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 ret;
 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         return ret;
 338 }
 339
 340 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 341                 struct file *filp)
 342 {
 343         long err = -EINVAL;
 344
 345         switch (cmd) {
 346         case F_DUPFD:
 347         case F_DUPFD_CLOEXEC:
 348                 if (arg >= rlimit(RLIMIT_NOFILE))
 349                         break;
 350                 err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
 351                 if (err >= 0) {
 352                         get_file(filp);
 353                         fd_install(err, filp);
 354                 }
 355                 break;
 356         case F_GETFD:
 357                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 358                 break;
 359         case F_SETFD:
 360                 err = 0;
 361                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 362                 break;
 363         case F_GETFL:
 364                 err = filp->f_flags;
 365                 break;
 366         case F_SETFL:
 367                 err = setfl(fd, filp, arg);
 368                 break;
 369         case F_GETLK:
 370                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 371                 break;
 372         case F_SETLK:
 373         case F_SETLKW:
 374                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 375                 break;
 376         case F_GETOWN:
 377                 /*
 378                  * XXX If f_owner is a process group, the
 379                  * negative return value will get converted
 380                  * into an error.  Oops.  If we keep the
 381                  * current syscall conventions, the only way
 382                  * to fix this will be in libc.
 383                  */
 384                 err = f_getown(filp);
 385                 force_successful_syscall_return();
 386                 break;
 387         case F_SETOWN:
 388                 err = f_setown(filp, arg, 1);
 389                 break;
 390         case F_GETOWN_EX:
 391                 err = f_getown_ex(filp, arg);
 392                 break;
 393         case F_SETOWN_EX:
 394                 err = f_setown_ex(filp, arg);
 395                 break;
 396         case F_GETSIG:
 397                 err = filp->f_owner.signum;
 398                 break;
 399         case F_SETSIG:
 400                 /* arg == 0 restores default behaviour. */
 401                 if (!valid_signal(arg)) {
 402                         break;
 403                 }
 404                 err = 0;
 405                 filp->f_owner.signum = arg;
 406                 break;
 407         case F_GETLEASE:
 408                 err = fcntl_getlease(filp);
 409                 break;
 410         case F_SETLEASE:
 411                 err = fcntl_setlease(fd, filp, arg);
 412                 break;
 413         case F_NOTIFY:
 414                 err = fcntl_dirnotify(fd, filp, arg);
 415                 break;
 416         case F_SETPIPE_SZ:
 417         case F_GETPIPE_SZ:
 418                 err = pipe_fcntl(filp, cmd, arg);
 419                 break;
 420         default:
 421                 break;
 422         }
 423         return err;
 424 }
 425
 426 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
 427 {
 428         struct file *filp;
 429         long err = -EBADF;
 430
 431         filp = fget(fd);
 432         if (!filp)
 433                 goto out;
 434
 435         err = security_file_fcntl(filp, cmd, arg);
 436         if (err) {
 437                 fput(filp);
 438                 return err;
 439         }
 440
 441         err = do_fcntl(fd, cmd, arg, filp);
 442
 443         fput(filp);
 444 out:
 445         return err;
 446 }
 447
 448 #if BITS_PER_LONG == 32
 449 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 450                 unsigned long, arg)
 451 {
 452         struct file * filp;
 453         long err;
 454
 455         err = -EBADF;
 456         filp = fget(fd);
 457         if (!filp)
 458                 goto out;
 459
 460         err = security_file_fcntl(filp, cmd, arg);
 461         if (err) {
 462                 fput(filp);
 463                 return err;
 464         }
 465         err = -EBADF;
 466
 467         switch (cmd) {
 468                 case F_GETLK64:
 469                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 470                         break;
 471                 case F_SETLK64:
 472                 case F_SETLKW64:
 473                         err = fcntl_setlk64(fd, filp, cmd,
 474                                         (struct flock64 __user *) arg);
 475                         break;
 476                 default:
 477                         err = do_fcntl(fd, cmd, arg, filp);
 478                         break;
 479         }
 480         fput(filp);
 481 out:
 482         return err;
 483 }
 484 #endif
 485
 486 /* Table to convert sigio signal codes into poll band bitmaps */
 487
 488 static const long band_table[NSIGPOLL] = {
 489         POLLIN | POLLRDNORM,                    /* POLL_IN */
 490         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 491         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 492         POLLERR,                                /* POLL_ERR */
 493         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 494         POLLHUP | POLLERR                       /* POLL_HUP */
 495 };
 496
 497 static inline int sigio_perm(struct task_struct *p,
 498                              struct fown_struct *fown, int sig)
 499 {
 500         const struct cred *cred;
 501         int ret;
 502
 503         rcu_read_lock();
 504         cred = __task_cred(p);
 505         ret = ((fown->euid == 0 ||
 506                 fown->euid == cred->suid || fown->euid == cred->uid ||
 507                 fown->uid  == cred->suid || fown->uid  == cred->uid) &&
 508                !security_file_send_sigiotask(p, fown, sig));
 509         rcu_read_unlock();
 510         return ret;
 511 }
 512
 513 static void send_sigio_to_task(struct task_struct *p,
 514                                struct fown_struct *fown,
 515                                int fd, int reason, int group)
 516 {
 517         /*
 518          * F_SETSIG can change ->signum lockless in parallel, make
 519          * sure we read it once and use the same value throughout.
