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 #include <linux/user_namespace.h>
  24 #include <linux/shmem_fs.h>
  25
  26 #include <asm/poll.h>
  27 #include <asm/siginfo.h>
  28 #include <asm/uaccess.h>
  29
  30 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
  31
  32 static int setfl(int fd, struct file * filp, unsigned long arg)
  33 {
  34         struct inode * inode = file_inode(filp);
  35         int error = 0;
  36
  37         /*
  38          * O_APPEND cannot be cleared if the file is marked as append-only
  39          * and the file is open for write.
  40          */
  41         if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
  42                 return -EPERM;
  43
  44         /* O_NOATIME can only be set by the owner or superuser */
  45         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
  46                 if (!inode_owner_or_capable(inode))
  47                         return -EPERM;
  48
  49         /* required for strict SunOS emulation */
  50         if (O_NONBLOCK != O_NDELAY)
  51                if (arg & O_NDELAY)
  52                    arg |= O_NONBLOCK;
  53
  54         /* Pipe packetized mode is controlled by O_DIRECT flag */
  55         if (!S_ISFIFO(filp->f_inode->i_mode) && (arg & O_DIRECT)) {
  56                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
  57                         !filp->f_mapping->a_ops->direct_IO)
  58                                 return -EINVAL;
  59         }
  60
  61         if (filp->f_op->check_flags)
  62                 error = filp->f_op->check_flags(arg);
  63         if (error)
  64                 return error;
  65
  66         /*
  67          * ->fasync() is responsible for setting the FASYNC bit.
  68          */
  69         if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op->fasync) {
  70                 error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
  71                 if (error < 0)
  72                         goto out;
  73                 if (error > 0)
  74                         error = 0;
  75         }
  76         spin_lock(&filp->f_lock);
  77         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
  78         spin_unlock(&filp->f_lock);
  79
  80  out:
  81         return error;
  82 }
  83
  84 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
  85                      int force)
  86 {
  87         write_lock_irq(&filp->f_owner.lock);
  88         if (force || !filp->f_owner.pid) {
  89                 put_pid(filp->f_owner.pid);
  90                 filp->f_owner.pid = get_pid(pid);
  91                 filp->f_owner.pid_type = type;
  92
  93                 if (pid) {
  94                         const struct cred *cred = current_cred();
  95                         filp->f_owner.uid = cred->uid;
  96                         filp->f_owner.euid = cred->euid;
  97                 }
  98         }
  99         write_unlock_irq(&filp->f_owner.lock);
 100 }
 101
 102 void __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
 103                 int force)
 104 {
 105         security_file_set_fowner(filp);
 106         f_modown(filp, pid, type, force);
 107 }
 108 EXPORT_SYMBOL(__f_setown);
 109
 110 void f_setown(struct file *filp, unsigned long arg, int force)
 111 {
 112         enum pid_type type;
 113         struct pid *pid;
 114         int who = arg;
 115         type = PIDTYPE_PID;
 116         if (who < 0) {
 117                 type = PIDTYPE_PGID;
 118                 who = -who;
 119         }
 120         rcu_read_lock();
 121         pid = find_vpid(who);
 122         __f_setown(filp, pid, type, force);
 123         rcu_read_unlock();
 124 }
 125 EXPORT_SYMBOL(f_setown);
 126
 127 void f_delown(struct file *filp)
 128 {
 129         f_modown(filp, NULL, PIDTYPE_PID, 1);
 130 }
 131
 132 pid_t f_getown(struct file *filp)
 133 {
 134         pid_t pid;
 135         read_lock(&filp->f_owner.lock);
 136         pid = pid_vnr(filp->f_owner.pid);
 137         if (filp->f_owner.pid_type == PIDTYPE_PGID)
 138                 pid = -pid;
 139         read_unlock(&filp->f_owner.lock);
 140         return pid;
 141 }
 142
 143 static int f_setown_ex(struct file *filp, unsigned long arg)
 144 {
 145         struct f_owner_ex __user *owner_p = (void __user *)arg;
 146         struct f_owner_ex owner;
 147         struct pid *pid;
 148         int type;
 149         int ret;
 150
 151         ret = copy_from_user(&owner, owner_p, sizeof(owner));
