root/fs/fcntl.c

/*
 *  linux/fs/fcntl.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/dnotify.h>
#include <linux/smp_lock.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/ptrace.h>

#include <asm/poll.h>
#include <asm/siginfo.h>
#include <asm/uaccess.h>

void fastcall set_close_on_exec(unsigned int fd, int flag)
{
        struct files_struct *files = current->files;
        spin_lock(&files->file_lock);
        if (flag)
                FD_SET(fd, files->close_on_exec);
        else
                FD_CLR(fd, files->close_on_exec);
        spin_unlock(&files->file_lock);
}

static inline int get_close_on_exec(unsigned int fd)
{
        struct files_struct *files = current->files;
        int res;
        spin_lock(&files->file_lock);
        res = FD_ISSET(fd, files->close_on_exec);
        spin_unlock(&files->file_lock);
        return res;
}


/* Expand files.  Return <0 on error; 0 nothing done; 1 files expanded,
 * we may have blocked. 
 *
 * Should be called with the files->file_lock spinlock held for write.
 */
static int expand_files(struct files_struct *files, int nr)
{
        int err, expand = 0;
#ifdef FDSET_DEBUG      
        printk (KERN_ERR "%s %d: nr = %d\n", __FUNCTION__, current->pid, nr);
#endif
        
        if (nr >= files->max_fdset) {
                expand = 1;
                if ((err = expand_fdset(files, nr)))
                        goto out;
        }
        if (nr >= files->max_fds) {
                expand = 1;
                if ((err = expand_fd_array(files, nr)))
                        goto out;
        }
        err = expand;
 out:
#ifdef FDSET_DEBUG      
        if (err)
                printk (KERN_ERR "%s %d: return %d\n", __FUNCTION__, current->pid, err);
#endif
        return err;
}

/*
 * locate_fd finds a free file descriptor in the open_fds fdset,
 * expanding the fd arrays if necessary.  Must be called with the
 * file_lock held for write.
 */

static int locate_fd(struct files_struct *files, 
                            struct file *file, unsigned int orig_start)
{
        unsigned int newfd;
        unsigned int start;
        int error;

        error = -EINVAL;
        if (orig_start >= current->rlim[RLIMIT_NOFILE].rlim_cur)
                goto out;

repeat:
        /*
         * Someone might have closed fd's in the range
         * orig_start..files->next_fd
         */
        start = orig_start;
        if (start < files->next_fd)
                start = files->next_fd;

        newfd = start;
        if (start < files->max_fdset) {
                newfd = find_next_zero_bit(files->open_fds->fds_bits,
                        files->max_fdset, start);
        }
        
        error = -EMFILE;
        if (newfd >= current->rlim[RLIMIT_NOFILE].rlim_cur)
                goto out;

        error = expand_files(files, newfd);
        if (error < 0)
                goto out;

        /*
         * If we needed to expand the fs array we
         * might have blocked - try again.
         */
        if (error)
                goto repeat;

        if (start <= files->next_fd)
                files->next_fd = newfd + 1;
        
        error = newfd;
        
out:
        return error;
}

static int dupfd(struct file *file, unsigned int start)
{
        struct files_struct * files = current->files;
        int fd;

        spin_lock(&files->file_lock);
        fd = locate_fd(files, file, start);
        if (fd >= 0) {
                FD_SET(fd, files->open_fds);
                FD_CLR(fd, files->close_on_exec);
                spin_unlock(&files->file_lock);
                fd_install(fd, file);
        } else {
                spin_unlock(&files->file_lock);
                fput(file);
        }

        return fd;
}

asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
{
        int err = -EBADF;
        struct file * file, *tofree;
        struct files_struct * files = current->files;

        spin_lock(&files->file_lock);
        if (!(file = fcheck(oldfd)))
                goto out_unlock;
        err = newfd;
        if (newfd == oldfd)
                goto out_unlock;
        err = -EBADF;
        if (newfd >= current->rlim[RLIMIT_NOFILE].rlim_cur)
                goto out_unlock;
        get_file(file);                 /* We are now finished with oldfd */

        err = expand_files(files, newfd);
        if (err < 0)
                goto out_fput;