 520          */
 521         int signum = ACCESS_ONCE(fown->signum);
 522
 523         if (!sigio_perm(p, fown, signum))
 524                 return;
 525
 526         switch (signum) {
 527                 siginfo_t si;
 528                 default:
 529                         /* Queue a rt signal with the appropriate fd as its
 530                            value.  We use SI_SIGIO as the source, not
 531                            SI_KERNEL, since kernel signals always get
 532                            delivered even if we can't queue.  Failure to
 533                            queue in this case _should_ be reported; we fall
 534                            back to SIGIO in that case. --sct */
 535                         si.si_signo = signum;
 536                         si.si_errno = 0;
 537                         si.si_code  = reason;
 538                         /* Make sure we are called with one of the POLL_*
 539                            reasons, otherwise we could leak kernel stack into
 540                            userspace.  */
 541                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 542                         if (reason - POLL_IN >= NSIGPOLL)
 543                                 si.si_band  = ~0L;
 544                         else
 545                                 si.si_band = band_table[reason - POLL_IN];
 546                         si.si_fd    = fd;
 547                         if (!do_send_sig_info(signum, &si, p, group))
 548                                 break;
 549                 /* fall-through: fall back on the old plain SIGIO signal */
 550                 case 0:
 551                         do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group);
 552         }
 553 }
 554
 555 void send_sigio(struct fown_struct *fown, int fd, int band)
 556 {
 557         struct task_struct *p;
 558         enum pid_type type;
 559         struct pid *pid;
 560         int group = 1;
 561
 562         read_lock(&fown->lock);
 563
 564         type = fown->pid_type;
 565         if (type == PIDTYPE_MAX) {
 566                 group = 0;
 567                 type = PIDTYPE_PID;
 568         }
 569
 570         pid = fown->pid;
 571         if (!pid)
 572                 goto out_unlock_fown;
 573
 574         read_lock(&tasklist_lock);
 575         do_each_pid_task(pid, type, p) {
 576                 send_sigio_to_task(p, fown, fd, band, group);
 577         } while_each_pid_task(pid, type, p);
 578         read_unlock(&tasklist_lock);
 579  out_unlock_fown:
 580         read_unlock(&fown->lock);
 581 }
 582
 583 static void send_sigurg_to_task(struct task_struct *p,
 584                                 struct fown_struct *fown, int group)
 585 {
 586         if (sigio_perm(p, fown, SIGURG))
 587                 do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group);
 588 }
 589
 590 int send_sigurg(struct fown_struct *fown)
 591 {
 592         struct task_struct *p;
 593         enum pid_type type;
 594         struct pid *pid;
 595         int group = 1;
 596         int ret = 0;
 597
 598         read_lock(&fown->lock);
 599
 600         type = fown->pid_type;
 601         if (type == PIDTYPE_MAX) {
 602                 group = 0;
 603                 type = PIDTYPE_PID;
 604         }
 605
 606         pid = fown->pid;
 607         if (!pid)
 608                 goto out_unlock_fown;
 609
 610         ret = 1;
 611
 612         read_lock(&tasklist_lock);
 613         do_each_pid_task(pid, type, p) {
 614                 send_sigurg_to_task(p, fown, group);
 615         } while_each_pid_task(pid, type, p);
 616         read_unlock(&tasklist_lock);
 617  out_unlock_fown:
 618         read_unlock(&fown->lock);
 619         return ret;
 620 }
 621
 622 static DEFINE_SPINLOCK(fasync_lock);
 623 static struct kmem_cache *fasync_cache __read_mostly;
 624
 625 static void fasync_free_rcu(struct rcu_head *head)
 626 {
 627         kmem_cache_free(fasync_cache,
 628                         container_of(head, struct fasync_struct, fa_rcu));
 629 }
 630
 631 /*
 632  * Remove a fasync entry. If successfully removed, return
 633  * positive and clear the FASYNC flag. If no entry exists,
 634  * do nothing and return 0.
