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 #include <linux/signal.h>
  19 #include <linux/rcupdate.h>
  20
  21 #include <asm/poll.h>
  22 #include <asm/siginfo.h>
  23 #include <asm/uaccess.h>
  24
  25 void fastcall set_close_on_exec(unsigned int fd, int flag)
  26 {
  27         struct files_struct *files = current->files;
  28         struct fdtable *fdt;
  29         spin_lock(&files->file_lock);
  30         fdt = files_fdtable(files);
  31         if (flag)
  32                 FD_SET(fd, fdt->close_on_exec);
  33         else
  34                 FD_CLR(fd, fdt->close_on_exec);
  35         spin_unlock(&files->file_lock);
  36 }
  37
  38 static inline int get_close_on_exec(unsigned int fd)
  39 {
  40         struct files_struct *files = current->files;
  41         struct fdtable *fdt;
  42         int res;
  43         rcu_read_lock();
  44         fdt = files_fdtable(files);
  45         res = FD_ISSET(fd, fdt->close_on_exec);
  46         rcu_read_unlock();
  47         return res;
  48 }
  49
  50 /*
  51  * locate_fd finds a free file descriptor in the open_fds fdset,
  52  * expanding the fd arrays if necessary.  Must be called with the
  53  * file_lock held for write.
  54  */
  55
  56 static int locate_fd(struct files_struct *files,
  57                             struct file *file, unsigned int orig_start)
  58 {
  59         unsigned int newfd;
  60         unsigned int start;
  61         int error;
  62         struct fdtable *fdt;
  63
  64         error = -EINVAL;
  65         if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  66                 goto out;
  67
  68 repeat:
  69         fdt = files_fdtable(files);
  70         /*
  71          * Someone might have closed fd's in the range
  72          * orig_start..fdt->next_fd
  73          */
  74         start = orig_start;
  75         if (start < fdt->next_fd)
  76                 start = fdt->next_fd;
  77
  78         newfd = start;
  79         if (start < fdt->max_fdset) {
  80                 newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
  81                         fdt->max_fdset, start);
  82         }
  83
  84         error = -EMFILE;
  85         if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  86                 goto out;
  87
  88         error = expand_files(files, newfd);
  89         if (error < 0)
  90                 goto out;
  91
  92         /*
  93          * If we needed to expand the fs array we
  94          * might have blocked - try again.
  95          */
  96         if (error)
  97                 goto repeat;
  98
  99         /*
 100          * We reacquired files_lock, so we are safe as long as
 101          * we reacquire the fdtable pointer and use it while holding
 102          * the lock, no one can free it during that time.
 103          */
 104         fdt = files_fdtable(files);
 105         if (start <= fdt->next_fd)
 106                 fdt->next_fd = newfd + 1;
 107
 108         error = newfd;
 109
 110 out:
 111         return error;
 112 }
 113
 114 static int dupfd(struct file *file, unsigned int start)
 115 {
 116         struct files_struct * files = current->files;
 117         struct fdtable *fdt;
 118         int fd;
 119
 120         spin_lock(&files->file_lock);
 121         fd = locate_fd(files, file, start);
 122         if (fd >= 0) {
 123                 /* locate_fd() may have expanded fdtable, load the ptr */
 124                 fdt = files_fdtable(files);
 125                 FD_SET(fd, fdt->open_fds);
 126                 FD_CLR(fd, fdt->close_on_exec);
 127                 spin_unlock(&files->file_lock);
 128                 fd_install(fd, file);
 129         } else {
 130                 spin_unlock(&files->file_lock);
 131                 fput(file);
 132         }
 133
 134         return fd;
 135 }
 136
 137 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 138 {
 139         int err = -EBADF;
 140         struct file * file, *tofree;
 141         struct files_struct * files = current->files;
 142         struct fdtable *fdt;
 143
 144         spin_lock(&files->file_lock);
 145         if (!(file = fcheck(oldfd)))
 146                 goto out_unlock;
 147         err = newfd;
 148         if (newfd == oldfd)
 149                 goto out_unlock;
 150         err = -EBADF;
 151         if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 152                 goto out_unlock;
 153         get_file(file);                 /* We are now finished with oldfd */
 154
 155         err = expand_files(files, newfd);
 156         if (err < 0)
 157                 goto out_fput;
 158
 159         /* To avoid races with open() and dup(), we will mark the fd as
 160          * in-use in the open-file bitmap throughout the entire dup2()
 161          * process.  This is quite safe: do_close() uses the fd array
 162          * entry, not the bitmap, to decide what work needs to be
 163          * done.  --sct */
 164         /* Doesn't work. open() might be there first. --AV */
 165
 166         /* Yes. It's a race. In user space. Nothing sane to do */
