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/capability.h>
  13 #include <linux/dnotify.h>
  14 #include <linux/smp_lock.h>
  15 #include <linux/slab.h>
  16 #include <linux/module.h>
  17 #include <linux/security.h>
  18 #include <linux/ptrace.h>
  19 #include <linux/signal.h>
  20 #include <linux/rcupdate.h>
  21
  22 #include <asm/poll.h>
  23 #include <asm/siginfo.h>
  24 #include <asm/uaccess.h>
  25
  26 void fastcall set_close_on_exec(unsigned int fd, int flag)
  27 {
  28         struct files_struct *files = current->files;
  29         struct fdtable *fdt;
  30         spin_lock(&files->file_lock);
  31         fdt = files_fdtable(files);
  32         if (flag)
  33                 FD_SET(fd, fdt->close_on_exec);
  34         else
  35                 FD_CLR(fd, fdt->close_on_exec);
  36         spin_unlock(&files->file_lock);
  37 }
  38
  39 static int get_close_on_exec(unsigned int fd)
  40 {
  41         struct files_struct *files = current->files;
  42         struct fdtable *fdt;
  43         int res;
  44         rcu_read_lock();
  45         fdt = files_fdtable(files);
  46         res = FD_ISSET(fd, fdt->close_on_exec);
  47         rcu_read_unlock();
  48         return res;
  49 }
  50
  51 /*
  52  * locate_fd finds a free file descriptor in the open_fds fdset,
  53  * expanding the fd arrays if necessary.  Must be called with the
  54  * file_lock held for write.
  55  */
  56
  57 static int locate_fd(struct files_struct *files,
  58                             struct file *file, unsigned int orig_start)
  59 {
  60         unsigned int newfd;
  61         unsigned int start;
  62         int error;
  63         struct fdtable *fdt;
  64
  65         error = -EINVAL;
  66         if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  67                 goto out;
  68
  69 repeat:
  70         fdt = files_fdtable(files);
  71         /*
  72          * Someone might have closed fd's in the range
  73          * orig_start..fdt->next_fd
  74          */
  75         start = orig_start;
  76         if (start < files->next_fd)
  77                 start = files->next_fd;
  78
  79         newfd = start;
  80         if (start < fdt->max_fdset) {
  81                 newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
  82                         fdt->max_fdset, start);
  83         }
  84
  85         error = -EMFILE;
  86         if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  87                 goto out;
  88
  89         error = expand_files(files, newfd);
  90         if (error < 0)
  91                 goto out;
  92
  93         /*
  94          * If we needed to expand the fs array we
  95          * might have blocked - try again.
  96          */
  97         if (error)
  98                 goto repeat;
  99
 100         /*
 101          * We reacquired files_lock, so we are safe as long as
 102          * we reacquire the fdtable pointer and use it while holding
 103          * the lock, no one can free it during that time.
 104          */
 105         if (start <= files->next_fd)
 106                 files->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         /*
 211          * O_APPEND cannot be cleared if the file is marked as append-only
 212          * and the file is open for write.
