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/fdtable.h>
  13 #include <linux/capability.h>
  14 #include <linux/dnotify.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 #include <linux/pid_namespace.h>
  22 #include <linux/smp_lock.h>
  23
  24 #include <asm/poll.h>
  25 #include <asm/siginfo.h>
  26 #include <asm/uaccess.h>
  27
  28 void set_close_on_exec(unsigned int fd, int flag)
  29 {
  30         struct files_struct *files = current->files;
  31         struct fdtable *fdt;
  32         spin_lock(&files->file_lock);
  33         fdt = files_fdtable(files);
  34         if (flag)
  35                 FD_SET(fd, fdt->close_on_exec);
  36         else
  37                 FD_CLR(fd, fdt->close_on_exec);
  38         spin_unlock(&files->file_lock);
  39 }
  40
  41 static int get_close_on_exec(unsigned int fd)
  42 {
  43         struct files_struct *files = current->files;
  44         struct fdtable *fdt;
  45         int res;
  46         rcu_read_lock();
  47         fdt = files_fdtable(files);
  48         res = FD_ISSET(fd, fdt->close_on_exec);
  49         rcu_read_unlock();
  50         return res;
  51 }
  52
  53 asmlinkage long sys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
  54 {
  55         int err = -EBADF;
  56         struct file * file, *tofree;
  57         struct files_struct * files = current->files;
  58         struct fdtable *fdt;
  59
  60         if ((flags & ~O_CLOEXEC) != 0)
  61                 return -EINVAL;
  62
  63         if (unlikely(oldfd == newfd))
  64                 return -EINVAL;
  65
  66         spin_lock(&files->file_lock);
  67         err = expand_files(files, newfd);
  68         file = fcheck(oldfd);
  69         if (unlikely(!file))
  70                 goto Ebadf;
  71         if (unlikely(err < 0)) {
  72                 if (err == -EMFILE)
  73                         goto Ebadf;
  74                 goto out_unlock;
  75         }
  76         /*
  77          * We need to detect attempts to do dup2() over allocated but still
  78          * not finished descriptor.  NB: OpenBSD avoids that at the price of
  79          * extra work in their equivalent of fget() - they insert struct
  80          * file immediately after grabbing descriptor, mark it larval if
  81          * more work (e.g. actual opening) is needed and make sure that
  82          * fget() treats larval files as absent.  Potentially interesting,
  83          * but while extra work in fget() is trivial, locking implications
  84          * and amount of surgery on open()-related paths in VFS are not.
  85          * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
  86          * deadlocks in rather amusing ways, AFAICS.  All of that is out of
  87          * scope of POSIX or SUS, since neither considers shared descriptor
  88          * tables and this condition does not arise without those.
  89          */
  90         err = -EBUSY;
  91         fdt = files_fdtable(files);
  92         tofree = fdt->fd[newfd];
  93         if (!tofree && FD_ISSET(newfd, fdt->open_fds))
  94                 goto out_unlock;
  95         get_file(file);
  96         rcu_assign_pointer(fdt->fd[newfd], file);
  97         FD_SET(newfd, fdt->open_fds);
  98         if (flags & O_CLOEXEC)
  99                 FD_SET(newfd, fdt->close_on_exec);
 100         else
 101                 FD_CLR(newfd, fdt->close_on_exec);
 102         spin_unlock(&files->file_lock);
 103
 104         if (tofree)
 105                 filp_close(tofree, files);
 106
 107         return newfd;
 108
 109 Ebadf:
 110         err = -EBADF;
 111 out_unlock:
 112         spin_unlock(&files->file_lock);
 113         return err;
 114 }
 115
 116 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 117 {
 118         if (unlikely(newfd == oldfd)) { /* corner case */
 119                 struct files_struct *files = current->files;
 120                 rcu_read_lock();
 121                 if (!fcheck_files(files, oldfd))
 122                         oldfd = -EBADF;
 123                 rcu_read_unlock();
 124                 return oldfd;
 125         }
 126         return sys_dup3(oldfd, newfd, 0);
 127 }
 128
 129 asmlinkage long sys_dup(unsigned int fildes)
 130 {
 131         int ret = -EBADF;
 132         struct file *file = fget(fildes);
 133
 134         if (file) {
 135                 ret = get_unused_fd();
 136                 if (ret >= 0)
 137                         fd_install(ret, file);
 138                 else
 139                         fput(file);
 140         }
 141         return ret;
 142 }
 143
 144 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
 145
 146 static int setfl(int fd, struct file * filp, unsigned long arg)
 147 {
 148         struct inode * inode = filp->f_path.dentry->d_inode;
 149         int error = 0;
 150
 151         /*
 152          * O_APPEND cannot be cleared if the file is marked as append-only
 153          * and the file is open for write.