 152         if (ret)
 153                 return -EFAULT;
 154
 155         switch (owner.type) {
 156         case F_OWNER_TID:
 157                 type = PIDTYPE_MAX;
 158                 break;
 159
 160         case F_OWNER_PID:
 161                 type = PIDTYPE_PID;
 162                 break;
 163
 164         case F_OWNER_PGRP:
 165                 type = PIDTYPE_PGID;
 166                 break;
 167
 168         default:
 169                 return -EINVAL;
 170         }
 171
 172         rcu_read_lock();
 173         pid = find_vpid(owner.pid);
 174         if (owner.pid && !pid)
 175                 ret = -ESRCH;
 176         else
 177                  __f_setown(filp, pid, type, 1);
 178         rcu_read_unlock();
 179
 180         return ret;
 181 }
 182
 183 static int f_getown_ex(struct file *filp, unsigned long arg)
 184 {
 185         struct f_owner_ex __user *owner_p = (void __user *)arg;
 186         struct f_owner_ex owner;
 187         int ret = 0;
 188
 189         read_lock(&filp->f_owner.lock);
 190         owner.pid = pid_vnr(filp->f_owner.pid);
 191         switch (filp->f_owner.pid_type) {
 192         case PIDTYPE_MAX:
 193                 owner.type = F_OWNER_TID;
 194                 break;
 195
 196         case PIDTYPE_PID:
 197                 owner.type = F_OWNER_PID;
 198                 break;
 199
 200         case PIDTYPE_PGID:
 201                 owner.type = F_OWNER_PGRP;
 202                 break;
 203
 204         default:
 205                 WARN_ON(1);
 206                 ret = -EINVAL;
 207                 break;
 208         }
 209         read_unlock(&filp->f_owner.lock);
 210
 211         if (!ret) {
 212                 ret = copy_to_user(owner_p, &owner, sizeof(owner));
 213                 if (ret)
 214                         ret = -EFAULT;
 215         }
 216         return ret;
 217 }
 218
 219 #ifdef CONFIG_CHECKPOINT_RESTORE
 220 static int f_getowner_uids(struct file *filp, unsigned long arg)
 221 {
 222         struct user_namespace *user_ns = current_user_ns();
 223         uid_t __user *dst = (void __user *)arg;
 224         uid_t src[2];
 225         int err;
 226
 227         read_lock(&filp->f_owner.lock);
 228         src[0] = from_kuid(user_ns, filp->f_owner.uid);
 229         src[1] = from_kuid(user_ns, filp->f_owner.euid);
 230         read_unlock(&filp->f_owner.lock);
 231
 232         err  = put_user(src[0], &dst[0]);
 233         err |= put_user(src[1], &dst[1]);
 234
 235         return err;
 236 }
 237 #else
 238 static int f_getowner_uids(struct file *filp, unsigned long arg)
 239 {
 240         return -EINVAL;
 241 }
 242 #endif
 243
 244 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 245                 struct file *filp)
 246 {
 247         long err = -EINVAL;
 248
 249         switch (cmd) {
 250         case F_DUPFD:
 251                 err = f_dupfd(arg, filp, 0);
 252                 break;
 253         case F_DUPFD_CLOEXEC:
 254                 err = f_dupfd(arg, filp, O_CLOEXEC);
 255                 break;
 256         case F_GETFD:
 257                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 258                 break;
 259         case F_SETFD:
 260                 err = 0;
 261                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 262                 break;
 263         case F_GETFL:
 264                 err = filp->f_flags;
 265                 break;
 266         case F_SETFL:
 267                 err = setfl(fd, filp, arg);
 268                 break;
 269 #if BITS_PER_LONG != 32
 270         /* 32-bit arches must use fcntl64() */
 271         case F_OFD_GETLK:
 272 #endif
 273         case F_GETLK:
 274                 err = fcntl_getlk(filp, cmd, (struct flock __user *) arg);
 275                 break;
 276 #if BITS_PER_LONG != 32
 277         /* 32-bit arches must use fcntl64() */
 278         case F_OFD_SETLK:
 279         case F_OFD_SETLKW:
 280 #endif
 281                 /* Fallthrough */
 282         case F_SETLK:
 283         case F_SETLKW:
 284                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 285                 break;
 286         case F_GETOWN:
 287                 /*
 288                  * XXX If f_owner is a process group, the
 289                  * negative return value will get converted
 290                  * into an error.  Oops.  If we keep the
 291                  * current syscall conventions, the only way
 292                  * to fix this will be in libc.
