/*
   *  linux/fs/fcntl.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  #include <linux/syscalls.h>
  #include <linux/init.h>
  #include <linux/mm.h>
  #include <linux/fs.h>
  #include <linux/file.h>

  #include <linux/fdtable.h>

  #include <linux/capability.h>

  #include <linux/dnotify.h>

  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/security.h>
  #include <linux/ptrace.h>

  #include <linux/signal.h>

  #include <linux/rcupdate.h>

  #include <linux/pid_namespace.h>

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

  void set_close_on_exec(unsigned int fd, int flag)

  {
  	struct files_struct *files = current->files;

  	struct fdtable *fdt;

  	spin_lock(&files->file_lock);

  	fdt = files_fdtable(files);

  	if (flag)

  		FD_SET(fd, fdt->close_on_exec);

  	else

  		FD_CLR(fd, fdt->close_on_exec);

  	spin_unlock(&files->file_lock);
  }

  static int get_close_on_exec(unsigned int fd)

  {
  	struct files_struct *files = current->files;

  	struct fdtable *fdt;

  	int res;

  	rcu_read_lock();

  	fdt = files_fdtable(files);
  	res = FD_ISSET(fd, fdt->close_on_exec);

  	rcu_read_unlock();

  	return res;
  }

  SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)

  {
  	int err = -EBADF;
  	struct file * file, *tofree;
  	struct files_struct * files = current->files;

  	struct fdtable *fdt;

  	if ((flags & ~O_CLOEXEC) != 0)
  		return -EINVAL;

  	if (unlikely(oldfd == newfd))
  		return -EINVAL;

  	spin_lock(&files->file_lock);

  	err = expand_files(files, newfd);

  	file = fcheck(oldfd);
  	if (unlikely(!file))
  		goto Ebadf;

  	if (unlikely(err < 0)) {
  		if (err == -EMFILE)

  			goto Ebadf;
  		goto out_unlock;

  	}

  	/*
  	 * We need to detect attempts to do dup2() over allocated but still
  	 * not finished descriptor.  NB: OpenBSD avoids that at the price of
  	 * extra work in their equivalent of fget() - they insert struct
  	 * file immediately after grabbing descriptor, mark it larval if
  	 * more work (e.g. actual opening) is needed and make sure that
  	 * fget() treats larval files as absent.  Potentially interesting,
  	 * but while extra work in fget() is trivial, locking implications
  	 * and amount of surgery on open()-related paths in VFS are not.
  	 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
  	 * deadlocks in rather amusing ways, AFAICS.  All of that is out of
  	 * scope of POSIX or SUS, since neither considers shared descriptor
  	 * tables and this condition does not arise without those.
  	 */

  	err = -EBUSY;

  	fdt = files_fdtable(files);
  	tofree = fdt->fd[newfd];
  	if (!tofree && FD_ISSET(newfd, fdt->open_fds))

  		goto out_unlock;
  	get_file(file);

  	rcu_assign_pointer(fdt->fd[newfd], file);

  	FD_SET(newfd, fdt->open_fds);

  	if (flags & O_CLOEXEC)
  		FD_SET(newfd, fdt->close_on_exec);
  	else
  		FD_CLR(newfd, fdt->close_on_exec);

  	spin_unlock(&files->file_lock);
  
  	if (tofree)
  		filp_close(tofree, files);

  	return newfd;
  
  Ebadf:
  	err = -EBADF;
  out_unlock:

  	spin_unlock(&files->file_lock);

  	return err;

  }

  SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)

  {

  	if (unlikely(newfd == oldfd)) { /* corner case */
  		struct files_struct *files = current->files;

  		int retval = oldfd;

  		rcu_read_lock();
  		if (!fcheck_files(files, oldfd))

  			retval = -EBADF;

  		rcu_read_unlock();

  		return retval;

  	}

  	return sys_dup3(oldfd, newfd, 0);
  }

  SYSCALL_DEFINE1(dup, unsigned int, fildes)

  {
  	int ret = -EBADF;

  	struct file *file = fget(fildes);
  
  	if (file) {
  		ret = get_unused_fd();
  		if (ret >= 0)
  			fd_install(ret, file);
  		else
  			fput(file);
  	}

  	return ret;
  }

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

  
  static int setfl(int fd, struct file * filp, unsigned long arg)
  {

  	struct inode * inode = filp->f_path.dentry->d_inode;

  	int error = 0;

  	/*
  	 * O_APPEND cannot be cleared if the file is marked as append-only
  	 * and the file is open for write.
  	 */
  	if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))

  		return -EPERM;
  
  	/* O_NOATIME can only be set by the owner or superuser */
  	if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))

  		if (!is_owner_or_cap(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;
  	}
  
  	if (filp->f_op && filp->f_op->check_flags)
  		error = filp->f_op->check_flags(arg);
  	if (error)
  		return error;

  	/*

  	 * ->fasync() is responsible for setting the FASYNC bit.

