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_fds)
  81                 newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
  82                                            fdt->max_fds, start);
  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         if (start <= files->next_fd)
 105                 files->next_fd = newfd + 1;
 106
 107         error = newfd;
 108
 109 out:
 110         return error;
 111 }
 112
 113 static int dupfd(struct file *file, unsigned int start)
 114 {
 115         struct files_struct * files = current->files;
 116         struct fdtable *fdt;
 117         int fd;
 118
 119         spin_lock(&files->file_lock);
 120         fd = locate_fd(files, file, start);
 121         if (fd >= 0) {
 122                 /* locate_fd() may have expanded fdtable, load the ptr */
 123                 fdt = files_fdtable(files);
 124                 FD_SET(fd, fdt->open_fds);
 125                 FD_CLR(fd, fdt->close_on_exec);
 126                 spin_unlock(&files->file_lock);
 127                 fd_install(fd, file);
 128         } else {
 129                 spin_unlock(&files->file_lock);
 130                 fput(file);
 131         }
 132
 133         return fd;
 134 }
 135
 136 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 137 {
 138         int err = -EBADF;
 139         struct file * file, *tofree;
 140         struct files_struct * files = current->files;
 141         struct fdtable *fdt;
 142
 143         spin_lock(&files->file_lock);
 144         if (!(file = fcheck(oldfd)))
 145                 goto out_unlock;
 146         err = newfd;
 147         if (newfd == oldfd)
 148                 goto out_unlock;
 149         err = -EBADF;
 150         if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 151                 goto out_unlock;
 152         get_file(file);                 /* We are now finished with oldfd */
 153
 154         err = expand_files(files, newfd);
 155         if (err < 0)
 156                 goto out_fput;
 157
 158         /* To avoid races with open() and dup(), we will mark the fd as
 159          * in-use in the open-file bitmap throughout the entire dup2()
 160          * process.  This is quite safe: do_close() uses the fd array
 161          * entry, not the bitmap, to decide what work needs to be
 162          * done.  --sct */
 163         /* Doesn't work. open() might be there first. --AV */
 164
 165         /* Yes. It's a race. In user space. Nothing sane to do */
 166         err = -EBUSY;
 167         fdt = files_fdtable(files);
 168         tofree = fdt->fd[newfd];
 169         if (!tofree && FD_ISSET(newfd, fdt->open_fds))
 170                 goto out_fput;
 171
 172         rcu_assign_pointer(fdt->fd[newfd], file);
 173         FD_SET(newfd, fdt->open_fds);
 174         FD_CLR(newfd, fdt->close_on_exec);
 175         spin_unlock(&files->file_lock);
 176
 177         if (tofree)
 178                 filp_close(tofree, files);
 179         err = newfd;
 180 out:
 181         return err;
 182 out_unlock:
 183         spin_unlock(&files->file_lock);
 184         goto out;
 185
 186 out_fput:
 187         spin_unlock(&files->file_lock);
 188         fput(file);
 189         goto out;
 190 }
 191
 192 asmlinkage long sys_dup(unsigned int fildes)
 193 {
 194         int ret = -EBADF;
 195         struct file * file = fget(fildes);
 196
 197         if (file)
 198                 ret = dupfd(file, 0);
 199         return ret;
 200 }
 201
 202 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
 203
 204 static int setfl(int fd, struct file * filp, unsigned long arg)
 205 {
 206         struct inode * inode = filp->f_path.dentry->d_inode;
 207         int error = 0;
 208
 209         /*
 210          * O_APPEND cannot be cleared if the file is marked as append-only
 211          * and the file is open for write.
