linux/fs/fcntl.c
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   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#include <linux/pid_namespace.h>
  22
  23#include <asm/poll.h>
  24#include <asm/siginfo.h>
  25#include <asm/uaccess.h>
  26
  27void set_close_on_exec(unsigned int fd, int flag)
  28{
  29        struct files_struct *files = current->files;
  30        struct fdtable *fdt;
  31        spin_lock(&files->file_lock);
  32        fdt = files_fdtable(files);
  33        if (flag)
  34                FD_SET(fd, fdt->close_on_exec);
  35        else
  36                FD_CLR(fd, fdt->close_on_exec);
  37        spin_unlock(&files->file_lock);
  38}
  39
  40static int get_close_on_exec(unsigned int fd)
  41{
  42        struct files_struct *files = current->files;
  43        struct fdtable *fdt;
  44        int res;
  45        rcu_read_lock();
  46        fdt = files_fdtable(files);
  47        res = FD_ISSET(fd, fdt->close_on_exec);
  48        rcu_read_unlock();
  49        return res;
  50}
  51
  52/*
  53 * locate_fd finds a free file descriptor in the open_fds fdset,
  54 * expanding the fd arrays if necessary.  Must be called with the
  55 * file_lock held for write.
  56 */
  57
  58static int locate_fd(struct files_struct *files, 
  59                            struct file *file, unsigned int orig_start)
  60{
  61        unsigned int newfd;
  62        unsigned int start;
  63        int error;
  64        struct fdtable *fdt;
  65
  66        error = -EINVAL;
  67        if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  68                goto out;
  69
  70repeat:
  71        fdt = files_fdtable(files);
  72        /*
  73         * Someone might have closed fd's in the range
  74         * orig_start..fdt->next_fd
  75         */
  76        start = orig_start;
  77        if (start < files->next_fd)
  78                start = files->next_fd;
  79
  80        newfd = start;
  81        if (start < fdt->max_fds)
  82                newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
  83                                           fdt->max_fds, start);
  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        
 110out:
 111        return error;
 112}
 113
 114static int dupfd(struct file *file, unsigned int start, int cloexec)
 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                if (cloexec)
 127                        FD_SET(fd, fdt->close_on_exec);
 128                else
 129                        FD_CLR(fd, fdt->close_on_exec);
 130                spin_unlock(&files->file_lock);
 131                fd_install(fd, file);
 132        } else {
 133                spin_unlock(&files->file_lock);
 134                fput(file);
 135        }
 136
 137        return fd;
 138}
 139
 140asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 141{
 142        int err = -EBADF;
 143        struct file * file, *tofree;
 144        struct files_struct * files = current->files;
 145        struct fdtable *fdt;
 146
 147        spin_lock(&files->file_lock);
 148        if (!(file = fcheck(oldfd)))
 149                goto out_unlock;
 150        err = newfd;
 151        if (newfd == oldfd)
 152                goto out_unlock;
 153        err = -EBADF;
 154        if (newfd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 155                goto out_unlock;
 156        get_file(file);                 /* We are now finished with oldfd */
 157
 158        err = expand_files(files, newfd);
 159        if (err < 0)
 160                goto out_fput;
 161
 162        /* To avoid races with open() and dup(), we will mark the fd as
 163         * in-use in the open-file bitmap throughout the entire dup2()
 164         * process.  This is quite safe: do_close() uses the fd array
 165         * entry, not the bitmap, to decide what work needs to be
 166         * done.  --sct */
 167        /* Doesn't work. open() might be there first. --AV */
 168
 169        /* Yes. It's a race. In user space. Nothing sane to do */
 170        err = -EBUSY;
 171        fdt = files_fdtable(files);
 172        tofree = fdt->fd[newfd];
 173        if (!tofree && FD_ISSET(newfd, fdt->open_fds))
 174                goto out_fput;
 175
 176        rcu_assign_pointer(fdt->fd[newfd], file);
 177        FD_SET(newfd, fdt->open_fds);
 178        FD_CLR(newfd, fdt->close_on_exec);
 179        spin_unlock(&files->file_lock);
 180
 181        if (tofree)
 182                filp_close(tofree, files);
 183        err = newfd;
 184out:
 185        return err;
 186out_unlock:
 187        spin_unlock(&files->file_lock);
 188        goto out;
 189
 190out_fput:
 191        spin_unlock(&files->file_lock);
 192        fput(file);
 193        goto out;
 194}
 195
 196asmlinkage long sys_dup(unsigned int fildes)
 197{
 198        int ret = -EBADF;
 199        struct file * file = fget(fildes);
 200
 201        if (file)
 202                ret = dupfd(file, 0, 0);
 203        return ret;
 204}
 205
 206#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
 207
 208static int setfl(int fd, struct file * filp, unsigned long arg)
 209{
 210        struct inode * inode = filp->f_path.dentry->d_inode;
 211        int error = 0;
 212
 213        /*
 214         * O_APPEND cannot be cleared if the file is marked as append-only
 215         * and the file is open for write.