 154          */
 155         if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
 156                 return -EPERM;
 157
 158         /* O_NOATIME can only be set by the owner or superuser */
 159         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 160                 if (!is_owner_or_cap(inode))
 161                         return -EPERM;
 162
 163         /* required for strict SunOS emulation */
 164         if (O_NONBLOCK != O_NDELAY)
 165                if (arg & O_NDELAY)
 166                    arg |= O_NONBLOCK;
 167
 168         if (arg & O_DIRECT) {
 169                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 170                         !filp->f_mapping->a_ops->direct_IO)
 171                                 return -EINVAL;
 172         }
 173
 174         if (filp->f_op && filp->f_op->check_flags)
 175                 error = filp->f_op->check_flags(arg);
 176         if (error)
 177                 return error;
 178
 179         /*
 180          * We still need a lock here for now to keep multiple FASYNC calls
 181          * from racing with each other.
 182          */
 183         lock_kernel();
 184         if ((arg ^ filp->f_flags) & FASYNC) {
 185                 if (filp->f_op && filp->f_op->fasync) {
 186                         error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 187                         if (error < 0)
 188                                 goto out;
 189                 }
 190         }
 191
 192         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 193  out:
 194         unlock_kernel();
 195         return error;
 196 }
 197
 198 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
 199                      uid_t uid, uid_t euid, int force)
 200 {
 201         write_lock_irq(&filp->f_owner.lock);
 202         if (force || !filp->f_owner.pid) {
 203                 put_pid(filp->f_owner.pid);
 204                 filp->f_owner.pid = get_pid(pid);
 205                 filp->f_owner.pid_type = type;
 206                 filp->f_owner.uid = uid;
 207                 filp->f_owner.euid = euid;
 208         }
 209         write_unlock_irq(&filp->f_owner.lock);
 210 }
 211
 212 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
 213                 int force)
 214 {
 215         int err;
 216
 217         err = security_file_set_fowner(filp);
 218         if (err)
 219                 return err;
 220
 221         f_modown(filp, pid, type, current->uid, current->euid, force);
 222         return 0;
 223 }
 224 EXPORT_SYMBOL(__f_setown);
 225
 226 int f_setown(struct file *filp, unsigned long arg, int force)
 227 {
 228         enum pid_type type;
 229         struct pid *pid;
 230         int who = arg;
 231         int result;
 232         type = PIDTYPE_PID;
 233         if (who < 0) {
 234                 type = PIDTYPE_PGID;
 235                 who = -who;
 236         }
 237         rcu_read_lock();
 238         pid = find_vpid(who);
 239         result = __f_setown(filp, pid, type, force);
 240         rcu_read_unlock();
 241         return result;
 242 }
 243 EXPORT_SYMBOL(f_setown);
 244
 245 void f_delown(struct file *filp)
 246 {
 247         f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
 248 }
 249
 250 pid_t f_getown(struct file *filp)
 251 {
 252         pid_t pid;
 253         read_lock(&filp->f_owner.lock);
 254         pid = pid_vnr(filp->f_owner.pid);
 255         if (filp->f_owner.pid_type == PIDTYPE_PGID)
 256                 pid = -pid;
 257         read_unlock(&filp->f_owner.lock);
 258         return pid;
 259 }
 260
 261 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 262                 struct file *filp)
 263 {
 264         long err = -EINVAL;
 265
 266         switch (cmd) {
 267         case F_DUPFD:
 268         case F_DUPFD_CLOEXEC:
 269                 if (arg >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 270                         break;
 271                 err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
 272                 if (err >= 0) {
 273                         get_file(filp);
 274                         fd_install(err, filp);
 275                 }
 276                 break;
 277         case F_GETFD:
 278                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 279                 break;
 280         case F_SETFD:
 281                 err = 0;
 282                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 283                 break;
 284         case F_GETFL:
 285                 err = filp->f_flags;
 286                 break;
 287         case F_SETFL:
 288                 err = setfl(fd, filp, arg);
 289                 break;
 290         case F_GETLK:
 291                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 292                 break;
 293         case F_SETLK:
 294         case F_SETLKW:
 295                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 296                 break;
 297         case F_GETOWN:
 298                 /*
 299                  * XXX If f_owner is a process group, the
 300                  * negative return value will get converted
 301                  * into an error.  Oops.  If we keep the
 302                  * current syscall conventions, the only way
 303                  * to fix this will be in libc.