 212          */
 213         if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
 214                 return -EPERM;
 215
 216         /* O_NOATIME can only be set by the owner or superuser */
 217         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 218                 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
 219                         return -EPERM;
 220
 221         /* required for strict SunOS emulation */
 222         if (O_NONBLOCK != O_NDELAY)
 223                if (arg & O_NDELAY)
 224                    arg |= O_NONBLOCK;
 225
 226         if (arg & O_DIRECT) {
 227                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 228                         !filp->f_mapping->a_ops->direct_IO)
 229                                 return -EINVAL;
 230         }
 231
 232         if (filp->f_op && filp->f_op->check_flags)
 233                 error = filp->f_op->check_flags(arg);
 234         if (error)
 235                 return error;
 236
 237         lock_kernel();
 238         if ((arg ^ filp->f_flags) & FASYNC) {
 239                 if (filp->f_op && filp->f_op->fasync) {
 240                         error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 241                         if (error < 0)
 242                                 goto out;
 243                 }
 244         }
 245
 246         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 247  out:
 248         unlock_kernel();
 249         return error;
 250 }
 251
 252 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
 253                      uid_t uid, uid_t euid, int force)
 254 {
 255         write_lock_irq(&filp->f_owner.lock);
 256         if (force || !filp->f_owner.pid) {
 257                 put_pid(filp->f_owner.pid);
 258                 filp->f_owner.pid = get_pid(pid);
 259                 filp->f_owner.pid_type = type;
 260                 filp->f_owner.uid = uid;
 261                 filp->f_owner.euid = euid;
 262         }
 263         write_unlock_irq(&filp->f_owner.lock);
 264 }
 265
 266 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
 267                 int force)
 268 {
 269         int err;
 270
 271         err = security_file_set_fowner(filp);
 272         if (err)
 273                 return err;
 274
 275         f_modown(filp, pid, type, current->uid, current->euid, force);
 276         return 0;
 277 }
 278 EXPORT_SYMBOL(__f_setown);
 279
 280 int f_setown(struct file *filp, unsigned long arg, int force)
 281 {
 282         enum pid_type type;
 283         struct pid *pid;
 284         int who = arg;
 285         int result;
 286         type = PIDTYPE_PID;
 287         if (who < 0) {
 288                 type = PIDTYPE_PGID;
 289                 who = -who;
 290         }
 291         rcu_read_lock();
 292         pid = find_pid(who);
 293         result = __f_setown(filp, pid, type, force);
 294         rcu_read_unlock();
 295         return result;
 296 }
 297 EXPORT_SYMBOL(f_setown);
 298
 299 void f_delown(struct file *filp)
 300 {
 301         f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
 302 }
 303
 304 pid_t f_getown(struct file *filp)
 305 {
 306         pid_t pid;
 307         read_lock(&filp->f_owner.lock);
 308         pid = pid_nr(filp->f_owner.pid);
 309         if (filp->f_owner.pid_type == PIDTYPE_PGID)
 310                 pid = -pid;
 311         read_unlock(&filp->f_owner.lock);
 312         return pid;
 313 }
 314
 315 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 316                 struct file *filp)
 317 {
 318         long err = -EINVAL;
 319
 320         switch (cmd) {
 321         case F_DUPFD:
 322                 get_file(filp);
 323                 err = dupfd(filp, arg);
 324                 break;
 325         case F_GETFD:
 326                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 327                 break;
 328         case F_SETFD:
 329                 err = 0;
 330                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 331                 break;
 332         case F_GETFL:
 333                 err = filp->f_flags;
 334                 break;
 335         case F_SETFL:
 336                 err = setfl(fd, filp, arg);
 337                 break;
 338         case F_GETLK:
 339                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 340                 break;
 341         case F_SETLK:
 342         case F_SETLKW:
 343                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 344                 break;
 345         case F_GETOWN:
 346                 /*
 347                  * XXX If f_owner is a process group, the
 348                  * negative return value will get converted
 349                  * into an error.  Oops.  If we keep the
 350                  * current syscall conventions, the only way
 351                  * to fix this will be in libc.
