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 SYSCALL_DEFINE3(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 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 117 {
 118         if (unlikely(newfd == oldfd)) { /* corner case */
 119                 struct files_struct *files = current->files;
 120                 int retval = oldfd;
 121
 122                 rcu_read_lock();
 123                 if (!fcheck_files(files, oldfd))
 124                         retval = -EBADF;
 125                 rcu_read_unlock();
 126                 return retval;
 127         }
 128         return sys_dup3(oldfd, newfd, 0);
 129 }
 130
 131 SYSCALL_DEFINE1(dup, unsigned int, fildes)
 132 {
 133         int ret = -EBADF;
 134         struct file *file = fget(fildes);
 135
 136         if (file) {
 137                 ret = get_unused_fd();
 138                 if (ret >= 0)
 139                         fd_install(ret, file);
 140                 else
 141                         fput(file);
 142         }
 143         return ret;
 144 }
 145
 146 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
 147
 148 static int setfl(int fd, struct file * filp, unsigned long arg)
 149 {
 150         struct inode * inode = filp->f_path.dentry->d_inode;
 151         int error = 0;
 152
 153         /*
 154          * O_APPEND cannot be cleared if the file is marked as append-only
 155          * and the file is open for write.
 156          */
 157         if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
 158                 return -EPERM;
 159
 160         /* O_NOATIME can only be set by the owner or superuser */
 161         if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 162                 if (!is_owner_or_cap(inode))
 163                         return -EPERM;
 164
 165         /* required for strict SunOS emulation */
 166         if (O_NONBLOCK != O_NDELAY)
 167                if (arg & O_NDELAY)
 168                    arg |= O_NONBLOCK;
 169
 170         if (arg & O_DIRECT) {
 171                 if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 172                         !filp->f_mapping->a_ops->direct_IO)
 173                                 return -EINVAL;
 174         }
 175
 176         if (filp->f_op && filp->f_op->check_flags)
 177                 error = filp->f_op->check_flags(arg);
 178         if (error)
 179                 return error;
 180
 181         /*
 182          * ->fasync() is responsible for setting the FASYNC bit.
 183          */
 184         if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op &&
 185                         filp->f_op->fasync) {
 186                 error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 187                 if (error < 0)
 188                         goto out;
 189                 if (error > 0)
 190                         error = 0;
 191         }
 192         spin_lock(&filp->f_lock);
 193         filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 194         spin_unlock(&filp->f_lock);
 195
 196  out:
 197         return error;
 198 }
 199
 200 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
 201                      uid_t uid, uid_t euid, int force)
 202 {
 203         write_lock_irq(&filp->f_owner.lock);
 204         if (force || !filp->f_owner.pid) {
 205                 put_pid(filp->f_owner.pid);
 206                 filp->f_owner.pid = get_pid(pid);
 207                 filp->f_owner.pid_type = type;
 208                 filp->f_owner.uid = uid;
 209                 filp->f_owner.euid = euid;
 210         }
 211         write_unlock_irq(&filp->f_owner.lock);
 212 }
 213
 214 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
 215                 int force)
 216 {
 217         const struct cred *cred = current_cred();
 218         int err;
 219
 220         err = security_file_set_fowner(filp);
 221         if (err)
 222                 return err;
 223
 224         f_modown(filp, pid, type, cred->uid, cred->euid, force);
 225         return 0;
 226 }
 227 EXPORT_SYMBOL(__f_setown);
 228
 229 int f_setown(struct file *filp, unsigned long arg, int force)
 230 {
 231         enum pid_type type;
 232         struct pid *pid;
 233         int who = arg;
 234         int result;
 235         type = PIDTYPE_PID;
 236         if (who < 0) {
 237                 type = PIDTYPE_PGID;
 238                 who = -who;
 239         }
 240         rcu_read_lock();
 241         pid = find_vpid(who);
 242         result = __f_setown(filp, pid, type, force);
 243         rcu_read_unlock();
 244         return result;
 245 }
 246 EXPORT_SYMBOL(f_setown);
 247
 248 void f_delown(struct file *filp)
 249 {
 250         f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
 251 }
 252
 253 pid_t f_getown(struct file *filp)
 254 {
 255         pid_t pid;
 256         read_lock(&filp->f_owner.lock);