 304                  */
 305                 err = f_getown(filp);
 306                 force_successful_syscall_return();
 307                 break;
 308         case F_SETOWN:
 309                 err = f_setown(filp, arg, 1);
 310                 break;
 311         case F_GETSIG:
 312                 err = filp->f_owner.signum;
 313                 break;
 314         case F_SETSIG:
 315                 /* arg == 0 restores default behaviour. */
 316                 if (!valid_signal(arg)) {
 317                         break;
 318                 }
 319                 err = 0;
 320                 filp->f_owner.signum = arg;
 321                 break;
 322         case F_GETLEASE:
 323                 err = fcntl_getlease(filp);
 324                 break;
 325         case F_SETLEASE:
 326                 err = fcntl_setlease(fd, filp, arg);
 327                 break;
 328         case F_NOTIFY:
 329                 err = fcntl_dirnotify(fd, filp, arg);
 330                 break;
 331         default:
 332                 break;
 333         }
 334         return err;
 335 }
 336
 337 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
 338 {
 339         struct file *filp;
 340         long err = -EBADF;
 341
 342         filp = fget(fd);
 343         if (!filp)
 344                 goto out;
 345
 346         err = security_file_fcntl(filp, cmd, arg);
 347         if (err) {
 348                 fput(filp);
 349                 return err;
 350         }
 351
 352         err = do_fcntl(fd, cmd, arg, filp);
 353
 354         fput(filp);
 355 out:
 356         return err;
 357 }
 358
 359 #if BITS_PER_LONG == 32
 360 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 361 {
 362         struct file * filp;
 363         long err;
 364
 365         err = -EBADF;
 366         filp = fget(fd);
 367         if (!filp)
 368                 goto out;
 369
 370         err = security_file_fcntl(filp, cmd, arg);
 371         if (err) {
 372                 fput(filp);
 373                 return err;
 374         }
 375         err = -EBADF;
 376
 377         switch (cmd) {
 378                 case F_GETLK64:
 379                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 380                         break;
 381                 case F_SETLK64:
 382                 case F_SETLKW64:
 383                         err = fcntl_setlk64(fd, filp, cmd,
 384                                         (struct flock64 __user *) arg);
 385                         break;
 386                 default:
 387                         err = do_fcntl(fd, cmd, arg, filp);
 388                         break;
 389         }
 390         fput(filp);
 391 out:
 392         return err;
 393 }
 394 #endif
 395
 396 /* Table to convert sigio signal codes into poll band bitmaps */
 397
 398 static const long band_table[NSIGPOLL] = {
 399         POLLIN | POLLRDNORM,                    /* POLL_IN */
 400         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 401         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 402         POLLERR,                                /* POLL_ERR */
 403         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 404         POLLHUP | POLLERR                       /* POLL_HUP */
 405 };
 406
 407 static inline int sigio_perm(struct task_struct *p,
 408                              struct fown_struct *fown, int sig)
 409 {
 410         return (((fown->euid == 0) ||
 411                  (fown->euid == p->suid) || (fown->euid == p->uid) ||
 412                  (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 413                 !security_file_send_sigiotask(p, fown, sig));
 414 }
 415
 416 static void send_sigio_to_task(struct task_struct *p,
 417                                struct fown_struct *fown,
 418                                int fd,
 419                                int reason)
 420 {
 421         if (!sigio_perm(p, fown, fown->signum))
 422                 return;
 423
 424         switch (fown->signum) {
 425                 siginfo_t si;
 426                 default:
 427                         /* Queue a rt signal with the appropriate fd as its
 428                            value.  We use SI_SIGIO as the source, not
 429                            SI_KERNEL, since kernel signals always get
 430                            delivered even if we can't queue.  Failure to
 431                            queue in this case _should_ be reported; we fall
 432                            back to SIGIO in that case. --sct */
 433                         si.si_signo = fown->signum;
 434                         si.si_errno = 0;
 435                         si.si_code  = reason;
 436                         /* Make sure we are called with one of the POLL_*
 437                            reasons, otherwise we could leak kernel stack into
 438                            userspace.  */
 439                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 440                         if (reason - POLL_IN >= NSIGPOLL)
 441                                 si.si_band  = ~0L;
 442                         else
 443                                 si.si_band = band_table[reason - POLL_IN];