        /* To avoid races with open() and dup(), we will mark the fd as
         * in-use in the open-file bitmap throughout the entire dup2()
         * process.  This is quite safe: do_close() uses the fd array
         * entry, not the bitmap, to decide what work needs to be
         * done.  --sct */
        /* Doesn't work. open() might be there first. --AV */

        /* Yes. It's a race. In user space. Nothing sane to do */
        err = -EBUSY;
        tofree = files->fd[newfd];
        if (!tofree && FD_ISSET(newfd, files->open_fds))
                goto out_fput;

        files->fd[newfd] = file;
        FD_SET(newfd, files->open_fds);
        FD_CLR(newfd, files->close_on_exec);
        spin_unlock(&files->file_lock);

        if (tofree)
                filp_close(tofree, files);
        err = newfd;
out:
        return err;
out_unlock:
        spin_unlock(&files->file_lock);
        goto out;

out_fput:
        spin_unlock(&files->file_lock);
        fput(file);
        goto out;
}

asmlinkage long sys_dup(unsigned int fildes)
{
        int ret = -EBADF;
        struct file * file = fget(fildes);

        if (file)
                ret = dupfd(file, 0);
        return ret;
}

#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT)

static int setfl(int fd, struct file * filp, unsigned long arg)
{
        struct inode * inode = filp->f_dentry->d_inode;
        int error = 0;

        /* O_APPEND cannot be cleared if the file is marked as append-only */
        if (!(arg & O_APPEND) && IS_APPEND(inode))
                return -EPERM;

        /* required for strict SunOS emulation */
        if (O_NONBLOCK != O_NDELAY)
               if (arg & O_NDELAY)
                   arg |= O_NONBLOCK;

        if (arg & O_DIRECT) {
                if (!filp->f_mapping || !filp->f_mapping->a_ops ||
                        !filp->f_mapping->a_ops->direct_IO)
                                return -EINVAL;
        }

        lock_kernel();
        if ((arg ^ filp->f_flags) & FASYNC) {
                if (filp->f_op && filp->f_op->fasync) {
                        error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
                        if (error < 0)
                                goto out;
                }
        }

        filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
 out:
        unlock_kernel();
        return error;
}

static void f_modown(struct file *filp, unsigned long pid,
                     uid_t uid, uid_t euid, int force)
{
        write_lock_irq(&filp->f_owner.lock);
        if (force || !filp->f_owner.pid) {
                filp->f_owner.pid = pid;
                filp->f_owner.uid = uid;
                filp->f_owner.euid = euid;
        }
        write_unlock_irq(&filp->f_owner.lock);
}

int f_setown(struct file *filp, unsigned long arg, int force)
{
        int err;
        
        err = security_file_set_fowner(filp);
        if (err)
                return err;

        f_modown(filp, arg, current->uid, current->euid, force);
        return 0;
}

EXPORT_SYMBOL(f_setown);

void f_delown(struct file *filp)
{
        f_modown(filp, 0, 0, 0, 1);
}

EXPORT_SYMBOL(f_delown);

long generic_file_fcntl(int fd, unsigned int cmd,
                        unsigned long arg, struct file *filp)
{
        long err = -EINVAL;

        switch (cmd) {
        case F_DUPFD:
                get_file(filp);
                err = dupfd(filp, arg);
                break;
        case F_GETFD:
                err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
                break;
        case F_SETFD:
                err = 0;
                set_close_on_exec(fd, arg & FD_CLOEXEC);
                break;
        case F_GETFL:
                err = filp->f_flags;
                break;
        case F_SETFL:
                err = setfl(fd, filp, arg);
                break;
        case F_GETLK:
                err = fcntl_getlk(filp, (struct flock __user *) arg);
                break;
        case F_SETLK:
        case F_SETLKW:
                err = fcntl_setlk(filp, cmd, (struct flock __user *) arg);
                break;
        case F_GETOWN:
                /*
                 * XXX If f_owner is a process group, the
                 * negative return value will get converted
                 * into an error.  Oops.  If we keep the
                 * current syscall conventions, the only way
                 * to fix this will be in libc.
                 */
                err = filp->f_owner.pid;
                force_successful_syscall_return();
                break;
        case F_SETOWN:
                err = f_setown(filp, arg, 1);
                break;
        case F_GETSIG:
                err = filp->f_owner.signum;
                break;
        case F_SETSIG:
                /* arg == 0 restores default behaviour. */
                if (arg < 0 || arg > _NSIG) {
                        break;
                }
                err = 0;
                filp->f_owner.signum = arg;
                break;
        case F_GETLEASE:
                err = fcntl_getlease(filp);
                break;
        case F_SETLEASE:
                err = fcntl_setlease(fd, filp, arg);
                break;
        case F_NOTIFY:
                err = fcntl_dirnotify(fd, filp, arg);
                break;
        default:
                break;
        }
        return err;
}
EXPORT_SYMBOL(generic_file_fcntl);

