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