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