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/dnotify.h>
  13 #include <linux/smp_lock.h>
  14 #include <linux/slab.h>
  15 #include <linux/module.h>
  16 #include <linux/security.h>
  17 #include <linux/ptrace.h>
  18
  19 #include <asm/poll.h>
  20 #include <asm/siginfo.h>
  21 #include <asm/uaccess.h>
  22
  23 void fastcall set_close_on_exec(unsigned int fd, int flag)
  24 {
  25         struct files_struct *files = current->files;
  26         spin_lock(&files->file_lock);
  27         if (flag)
  28                 FD_SET(fd, files->close_on_exec);
  29         else
  30                 FD_CLR(fd, files->close_on_exec);
  31         spin_unlock(&files->file_lock);
  32 }
  33
  34 static inline int get_close_on_exec(unsigned int fd)
  35 {
  36         struct files_struct *files = current->files;
  37         int res;
  38         spin_lock(&files->file_lock);
  39         res = FD_ISSET(fd, files->close_on_exec);
  40         spin_unlock(&files->file_lock);
  41         return res;
  42 }
  43
  44 /*
  45  * locate_fd finds a free file descriptor in the open_fds fdset,
  46  * expanding the fd arrays if necessary.  Must be called with the
  47  * file_lock held for write.
  48  */
  49
  50 static int locate_fd(struct files_struct *files,
  51                             struct file *file, unsigned int orig_start)
  52 {
  53         unsigned int newfd;
  54         unsigned int start;
  55         int error;
  56
  57         error = -EINVAL;
  58         if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  59                 goto out;
  60
  61 repeat:
  62         /*
  63          * Someone might have closed fd's in the range
  64          * orig_start..files->next_fd
  65          */
  66         start = orig_start;
  67         if (start < files->next_fd)
  68                 start = files->next_fd;
  69
  70         newfd = start;
  71         if (start < files->max_fdset) {
  72                 newfd = find_next_zero_bit(files->open_fds->fds_bits,
  73                         files->max_fdset, start);
  74         }
  75
  76         error = -EMFILE;
  77         if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  78                 goto out;
  79
  80         error = expand_files(files, newfd);
  81         if (error < 0)
  82                 goto out;
  83
  84         /*
  85          * If we needed to expand the fs array we
  86          * might have blocked - try again.
  87          */
  88         if (error)
  89                 goto repeat;
  90
  91         if (start <= files->next_fd)
  92                 files->next_fd = newfd + 1;
  93
  94         error = newfd;
  95
  96 out:
  97         return error;
  98 }
  99
 100 static int dupfd(struct file *file, unsigned int start)
 101 {
 102         struct files_struct * files = current->files;
 103         int fd;
 104
 105         spin_lock(&files->file_lock);
 106         fd = locate_fd(files, file, start);
 107         if (fd >= 0) {
 108                 FD_SET(fd, files->open_fds);
 109                 FD_CLR(fd, files->close_on_exec);
 110                 spin_unlock(&files->file_lock);
 111                 fd_install(fd, file);
 112         } else {
 113                 spin_unlock(&files->file_lock);
 114                 fput(file);
 115         }
 116
 117         return fd;
 118 }
 119
 120 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 121 {
 122         int err = -EBADF;
 123         struct file * file, *tofree;
 124         struct files_struct * files = current->files;
 125
 126         spin_lock(&files->file_lock);
 127         if (!(file = fcheck(oldfd)))
 128                 goto out_unlock;
 129         err = newfd;
 130         if (newfd == oldfd)
 131                 goto out_unlock;
 132         err = -EBADF;
 133         if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 134                 goto out_unlock;
 135         get_file(file);                 /* We are now finished with oldfd */
 136
 137         err = expand_files(files, newfd);
 138         if (err < 0)
 139                 goto out_fput;
 140
 141         /* To avoid races with open() and dup(), we will mark the fd as
 142          * in-use in the open-file bitmap throughout the entire dup2()
 143          * process.  This is quite safe: do_close() uses the fd array
 144          * entry, not the bitmap, to decide what work needs to be
 145          * done.  --sct */
 146         /* Doesn't work. open() might be there first. --AV */
 147
 148         /* Yes. It's a race. In user space. Nothing sane to do */
 149         err = -EBUSY;
 150         tofree = files->fd[newfd];
 151         if (!tofree && FD_ISSET(newfd, files->open_fds))
 152                 goto out_fput;
 153
 154         files->fd[newfd] = file;
 155         FD_SET(newfd, files->open_fds);