 167         err = -EBUSY;
 168         fdt = files_fdtable(files);
 169         tofree = fdt->fd[newfd];
 170         if (!tofree && FD_ISSET(newfd, fdt->open_fds))
 171                 goto out_fput;
 172
 173         rcu_assign_pointer(fdt->fd[newfd], file);
 174         FD_SET(newfd, fdt->open_fds);
 175         FD_CLR(newfd, fdt->close_on_exec);
 176         spin_unlock(&files->file_lock);
 177
 178         if (tofree)
 179                 filp_close(tofree, files);
 180         err = newfd;
 181 out:
 182         return err;
 183 out_unlock:
 184         spin_unlock(&files->file_lock);
 185         goto out;
 186
 187 out_fput:
 188         spin_unlock(&files->file_lock);
 189         fput(file);
 190         goto out;
 191 }
 192
 193 asmlinkage long sys_dup(unsigned int fildes)
 194 {
 195         int ret = -EBADF;
 196         struct file * file = fget(fildes);
 197
 198         if (file)
 199                 ret = dupfd(file, 0);
 200         return ret;
 201 }
 202
 203 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
 204
 205 static int setfl(int fd, struct file * filp, unsigned long arg)
 206 {
 207         struct inode * inode = filp->f_dentry->d_inode;
 208         int error = 0;
 209
 210         /* O_APPEND cannot be cleared if the file is marked as append-only */
 211         if (!(arg & O_APPEND) && IS_APPEND(inode))
 212                 return -EPERM;
 213
 214         /* O_NOATIME can only be set by the owner or superuser */
 215         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 216                 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
 217                         return -EPERM;
 218
 219         /* required for strict SunOS emulation */
 220         if (O_NONBLOCK != O_NDELAY)
 221                if (arg & O_NDELAY)
 222                    arg |= O_NONBLOCK;
 223
 224         if (arg & O_DIRECT) {
 225                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 226                         !filp->f_mapping->a_ops->direct_IO)
 227                                 return -EINVAL;
 228         }
 229
 230         if (filp->f_op && filp->f_op->check_flags)
 231                 error = filp->f_op->check_flags(arg);
 232         if (error)
 233                 return error;
 234
 235         lock_kernel();
 236         if ((arg ^ filp->f_flags) & FASYNC) {
 237                 if (filp->f_op && filp->f_op->fasync) {
 238                         error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 239                         if (error < 0)
 240                                 goto out;
 241                 }
 242         }
 243
 244         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 245  out:
 246         unlock_kernel();
 247         return error;
 248 }
 249
 250 static void f_modown(struct file *filp, unsigned long pid,
 251                      uid_t uid, uid_t euid, int force)
 252 {
 253         write_lock_irq(&filp->f_owner.lock);
 254         if (force || !filp->f_owner.pid) {
 255                 filp->f_owner.pid = pid;
 256                 filp->f_owner.uid = uid;
 257                 filp->f_owner.euid = euid;
 258         }
 259         write_unlock_irq(&filp->f_owner.lock);
 260 }
 261
 262 int f_setown(struct file *filp, unsigned long arg, int force)
 263 {
 264         int err;
 265
 266         err = security_file_set_fowner(filp);
 267         if (err)
 268                 return err;
 269
 270         f_modown(filp, arg, current->uid, current->euid, force);
 271         return 0;
 272 }
 273
 274 EXPORT_SYMBOL(f_setown);
 275
 276 void f_delown(struct file *filp)
 277 {
 278         f_modown(filp, 0, 0, 0, 1);
 279 }
 280
 281 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 282                 struct file *filp)
 283 {
 284         long err = -EINVAL;
 285
 286         switch (cmd) {
 287         case F_DUPFD:
 288                 get_file(filp);
 289                 err = dupfd(filp, arg);
 290                 break;
 291         case F_GETFD:
 292                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 293                 break;
 294         case F_SETFD:
 295                 err = 0;
 296                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 297                 break;
 298         case F_GETFL:
 299                 err = filp->f_flags;
 300                 break;
 301         case F_SETFL:
 302                 err = setfl(fd, filp, arg);
 303                 break;
 304         case F_GETLK:
 305                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 306                 break;
 307         case F_SETLK:
 308         case F_SETLKW:
 309                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 310                 break;
 311         case F_GETOWN:
 312                 /*
 313                  * XXX If f_owner is a process group, the
 314                  * negative return value will get converted
 315                  * into an error.  Oops.  If we keep the
 316                  * current syscall conventions, the only way
 317                  * to fix this will be in libc.