 293                  */
 294                 err = f_getown(filp);
 295                 force_successful_syscall_return();
 296                 break;
 297         case F_SETOWN:
 298                 f_setown(filp, arg, 1);
 299                 err = 0;
 300                 break;
 301         case F_GETOWN_EX:
 302                 err = f_getown_ex(filp, arg);
 303                 break;
 304         case F_SETOWN_EX:
 305                 err = f_setown_ex(filp, arg);
 306                 break;
 307         case F_GETOWNER_UIDS:
 308                 err = f_getowner_uids(filp, arg);
 309                 break;
 310         case F_GETSIG:
 311                 err = filp->f_owner.signum;
 312                 break;
 313         case F_SETSIG:
 314                 /* arg == 0 restores default behaviour. */
 315                 if (!valid_signal(arg)) {
 316                         break;
 317                 }
 318                 err = 0;
 319                 filp->f_owner.signum = arg;
 320                 break;
 321         case F_GETLEASE:
 322                 err = fcntl_getlease(filp);
 323                 break;
 324         case F_SETLEASE:
 325                 err = fcntl_setlease(fd, filp, arg);
 326                 break;
 327         case F_NOTIFY:
 328                 err = fcntl_dirnotify(fd, filp, arg);
 329                 break;
 330         case F_SETPIPE_SZ:
 331         case F_GETPIPE_SZ:
 332                 err = pipe_fcntl(filp, cmd, arg);
 333                 break;
 334         case F_ADD_SEALS:
 335         case F_GET_SEALS:
 336                 err = shmem_fcntl(filp, cmd, arg);
 337                 break;
 338         default:
 339                 break;
 340         }
 341         return err;
 342 }
 343
 344 static int check_fcntl_cmd(unsigned cmd)
 345 {
 346         switch (cmd) {
 347         case F_DUPFD:
 348         case F_DUPFD_CLOEXEC:
 349         case F_GETFD:
 350         case F_SETFD:
 351         case F_GETFL:
 352                 return 1;
 353         }
 354         return 0;
 355 }
 356
 357 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
 358 {
 359         struct fd f = fdget_raw(fd);
 360         long err = -EBADF;
 361
 362         if (!f.file)
 363                 goto out;
 364
 365         if (unlikely(f.file->f_mode & FMODE_PATH)) {
 366                 if (!check_fcntl_cmd(cmd))
 367                         goto out1;
 368         }
 369
 370         err = security_file_fcntl(f.file, cmd, arg);
 371         if (!err)
 372                 err = do_fcntl(fd, cmd, arg, f.file);
 373
 374 out1:
 375         fdput(f);
 376 out:
 377         return err;
 378 }
 379
 380 #if BITS_PER_LONG == 32
 381 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 382                 unsigned long, arg)
 383 {
 384         struct fd f = fdget_raw(fd);
 385         long err = -EBADF;
 386
 387         if (!f.file)
 388                 goto out;
 389
 390         if (unlikely(f.file->f_mode & FMODE_PATH)) {
 391                 if (!check_fcntl_cmd(cmd))
 392                         goto out1;
 393         }
 394
 395         err = security_file_fcntl(f.file, cmd, arg);
 396         if (err)
 397                 goto out1;
 398
 399         switch (cmd) {
 400         case F_GETLK64:
 401         case F_OFD_GETLK:
 402                 err = fcntl_getlk64(f.file, cmd, (struct flock64 __user *) arg);
 403                 break;
 404         case F_SETLK64:
 405         case F_SETLKW64:
 406         case F_OFD_SETLK:
 407         case F_OFD_SETLKW:
 408                 err = fcntl_setlk64(fd, f.file, cmd,
 409                                 (struct flock64 __user *) arg);
 410                 break;
 411         default:
 412                 err = do_fcntl(fd, cmd, arg, f.file);
 413                 break;