 156         FD_CLR(newfd, files->close_on_exec);
 157         spin_unlock(&files->file_lock);
 158
 159         if (tofree)
 160                 filp_close(tofree, files);
 161         err = newfd;
 162 out:
 163         return err;
 164 out_unlock:
 165         spin_unlock(&files->file_lock);
 166         goto out;
 167
 168 out_fput:
 169         spin_unlock(&files->file_lock);
 170         fput(file);
 171         goto out;
 172 }
 173
 174 asmlinkage long sys_dup(unsigned int fildes)
 175 {
 176         int ret = -EBADF;
 177         struct file * file = fget(fildes);
 178
 179         if (file)
 180                 ret = dupfd(file, 0);
 181         return ret;
 182 }
 183
 184 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
 185
 186 static int setfl(int fd, struct file * filp, unsigned long arg)
 187 {
 188         struct inode * inode = filp->f_dentry->d_inode;
 189         int error = 0;
 190
 191         /* O_APPEND cannot be cleared if the file is marked as append-only */
 192         if (!(arg & O_APPEND) && IS_APPEND(inode))
 193                 return -EPERM;
 194
 195         /* O_NOATIME can only be set by the owner or superuser */
 196         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 197                 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
 198                         return -EPERM;
 199
 200         /* required for strict SunOS emulation */
 201         if (O_NONBLOCK != O_NDELAY)
 202                if (arg & O_NDELAY)
 203                    arg |= O_NONBLOCK;
 204
 205         if (arg & O_DIRECT) {
 206                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 207                         !filp->f_mapping->a_ops->direct_IO)
 208                                 return -EINVAL;
 209         }
 210
 211         if (filp->f_op && filp->f_op->check_flags)
 212                 error = filp->f_op->check_flags(arg);
 213         if (error)
 214                 return error;
 215
 216         lock_kernel();
 217         if ((arg ^ filp->f_flags) & FASYNC) {
 218                 if (filp->f_op && filp->f_op->fasync) {
 219                         error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 220                         if (error < 0)
 221                                 goto out;
 222                 }
 223         }
 224
 225         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 226  out:
 227         unlock_kernel();
 228         return error;
 229 }
 230
 231 static void f_modown(struct file *filp, unsigned long pid,
 232                      uid_t uid, uid_t euid, int force)
 233 {
 234         write_lock_irq(&filp->f_owner.lock);
 235         if (force || !filp->f_owner.pid) {
 236                 filp->f_owner.pid = pid;
 237                 filp->f_owner.uid = uid;
 238                 filp->f_owner.euid = euid;
 239         }
 240         write_unlock_irq(&filp->f_owner.lock);
 241 }
 242
 243 int f_setown(struct file *filp, unsigned long arg, int force)
 244 {
 245         int err;
 246
 247         err = security_file_set_fowner(filp);
 248         if (err)
 249                 return err;
 250
 251         f_modown(filp, arg, current->uid, current->euid, force);
 252         return 0;
 253 }
 254
 255 EXPORT_SYMBOL(f_setown);
 256
 257 void f_delown(struct file *filp)
 258 {
 259         f_modown(filp, 0, 0, 0, 1);
 260 }
 261
 262 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 263                 struct file *filp)
 264 {
 265         long err = -EINVAL;
 266
 267         switch (cmd) {
 268         case F_DUPFD:
 269                 get_file(filp);
 270                 err = dupfd(filp, arg);
 271                 break;
 272         case F_GETFD:
 273                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 274                 break;
 275         case F_SETFD:
 276                 err = 0;
 277                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 278                 break;
 279         case F_GETFL:
 280                 err = filp->f_flags;
 281                 break;
 282         case F_SETFL:
 283                 err = setfl(fd, filp, arg);
 284                 break;
 285         case F_GETLK:
 286                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 287                 break;
 288         case F_SETLK:
 289         case F_SETLKW:
 290                 err = fcntl_setlk(filp, cmd, (struct flock __user *) arg);
 291                 break;
 292         case F_GETOWN:
 293                 /*
 294                  * XXX If f_owner is a process group, the
 295                  * negative return value will get converted
 296                  * into an error.  Oops.  If we keep the
 297                  * current syscall conventions, the only way
 298                  * to fix this will be in libc.