 213          */
 214         if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
 215                 return -EPERM;
 216
 217         /* O_NOATIME can only be set by the owner or superuser */
 218         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 219                 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
 220                         return -EPERM;
 221
 222         /* required for strict SunOS emulation */
 223         if (O_NONBLOCK != O_NDELAY)
 224                if (arg & O_NDELAY)
 225                    arg |= O_NONBLOCK;
 226
 227         if (arg & O_DIRECT) {
 228                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 229                         !filp->f_mapping->a_ops->direct_IO)
 230                                 return -EINVAL;
 231         }
 232
 233         if (filp->f_op && filp->f_op->check_flags)
 234                 error = filp->f_op->check_flags(arg);
 235         if (error)
 236                 return error;
 237
 238         lock_kernel();
 239         if ((arg ^ filp->f_flags) & FASYNC) {
 240                 if (filp->f_op && filp->f_op->fasync) {
 241                         error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 242                         if (error < 0)
 243                                 goto out;
 244                 }
 245         }
 246
 247         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 248  out:
 249         unlock_kernel();
 250         return error;
 251 }
 252
 253 static void f_modown(struct file *filp, unsigned long pid,
 254                      uid_t uid, uid_t euid, int force)
 255 {
 256         write_lock_irq(&filp->f_owner.lock);
 257         if (force || !filp->f_owner.pid) {
 258                 filp->f_owner.pid = pid;
 259                 filp->f_owner.uid = uid;
 260                 filp->f_owner.euid = euid;
 261         }
 262         write_unlock_irq(&filp->f_owner.lock);
 263 }
 264
 265 int f_setown(struct file *filp, unsigned long arg, int force)
 266 {
 267         int err;
 268
 269         err = security_file_set_fowner(filp);
 270         if (err)
 271                 return err;
 272
 273         f_modown(filp, arg, current->uid, current->euid, force);
 274         return 0;
 275 }
 276
 277 EXPORT_SYMBOL(f_setown);
 278
 279 void f_delown(struct file *filp)
 280 {
 281         f_modown(filp, 0, 0, 0, 1);
 282 }
 283
 284 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 285                 struct file *filp)
 286 {
 287         long err = -EINVAL;
 288
 289         switch (cmd) {
 290         case F_DUPFD:
 291                 get_file(filp);
 292                 err = dupfd(filp, arg);
 293                 break;
 294         case F_GETFD:
 295                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 296                 break;
 297         case F_SETFD:
 298                 err = 0;
 299                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 300                 break;
 301         case F_GETFL:
 302                 err = filp->f_flags;
 303                 break;
 304         case F_SETFL:
 305                 err = setfl(fd, filp, arg);
 306                 break;
 307         case F_GETLK:
 308                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 309                 break;
 310         case F_SETLK:
 311         case F_SETLKW:
 312                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 313                 break;
 314         case F_GETOWN:
 315                 /*
 316                  * XXX If f_owner is a process group, the
 317                  * negative return value will get converted
 318                  * into an error.  Oops.  If we keep the
 319                  * current syscall conventions, the only way
 320                  * to fix this will be in libc.
 321                  */
 322                 err = filp->f_owner.pid;
 323                 force_successful_syscall_return();
 324                 break;
 325         case F_SETOWN:
 326                 err = f_setown(filp, arg, 1);
 327                 break;
 328         case F_GETSIG:
 329                 err = filp->f_owner.signum;
 330                 break;
 331         case F_SETSIG:
 332                 /* arg == 0 restores default behaviour. */
 333                 if (!valid_signal(arg)) {
 334                         break;
 335                 }
 336                 err = 0;
 337                 filp->f_owner.signum = arg;
 338                 break;
 339         case F_GETLEASE:
 340                 err = fcntl_getlease(filp);
 341                 break;
 342         case F_SETLEASE:
 343                 err = fcntl_setlease(fd, filp, arg);
 344                 break;
 345         case F_NOTIFY:
 346                 err = fcntl_dirnotify(fd, filp, arg);
 347                 break;
 348         default:
 349                 break;
 350         }
 351         return err;
 352 }