 414         }
 415 out1:
 416         fdput(f);
 417 out:
 418         return err;
 419 }
 420 #endif
 421
 422 /* Table to convert sigio signal codes into poll band bitmaps */
 423
 424 static const long band_table[NSIGPOLL] = {
 425         POLLIN | POLLRDNORM,                    /* POLL_IN */
 426         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 427         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 428         POLLERR,                                /* POLL_ERR */
 429         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 430         POLLHUP | POLLERR                       /* POLL_HUP */
 431 };
 432
 433 static inline int sigio_perm(struct task_struct *p,
 434                              struct fown_struct *fown, int sig)
 435 {
 436         const struct cred *cred;
 437         int ret;
 438
 439         rcu_read_lock();
 440         cred = __task_cred(p);
 441         ret = ((uid_eq(fown->euid, GLOBAL_ROOT_UID) ||
 442                 uid_eq(fown->euid, cred->suid) || uid_eq(fown->euid, cred->uid) ||
 443                 uid_eq(fown->uid,  cred->suid) || uid_eq(fown->uid,  cred->uid)) &&
 444                !security_file_send_sigiotask(p, fown, sig));
 445         rcu_read_unlock();
 446         return ret;
 447 }
 448
 449 static void send_sigio_to_task(struct task_struct *p,
 450                                struct fown_struct *fown,
 451                                int fd, int reason, int group)
 452 {
 453         /*
 454          * F_SETSIG can change ->signum lockless in parallel, make
 455          * sure we read it once and use the same value throughout.
 456          */
 457         int signum = ACCESS_ONCE(fown->signum);
 458
 459         if (!sigio_perm(p, fown, signum))
 460                 return;
 461
 462         switch (signum) {
 463                 siginfo_t si;
 464                 default:
 465                         /* Queue a rt signal with the appropriate fd as its
 466                            value.  We use SI_SIGIO as the source, not
 467                            SI_KERNEL, since kernel signals always get
 468                            delivered even if we can't queue.  Failure to
 469                            queue in this case _should_ be reported; we fall
 470                            back to SIGIO in that case. --sct */
 471                         si.si_signo = signum;
 472                         si.si_errno = 0;
 473                         si.si_code  = reason;
 474                         /* Make sure we are called with one of the POLL_*
 475                            reasons, otherwise we could leak kernel stack into
 476                            userspace.  */
 477                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 478                         if (reason - POLL_IN >= NSIGPOLL)
 479                                 si.si_band  = ~0L;
 480                         else
 481                                 si.si_band = band_table[reason - POLL_IN];
 482                         si.si_fd    = fd;
 483                         if (!do_send_sig_info(signum, &si, p, group))
 484                                 break;
 485                 /* fall-through: fall back on the old plain SIGIO signal */
 486                 case 0:
 487                         do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, group);
 488         }
 489 }
 490
 491 void send_sigio(struct fown_struct *fown, int fd, int band)
 492 {
 493         struct task_struct *p;
 494         enum pid_type type;
 495         struct pid *pid;
 496         int group = 1;
 497
 498         read_lock(&fown->lock);
 499
 500         type = fown->pid_type;
 501         if (type == PIDTYPE_MAX) {
 502                 group = 0;
 503                 type = PIDTYPE_PID;