static long do_fcntl(int fd, unsigned int cmd,
                        unsigned long arg, struct file *filp)
{
        if (filp->f_op && filp->f_op->fcntl)
                return filp->f_op->fcntl(fd, cmd, arg, filp);
        return generic_file_fcntl(fd, cmd, arg, filp);
}

asmlinkage long sys_fcntl(int fd, unsigned int cmd, unsigned long arg)
{       
        struct file *filp;
        long err = -EBADF;

        filp = fget(fd);
        if (!filp)
                goto out;

        err = security_file_fcntl(filp, cmd, arg);
        if (err) {
                fput(filp);
                return err;
        }

        err = do_fcntl(fd, cmd, arg, filp);

        fput(filp);
out:
        return err;
}

#if BITS_PER_LONG == 32
asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
{       
        struct file * filp;
        long err;

        err = -EBADF;
        filp = fget(fd);
        if (!filp)
                goto out;

        err = security_file_fcntl(filp, cmd, arg);
        if (err) {
                fput(filp);
                return err;
        }
        err = -EBADF;
        
        switch (cmd) {
                case F_GETLK64:
                        err = fcntl_getlk64(filp, (struct flock64 __user *) arg);
                        break;
                case F_SETLK64:
                case F_SETLKW64:
                        err = fcntl_setlk64(filp, cmd, (struct flock64 __user *) arg);
                        break;
                default:
                        err = do_fcntl(fd, cmd, arg, filp);
                        break;
        }
        fput(filp);
out:
        return err;
}
#endif

/* Table to convert sigio signal codes into poll band bitmaps */

static long band_table[NSIGPOLL] = {
        POLLIN | POLLRDNORM,                    /* POLL_IN */
        POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
        POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
        POLLERR,                                /* POLL_ERR */
        POLLPRI | POLLRDBAND,                   /* POLL_PRI */
        POLLHUP | POLLERR                       /* POLL_HUP */
};

static inline int sigio_perm(struct task_struct *p,
                             struct fown_struct *fown)
{
        return ((fown->euid == 0) ||
                (fown->euid == p->suid) || (fown->euid == p->uid) ||
                (fown->uid == p->suid) || (fown->uid == p->uid));
}

static void send_sigio_to_task(struct task_struct *p,
                               struct fown_struct *fown, 
                               int fd,
                               int reason)
{
        if (!sigio_perm(p, fown))
                return;

        if (security_file_send_sigiotask(p, fown, fd, reason))
                return;

        switch (fown->signum) {
                siginfo_t si;
                default:
                        /* Queue a rt signal with the appropriate fd as its
                           value.  We use SI_SIGIO as the source, not 
                           SI_KERNEL, since kernel signals always get 
                           delivered even if we can't queue.  Failure to
                           queue in this case _should_ be reported; we fall
                           back to SIGIO in that case. --sct */
                        si.si_signo = fown->signum;
                        si.si_errno = 0;
                        si.si_code  = reason;
                        /* Make sure we are called with one of the POLL_*
                           reasons, otherwise we could leak kernel stack into
                           userspace.  */
                        if ((reason & __SI_MASK) != __SI_POLL)
                                BUG();
                        if (reason - POLL_IN >= NSIGPOLL)
                                si.si_band  = ~0L;
                        else
                                si.si_band = band_table[reason - POLL_IN];
                        si.si_fd    = fd;
                        if (!send_sig_info(fown->signum, &si, p))
                                break;
                /* fall-through: fall back on the old plain SIGIO signal */
                case 0:
                        send_group_sig_info(SIGIO, SEND_SIG_PRIV, p);
        }
}

void send_sigio(struct fown_struct *fown, int fd, int band)
{
        struct task_struct *p;
        int pid;
        