 299                  */
 300                 err = filp->f_owner.pid;
 301                 force_successful_syscall_return();
 302                 break;
 303         case F_SETOWN:
 304                 err = f_setown(filp, arg, 1);
 305                 break;
 306         case F_GETSIG:
 307                 err = filp->f_owner.signum;
 308                 break;
 309         case F_SETSIG:
 310                 /* arg == 0 restores default behaviour. */
 311                 if (arg < 0 || arg > _NSIG) {
 312                         break;
 313                 }
 314                 err = 0;
 315                 filp->f_owner.signum = arg;
 316                 break;
 317         case F_GETLEASE:
 318                 err = fcntl_getlease(filp);
 319                 break;
 320         case F_SETLEASE:
 321                 err = fcntl_setlease(fd, filp, arg);
 322                 break;
 323         case F_NOTIFY:
 324                 err = fcntl_dirnotify(fd, filp, arg);
 325                 break;
 326         default:
 327                 break;
 328         }
 329         return err;
 330 }
 331
 332 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
 333 {
 334         struct file *filp;
 335         long err = -EBADF;
 336
 337         filp = fget(fd);
 338         if (!filp)
 339                 goto out;
 340
 341         err = security_file_fcntl(filp, cmd, arg);
 342         if (err) {
 343                 fput(filp);
 344                 return err;
 345         }
 346
 347         err = do_fcntl(fd, cmd, arg, filp);
 348
 349         fput(filp);
 350 out:
 351         return err;
 352 }
 353
 354 #if BITS_PER_LONG == 32
 355 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 356 {
 357         struct file * filp;
 358         long err;
 359
 360         err = -EBADF;
 361         filp = fget(fd);
 362         if (!filp)
 363                 goto out;
 364
 365         err = security_file_fcntl(filp, cmd, arg);
 366         if (err) {
 367                 fput(filp);
 368                 return err;
 369         }
 370         err = -EBADF;
 371
 372         switch (cmd) {
 373                 case F_GETLK64:
 374                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 375                         break;
 376                 case F_SETLK64:
 377                 case F_SETLKW64:
 378                         err = fcntl_setlk64(filp, cmd, (struct flock64 __user *) arg);
 379                         break;
 380                 default:
 381                         err = do_fcntl(fd, cmd, arg, filp);
 382                         break;
 383         }
 384         fput(filp);
 385 out:
 386         return err;
 387 }
 388 #endif
 389
 390 /* Table to convert sigio signal codes into poll band bitmaps */
 391
 392 static long band_table[NSIGPOLL] = {
 393         POLLIN | POLLRDNORM,                    /* POLL_IN */
 394         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 395         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 396         POLLERR,                                /* POLL_ERR */
 397         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 398         POLLHUP | POLLERR                       /* POLL_HUP */
 399 };
 400
 401 static inline int sigio_perm(struct task_struct *p,
 402                              struct fown_struct *fown, int sig)
 403 {
 404         return (((fown->euid == 0) ||
 405                  (fown->euid == p->suid) || (fown->euid == p->uid) ||
 406                  (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 407                 !security_file_send_sigiotask(p, fown, sig));
 408 }
 409
 410 static void send_sigio_to_task(struct task_struct *p,
 411                                struct fown_struct *fown,
 412                                int fd,
 413                                int reason)
 414 {
 415         if (!sigio_perm(p, fown, fown->signum))
 416                 return;
 417
 418         switch (fown->signum) {
 419                 siginfo_t si;
 420                 default:
 421                         /* Queue a rt signal with the appropriate fd as its
 422                            value.  We use SI_SIGIO as the source, not
 423                            SI_KERNEL, since kernel signals always get
 424                            delivered even if we can't queue.  Failure to
 425                            queue in this case _should_ be reported; we fall
 426                            back to SIGIO in that case. --sct */
 427                         si.si_signo = fown->signum;
 428                         si.si_errno = 0;
 429                         si.si_code  = reason;
 430                         /* Make sure we are called with one of the POLL_*
 431                            reasons, otherwise we could leak kernel stack into
 432                            userspace.  */
 433                         if ((reason & __SI_MASK) != __SI_POLL)
 434                                 BUG();
 435                         if (reason - POLL_IN >= NSIGPOLL)
 436                                 si.si_band  = ~0L;
 437                         else
 438                                 si.si_band = band_table[reason - POLL_IN];
 439                         si.si_fd    = fd;
 440                         if (!send_group_sig_info(fown->signum, &si, p))
 441                                 break;
 442                 /* fall-through: fall back on the old plain SIGIO signal */