 257         pid = pid_vnr(filp->f_owner.pid);
 258         if (filp->f_owner.pid_type == PIDTYPE_PGID)
 259                 pid = -pid;
 260         read_unlock(&filp->f_owner.lock);
 261         return pid;
 262 }
 263
 264 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 265                 struct file *filp)
 266 {
 267         long err = -EINVAL;
 268
 269         switch (cmd) {
 270         case F_DUPFD:
 271         case F_DUPFD_CLOEXEC:
 272                 if (arg >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 273                         break;
 274                 err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
 275                 if (err >= 0) {
 276                         get_file(filp);
 277                         fd_install(err, filp);
 278                 }
 279                 break;
 280         case F_GETFD:
 281                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 282                 break;
 283         case F_SETFD:
 284                 err = 0;
 285                 set_close_on_exec(fd, arg & FD_CLOEXEC);
 286                 break;
 287         case F_GETFL:
 288                 err = filp->f_flags;
 289                 break;
 290         case F_SETFL:
 291                 err = setfl(fd, filp, arg);
 292                 break;
 293         case F_GETLK:
 294                 err = fcntl_getlk(filp, (struct flock __user *) arg);
 295                 break;
 296         case F_SETLK:
 297         case F_SETLKW:
 298                 err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 299                 break;
 300         case F_GETOWN:
 301                 /*
 302                  * XXX If f_owner is a process group, the
 303                  * negative return value will get converted
 304                  * into an error.  Oops.  If we keep the
 305                  * current syscall conventions, the only way
 306                  * to fix this will be in libc.
 307                  */
 308                 err = f_getown(filp);
 309                 force_successful_syscall_return();
 310                 break;
 311         case F_SETOWN:
 312                 err = f_setown(filp, arg, 1);
 313                 break;
 314         case F_GETSIG:
 315                 err = filp->f_owner.signum;
 316                 break;
 317         case F_SETSIG:
 318                 /* arg == 0 restores default behaviour. */
 319                 if (!valid_signal(arg)) {
 320                         break;
 321                 }
 322                 err = 0;
 323                 filp->f_owner.signum = arg;
 324                 break;
 325         case F_GETLEASE:
 326                 err = fcntl_getlease(filp);
 327                 break;
 328         case F_SETLEASE:
 329                 err = fcntl_setlease(fd, filp, arg);
 330                 break;
 331         case F_NOTIFY:
 332                 err = fcntl_dirnotify(fd, filp, arg);
 333                 break;
 334         default:
 335                 break;
 336         }
 337         return err;
 338 }
 339
 340 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
 341 {
 342         struct file *filp;
 343         long err = -EBADF;
 344
 345         filp = fget(fd);
 346         if (!filp)
 347                 goto out;
 348
 349         err = security_file_fcntl(filp, cmd, arg);
 350         if (err) {
 351                 fput(filp);
 352                 return err;
 353         }
 354
 355         err = do_fcntl(fd, cmd, arg, filp);
 356
 357         fput(filp);
 358 out:
 359         return err;
 360 }
 361
 362 #if BITS_PER_LONG == 32
 363 SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 364                 unsigned long, arg)
 365 {
 366         struct file * filp;
 367         long err;
 368
 369         err = -EBADF;
 370         filp = fget(fd);
 371         if (!filp)
 372                 goto out;
 373
 374         err = security_file_fcntl(filp, cmd, arg);
 375         if (err) {
 376                 fput(filp);
 377                 return err;
 378         }
 379         err = -EBADF;
 380
 381         switch (cmd) {
 382                 case F_GETLK64:
 383                         err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 384                         break;
 385                 case F_SETLK64:
 386                 case F_SETLKW64:
 387                         err = fcntl_setlk64(fd, filp, cmd,
 388                                         (struct flock64 __user *) arg);
 389                         break;
 390                 default:
 391                         err = do_fcntl(fd, cmd, arg, filp);
 392                         break;
 393         }
 394         fput(filp);
 395 out:
 396         return err;
 397 }
 398 #endif
 399
 400 /* Table to convert sigio signal codes into poll band bitmaps */
 401
 402 static const long band_table[NSIGPOLL] = {
