (!filp)
 461                 goto out;
 462
 463         err = security_file_fcntl(filp, cmd, arg);
 464         if (err) {
 465                 fput(filp);
 466                 return err;
 467         }
 468         err = -EBADF;
 469
 470         switch (cmd) {
 471                 case F_GETLK64:
 472                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 473                         break;
 474                 case F_SETLK64:
 475                 case F_SETLKW64:
 476                         err = fcntl_setlk64(fd, filp, cmd,
 477                                         (struct flock64 __user *) arg);
 478                         break;
 479                 default:
 480                         err = do_fcntl(fd, cmd, arg, filp);
 481                         break;
 482         }
 483         fput(filp);
 484 out:
 485         return err;
 486 }
 487 #endif
 488
 489 /* Table to convert sigio signal codes into poll band bitmaps */
 490
 491 static const long band_table[NSIGPOLL] = {
 492         POLLIN | POLLRDNORM,                    /* POLL_IN */
 493         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 494         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 495         POLLERR,                                /* POLL_ERR */
 496         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 497         POLLHUP | POLLERR                       /* POLL_HUP */
 498 };
 499
 500 static inline int sigio_perm(struct task_struct *p,
 501                              struct fown_struct *fown, int sig)
 502 {
 503         const struct cred *cred;
 504         int ret;
 505
 506         rcu_read_lock();
 507         cred = __task_cred(p);
 508         ret = ((fown->euid == 0 ||
 509                 fown->euid == cred->suid || fown->euid == cred->uid ||
 510                 fown->uid  == cred->suid || fown->uid  == cred->uid) &&
 511                !security_file_send_sigiotask(p, fown, sig));
 512         rcu_read_unlock();
 513         return ret;
 514 }
 515
 516 static void send_sigio_to_task(struct task_struct *p,
 517                                struct fown_struct *fown,
 518                                int fd, int reason, int group)
 519 {
 520         /*
 521          * F_SETSIG can change ->signum lockless in parallel, make
 522          * sure we read it once and use the same value throughout.
 523          */
 524         int signum = ACCESS_ONCE(fown->signum);
 525
 526         if (!sigio_perm(p, fown, signum))
 527                 return;
 528
 529         switch (signum) {
 530                 siginfo_t si;
 531                 default:
 532                         /* Queue a rt signal with the appropriate fd as its
 533                            value.  We use SI_SIGIO as the source, not
 534                            SI_KERNEL, since kernel signals always get
 535                            delivered even if we can't queue.  Failure to
 536                            queue in this case _should_ be reported; we fall
 537                            back to SIGIO in that case. --sct */
 538                         si.si_signo = signum;
 539                         si.si_errno = 0;
 540                         si.si_code  = reason;
 541                         /* Make sure we are called with one of the POLL_*
 542                            reasons, otherwise we could leak kernel stack into
 543                            userspace.  */
 544                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 545                         if (reason - POLL_IN >= NSIGPOLL)
 546                                 si.si_band  = ~0L;
 547                         else
 548                                 si.si_band = band_table[reason - POLL_IN];
 549                         si.si_fd    = fd;
 550                         if (!do_send_sig_info(signum, &si, p, group))
 551                                 break;
 552                 /* fall-through: fall back on the old plain SIGIO signal */
 553                 case 0:
 554                         do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group);
 555         }
 556 }
 557
 558 void send_sigio(struct fown_struct *fown, int fd, int band)
 559 {
 560         struct task_struct *p;
 561         enum pid_type type;
 562         struct pid *pid;
 563         int group = 1;
 564
 565         read_lock(&fown->lock);
 566
 567         type = fown->pid_type;
 568         if (type == PIDTYPE_MAX) {
 569                 group = 0;
 570                 type = PIDTYPE_PID;
 571         }
 572
 573         pid = fown->pid;
 574         if (!pid)
 575                 goto out_unlock_fown;
 576
 577         read_lock(&tasklist_lock);
 578         do_each_pid_task(pid, type, p) {
 579                 send_sigio_to_task(p, fown, fd, band, group);
 580         } while_each_pid_task(pid, type, p);
 581         read_unlock(&tasklist_lock);
 582  out_unlock_fown:
 583         read_unlock(&fown->lock);
 584 }
 585
 586 static void send_sigurg_to_task(struct task_struct *p,
 587                                 struct fown_struct *fown, int group)
 588 {
 589         if (sigio_perm(p, fown, SIGURG))
 590                 do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group);
 591 }
 592
 593 int send_sigurg(struct fown_struct *fown)
 594 {
 595         struct task_struct *p;
 596         enum pid_type type;
 597         struct pid *pid;
 598         int group = 1;
 599         int ret = 0;
 600
 601         read_lock(&fown->lock);
 602
 603         type = fown->pid_type;
 604         if (type == PIDTYPE_MAX) {
 605                 group = 0;
 606                 type = PIDTYPE_PID;
 607         }
 608
 609         pid = fown->pid;
 610         if (!pid)
 611                 goto out_unlock_fown;
 612
 613         ret = 1;
 614
 615         read_lock(&tasklist_lock);
 616         do_each_pid_task(pid, type, p) {
 617                 send_sigurg_to_task(p, fown, group);
 618         } while_each_pid_task(pid, type, p);
 619         read_unlock(&tasklist_lock);
 620  out_unlock_fown:
 621         read_unlock(&fown->lock);
 622         return ret;
 623 }
 624
 625 static DEFINE_SPINLOCK(fasync_lock);
 626 static struct kmem_cache *fasync_cache __read_mostly;
 627
 628 static void fasync_free_rcu(struct rcu_head *head)
 629 {
 630         kmem_cache_free(fasync_cache,
 631                         container_of(head, struct fasync_struct, fa_rcu));
 632 }
 633
 634 /*
 635  * Remove a fasync entry. If successfully removed, return
 636  * positive and clear the FASYNC flag. If no entry exists,
 637  * do nothing and return 0.
