// SPDX-License-Identifier: GPL-2.0

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

  #include <linux/sched/task.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/pipe_fs_i.h>

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

  #include <linux/signal.h>

  #include <linux/rcupdate.h>

  #include <linux/pid_namespace.h>

  #include <linux/user_namespace.h>

  #include <linux/memfd.h>

  #include <linux/compat.h>

  #include <linux/poll.h>

  #include <asm/siginfo.h>

  #include <linux/uaccess.h>

  #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 = file_inode(filp);

  	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 (!inode_owner_or_capable(inode))

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

  	/* Pipe packetized mode is controlled by O_DIRECT flag */

  	if (!S_ISFIFO(inode->i_mode) && (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->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->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);

  }

  void __f_setown(struct file *filp, struct pid *pid, enum pid_type type,

  		int force)

  {

  	security_file_set_fowner(filp);

  	f_modown(filp, pid, type, force);

  }

  EXPORT_SYMBOL(__f_setown);

  int f_setown(struct file *filp, unsigned long arg, int force)

  {
  	enum pid_type type;

  	struct pid *pid = NULL;
  	int who = arg, ret = 0;

  	type = PIDTYPE_TGID;

  	if (who < 0) {

  		/* avoid overflow below */
  		if (who == INT_MIN)
  			return -EINVAL;

  		type = PIDTYPE_PGID;
  		who = -who;
  	}

  	rcu_read_lock();

  	if (who) {
  		pid = find_vpid(who);
  		if (!pid)
  			ret = -ESRCH;
  	}
  
  	if (!ret)
  		__f_setown(filp, pid, type, force);

  	rcu_read_unlock();

  	return ret;

  }

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

  	f_modown(filp, NULL, PIDTYPE_TGID, 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 int f_setown_ex(struct file *filp, unsigned long arg)
  {

  	struct f_owner_ex __user *owner_p = (void __user *)arg;

  	struct f_owner_ex owner;
  	struct pid *pid;
  	int type;
  	int ret;
  
  	ret = copy_from_user(&owner, owner_p, sizeof(owner));
  	if (ret)

  		return -EFAULT;

  
  	switch (owner.type) {
  	case F_OWNER_TID:

  		type = PIDTYPE_PID;

  		break;
  
  	case F_OWNER_PID:

  		type = PIDTYPE_TGID;

  		break;

  	case F_OWNER_PGRP:

  		type = PIDTYPE_PGID;
  		break;
  
  	default:
  		return -EINVAL;
  	}
  
  	rcu_read_lock();
  	pid = find_vpid(owner.pid);
  	if (owner.pid && !pid)
  		ret = -ESRCH;
  	else

  		 __f_setown(filp, pid, type, 1);

  	rcu_read_unlock();
  
  	return ret;
  }
  
  static int f_getown_ex(struct file *filp, unsigned long arg)
  {

  	struct f_owner_ex __user *owner_p = (void __user *)arg;

  	struct f_owner_ex owner;
  	int ret = 0;
  
  	read_lock(&filp->f_owner.lock);
  	owner.pid = pid_vnr(filp->f_owner.pid);
  	switch (filp->f_owner.pid_type) {

  	case PIDTYPE_PID:

  		owner.type = F_OWNER_TID;
  		break;

  	case PIDTYPE_TGID:

  		owner.type = F_OWNER_PID;
  		break;
  
  	case PIDTYPE_PGID:

  		owner.type = F_OWNER_PGRP;

  		break;
  
  	default:
  		WARN_ON(1);
  		ret = -EINVAL;
  		break;
  	}
  	read_unlock(&filp->f_owner.lock);

  	if (!ret) {

  		ret = copy_to_user(owner_p, &owner, sizeof(owner));

  		if (ret)
  			ret = -EFAULT;
  	}

  	return ret;
  }

  #ifdef CONFIG_CHECKPOINT_RESTORE
  static int f_getowner_uids(struct file *filp, unsigned long arg)
  {
  	struct user_namespace *user_ns = current_user_ns();

  	uid_t __user *dst = (void __user *)arg;

  	uid_t src[2];
  	int err;
  
  	read_lock(&filp->f_owner.lock);
  	src[0] = from_kuid(user_ns, filp->f_owner.uid);
  	src[1] = from_kuid(user_ns, filp->f_owner.euid);
  	read_unlock(&filp->f_owner.lock);
  
  	err  = put_user(src[0], &dst[0]);
  	err |= put_user(src[1], &dst[1]);
  
  	return err;
  }
  #else
  static int f_getowner_uids(struct file *filp, unsigned long arg)
  {
  	return -EINVAL;
  }
  #endif

  static bool rw_hint_valid(enum rw_hint hint)
  {
  	switch (hint) {

  	case RWH_WRITE_LIFE_NOT_SET:

  	case RWH_WRITE_LIFE_NONE:
  	case RWH_WRITE_LIFE_SHORT:
  	case RWH_WRITE_LIFE_MEDIUM:
  	case RWH_WRITE_LIFE_LONG:
  	case RWH_WRITE_LIFE_EXTREME:
  		return true;
  	default:
  		return false;
  	}
  }
  