 352                  */
 353                 err = f_getown(filp);
 354                 force_successful_syscall_return();
 355                 break;
 356         case F_SETOWN:
 357                 err = f_setown(filp, arg, 1);
 358                 break;
 359         case F_GETSIG:
 360                 err = filp->f_owner.signum;
 361                 break;
 362         case F_SETSIG:
 363                 /* arg == 0 restores default behaviour. */
 364                 if (!valid_signal(arg)) {
 365                         break;
 366                 }
 367                 err = 0;
 368                 filp->f_owner.signum = arg;
 369                 break;
 370         case F_GETLEASE:
 371                 err = fcntl_getlease(filp);
 372                 break;
 373         case F_SETLEASE:
 374                 err = fcntl_setlease(fd, filp, arg);
 375                 break;
 376         case F_NOTIFY:
 377                 err = fcntl_dirnotify(fd, filp, arg);
 378                 break;
 379         default:
 380                 break;
 381         }
 382         return err;
 383 }
 384
 385 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
 386 {
 387         struct file *filp;
 388         long err = -EBADF;
 389
 390         filp = fget(fd);
 391         if (!filp)
 392                 goto out;
 393
 394         err = security_file_fcntl(filp, cmd, arg);
 395         if (err) {
 396                 fput(filp);
 397                 return err;
 398         }
 399
 400         err = do_fcntl(fd, cmd, arg, filp);
 401
 402         fput(filp);
 403 out:
 404         return err;
 405 }
 406
 407 #if BITS_PER_LONG == 32
 408 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 409 {
 410         struct file * filp;
 411         long err;
 412
 413         err = -EBADF;
 414         filp = fget(fd);
 415         if (!filp)
 416                 goto out;
 417
 418         err = security_file_fcntl(filp, cmd, arg);
 419         if (err) {
 420                 fput(filp);
 421                 return err;
 422         }
 423         err = -EBADF;
 424
 425         switch (cmd) {
 426                 case F_GETLK64:
 427                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 428                         break;
 429                 case F_SETLK64:
 430                 case F_SETLKW64:
 431                         err = fcntl_setlk64(fd, filp, cmd,
 432                                         (struct flock64 __user *) arg);
 433                         break;
 434                 default:
 435                         err = do_fcntl(fd, cmd, arg, filp);
 436                         break;
 437         }
 438         fput(filp);
 439 out:
 440         return err;
 441 }
 442 #endif
 443
 444 /* Table to convert sigio signal codes into poll band bitmaps */
 445
 446 static const long band_table[NSIGPOLL] = {
 447         POLLIN | POLLRDNORM,                    /* POLL_IN */
 448         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 449         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 450         POLLERR,                                /* POLL_ERR */
 451         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 452         POLLHUP | POLLERR                       /* POLL_HUP */
 453 };
 454
 455 static inline int sigio_perm(struct task_struct *p,
 456                              struct fown_struct *fown, int sig)
 457 {
 458         return (((fown->euid == 0) ||
 459                  (fown->euid == p->suid) || (fown->euid == p->uid) ||
 460                  (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 461                 !security_file_send_sigiotask(p, fown, sig));
 462 }
 463
 464 static void send_sigio_to_task(struct task_struct *p,
 465                                struct fown_struct *fown,
 466                                int fd,
 467                                int reason)
 468 {
 469         if (!sigio_perm(p, fown, fown->signum))
 470                 return;
 471
 472         switch (fown->signum) {
 473                 siginfo_t si;
 474                 default:
 475                         /* Queue a rt signal with the appropriate fd as its
 476                            value.  We use SI_SIGIO as the source, not
 477                            SI_KERNEL, since kernel signals always get
 478                            delivered even if we can't queue.  Failure to
 479                            queue in this case _should_ be reported; we fall
 480                            back to SIGIO in that case. --sct */
 481                         si.si_signo = fown->signum;
 482                         si.si_errno = 0;
 483                         si.si_code  = reason;
 484                         /* Make sure we are called with one of the POLL_*
 485                            reasons, otherwise we could leak kernel stack into
 486                            userspace.  */
 487                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 488                         if (reason - POLL_IN >= NSIGPOLL)
 489                                 si.si_band  = ~0L;
 490                         else
 491                                 si.si_band = band_table[reason - POLL_IN];
 492                         si.si_fd    = fd;
 493                         if (!group_send_sig_info(fown->signum, &si, p))