 443                 case 0:
 444                         send_group_sig_info(SIGIO, SEND_SIG_PRIV, p);
 445         }
 446 }
 447
 448 void send_sigio(struct fown_struct *fown, int fd, int band)
 449 {
 450         struct task_struct *p;
 451         int pid;
 452
 453         read_lock(&fown->lock);
 454         pid = fown->pid;
 455         if (!pid)
 456                 goto out_unlock_fown;
 457
 458         read_lock(&tasklist_lock);
 459         if (pid > 0) {
 460                 p = find_task_by_pid(pid);
 461                 if (p) {
 462                         send_sigio_to_task(p, fown, fd, band);
 463                 }
 464         } else {
 465                 do_each_task_pid(-pid, PIDTYPE_PGID, p) {
 466                         send_sigio_to_task(p, fown, fd, band);
 467                 } while_each_task_pid(-pid, PIDTYPE_PGID, p);
 468         }
 469         read_unlock(&tasklist_lock);
 470  out_unlock_fown:
 471         read_unlock(&fown->lock);
 472 }
 473
 474 static void send_sigurg_to_task(struct task_struct *p,
 475                                 struct fown_struct *fown)
 476 {
 477         if (sigio_perm(p, fown, SIGURG))
 478                 send_group_sig_info(SIGURG, SEND_SIG_PRIV, p);
 479 }
 480
 481 int send_sigurg(struct fown_struct *fown)
 482 {
 483         struct task_struct *p;
 484         int pid, ret = 0;
 485
 486         read_lock(&fown->lock);
 487         pid = fown->pid;
 488         if (!pid)
 489                 goto out_unlock_fown;
 490
 491         ret = 1;
 492
 493         read_lock(&tasklist_lock);
 494         if (pid > 0) {
 495                 p = find_task_by_pid(pid);
 496                 if (p) {
 497                         send_sigurg_to_task(p, fown);
 498                 }
 499         } else {
 500                 do_each_task_pid(-pid, PIDTYPE_PGID, p) {
 501                         send_sigurg_to_task(p, fown);
 502                 } while_each_task_pid(-pid, PIDTYPE_PGID, p);
 503         }
 504         read_unlock(&tasklist_lock);
 505  out_unlock_fown:
 506         read_unlock(&fown->lock);
 507         return ret;
 508 }
 509
 510 static DEFINE_RWLOCK(fasync_lock);
 511 static kmem_cache_t *fasync_cache;
 512
 513 /*
 514  * fasync_helper() is used by some character device drivers (mainly mice)
 515  * to set up the fasync queue. It returns negative on error, 0 if it did
 516  * no changes and positive if it added/deleted the entry.
 517  */
 518 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 519 {
 520         struct fasync_struct *fa, **fp;
 521         struct fasync_struct *new = NULL;
 522         int result = 0;
 523
 524         if (on) {
 525                 new = kmem_cache_alloc(fasync_cache, SLAB_KERNEL);
 526                 if (!new)
 527                         return -ENOMEM;
 528         }
 529         write_lock_irq(&fasync_lock);
 530         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 531                 if (fa->fa_file == filp) {
 532                         if(on) {
 533                                 fa->fa_fd = fd;
 534                                 kmem_cache_free(fasync_cache, new);
 535                         } else {
 536                                 *fp = fa->fa_next;
 537                                 kmem_cache_free(fasync_cache, fa);
 538                                 result = 1;
 539                         }
 540                         goto out;
 541                 }
 542         }
 543
 544         if (on) {
 545                 new->magic = FASYNC_MAGIC;
 546                 new->fa_file = filp;
 547                 new->fa_fd = fd;
 548                 new->fa_next = *fapp;
 549                 *fapp = new;
 550                 result = 1;
 551         }
 552 out:
 553         write_unlock_irq(&fasync_lock);
 554         return result;
 555 }
 556
 557 EXPORT_SYMBOL(fasync_helper);
 558
 559 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 560 {
 561         while (fa) {
 562                 struct fown_struct * fown;
 563                 if (fa->magic != FASYNC_MAGIC) {
 564                         printk(KERN_ERR "kill_fasync: bad magic number in "
 565                                "fasync_struct!\n");
 566                         return;
 567                 }
 568                 fown = &fa->fa_file->f_owner;
 569                 /* Don't send SIGURG to processes which have not set a
 570                    queued signum: SIGURG has its own default signalling
 571                    mechanism. */
 572                 if (!(sig == SIGURG && fown->signum == 0))
 573                         send_sigio(fown, fa->fa_fd, band);
 574                 fa = fa->fa_next;
 575         }
 576 }
 577
 578 EXPORT_SYMBOL(__kill_fasync);
 579
 580 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 581 {
 582         /* First a quick test without locking: usually
 583          * the list is empty.
 584          */
 585         if (*fp) {
 586                 read_lock(&fasync_lock);
 587                 /* reread *fp after obtaining the lock */
 588                 __kill_fasync(*fp, sig, band);
 589                 read_unlock(&fasync_lock);
 590         }
 591 }
 592 EXPORT_SYMBOL(kill_fasync);
 593
 594 static int __init fasync_init(void)
 595 {
 596         fasync_cache = kmem_cache_create("fasync_cache",
 597                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
 598         return 0;
 599 }
 600
 601 module_init(fasync_init)