 403         POLLIN | POLLRDNORM,                    /* POLL_IN */
 404         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 405         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 406         POLLERR,                                /* POLL_ERR */
 407         POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 408         POLLHUP | POLLERR                       /* POLL_HUP */
 409 };
 410
 411 static inline int sigio_perm(struct task_struct *p,
 412                              struct fown_struct *fown, int sig)
 413 {
 414         const struct cred *cred;
 415         int ret;
 416
 417         rcu_read_lock();
 418         cred = __task_cred(p);
 419         ret = ((fown->euid == 0 ||
 420                 fown->euid == cred->suid || fown->euid == cred->uid ||
 421                 fown->uid  == cred->suid || fown->uid  == cred->uid) &&
 422                !security_file_send_sigiotask(p, fown, sig));
 423         rcu_read_unlock();
 424         return ret;
 425 }
 426
 427 static void send_sigio_to_task(struct task_struct *p,
 428                                struct fown_struct *fown,
 429                                int fd,
 430                                int reason)
 431 {
 432         if (!sigio_perm(p, fown, fown->signum))
 433                 return;
 434
 435         switch (fown->signum) {
 436                 siginfo_t si;
 437                 default:
 438                         /* Queue a rt signal with the appropriate fd as its
 439                            value.  We use SI_SIGIO as the source, not
 440                            SI_KERNEL, since kernel signals always get
 441                            delivered even if we can't queue.  Failure to
 442                            queue in this case _should_ be reported; we fall
 443                            back to SIGIO in that case. --sct */
 444                         si.si_signo = fown->signum;
 445                         si.si_errno = 0;
 446                         si.si_code  = reason;
 447                         /* Make sure we are called with one of the POLL_*
 448                            reasons, otherwise we could leak kernel stack into
 449                            userspace.  */
 450                         BUG_ON((reason & __SI_MASK) != __SI_POLL);
 451                         if (reason - POLL_IN >= NSIGPOLL)
 452                                 si.si_band  = ~0L;
 453                         else
 454                                 si.si_band = band_table[reason - POLL_IN];
 455                         si.si_fd    = fd;
 456                         if (!group_send_sig_info(fown->signum, &si, p))
 457                                 break;
 458                 /* fall-through: fall back on the old plain SIGIO signal */
 459                 case 0:
 460                         group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
 461         }
 462 }
 463
 464 void send_sigio(struct fown_struct *fown, int fd, int band)
 465 {
 466         struct task_struct *p;
 467         enum pid_type type;
 468         struct pid *pid;
 469
 470         read_lock(&fown->lock);
 471         type = fown->pid_type;
 472         pid = fown->pid;
 473         if (!pid)
 474                 goto out_unlock_fown;
 475
 476         read_lock(&tasklist_lock);
 477         do_each_pid_task(pid, type, p) {
 478                 send_sigio_to_task(p, fown, fd, band);
 479         } while_each_pid_task(pid, type, p);
 480         read_unlock(&tasklist_lock);
 481  out_unlock_fown:
 482         read_unlock(&fown->lock);
 483 }
 484
 485 static void send_sigurg_to_task(struct task_struct *p,
 486                                 struct fown_struct *fown)
 487 {
 488         if (sigio_perm(p, fown, SIGURG))
 489                 group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
 490 }
 491
 492 int send_sigurg(struct fown_struct *fown)
 493 {
 494         struct task_struct *p;
 495         enum pid_type type;
 496         struct pid *pid;
 497         int ret = 0;
 498
 499         read_lock(&fown->lock);
 500         type = fown->pid_type;
 501         pid = fown->pid;
 502         if (!pid)
 503                 goto out_unlock_fown;
 504
 505         ret = 1;
 506
 507         read_lock(&tasklist_lock);
 508         do_each_pid_task(pid, type, p) {
 509                 send_sigurg_to_task(p, fown);
 510         } while_each_pid_task(pid, type, p);
 511         read_unlock(&tasklist_lock);
 512  out_unlock_fown:
 513         read_unlock(&fown->lock);
 514         return ret;
 515 }
 516
 517 static DEFINE_RWLOCK(fasync_lock);
 518 static struct kmem_cache *fasync_cache __read_mostly;
 519
 520 /*
 521  * fasync_helper() is used by almost all character device drivers
 522  * to set up the fasync queue. It returns negative on error, 0 if it did
 523  * no changes and positive if it added/deleted the entry.