 504         }
 505
 506         pid = fown->pid;
 507         if (!pid)
 508                 goto out_unlock_fown;
 509
 510         read_lock(&tasklist_lock);
 511         do_each_pid_task(pid, type, p) {
 512                 send_sigio_to_task(p, fown, fd, band, group);
 513         } while_each_pid_task(pid, type, p);
 514         read_unlock(&tasklist_lock);
 515  out_unlock_fown:
 516         read_unlock(&fown->lock);
 517 }
 518
 519 static void send_sigurg_to_task(struct task_struct *p,
 520                                 struct fown_struct *fown, int group)
 521 {
 522         if (sigio_perm(p, fown, SIGURG))
 523                 do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, group);
 524 }
 525
 526 int send_sigurg(struct fown_struct *fown)
 527 {
 528         struct task_struct *p;
 529         enum pid_type type;
 530         struct pid *pid;
 531         int group = 1;
 532         int ret = 0;
 533
 534         read_lock(&fown->lock);
 535
 536         type = fown->pid_type;
 537         if (type == PIDTYPE_MAX) {
 538                 group = 0;
 539                 type = PIDTYPE_PID;
 540         }
 541
 542         pid = fown->pid;
 543         if (!pid)
 544                 goto out_unlock_fown;
 545
 546         ret = 1;
 547
 548         read_lock(&tasklist_lock);
 549         do_each_pid_task(pid, type, p) {
 550                 send_sigurg_to_task(p, fown, group);
 551         } while_each_pid_task(pid, type, p);
 552         read_unlock(&tasklist_lock);
 553  out_unlock_fown:
 554         read_unlock(&fown->lock);
 555         return ret;
 556 }
 557
 558 static DEFINE_SPINLOCK(fasync_lock);
 559 static struct kmem_cache *fasync_cache __read_mostly;
 560
 561 static void fasync_free_rcu(struct rcu_head *head)
 562 {
 563         kmem_cache_free(fasync_cache,
 564                         container_of(head, struct fasync_struct, fa_rcu));
 565 }
 566
 567 /*
 568  * Remove a fasync entry. If successfully removed, return
 569  * positive and clear the FASYNC flag. If no entry exists,
 570  * do nothing and return 0.
 571  *
 572  * NOTE! It is very important that the FASYNC flag always
 573  * match the state "is the filp on a fasync list".
 574  *
 575  */
 576 int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
 577 {
 578         struct fasync_struct *fa, **fp;
 579         int result = 0;
 580
 581         spin_lock(&filp->f_lock);
 582         spin_lock(&fasync_lock);
 583         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 584                 if (fa->fa_file != filp)
 585                         continue;
 586
 587                 spin_lock_irq(&fa->fa_lock);
 588                 fa->fa_file = NULL;
 589                 spin_unlock_irq(&fa->fa_lock);
 590
 591                 *fp = fa->fa_next;
 592                 call_rcu(&fa->fa_rcu, fasync_free_rcu);
 593                 filp->f_flags &= ~FASYNC;
 594                 result = 1;
 595                 break;
 596         }
 597         spin_unlock(&fasync_lock);
 598         spin_unlock(&filp->f_lock);
 599         return result;
 600 }
 601
 602 struct fasync_struct *fasync_alloc(void)
 603 {
 604         return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 605 }
 606
 607 /*
 608  * NOTE! This can be used only for unused fasync entries:
 609  * entries that actually got inserted on the fasync list
 610  * need to be released by rcu - see fasync_remove_entry.
 611  */
 612 void fasync_free(struct fasync_struct *new)
 613 {
 614         kmem_cache_free(fasync_cache, new);
 615 }
 616
 617 /*
 618  * Insert a new entry into the fasync list.  Return the pointer to the
 619  * old one if we didn't use the new one.
 620  *
 621  * NOTE! It is very important that the FASYNC flag always
 622  * match the state "is the filp on a fasync list".