 353
 354 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
 355 {
 356         struct file *filp;
 357         long err = -EBADF;
 358
 359         filp = fget(fd);
 360         if (!filp)
 361                 goto out;
 362
 363         err = security_file_fcntl(filp, cmd, arg);
 364         if (err) {
 365                 fput(filp);
 366                 return err;
 367         }
 368
 369         err = do_fcntl(fd, cmd, arg, filp);
 370
 371         fput(filp);
 372 out:
 373         return err;
 374 }
 375
 376 #if BITS_PER_LONG == 32
 377 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 378 {
 379         struct file * filp;
 380         long err;
 381
 382         err = -EBADF;
 383         filp = fget(fd);
 384         if (!filp)
 385                 goto out;
 386
 387         err = security_file_fcntl(filp, cmd, arg);
 388         if (err) {
 389                 fput(filp);
 390                 return err;
 391         }
 392         err = -EBADF;
 393
 394         switch (cmd) {
 395                 case F_GETLK64:
 396                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 397                         break;
 398                 case F_SETLK64:
 399                 case F_SETLKW64:
 400                         err = fcntl_setlk64(fd, filp, cmd,
 401                                         (struct flock64 __user *) arg);
 402                         break;
 403                 default:
 404                         err = do_fcntl(fd, cmd, arg, filp);
 405                         break;
 406         }
 407         fput(filp);
 408 out:
 409         return err;
 410 }
 411 #endif
 412
 413 /* Table to convert sigio signal codes into poll band bitmaps */
 414
 415 static const long band_table[NSIGPOLL] = {
 416         POLLIN | POLLRDNORM,                    /* POLL_IN */
 417         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 418         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 419         POLLERR,                                /* POLL_ERR */
 420         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 421         POLLHUP | POLLERR                       /* POLL_HUP */
 422 };
 423
 424 static inline int sigio_perm(struct task_struct *p,
 425                              struct fown_struct *fown, int sig)
 426 {
 427         return (((fown->euid == 0) ||
 428                  (fown->euid == p->suid) || (fown->euid == p->uid) ||
 429                  (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 430                 !security_file_send_sigiotask(p, fown, sig));
 431 }
 432
 433 static void send_sigio_to_task(struct task_struct *p,
 434                                struct fown_struct *fown,
 435                                int fd,
 436                                int reason)
 437 {
 438         if (!sigio_perm(p, fown, fown->signum))
 439                 return;
 440
 441         switch (fown->signum) {
 442                 siginfo_t si;
 443                 default:
 444                         /* Queue a rt signal with the appropriate fd as its
 445                            value.  We use SI_SIGIO as the source, not
 446                            SI_KERNEL, since kernel signals always get
 447                            delivered even if we can't queue.  Failure to
 448                            queue in this case _should_ be reported; we fall
 449                            back to SIGIO in that case. --sct */
 450                         si.si_signo = fown->signum;
 451                         si.si_errno = 0;
 452                         si.si_code  = reason;
 453                         /* Make sure we are called with one of the POLL_*
 454                            reasons, otherwise we could leak kernel stack into
 455                            userspace.  */
 456                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 457                         if (reason - POLL_IN >= NSIGPOLL)
 458                                 si.si_band  = ~0L;
 459                         else
 460                                 si.si_band = band_table[reason - POLL_IN];
 461                         si.si_fd    = fd;
 462                         if (!group_send_sig_info(fown->signum, &si, p))
 463                                 break;
 464                 /* fall-through: fall back on the old plain SIGIO signal */
 465                 case 0:
 466                         group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
 467         }
 468 }
 469
 470 void send_sigio(struct fown_struct *fown, int fd, int band)
 471 {
 472         struct task_struct *p;
 473         int pid;
 474
 475         read_lock(&fown->lock);
 476         pid = fown->pid;
 477         if (!pid)
 478                 goto out_unlock_fown;
 479
 480         read_lock(&tasklist_lock);
 481         if (pid > 0) {
 482                 p = find_task_by_pid(pid);
 483                 if (p) {