  	 */

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

  		if (error > 0)
  			error = 0;

  	}

  	spin_lock(&filp->f_lock);

  	filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);

  	spin_unlock(&filp->f_lock);

   out:

  	return error;
  }

  static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,

                       int force)

  {
  	write_lock_irq(&filp->f_owner.lock);
  	if (force || !filp->f_owner.pid) {

  		put_pid(filp->f_owner.pid);
  		filp->f_owner.pid = get_pid(pid);
  		filp->f_owner.pid_type = type;

  
  		if (pid) {
  			const struct cred *cred = current_cred();
  			filp->f_owner.uid = cred->uid;
  			filp->f_owner.euid = cred->euid;
  		}

  	}
  	write_unlock_irq(&filp->f_owner.lock);
  }

  int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
  		int force)

  {
  	int err;

  	err = security_file_set_fowner(filp);
  	if (err)
  		return err;

  	f_modown(filp, pid, type, force);

  	return 0;
  }

  EXPORT_SYMBOL(__f_setown);

  int f_setown(struct file *filp, unsigned long arg, int force)
  {
  	enum pid_type type;
  	struct pid *pid;
  	int who = arg;
  	int result;
  	type = PIDTYPE_PID;
  	if (who < 0) {
  		type = PIDTYPE_PGID;
  		who = -who;
  	}
  	rcu_read_lock();

  	pid = find_vpid(who);

  	result = __f_setown(filp, pid, type, force);
  	rcu_read_unlock();
  	return result;
  }

  EXPORT_SYMBOL(f_setown);
  
  void f_delown(struct file *filp)
  {

  	f_modown(filp, NULL, PIDTYPE_PID, 1);

  }
  
  pid_t f_getown(struct file *filp)
  {
  	pid_t pid;

  	read_lock(&filp->f_owner.lock);

  	pid = pid_vnr(filp->f_owner.pid);

  	if (filp->f_owner.pid_type == PIDTYPE_PGID)
  		pid = -pid;

  	read_unlock(&filp->f_owner.lock);

  	return pid;

  }
  
  static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
  		struct file *filp)
  {
  	long err = -EINVAL;
  
  	switch (cmd) {
  	case F_DUPFD:

  	case F_DUPFD_CLOEXEC:

  		if (arg >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
  			break;

  		err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
  		if (err >= 0) {
  			get_file(filp);
  			fd_install(err, filp);
  		}

  		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(fd, 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 = f_getown(filp);

  		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 (!valid_signal(arg)) {

  			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;
  }

  SYSCALL_DEFINE3(fcntl, unsigned 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

  SYSCALL_DEFINE3(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(fd, 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 const 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, int sig)
  {

  	const struct cred *cred;
  	int ret;
  
  	rcu_read_lock();
  	cred = __task_cred(p);
  	ret = ((fown->euid == 0 ||
  		fown->euid == cred->suid || fown->euid == cred->uid ||
  		fown->uid  == cred->suid || fown->uid  == cred->uid) &&
  	       !security_file_send_sigiotask(p, fown, sig));
  	rcu_read_unlock();
  	return ret;

  }
  
  static void send_sigio_to_task(struct task_struct *p,

  			       struct fown_struct *fown,

  			       int fd,
  			       int reason)
  {

  	/*
  	 * F_SETSIG can change ->signum lockless in parallel, make
  	 * sure we read it once and use the same value throughout.
  	 */
  	int signum = ACCESS_ONCE(fown->signum);
  
  	if (!sigio_perm(p, fown, signum))

  		return;

  	switch (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 = 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.  */

  			BUG_ON((reason & __SI_MASK) != __SI_POLL);

  			if (reason - POLL_IN >= NSIGPOLL)
  				si.si_band  = ~0L;
  			else
  				si.si_band = band_table[reason - POLL_IN];
  			si.si_fd    = fd;

  			if (!group_send_sig_info(signum, &si, p))

  				break;
  		/* fall-through: fall back on the old plain SIGIO signal */
  		case 0:

  			group_send_sig_info(SIGIO, SEND_SIG_PRIV, p);

  	}
  }
  
  void send_sigio(struct fown_struct *fown, int fd, int band)
  {
  	struct task_struct *p;

  	enum pid_type type;
  	struct pid *pid;

  	
  	read_lock(&fown->lock);

  	type = fown->pid_type;

  	pid = fown->pid;
  	if (!pid)
  		goto out_unlock_fown;
  	
  	read_lock(&tasklist_lock);

  	do_each_pid_task(pid, type, p) {
  		send_sigio_to_task(p, fown, fd, band);
  	} while_each_pid_task(pid, type, p);

  	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, SIGURG))

  		group_send_sig_info(SIGURG, SEND_SIG_PRIV, p);

  }
  
  int send_sigurg(struct fown_struct *fown)
  {
  	struct task_struct *p;

  	enum pid_type type;
  	struct pid *pid;
  	int ret = 0;

  	
  	read_lock(&fown->lock);

  	type = fown->pid_type;

  	pid = fown->pid;
  	if (!pid)
  		goto out_unlock_fown;
  
  	ret = 1;
  	
  	read_lock(&tasklist_lock);

  	do_each_pid_task(pid, type, p) {
  		send_sigurg_to_task(p, fown);
  	} while_each_pid_task(pid, type, p);

  	read_unlock(&tasklist_lock);
   out_unlock_fown:
  	read_unlock(&fown->lock);
  	return ret;
  }
  
  static DEFINE_RWLOCK(fasync_lock);

  static struct kmem_cache *fasync_cache __read_mostly;

  
  /*

   * fasync_helper() is used by almost all character device drivers

   * 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, GFP_KERNEL);

  		if (!new)
  			return -ENOMEM;
  	}

  
  	/*
  	 * We need to take f_lock first since it's not an IRQ-safe
  	 * lock.
  	 */
  	spin_lock(&filp->f_lock);

  	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:

  	if (on)
  		filp->f_flags |= FASYNC;
  	else
  		filp->f_flags &= ~FASYNC;

  	write_unlock_irq(&fasync_lock);

  	spin_unlock(&filp->f_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!
  ");
  			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);

  	return 0;
  }
  
  module_init(fasync_init)