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/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
  28void 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
  41static 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
  53SYSCALL_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
 109Ebadf:
 110        err = -EBADF;
 111out_unlock:
 112        spin_unlock(&files->file_lock);
 113        return err;
 114}
 115
 116SYSCALL_DEFINE2(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
 129SYSCALL_DEFINE1(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
 146static 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
 198static 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
 212int __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}
 224EXPORT_SYMBOL(__f_setown);
 225
 226int 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}
 243EXPORT_SYMBOL(f_setown);
 244
 245void f_delown(struct file *filp)
 246{
 247        f_modown(filp, NULL, PIDTYPE_PID, 0, 0, 1);
 248}
 249
 250pid_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
 261static 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
 337SYSCALL_DEFINE3(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);
 355out:
 356        return err;
 357}
 358
 359#if BITS_PER_LONG == 32
 360SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 361                unsigned long, arg)
 362{       
 363        struct file * filp;
 364        long err;
 365
 366        err = -EBADF;
 367        filp = fget(fd);
 368        if (!filp)
 369                goto out;
 370
 371        err = security_file_fcntl(filp, cmd, arg);
 372        if (err) {
 373                fput(filp);
 374                return err;
 375        }
 376        err = -EBADF;
 377        
 378        switch (cmd) {
 379                case F_GETLK64:
 380                        err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
 381                        break;
 382                case F_SETLK64:
 383                case F_SETLKW64:
 384                        err = fcntl_setlk64(fd, filp, cmd,
 385                                        (struct flock64 __user *) arg);
 386                        break;
 387                default:
 388                        err = do_fcntl(fd, cmd, arg, filp);
 389                        break;
 390        }
 391        fput(filp);
 392out:
 393        return err;
 394}
 395#endif
 396
 397/* Table to convert sigio signal codes into poll band bitmaps */
 398
 399static const long band_table[NSIGPOLL] = {
 400        POLLIN | POLLRDNORM,                    /* POLL_IN */
 401        POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
 402        POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
 403        POLLERR,                                /* POLL_ERR */
 404        POLLPRI | POLLRDBAND,                   /* POLL_PRI */
 405        POLLHUP | POLLERR                       /* POLL_HUP */
 406};
 407
 408static inline int sigio_perm(struct task_struct *p,
 409                             struct fown_struct *fown, int sig)
 410{
 411        return (((fown->euid == 0) ||
 412                 (fown->euid == p->suid) || (fown->euid == p->uid) ||
 413                 (fown->uid == p->suid) || (fown->uid == p->uid)) &&
 414                !security_file_send_sigiotask(p, fown, sig));
 415}
 416
 417static void send_sigio_to_task(struct task_struct *p,
 418                               struct fown_struct *fown, 
 419                               int fd,
 420                               int reason)
 421{
 422        if (!sigio_perm(p, fown, fown->signum))
 423                return;
 424
 425        switch (fown->signum) {
 426                siginfo_t si;
 427                default:
 428                        /* Queue a rt signal with the appropriate fd as its
 429                           value.  We use SI_SIGIO as the source, not 
 430                           SI_KERNEL, since kernel signals always get 
 431                           delivered even if we can't queue.  Failure to
 432                           queue in this case _should_ be reported; we fall
 433                           back to SIGIO in that case. --sct */
 434                        si.si_signo = fown->signum;
 435                        si.si_errno = 0;
 436                        si.si_code  = reason;
 437                        /* Make sure we are called with one of the POLL_*
 438                           reasons, otherwise we could leak kernel stack into
 439                           userspace.  */
 440                        BUG_ON((reason & __SI_MASK) != __SI_POLL);
 441                        if (reason - POLL_IN >= NSIGPOLL)
 442                                si.si_band  = ~0L;
 443                        else
 444                                si.si_band = band_table[reason - POLL_IN];
 445                        si.si_fd    = fd;
 446                        if (!group_send_sig_info(fown->signum, &si, p))
 447                                break;
 448                /* fall-through: fall back on the old plain SIGIO signal */