 484                         send_sigio_to_task(p, fown, fd, band);
 485                 }
 486         } else {
 487                 do_each_task_pid(-pid, PIDTYPE_PGID, p) {
 488                         send_sigio_to_task(p, fown, fd, band);
 489                 } while_each_task_pid(-pid, PIDTYPE_PGID, p);
 490         }
 491         read_unlock(&tasklist_lock);
 492  out_unlock_fown:
 493         read_unlock(&fown->lock);
 494 }
 495
 496 static void send_sigurg_to_task(struct task_struct *p,
 497                                 struct fown_struct *fown)
 498 {
 499         if (sigio_perm(p, fown, SIGURG))
 500                 group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
 501 }
 502
 503 int send_sigurg(struct fown_struct *fown)
 504 {
 505         struct task_struct *p;
 506         int pid, ret = 0;
 507
 508         read_lock(&fown->lock);
 509         pid = fown->pid;
 510         if (!pid)
 511                 goto out_unlock_fown;
 512
 513         ret = 1;
 514
 515         read_lock(&tasklist_lock);
 516         if (pid > 0) {
 517                 p = find_task_by_pid(pid);
 518                 if (p) {
 519                         send_sigurg_to_task(p, fown);
 520                 }
 521         } else {
 522                 do_each_task_pid(-pid, PIDTYPE_PGID, p) {
 523                         send_sigurg_to_task(p, fown);
 524                 } while_each_task_pid(-pid, PIDTYPE_PGID, p);
 525         }
 526         read_unlock(&tasklist_lock);
 527  out_unlock_fown:
 528         read_unlock(&fown->lock);
 529         return ret;
 530 }
 531
 532 static DEFINE_RWLOCK(fasync_lock);
 533 static kmem_cache_t *fasync_cache __read_mostly;
 534
 535 /*
 536  * fasync_helper() is used by some character device drivers (mainly mice)
 537  * to set up the fasync queue. It returns negative on error, 0 if it did
 538  * no changes and positive if it added/deleted the entry.
 539  */
 540 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 541 {
 542         struct fasync_struct *fa, **fp;
 543         struct fasync_struct *new = NULL;
 544         int result = 0;
 545
 546         if (on) {
 547                 new = kmem_cache_alloc(fasync_cache, SLAB_KERNEL);
 548                 if (!new)
 549                         return -ENOMEM;
 550         }
 551         write_lock_irq(&fasync_lock);
 552         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 553                 if (fa->fa_file == filp) {
 554                         if(on) {
 555                                 fa->fa_fd = fd;
 556                                 kmem_cache_free(fasync_cache, new);
 557                         } else {
 558                                 *fp = fa->fa_next;
 559                                 kmem_cache_free(fasync_cache, fa);
 560                                 result = 1;
 561                         }
 562                         goto out;
 563                 }
 564         }
 565
 566         if (on) {
 567                 new->magic = FASYNC_MAGIC;
 568                 new->fa_file = filp;
 569                 new->fa_fd = fd;
 570                 new->fa_next = *fapp;
 571                 *fapp = new;
 572                 result = 1;
 573         }
 574 out:
 575         write_unlock_irq(&fasync_lock);
 576         return result;
 577 }
 578
 579 EXPORT_SYMBOL(fasync_helper);
 580
 581 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 582 {
 583         while (fa) {
 584                 struct fown_struct * fown;
 585                 if (fa->magic != FASYNC_MAGIC) {
 586                         printk(KERN_ERR "kill_fasync: bad magic number in "
 587                                "fasync_struct!\n");
 588                         return;
 589                 }
 590                 fown = &fa->fa_file->f_owner;
 591                 /* Don't send SIGURG to processes which have not set a
 592                    queued signum: SIGURG has its own default signalling
 593                    mechanism. */
 594                 if (!(sig == SIGURG && fown->signum == 0))
 595                         send_sigio(fown, fa->fa_fd, band);
 596                 fa = fa->fa_next;
 597         }
 598 }
 599
 600 EXPORT_SYMBOL(__kill_fasync);
 601
 602 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 603 {
 604         /* First a quick test without locking: usually
 605          * the list is empty.
 606          */
 607         if (*fp) {
 608                 read_lock(&fasync_lock);
 609                 /* reread *fp after obtaining the lock */
 610                 __kill_fasync(*fp, sig, band);
 611                 read_unlock(&fasync_lock);
 612         }
 613 }
 614 EXPORT_SYMBOL(kill_fasync);
 615
 616 static int __init fasync_init(void)
 617 {
 618         fasync_cache = kmem_cache_create("fasync_cache",
 619                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
 620         return 0;
 621 }
 622
 623 module_init(fasync_init)