 216         */
 217        if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
 218                return -EPERM;
 219
 220        /* O_NOATIME can only be set by the owner or superuser */
 221        if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
 222                if (!is_owner_or_cap(inode))
 223                        return -EPERM;
 224
 225        /* required for strict SunOS emulation */
 226        if (O_NONBLOCK != O_NDELAY)
 227               if (arg & O_NDELAY)
 228                   arg |= O_NONBLOCK;
 229
 230        if (arg & O_DIRECT) {
 231                if (!filp->f_mapping || !filp->f_mapping->a_ops ||
 232                        !filp->f_mapping->a_ops->direct_IO)
 233                                return -EINVAL;
 234        }
 235
 236        if (filp->f_op && filp->f_op->check_flags)
 237                error = filp->f_op->check_flags(arg);
 238        if (error)
 239                return error;
 240
 241        lock_kernel();
 242        if ((arg ^ filp->f_flags) & FASYNC) {
 243                if (filp->f_op && filp->f_op->fasync) {
 244                        error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 245                        if (error < 0)
 246                                goto out;
 247                }
 248        }
 249
 250        filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 251 out:
 252        unlock_kernel();
 253        return error;
 254}
 255
 256static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
 257                     uid_t uid, uid_t euid, int force)
 258{
 259        write_lock_irq(&filp->f_owner.lock);
 260        if (force || !filp->f_owner.pid) {
 261                put_pid(filp->f_owner.pid);
 262                filp->f_owner.pid = get_pid(pid);
 263                filp->f_owner.pid_type = type;
 264                filp->f_owner.uid = uid;
 265                filp->f_owner.euid = euid;
 266        }
 267        write_unlock_irq(&filp->f_owner.lock);
 268}
 269
 270int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
 271                int force)
 272{
 273        int err;
 274        
 275        err = security_file_set_fowner(filp);
 276        if (err)
 277                return err;
 278
 279        f_modown(filp, pid, type, current->uid, current->euid, force);
 280        return 0;
 281}
 282EXPORT_SYMBOL(__f_setown);
 283
 284int f_setown(struct file *filp, unsigned long arg, int force)
 285{
 286        enum pid_type type;
 287        struct pid *pid;
 288        int who = arg;
 289        int result;
 290        type = PIDTYPE_PID;
 291        if (who < 0) {
 292                type = PIDTYPE_PGID;
 293                who = -who;
 294        }
 295        rcu_read_lock();
 296        pid = find_vpid(who);
 297        result = __f_setown(filp, pid, type, force);
 298        rcu_read_unlock();
 299        return result;
 300}
 301EXPORT_SYMBOL(f_setown);
 302
 303void f_delown(struct file *filp)
 304{
 305        f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
 306}
 307
 308pid_t f_getown(struct file *filp)
 309{
 310        pid_t pid;
 311        read_lock(&filp->f_owner.lock);
 312        pid = pid_vnr(filp->f_owner.pid);
 313        if (filp->f_owner.pid_type == PIDTYPE_PGID)
 314                pid = -pid;
 315        read_unlock(&filp->f_owner.lock);
 316        return pid;
 317}
 318
 319static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 320                struct file *filp)
 321{
 322        long err = -EINVAL;
 323
 324        switch (cmd) {
 325        case F_DUPFD:
 326        case F_DUPFD_CLOEXEC:
 327                get_file(filp);
 328                err = dupfd(filp, arg, cmd == F_DUPFD_CLOEXEC);
 329                break;
 330        case F_GETFD:
 331                err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
 332                break;
 333        case F_SETFD:
 334                err = 0;
 335                set_close_on_exec(fd, arg & FD_CLOEXEC);
 336                break;
 337        case F_GETFL:
 338                err = filp->f_flags;
 339                break;
 340        case F_SETFL:
 341                err = setfl(fd, filp, arg);
 342                break;
 343        case F_GETLK:
 344                err = fcntl_getlk(filp, (struct flock __user *) arg);
 345                break;
 346        case F_SETLK:
 347        case F_SETLKW:
 348                err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
 349                break;
 350        case F_GETOWN:
 351                /*
 352                 * XXX If f_owner is a process group, the
 353                 * negative return value will get converted
 354                 * into an error.  Oops.  If we keep the
 355                 * current syscall conventions, the only way
 356                 * to fix this will be in libc.