        read_lock(&fown->lock);
        pid = fown->pid;
        if (!pid)
                goto out_unlock_fown;
        
        read_lock(&tasklist_lock);
        if (pid > 0) {
                p = find_task_by_pid(pid);
                if (p) {
                        send_sigio_to_task(p, fown, fd, band);
                }
        } else {
                struct list_head *l;
                struct pid *pidptr;
                for_each_task_pid(-pid, PIDTYPE_PGID, p, l, pidptr) {
                        send_sigio_to_task(p, fown, fd, band);
                }
        }
        read_unlock(&tasklist_lock);
 out_unlock_fown:
        read_unlock(&fown->lock);
}

static void send_sigurg_to_task(struct task_struct *p,
                                struct fown_struct *fown)
{
        if (sigio_perm(p, fown))
                send_group_sig_info(SIGURG, SEND_SIG_PRIV, p);
}

int send_sigurg(struct fown_struct *fown)
{
        struct task_struct *p;
        int pid, ret = 0;
        
        read_lock(&fown->lock);
        pid = fown->pid;
        if (!pid)
                goto out_unlock_fown;

        ret = 1;
        
        read_lock(&tasklist_lock);
        if (pid > 0) {
                p = find_task_by_pid(pid);
                if (p) {
                        send_sigurg_to_task(p, fown);
                }
        } else {
                struct list_head *l;
                struct pid *pidptr;
                for_each_task_pid(-pid, PIDTYPE_PGID, p, l, pidptr) {
                        send_sigurg_to_task(p, fown);
                }
        }
        read_unlock(&tasklist_lock);
 out_unlock_fown:
        read_unlock(&fown->lock);
        return ret;
}

static rwlock_t fasync_lock = RW_LOCK_UNLOCKED;
static kmem_cache_t *fasync_cache;

/*
 * fasync_helper() is used by some character device drivers (mainly mice)
 * to set up the fasync queue. It returns negative on error, 0 if it did
 * no changes and positive if it added/deleted the entry.
 */
int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
{
        struct fasync_struct *fa, **fp;
        struct fasync_struct *new = NULL;
        int result = 0;

        if (on) {
                new = kmem_cache_alloc(fasync_cache, SLAB_KERNEL);
                if (!new)
                        return -ENOMEM;
        }
        write_lock_irq(&fasync_lock);
        for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
                if (fa->fa_file == filp) {
                        if(on) {
                                fa->fa_fd = fd;
                                kmem_cache_free(fasync_cache, new);
                        } else {
                                *fp = fa->fa_next;
                                kmem_cache_free(fasync_cache, fa);
                                result = 1;
                        }
                        goto out;
                }
        }

        if (on) {
                new->magic = FASYNC_MAGIC;
                new->fa_file = filp;
                new->fa_fd = fd;
                new->fa_next = *fapp;
                *fapp = new;
                result = 1;
        }
out:
        write_unlock_irq(&fasync_lock);
        return result;
}

EXPORT_SYMBOL(fasync_helper);

void __kill_fasync(struct fasync_struct *fa, int sig, int band)
{
        while (fa) {
                struct fown_struct * fown;
                if (fa->magic != FASYNC_MAGIC) {
                        printk(KERN_ERR "kill_fasync: bad magic number in "
                               "fasync_struct!\n");
                        return;
                }
                fown = &fa->fa_file->f_owner;
                /* Don't send SIGURG to processes which have not set a
                   queued signum: SIGURG has its own default signalling
                   mechanism. */
                if (!(sig == SIGURG && fown->signum == 0))
                        send_sigio(fown, fa->fa_fd, band);
                fa = fa->fa_next;
        }
}

EXPORT_SYMBOL(__kill_fasync);

void kill_fasync(struct fasync_struct **fp, int sig, int band)
{
        /* First a quick test without locking: usually
         * the list is empty.
         */
        if (*fp) {
                read_lock(&fasync_lock);
                /* reread *fp after obtaining the lock */
                __kill_fasync(*fp, sig, band);
                read_unlock(&fasync_lock);
        }
}
EXPORT_SYMBOL(kill_fasync);

static int __init fasync_init(void)
{
        fasync_cache = kmem_cache_create("fasync_cache",
                sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL, NULL);
        return 0;
}

module_init(fasync_init)