 449                case 0:
 450                        group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);
 451        }
 452}
 453
 454void send_sigio(struct fown_struct *fown, int fd, int band)
 455{
 456        struct task_struct *p;
 457        enum pid_type type;
 458        struct pid *pid;
 459        
 460        read_lock(&fown->lock);
 461        type = fown->pid_type;
 462        pid = fown->pid;
 463        if (!pid)
 464                goto out_unlock_fown;
 465        
 466        read_lock(&tasklist_lock);
 467        do_each_pid_task(pid, type, p) {
 468                send_sigio_to_task(p, fown, fd, band);
 469        } while_each_pid_task(pid, type, p);
 470        read_unlock(&tasklist_lock);
 471 out_unlock_fown:
 472        read_unlock(&fown->lock);
 473}
 474
 475static void send_sigurg_to_task(struct task_struct *p,
 476                                struct fown_struct *fown)
 477{
 478        if (sigio_perm(p, fown, SIGURG))
 479                group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);
 480}
 481
 482int send_sigurg(struct fown_struct *fown)
 483{
 484        struct task_struct *p;
 485        enum pid_type type;
 486        struct pid *pid;
 487        int ret = 0;
 488        
 489        read_lock(&fown->lock);
 490        type = fown->pid_type;
 491        pid = fown->pid;
 492        if (!pid)
 493                goto out_unlock_fown;
 494
 495        ret = 1;
 496        
 497        read_lock(&tasklist_lock);
 498        do_each_pid_task(pid, type, p) {
 499                send_sigurg_to_task(p, fown);
 500        } while_each_pid_task(pid, type, p);
 501        read_unlock(&tasklist_lock);
 502 out_unlock_fown:
 503        read_unlock(&fown->lock);
 504        return ret;
 505}
 506
 507static DEFINE_RWLOCK(fasync_lock);
 508static struct kmem_cache *fasync_cache __read_mostly;
 509
 510/*
 511 * fasync_helper() is used by some character device drivers (mainly mice)
 512 * to set up the fasync queue. It returns negative on error, 0 if it did
 513 * no changes and positive if it added/deleted the entry.
 514 */
 515int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
 516{
 517        struct fasync_struct *fa, **fp;
 518        struct fasync_struct *new = NULL;
 519        int result = 0;
 520
 521        if (on) {
 522                new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
 523                if (!new)
 524                        return -ENOMEM;
 525        }
 526        write_lock_irq(&fasync_lock);
 527        for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
 528                if (fa->fa_file == filp) {
 529                        if(on) {
 530                                fa->fa_fd = fd;
 531                                kmem_cache_free(fasync_cache, new);
 532                        } else {
 533                                *fp = fa->fa_next;
 534                                kmem_cache_free(fasync_cache, fa);
 535                                result = 1;
 536                        }
 537                        goto out;
 538                }
 539        }
 540
 541        if (on) {
 542                new->magic = FASYNC_MAGIC;
 543                new->fa_file = filp;
 544                new->fa_fd = fd;
 545                new->fa_next = *fapp;
 546                *fapp = new;
 547                result = 1;
 548        }
 549out:
 550        write_unlock_irq(&fasync_lock);
 551        return result;
 552}
 553
 554EXPORT_SYMBOL(fasync_helper);
 555
 556void __kill_fasync(struct fasync_struct *fa, int sig, int band)
 557{
 558        while (fa) {
 559                struct fown_struct * fown;
 560                if (fa->magic != FASYNC_MAGIC) {
 561                        printk(KERN_ERR "kill_fasync: bad magic number in "
 562                               "fasync_struct!\n");
 563                        return;
 564                }
 565                fown = &fa->fa_file->f_owner;
 566                /* Don't send SIGURG to processes which have not set a
 567                   queued signum: SIGURG has its own default signalling
 568                   mechanism. */
 569                if (!(sig == SIGURG && fown->signum == 0))
 570                        send_sigio(fown, fa->fa_fd, band);
 571                fa = fa->fa_next;
 572        }
 573}
 574
 575EXPORT_SYMBOL(__kill_fasync);
 576
 577void kill_fasync(struct fasync_struct **fp, int sig, int band)
 578{
 579        /* First a quick test without locking: usually
 580         * the list is empty.
 581         */
 582        if (*fp) {
 583                read_lock(&fasync_lock);
 584                /* reread *fp after obtaining the lock */
 585                __kill_fasync(*fp, sig, band);
 586                read_unlock(&fasync_lock);
 587        }
 588}
 589EXPORT_SYMBOL(kill_fasync);
 590
 591static int __init fasync_init(void)
 592{
 593        fasync_cache = kmem_cache_create("fasync_cache",
 594                sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 595        return 0;
 596}
 597
 598module_init(fasync_init)
 599