 318                  */
 319                 err = filp->f_owner.pid;
 320                 force_successful_syscall_return();
 321                 break;
 322         case F_SETOWN:
 323                 err = f_setown(filp, arg, 1);
 324                 break;
 325         case F_GETSIG:
 326                 err = filp->f_owner.signum;
 327                 break;
 328         case F_SETSIG:
 329                 /* arg == 0 restores default behaviour. */
 330                 if (!valid_signal(arg)) {
 331                         break;
 332                 }
 333                 err = 0;
 334                 filp->f_owner.signum = arg;
 335                 break;
 336         case F_GETLEASE:
 337                 err = fcntl_getlease(filp);
 338                 break;
 339         case F_SETLEASE:
 340                 err = fcntl_setlease(fd, filp, arg);
 341                 break;
 342         case F_NOTIFY:
 343                 err = fcntl_dirnotify(fd, filp, arg);
 344                 break;
 345         default:
 346                 break;
 347         }
 348         return err;
 349 }
 350
 351 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
 352 {
 353         struct file *filp;
 354         long err = -EBADF;
 355
 356         filp = fget(fd);
 357         if (!filp)
 358                 goto out;
 359
 360         err = security_file_fcntl(filp, cmd, arg);
 361         if (err) {
 362                 fput(filp);
 363                 return err;
 364         }
 365
 366         err = do_fcntl(fd, cmd, arg, filp);
 367
 368         fput(filp);
 369 out:
 370         return err;
 371 }
 372
 373 #if BITS_PER_LONG == 32
 374 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 375 {
 376         struct file * filp;
 377         long err;
 378
 379         err = -EBADF;
 380         filp = fget(fd);
 381         if (!filp)
 382                 goto out;
 383
 384         err = security_file_fcntl(filp, cmd, arg);
 385         if (err) {
 386                 fput(filp);
 387                 return err;
 388         }
 389         err = -EBADF;
 390
 391         switch (cmd) {
 392                 case F_GETLK64:
 393                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 394                         break;
 395                 case F_SETLK64:
 396                 case F_SETLKW64:
 397                         err = fcntl_setlk64(fd, filp, cmd,
 398                                         (struct flock64 __user *) arg);
 399                         break;
 400                 default:
 401                         err = do_fcntl(fd, cmd, arg, filp);
 402                         break;
 403         }
 404         fput(filp);
 405 out:
 406         return err;
 407 }
 408 #endif
 409
 410 /* Table to convert sigio signal codes into poll band bitmaps */
 411
 412 static long band_table[NSIGPOLL] = {
 413         POLLIN | POLLRDNORM,                    /* POLL_IN */
 414         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 415         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 416         POLLERR,                                /* POLL_ERR */
 417         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 418         POLLHUP | POLLERR                       /* POLL_HUP */
 419 };
 420
 421 static inline int sigio_perm(struct task_struct *p,
 422                              struct fown_struct *fown, int sig)
 423 {
 424         return (((fown->euid == 0) ||
 425                  (fown->euid == p->suid) || (fown->euid == p->uid) ||
 426                  (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 427                 !security_file_send_sigiotask(p, fown, sig));
 428 }
 429
 430 static void send_sigio_to_task(struct task_struct *p,
 431                                struct fown_struct *fown,
 432                                int fd,
 433                                int reason)
 434 {
 435         if (!sigio_perm(p, fown, fown->signum))
 436                 return;
 437
 438         switch (fown->signum) {
 439                 siginfo_t si;
 440                 default:
 441                         /* Queue a rt signal with the appropriate fd as its
 442                            value.  We use SI_SIGIO as the source, not
 443                            SI_KERNEL, since kernel signals always get
 444                            delivered even if we can't queue.  Failure to
 445                            queue in this case _should_ be reported; we fall
 446                            back to SIGIO in that case. --sct */
 447                         si.si_signo = fown->signum;
 448                         si.si_errno = 0;
 449                         si.si_code  = reason;
 450                         /* Make sure we are called with one of the POLL_*
 451                            reasons, otherwise we could leak kernel stack into
 452                            userspace.  */
 453                         if ((reason & __SI_MASK) != __SI_POLL)
 454                                 BUG();
 455                         if (reason - POLL_IN >= NSIGPOLL)
 456                                 si.si_band  = ~0L;
 457                         else
 458                                 si.si_band = band_table[reason - POLL_IN];
 459                         si.si_fd    = fd;
 460                         if (!send_group_sig_info(fown->signum, &si, p))
 461                                 break;
 462                 /* fall-through: fall back on the old plain SIGIO signal */