 444                         si.si_fd    = fd;
 445                         if (!group_send_sig_info(fown->signum, &si, p))
 446                                 break;
 447                 /* fall-through: fall back on the old plain SIGIO signal */
 448                 case 0:
 449                         group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
 450         }
 451 }
 452
 453 void send_sigio(struct fown_struct *fown, int fd, int band)
 454 {
 455         struct task_struct *p;
 456         enum pid_type type;
 457         struct pid *pid;
 458
 459         read_lock(&fown->lock);
 460         type = fown->pid_type;
 461         pid = fown->pid;
 462         if (!pid)
 463                 goto out_unlock_fown;
 464
 465         read_lock(&tasklist_lock);
 466         do_each_pid_task(pid, type, p) {
 467                 send_sigio_to_task(p, fown, fd, band);
 468         } while_each_pid_task(pid, type, p);
 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                 group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
 479 }
 480
 481 int send_sigurg(struct fown_struct *fown)
 482 {
 483         struct task_struct *p;
 484         enum pid_type type;
 485         struct pid *pid;
 486         int ret = 0;
 487
 488         read_lock(&fown->lock);
 489         type = fown->pid_type;
 490         pid = fown->pid;
 491         if (!pid)
 492                 goto out_unlock_fown;
 493
 494         ret = 1;
 495
 496         read_lock(&tasklist_lock);
 497         do_each_pid_task(pid, type, p) {
 498                 send_sigurg_to_task(p, fown);
 499         } while_each_pid_task(pid, type, p);
 500         read_unlock(&tasklist_lock);
 501  out_unlock_fown:
 502         read_unlock(&fown->lock);
 503         return ret;
 504 }
 505
 506 static DEFINE_RWLOCK(fasync_lock);
 507 static struct kmem_cache *fasync_cache __read_mostly;
 508
 509 /*
 510  * fasync_helper() is used by some character device drivers (mainly mice)
 511  * to set up the fasync queue. It returns negative on error, 0 if it did
 512  * no changes and positive if it added/deleted the entry.
 513  */
 514 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 515 {
 516         struct fasync_struct *fa, **fp;
 517         struct fasync_struct *new = NULL;
 518         int result = 0;
 519
 520         if (on) {
 521                 new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 522                 if (!new)
 523                         return -ENOMEM;
 524         }
 525         write_lock_irq(&fasync_lock);
 526         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 527                 if (fa->fa_file == filp) {
 528                         if(on) {
 529                                 fa->fa_fd = fd;
 530                                 kmem_cache_free(fasync_cache, new);
 531                         } else {
 532                                 *fp = fa->fa_next;
 533                                 kmem_cache_free(fasync_cache, fa);
 534                                 result = 1;
 535                         }
 536                         goto out;
 537                 }
 538         }
 539
 540         if (on) {
 541                 new->magic = FASYNC_MAGIC;
 542                 new->fa_file = filp;
 543                 new->fa_fd = fd;
 544                 new->fa_next = *fapp;
 545                 *fapp = new;
 546                 result = 1;
 547         }
 548 out:
 549         write_unlock_irq(&fasync_lock);
 550         return result;
 551 }
 552
 553 EXPORT_SYMBOL(fasync_helper);
 554
 555 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 556 {
 557         while (fa) {
 558                 struct fown_struct * fown;
 559                 if (fa->magic != FASYNC_MAGIC) {
 560                         printk(KERN_ERR "kill_fasync: bad magic number in "
 561                                "fasync_struct!\n");
 562                         return;
 563                 }
 564                 fown = &fa->fa_file->f_owner;
 565                 /* Don't send SIGURG to processes which have not set a
 566                    queued signum: SIGURG has its own default signalling
 567                    mechanism. */
 568                 if (!(sig == SIGURG && fown->signum == 0))
 569                         send_sigio(fown, fa->fa_fd, band);
 570                 fa = fa->fa_next;
 571         }
 572 }
 573
 574 EXPORT_SYMBOL(__kill_fasync);
 575
 576 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 577 {
 578         /* First a quick test without locking: usually
 579          * the list is empty.
 580          */
 581         if (*fp) {
 582                 read_lock(&fasync_lock);
 583                 /* reread *fp after obtaining the lock */
 584                 __kill_fasync(*fp, sig, band);
 585                 read_unlock(&fasync_lock);
 586         }
 587 }
 588 EXPORT_SYMBOL(kill_fasync);
 589
 590 static int __init fasync_init(void)
 591 {
 592         fasync_cache = kmem_cache_create("fasync_cache",
 593                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 594         return 0;
 595 }
 596
 597 module_init(fasync_init)