 623  */
 624 struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
 625 {
 626         struct fasync_struct *fa, **fp;
 627
 628         spin_lock(&filp->f_lock);
 629         spin_lock(&fasync_lock);
 630         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 631                 if (fa->fa_file != filp)
 632                         continue;
 633
 634                 spin_lock_irq(&fa->fa_lock);
 635                 fa->fa_fd = fd;
 636                 spin_unlock_irq(&fa->fa_lock);
 637                 goto out;
 638         }
 639
 640         spin_lock_init(&new->fa_lock);
 641         new->magic = FASYNC_MAGIC;
 642         new->fa_file = filp;
 643         new->fa_fd = fd;
 644         new->fa_next = *fapp;
 645         rcu_assign_pointer(*fapp, new);
 646         filp->f_flags |= FASYNC;
 647
 648 out:
 649         spin_unlock(&fasync_lock);
 650         spin_unlock(&filp->f_lock);
 651         return fa;
 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 static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
 659 {
 660         struct fasync_struct *new;
 661
 662         new = fasync_alloc();
 663         if (!new)
 664                 return -ENOMEM;
 665
 666         /*
 667          * fasync_insert_entry() returns the old (update) entry if
 668          * it existed.
 669          *
 670          * So free the (unused) new entry and return 0 to let the
 671          * caller know that we didn't add any new fasync entries.
 672          */
 673         if (fasync_insert_entry(fd, filp, fapp, new)) {
 674                 fasync_free(new);
 675                 return 0;
 676         }
 677
 678         return 1;
 679 }
 680
 681 /*
 682  * fasync_helper() is used by almost all character device drivers
 683  * to set up the fasync queue, and for regular files by the file
 684  * lease code. It returns negative on error, 0 if it did no changes
 685  * and positive if it added/deleted the entry.
 686  */
 687 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 688 {
 689         if (!on)
 690                 return fasync_remove_entry(filp, fapp);
 691         return fasync_add_entry(fd, filp, fapp);
 692 }
 693
 694 EXPORT_SYMBOL(fasync_helper);
 695
 696 /*
 697  * rcu_read_lock() is held
 698  */
 699 static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
 700 {
 701         while (fa) {
 702                 struct fown_struct *fown;
 703                 unsigned long flags;
 704
 705                 if (fa->magic != FASYNC_MAGIC) {
 706                         printk(KERN_ERR "kill_fasync: bad magic number in "
 707                                "fasync_struct!\n");
 708                         return;
 709                 }
 710                 spin_lock_irqsave(&fa->fa_lock, flags);
 711                 if (fa->fa_file) {
 712                         fown = &fa->fa_file->f_owner;
 713                         /* Don't send SIGURG to processes which have not set a
 714                            queued signum: SIGURG has its own default signalling
 715                            mechanism. */
 716                         if (!(sig == SIGURG && fown->signum == 0))
 717                                 send_sigio(fown, fa->fa_fd, band);
 718                 }
 719                 spin_unlock_irqrestore(&fa->fa_lock, flags);
 720                 fa = rcu_dereference(fa->fa_next);
 721         }
 722 }
 723
 724 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 725 {
 726         /* First a quick test without locking: usually
 727          * the list is empty.
 728          */
 729         if (*fp) {
 730                 rcu_read_lock();
 731                 kill_fasync_rcu(rcu_dereference(*fp), sig, band);
 732                 rcu_read_unlock();
 733         }
 734 }
 735 EXPORT_SYMBOL(kill_fasync);
 736
 737 static int __init fcntl_init(void)
 738 {
 739         /*
 740          * Please add new bits here to ensure allocation uniqueness.
 741          * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
 742          * is defined as O_NONBLOCK on some platforms and not on others.
 743          */
 744         BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
 745                 HWEIGHT32(
 746                         (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
 747                         __FMODE_EXEC | __FMODE_NONOTIFY));
 748
 749         fasync_cache = kmem_cache_create("fasync_cache",
 750                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 751         return 0;
 752 }
 753
 754 module_init(fcntl_init)