 494                                 break;
 495                 /* fall-through: fall back on the old plain SIGIO signal */
 496                 case 0:
 497                         group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
 498         }
 499 }
 500
 501 void send_sigio(struct fown_struct *fown, int fd, int band)
 502 {
 503         struct task_struct *p;
 504         enum pid_type type;
 505         struct pid *pid;
 506
 507         read_lock(&fown->lock);
 508         type = fown->pid_type;
 509         pid = fown->pid;
 510         if (!pid)
 511                 goto out_unlock_fown;
 512
 513         read_lock(&tasklist_lock);
 514         do_each_pid_task(pid, type, p) {
 515                 send_sigio_to_task(p, fown, fd, band);
 516         } while_each_pid_task(pid, type, p);
 517         read_unlock(&tasklist_lock);
 518  out_unlock_fown:
 519         read_unlock(&fown->lock);
 520 }
 521
 522 static void send_sigurg_to_task(struct task_struct *p,
 523                                 struct fown_struct *fown)
 524 {
 525         if (sigio_perm(p, fown, SIGURG))
 526                 group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
 527 }
 528
 529 int send_sigurg(struct fown_struct *fown)
 530 {
 531         struct task_struct *p;
 532         enum pid_type type;
 533         struct pid *pid;
 534         int ret = 0;
 535
 536         read_lock(&fown->lock);
 537         type = fown->pid_type;
 538         pid = fown->pid;
 539         if (!pid)
 540                 goto out_unlock_fown;
 541
 542         ret = 1;
 543
 544         read_lock(&tasklist_lock);
 545         do_each_pid_task(pid, type, p) {
 546                 send_sigurg_to_task(p, fown);
 547         } while_each_pid_task(pid, type, p);
 548         read_unlock(&tasklist_lock);
 549  out_unlock_fown:
 550         read_unlock(&fown->lock);
 551         return ret;
 552 }
 553
 554 static DEFINE_RWLOCK(fasync_lock);
 555 static struct kmem_cache *fasync_cache __read_mostly;
 556
 557 /*
 558  * fasync_helper() is used by some character device drivers (mainly mice)
 559  * to set up the fasync queue. It returns negative on error, 0 if it did
 560  * no changes and positive if it added/deleted the entry.
 561  */
 562 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 563 {
 564         struct fasync_struct *fa, **fp;
 565         struct fasync_struct *new = NULL;
 566         int result = 0;
 567
 568         if (on) {
 569                 new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 570                 if (!new)
 571                         return -ENOMEM;
 572         }
 573         write_lock_irq(&fasync_lock);
 574         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 575                 if (fa->fa_file == filp) {
 576                         if(on) {
 577                                 fa->fa_fd = fd;
 578                                 kmem_cache_free(fasync_cache, new);
 579                         } else {
 580                                 *fp = fa->fa_next;
 581                                 kmem_cache_free(fasync_cache, fa);
 582                                 result = 1;
 583                         }
 584                         goto out;
 585                 }
 586         }
 587
 588         if (on) {
 589                 new->magic = FASYNC_MAGIC;
 590                 new->fa_file = filp;
 591                 new->fa_fd = fd;
 592                 new->fa_next = *fapp;
 593                 *fapp = new;
 594                 result = 1;
 595         }
 596 out:
 597         write_unlock_irq(&fasync_lock);
 598         return result;
 599 }
 600
 601 EXPORT_SYMBOL(fasync_helper);
 602
 603 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 604 {
 605         while (fa) {
 606                 struct fown_struct * fown;
 607                 if (fa->magic != FASYNC_MAGIC) {
 608                         printk(KERN_ERR "kill_fasync: bad magic number in "
 609                                "fasync_struct!\n");
 610                         return;
 611                 }
 612                 fown = &fa->fa_file->f_owner;
 613                 /* Don't send SIGURG to processes which have not set a
 614                    queued signum: SIGURG has its own default signalling
 615                    mechanism. */
 616                 if (!(sig == SIGURG && fown->signum == 0))
 617                         send_sigio(fown, fa->fa_fd, band);
 618                 fa = fa->fa_next;
 619         }
 620 }
 621
 622 EXPORT_SYMBOL(__kill_fasync);
 623
 624 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 625 {
 626         /* First a quick test without locking: usually
 627          * the list is empty.
 628          */
 629         if (*fp) {
 630                 read_lock(&fasync_lock);
 631                 /* reread *fp after obtaining the lock */
 632                 __kill_fasync(*fp, sig, band);
 633                 read_unlock(&fasync_lock);
 634         }
 635 }
 636 EXPORT_SYMBOL(kill_fasync);
 637
 638 static int __init fasync_init(void)
 639 {
 640         fasync_cache = kmem_cache_create("fasync_cache",
 641                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
 642         return 0;
 643 }
 644
 645 module_init(fasync_init)