 463                 case 0:
 464                         send_group_sig_info(SIGIO, SEND_SIG_PRIV, p);
 465         }
 466 }
 467
 468 void send_sigio(struct fown_struct *fown, int fd, int band)
 469 {
 470         struct task_struct *p;
 471         int pid;
 472
 473         read_lock(&fown->lock);
 474         pid = fown->pid;
 475         if (!pid)
 476                 goto out_unlock_fown;
 477
 478         read_lock(&tasklist_lock);
 479         if (pid > 0) {
 480                 p = find_task_by_pid(pid);
 481                 if (p) {
 482                         send_sigio_to_task(p, fown, fd, band);
 483                 }
 484         } else {
 485                 do_each_task_pid(-pid, PIDTYPE_PGID, p) {
 486                         send_sigio_to_task(p, fown, fd, band);
 487                 } while_each_task_pid(-pid, PIDTYPE_PGID, p);
 488         }
 489         read_unlock(&tasklist_lock);
 490  out_unlock_fown:
 491         read_unlock(&fown->lock);
 492 }
 493
 494 static void send_sigurg_to_task(struct task_struct *p,
 495                                 struct fown_struct *fown)
 496 {
 497         if (sigio_perm(p, fown, SIGURG))
 498                 send_group_sig_info(SIGURG, SEND_SIG_PRIV, p);
 499 }
 500
 501 int send_sigurg(struct fown_struct *fown)
 502 {
 503         struct task_struct *p;
 504         int pid, ret = 0;
 505
 506         read_lock(&fown->lock);
 507         pid = fown->pid;
 508         if (!pid)
 509                 goto out_unlock_fown;
 510
 511         ret = 1;
 512
 513         read_lock(&tasklist_lock);
 514         if (pid > 0) {
 515                 p = find_task_by_pid(pid);
 516                 if (p) {
 517                         send_sigurg_to_task(p, fown);
 518                 }
 519         } else {
 520                 do_each_task_pid(-pid, PIDTYPE_PGID, p) {
 521                         send_sigurg_to_task(p, fown);
 522                 } while_each_task_pid(-pid, PIDTYPE_PGID, p);
 523         }
 524         read_unlock(&tasklist_lock);
 525  out_unlock_fown:
 526         read_unlock(&fown->lock);
 527         return ret;
 528 }
 529
 530 static DEFINE_RWLOCK(fasync_lock);
 531 static kmem_cache_t *fasync_cache;
 532
 533 /*
 534  * fasync_helper() is used by some character device drivers (mainly mice)
 535  * to set up the fasync queue. It returns negative on error, 0 if it did
 536  * no changes and positive if it added/deleted the entry.
 537  */
 538 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 539 {
 540         struct fasync_struct *fa, **fp;
 541         struct fasync_struct *new = NULL;
 542         int result = 0;
 543
 544         if (on) {
 545                 new = kmem_cache_alloc(fasync_cache, SLAB_KERNEL);
 546                 if (!new)
 547                         return -ENOMEM;
 548         }
 549         write_lock_irq(&fasync_lock);
 550         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 551                 if (fa->fa_file == filp) {
 552                         if(on) {
 553                                 fa->fa_fd = fd;
 554                                 kmem_cache_free(fasync_cache, new);
 555                         } else {
 556                                 *fp = fa->fa_next;
 557                                 kmem_cache_free(fasync_cache, fa);
 558                                 result = 1;
 559                         }
 560                         goto out;
 561                 }
 562         }
 563
 564         if (on) {
 565                 new->magic = FASYNC_MAGIC;
 566                 new->fa_file = filp;
 567                 new->fa_fd = fd;
 568                 new->fa_next = *fapp;
 569                 *fapp = new;
 570                 result = 1;
 571         }
 572 out:
 573         write_unlock_irq(&fasync_lock);
 574         return result;
 575 }
 576
 577 EXPORT_SYMBOL(fasync_helper);
 578
 579 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 580 {
 581         while (fa) {
 582                 struct fown_struct * fown;
 583                 if (fa->magic != FASYNC_MAGIC) {
 584                         printk(KERN_ERR "kill_fasync: bad magic number in "
 585                                "fasync_struct!\n");
 586                         return;
 587                 }
 588                 fown = &fa->fa_file->f_owner;
 589                 /* Don't send SIGURG to processes which have not set a
 590                    queued signum: SIGURG has its own default signalling
 591                    mechanism. */
 592                 if (!(sig == SIGURG && fown->signum == 0))
 593                         send_sigio(fown, fa->fa_fd, band);
 594                 fa = fa->fa_next;
 595         }
 596 }
 597
 598 EXPORT_SYMBOL(__kill_fasync);
 599
 600 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 601 {
 602         /* First a quick test without locking: usually
 603          * the list is empty.
 604          */
 605         if (*fp) {
 606                 read_lock(&fasync_lock);
 607                 /* reread *fp after obtaining the lock */
 608                 __kill_fasync(*fp, sig, band);
 609                 read_unlock(&fasync_lock);
 610         }
 611 }
 612 EXPORT_SYMBOL(kill_fasync);
 613
 614 static int __init fasync_init(void)
 615 {
 616         fasync_cache = kmem_cache_create("fasync_cache",
 617                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
 618         return 0;
 619 }
 620
 621 module_init(fasync_init)