 635  *
 636  * NOTE! It is very important that the FASYNC flag always
 637  * match the state "is the filp on a fasync list".
 638  *
 639  */
 640 static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
 641 {
 642         struct fasync_struct *fa, **fp;
 643         int result = 0;
 644
 645         spin_lock(&filp->f_lock);
 646         spin_lock(&fasync_lock);
 647         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 648                 if (fa->fa_file != filp)
 649                         continue;
 650
 651                 spin_lock_irq(&fa->fa_lock);
 652                 fa->fa_file = NULL;
 653                 spin_unlock_irq(&fa->fa_lock);
 654
 655                 *fp = fa->fa_next;
 656                 call_rcu(&fa->fa_rcu, fasync_free_rcu);
 657                 filp->f_flags &= ~FASYNC;
 658                 result = 1;
 659                 break;
 660         }
 661         spin_unlock(&fasync_lock);
 662         spin_unlock(&filp->f_lock);
 663         return result;
 664 }
 665
 666 /*
 667  * Add a fasync entry. Return negative on error, positive if
 668  * added, and zero if did nothing but change an existing one.
 669  *
 670  * NOTE! It is very important that the FASYNC flag always
 671  * match the state "is the filp on a fasync list".
 672  */
 673 static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
 674 {
 675         struct fasync_struct *new, *fa, **fp;
 676         int result = 0;
 677
 678         new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 679         if (!new)
 680                 return -ENOMEM;
 681
 682         spin_lock(&filp->f_lock);
 683         spin_lock(&fasync_lock);
 684         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 685                 if (fa->fa_file != filp)
 686                         continue;
 687
 688                 spin_lock_irq(&fa->fa_lock);
 689                 fa->fa_fd = fd;
 690                 spin_unlock_irq(&fa->fa_lock);
 691
 692                 kmem_cache_free(fasync_cache, new);
 693                 goto out;
 694         }
 695
 696         spin_lock_init(&new->fa_lock);
 697         new->magic = FASYNC_MAGIC;
 698         new->fa_file = filp;
 699         new->fa_fd = fd;
 700         new->fa_next = *fapp;
 701         rcu_assign_pointer(*fapp, new);
 702         result = 1;
 703         filp->f_flags |= FASYNC;
 704
 705 out:
 706         spin_unlock(&fasync_lock);
 707         spin_unlock(&filp->f_lock);
 708         return result;
 709 }
 710
 711 /*
 712  * fasync_helper() is used by almost all character device drivers
 713  * to set up the fasync queue, and for regular files by the file
 714  * lease code. It returns negative on error, 0 if it did no changes
 715  * and positive if it added/deleted the entry.
 716  */
 717 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 718 {
 719         if (!on)
 720                 return fasync_remove_entry(filp, fapp);
 721         return fasync_add_entry(fd, filp, fapp);
 722 }
 723
 724 EXPORT_SYMBOL(fasync_helper);
 725
 726 /*
 727  * rcu_read_lock() is held
 728  */
 729 static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
 730 {
 731         while (fa) {
 732                 struct fown_struct *fown;
 733                 if (fa->magic != FASYNC_MAGIC) {
 734                         printk(KERN_ERR "kill_fasync: bad magic number in "
 735                                "fasync_struct!\n");
 736                         return;
 737                 }
 738                 spin_lock(&fa->fa_lock);
 739                 if (fa->fa_file) {
 740                         fown = &fa->fa_file->f_owner;
 741                         /* Don't send SIGURG to processes which have not set a
 742                            queued signum: SIGURG has its own default signalling
 743                            mechanism. */
 744                         if (!(sig == SIGURG && fown->signum == 0))
 745                                 send_sigio(fown, fa->fa_fd, band);
 746                 }
 747                 spin_unlock(&fa->fa_lock);
 748                 fa = rcu_dereference(fa->fa_next);
 749         }
 750 }
 751
 752 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 753 {
 754         /* First a quick test without locking: usually
 755          * the list is empty.
 756          */
 757         if (*fp) {
 758                 rcu_read_lock();
 759                 kill_fasync_rcu(rcu_dereference(*fp), sig, band);
 760                 rcu_read_unlock();
 761         }
 762 }
 763 EXPORT_SYMBOL(kill_fasync);
 764
 765 static int __init fasync_init(void)
 766 {
 767         fasync_cache = kmem_cache_create("fasync_cache",
 768                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 769         return 0;
 770 }
 771
 772 module_init(fasync_init)