 357                 */
 358                err = f_getown(filp);
 359                force_successful_syscall_return();
 360                break;
 361        case F_SETOWN:
 362                err = f_setown(filp, arg, 1);
 363                break;
 364        case F_GETSIG:
 365                err = filp->f_owner.signum;
 366                break;
 367        case F_SETSIG:
 368                /* arg == 0 restores default behaviour. */
 369                if (!valid_signal(arg)) {
 370                        break;
 371                }
 372                err = 0;
 373                filp->f_owner.signum = arg;
 374                break;
 375        case F_GETLEASE:
 376                err = fcntl_getlease(filp);
 377                break;
 378        case F_SETLEASE:
 379                err = fcntl_setlease(fd, filp, arg);
 380                break;
 381        case F_NOTIFY:
 382                err = fcntl_dirnotify(fd, filp, arg);
 383                break;
 384        default:
 385                break;
 386        }
 387        return err;
 388}
 389
 390asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
 391{       
 392        struct file *filp;
 393        long err = -EBADF;
 394
 395        filp = fget(fd);
 396        if (!filp)
 397                goto out;
 398
 399        err = security_file_fcntl(filp, cmd, arg);
 400        if (err) {
 401                fput(filp);
 402                return err;
 403        }
 404
 405        err = do_fcntl(fd, cmd, arg, filp);
 406
 407        fput(filp);
 408out:
 409        return err;
 410}
 411
 412#if BITS_PER_LONG == 32
 413asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 414{       
 415        struct file * filp;
 416        long err;
 417
 418        err = -EBADF;
 419        filp = fget(fd);
 420        if (!filp)
 421                goto out;
 422
 423        err = security_file_fcntl(filp, cmd, arg);
 424        if (err) {
 425                fput(filp);
 426                return err;
 427        }
 428        err = -EBADF;
 429        
 430        switch (cmd) {
 431                case F_GETLK64:
 432                        err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 433                        break;
 434                case F_SETLK64:
 435                case F_SETLKW64:
 436                        err = fcntl_setlk64(fd, filp, cmd,
 437                                        (struct flock64 __user *) arg);
 438                        break;
 439                default:
 440                        err = do_fcntl(fd, cmd, arg, filp);
 441                        break;
 442        }
 443        fput(filp);
 444out:
 445        return err;
 446}
 447#endif
 448
 449/* Table to convert sigio signal codes into poll band bitmaps */
 450
 451static const long band_table[NSIGPOLL] = {
 452        POLLIN | POLLRDNORM,                    /* POLL_IN */
 453        POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 454        POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 455        POLLERR,                                /* POLL_ERR */
 456        POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 457        POLLHUP | POLLERR                       /* POLL_HUP */
 458};
 459
 460static inline int sigio_perm(struct task_struct *p,
 461                             struct fown_struct *fown, int sig)
 462{
 463        return (((fown->euid == 0) ||
 464                 (fown->euid == p->suid) || (fown->euid == p->uid) ||
 465                 (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 466                !security_file_send_sigiotask(p, fown, sig));
 467}
 468
 469static void send_sigio_to_task(struct task_struct *p,
 470                               struct fown_struct *fown, 
 471                               int fd,
 472                               int reason)
 473{
 474        if (!sigio_perm(p, fown, fown->signum))
 475                return;
 476
 477        switch (fown->signum) {
 478                siginfo_t si;
 479                default:
 480                        /* Queue a rt signal with the appropriate fd as its
 481                           value.  We use SI_SIGIO as the source, not 
 482                           SI_KERNEL, since kernel signals always get 
 483                           delivered even if we can't queue.  Failure to
 484                           queue in this case _should_ be reported; we fall
 485                           back to SIGIO in that case. --sct */
 486                        si.si_signo = fown->signum;
 487                        si.si_errno = 0;
 488                        si.si_code  = reason;
 489                        /* Make sure we are called with one of the POLL_*
 490                           reasons, otherwise we could leak kernel stack into
 491                           userspace.  */
 492                        BUG_ON((reason & __SI_MASK) != __SI_POLL);
 493                        if (reason - POLL_IN >= NSIGPOLL)
 494                                si.si_band  = ~0L;
 495                        else
 496                                si.si_band = band_table[reason - POLL_IN];
 497                        si.si_fd    = fd;
 498                        if (!group_send_sig_info(fown->signum, &si, p))