 524  */
 525 int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 526 {
 527         struct fasync_struct *fa, **fp;
 528         struct fasync_struct *new = NULL;
 529         int result = 0;
 530
 531         if (on) {
 532                 new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 533                 if (!new)
 534                         return -ENOMEM;
 535         }
 536
 537         /*
 538          * We need to take f_lock first since it's not an IRQ-safe
 539          * lock.
 540          */
 541         spin_lock(&filp->f_lock);
 542         write_lock_irq(&fasync_lock);
 543         for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 544                 if (fa->fa_file == filp) {
 545                         if(on) {
 546                                 fa->fa_fd = fd;
 547                                 kmem_cache_free(fasync_cache, new);
 548                         } else {
 549                                 *fp = fa->fa_next;
 550                                 kmem_cache_free(fasync_cache, fa);
 551                                 result = 1;
 552                         }
 553                         goto out;
 554                 }
 555         }
 556
 557         if (on) {
 558                 new->magic = FASYNC_MAGIC;
 559                 new->fa_file = filp;
 560                 new->fa_fd = fd;
 561                 new->fa_next = *fapp;
 562                 *fapp = new;
 563                 result = 1;
 564         }
 565 out:
 566         if (on)
 567                 filp->f_flags |= FASYNC;
 568         else
 569                 filp->f_flags &= ~FASYNC;
 570         write_unlock_irq(&fasync_lock);
 571         spin_unlock(&filp->f_lock);
 572         return result;
 573 }
 574
 575 EXPORT_SYMBOL(fasync_helper);
 576
 577 void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 578 {
 579         while (fa) {
 580                 struct fown_struct * fown;
 581                 if (fa->magic != FASYNC_MAGIC) {
 582                         printk(KERN_ERR "kill_fasync: bad magic number in "
 583                                "fasync_struct!\n");
 584                         return;
 585                 }
 586                 fown = &fa->fa_file->f_owner;
 587                 /* Don't send SIGURG to processes which have not set a
 588                    queued signum: SIGURG has its own default signalling
 589                    mechanism. */
 590                 if (!(sig == SIGURG && fown->signum == 0))
 591                         send_sigio(fown, fa->fa_fd, band);
 592                 fa = fa->fa_next;
 593         }
 594 }
 595
 596 EXPORT_SYMBOL(__kill_fasync);
 597
 598 void kill_fasync(struct fasync_struct **fp, int sig, int band)
 599 {
 600         /* First a quick test without locking: usually
 601          * the list is empty.
 602          */
 603         if (*fp) {
 604                 read_lock(&fasync_lock);
 605                 /* reread *fp after obtaining the lock */
 606                 __kill_fasync(*fp, sig, band);
 607                 read_unlock(&fasync_lock);
 608         }
 609 }
 610 EXPORT_SYMBOL(kill_fasync);
 611
 612 static int __init fasync_init(void)
 613 {
 614         fasync_cache = kmem_cache_create("fasync_cache",
 615                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 616         return 0;
 617 }
 618
 619 module_init(fasync_init)