 638  *
 639  * NOTE! It is very important that the FASYNC flag always
 640  * match the state "is the filp on a fasync list".
 641  *
 642  */
 643 static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
 644 {
 645         struct fasync_struct *fa, **fp;
 646         int result = 0;
 647
 648         spin_lock(&filp->f_lock);
 649         spin_lock(&fasync_lock);
 650         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 651                 if (fa->fa_file != filp)
 652                         continue;
 653
 654                 spin_lock_irq(&fa->fa_lock);
 655                 fa->fa_file = NULL;
 656                 spin_unlock_irq(&fa->fa_lock);
 657
 658                 *fp = fa->fa_next;
 659                 call_rcu(&fa->fa_rcu, fasync_free_rcu);
 660                 filp->f_flags &= ~FASYNC;
 661                 result = 1;
 662                 break;
 663         }
 664         spin_unlock(&fasync_lock);
 665         spin_unlock(&filp->f_lock);
 666         return result;
 667 }
 668
 669 /*
 670  * Add a fasync entry. Return negative on error, positive if
 671  * added, and zero if did nothing but change an existing one.
 672  *
 673  * NOTE! It is very important that the FASYNC flag always
 674  * match the state "is the filp on a fasync list".
 675  */
 676 static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
 677 {
 678         struct fasync_struct *new, *fa, **fp;
 679         int result = 0;
 680
 681         new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 682         if (!new)
 683                 return -ENOMEM;
 684
 685         spin_lock(&filp->f_lock);
 686         spin_lock(&fasync_lock);
 687         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 688                 if (fa->fa_file != filp)
 689                         continue;
 690
 691                 spin_lock_irq(&fa->fa_lock);
 692                 fa->fa_fd = fd;
 693                 spin_unlock_irq(&fa->fa_lock);
 694
 695                 kmem_cache_free(fasync_cache, new);
 696                 goto out;
 697         }
 698
 699         spin_lock_init(&new->fa_lock);
 700         new->magic = FASYNC_MAGIC;
 701         new->fa_file = filp;
 702         new->fa_fd = fd;
 703         new->fa_next = *fapp;
 704         rcu_assign_pointer(*fapp, new);
 705         result = 1;
 706         filp->f_flags |= FASYNC;
 707
 708 out:
 709         spin_unlock(&fasync_lock);
 710         spin_unlock(&filp->f_lock);
 711         return result;
 712 }
 713
 714 /*
 715  * fasync_helper() is used by almost all character device drivers
 716  * to set up the fasync queue, and for regular files by the file
 717  * lease code. It returns negative on error, 0 if it did no changes
 718  * and positive if it added/deleted the entry.
 719  */
 720 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 721 {
 722         if (!on)
 723                 return fasync_remove_entry(filp, fapp);
 724         return fasync_add_entry(fd, filp, fapp);
 725 }
 726
 727 EXPORT_SYMBOL(fasync_helper);
 728
 729 /*
 730  * rcu_read_lock() is held
 731  */
 732 static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
 733 {
 734         while (fa) {
 735                 struct fown_struct *fown;
 736                 if (fa->magic != FASYNC_MAGIC) {
 737                         printk(KERN_ERR "kill_fasync: bad magic number in "
 738                                "fasync_struct!\n");
 739                         return;
 740                 }
 741                 spin_lock(&fa->fa_lock);
 742                 if (fa->fa_file) {
 743                         fown = &fa->fa_file->f_owner;
 744                         /* Don't send SIGURG to processes which have not set a
 745                            queued signum: SIGURG has its own default signalling
 746                            mechanism. */
 747                         if (!(sig == SIGURG && fown->signum == 0))
 748                                 send_sigio(fown, fa->fa_fd, band);
 749                 }
 750                 spin_unlock(&fa->fa_lock);
 751                 fa = rcu_dereference(fa->fa_next);
 752         }
 753 }
 754
 755 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 756 {
 757         /* First a quick test without locking: usually
 758          * the list is empty.
 759          */
 760         if (*fp) {
 761                 rcu_read_lock();
 762                 kill_fasync_rcu(rcu_dereference(*fp), sig, band);
 763                 rcu_read_unlock();
 764         }
 765 }
 766 EXPORT_SYMBOL(kill_fasync);
 767
 768 static int __init fasync_init(void)
 769 {
 770         fasync_cache = kmem_cache_create("fasync_cache",
 771                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 772         return 0;
 773 }
 774
 775 module_init(fasync_init)