 499                                break;
 500                /* fall-through: fall back on the old plain SIGIO signal */
 501                case 0:
 502                        group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
 503        }
 504}
 505
 506void send_sigio(struct fown_struct *fown, int fd, int band)
 507{
 508        struct task_struct *p;
 509        enum pid_type type;
 510        struct pid *pid;
 511        
 512        read_lock(&fown->lock);
 513        type = fown->pid_type;
 514        pid = fown->pid;
 515        if (!pid)
 516                goto out_unlock_fown;
 517        
 518        read_lock(&tasklist_lock);
 519        do_each_pid_task(pid, type, p) {
 520                send_sigio_to_task(p, fown, fd, band);
 521        } while_each_pid_task(pid, type, p);
 522        read_unlock(&tasklist_lock);
 523 out_unlock_fown:
 524        read_unlock(&fown->lock);
 525}
 526
 527static void send_sigurg_to_task(struct task_struct *p,
 528                                struct fown_struct *fown)
 529{
 530        if (sigio_perm(p, fown, SIGURG))
 531                group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
 532}
 533
 534int send_sigurg(struct fown_struct *fown)
 535{
 536        struct task_struct *p;
 537        enum pid_type type;
 538        struct pid *pid;
 539        int ret = 0;
 540        
 541        read_lock(&fown->lock);
 542        type = fown->pid_type;
 543        pid = fown->pid;
 544        if (!pid)
 545                goto out_unlock_fown;
 546
 547        ret = 1;
 548        
 549        read_lock(&tasklist_lock);
 550        do_each_pid_task(pid, type, p) {
 551                send_sigurg_to_task(p, fown);
 552        } while_each_pid_task(pid, type, p);
 553        read_unlock(&tasklist_lock);
 554 out_unlock_fown:
 555        read_unlock(&fown->lock);
 556        return ret;
 557}
 558
 559static DEFINE_RWLOCK(fasync_lock);
 560static struct kmem_cache *fasync_cache __read_mostly;
 561
 562/*
 563 * fasync_helper() is used by some character device drivers (mainly mice)
 564 * to set up the fasync queue. It returns negative on error, 0 if it did
 565 * no changes and positive if it added/deleted the entry.
 566 */
 567int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 568{
 569        struct fasync_struct *fa, **fp;
 570        struct fasync_struct *new = NULL;
 571        int result = 0;
 572
 573        if (on) {
 574                new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 575                if (!new)
 576                        return -ENOMEM;
 577        }
 578        write_lock_irq(&fasync_lock);
 579        for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 580                if (fa->fa_file == filp) {
 581                        if(on) {
 582                                fa->fa_fd = fd;
 583                                kmem_cache_free(fasync_cache, new);
 584                        } else {
 585                                *fp = fa->fa_next;
 586                                kmem_cache_free(fasync_cache, fa);
 587                                result = 1;
 588                        }
 589                        goto out;
 590                }
 591        }
 592
 593        if (on) {
 594                new->magic = FASYNC_MAGIC;
 595                new->fa_file = filp;
 596                new->fa_fd = fd;
 597                new->fa_next = *fapp;
 598                *fapp = new;
 599                result = 1;
 600        }
 601out:
 602        write_unlock_irq(&fasync_lock);
 603        return result;
 604}
 605
 606EXPORT_SYMBOL(fasync_helper);
 607
 608void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 609{
 610        while (fa) {
 611                struct fown_struct * fown;
 612                if (fa->magic != FASYNC_MAGIC) {
 613                        printk(KERN_ERR "kill_fasync: bad magic number in "
 614                               "fasync_struct!\n");
 615                        return;
 616                }
 617                fown = &fa->fa_file->f_owner;
 618                /* Don't send SIGURG to processes which have not set a
 619                   queued signum: SIGURG has its own default signalling
 620                   mechanism. */
 621                if (!(sig == SIGURG && fown->signum == 0))
 622                        send_sigio(fown, fa->fa_fd, band);
 623                fa = fa->fa_next;
 624        }
 625}
 626
 627EXPORT_SYMBOL(__kill_fasync);
 628
 629void kill_fasync(struct fasync_struct **fp, int sig, int band)
 630{
 631        /* First a quick test without locking: usually
 632         * the list is empty.
 633         */
 634        if (*fp) {
 635                read_lock(&fasync_lock);
 636                /* reread *fp after obtaining the lock */
 637                __kill_fasync(*fp, sig, band);
 638                read_unlock(&fasync_lock);
 639        }
 640}
 641EXPORT_SYMBOL(kill_fasync);
 642
 643static int __init fasync_init(void)
 644{
 645        fasync_cache = kmem_cache_create("fasync_cache",
 646                sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 647        return 0;
 648}
 649
 650module_init(fasync_init)
 651
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