  static long fcntl_rw_hint(struct file *file, unsigned int cmd,
  			  unsigned long arg)
  {
  	struct inode *inode = file_inode(file);

  	u64 __user *argp = (u64 __user *)arg;

  	enum rw_hint hint;

  	u64 h;

  
  	switch (cmd) {
  	case F_GET_FILE_RW_HINT:

  		h = file_write_hint(file);
  		if (copy_to_user(argp, &h, sizeof(*argp)))

  			return -EFAULT;
  		return 0;
  	case F_SET_FILE_RW_HINT:

  		if (copy_from_user(&h, argp, sizeof(h)))

  			return -EFAULT;

  		hint = (enum rw_hint) h;

  		if (!rw_hint_valid(hint))
  			return -EINVAL;
  
  		spin_lock(&file->f_lock);
  		file->f_write_hint = hint;
  		spin_unlock(&file->f_lock);
  		return 0;
  	case F_GET_RW_HINT:

  		h = inode->i_write_hint;
  		if (copy_to_user(argp, &h, sizeof(*argp)))

  			return -EFAULT;
  		return 0;
  	case F_SET_RW_HINT:

  		if (copy_from_user(&h, argp, sizeof(h)))

  			return -EFAULT;

  		hint = (enum rw_hint) h;

  		if (!rw_hint_valid(hint))
  			return -EINVAL;
  
  		inode_lock(inode);
  		inode->i_write_hint = hint;
  		inode_unlock(inode);
  		return 0;
  	default:
  		return -EINVAL;
  	}
  }

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

  	void __user *argp = (void __user *)arg;
  	struct flock flock;

  	long err = -EINVAL;
  
  	switch (cmd) {
  	case F_DUPFD:

  		err = f_dupfd(arg, filp, 0);
  		break;

  	case F_DUPFD_CLOEXEC:

  		err = f_dupfd(arg, filp, O_CLOEXEC);

  		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;

  #if BITS_PER_LONG != 32
  	/* 32-bit arches must use fcntl64() */

  	case F_OFD_GETLK:

  #endif

  	case F_GETLK:

  		if (copy_from_user(&flock, argp, sizeof(flock)))
  			return -EFAULT;
  		err = fcntl_getlk(filp, cmd, &flock);
  		if (!err && copy_to_user(argp, &flock, sizeof(flock)))
  			return -EFAULT;

  		break;

  #if BITS_PER_LONG != 32
  	/* 32-bit arches must use fcntl64() */

  	case F_OFD_SETLK:
  	case F_OFD_SETLKW:

  #endif

  		fallthrough;

  	case F_SETLK:
  	case F_SETLKW:

  		if (copy_from_user(&flock, argp, sizeof(flock)))
  			return -EFAULT;
  		err = fcntl_setlk(fd, filp, cmd, &flock);

  		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_GETOWN_EX:
  		err = f_getown_ex(filp, arg);
  		break;
  	case F_SETOWN_EX:
  		err = f_setown_ex(filp, arg);
  		break;

  	case F_GETOWNER_UIDS:
  		err = f_getowner_uids(filp, arg);
  		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;

  	case F_SETPIPE_SZ:
  	case F_GETPIPE_SZ:
  		err = pipe_fcntl(filp, cmd, arg);
  		break;

  	case F_ADD_SEALS:
  	case F_GET_SEALS:

  		err = memfd_fcntl(filp, cmd, arg);

  		break;

  	case F_GET_RW_HINT:
  	case F_SET_RW_HINT:
  	case F_GET_FILE_RW_HINT:
  	case F_SET_FILE_RW_HINT:
  		err = fcntl_rw_hint(filp, cmd, arg);
  		break;

  	default:
  		break;
  	}
  	return err;
  }

  static int check_fcntl_cmd(unsigned cmd)
  {
  	switch (cmd) {
  	case F_DUPFD:
  	case F_DUPFD_CLOEXEC:
  	case F_GETFD:
  	case F_SETFD:
  	case F_GETFL:
  		return 1;
  	}
  	return 0;
  }

  SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)

  {	

  	struct fd f = fdget_raw(fd);

  	long err = -EBADF;

  	if (!f.file)

  		goto out;

  	if (unlikely(f.file->f_mode & FMODE_PATH)) {

  		if (!check_fcntl_cmd(cmd))
  			goto out1;

  	}

  	err = security_file_fcntl(f.file, cmd, arg);

  	if (!err)

  		err = do_fcntl(fd, cmd, arg, f.file);

  out1:

   	fdput(f);

  out:
  	return err;
  }
  
  #if BITS_PER_LONG == 32

  SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
  		unsigned long, arg)

  {	

  	void __user *argp = (void __user *)arg;

  	struct fd f = fdget_raw(fd);

  	struct flock64 flock;

  	long err = -EBADF;

  	if (!f.file)

  		goto out;

  	if (unlikely(f.file->f_mode & FMODE_PATH)) {

  		if (!check_fcntl_cmd(cmd))
  			goto out1;

  	}

  	err = security_file_fcntl(f.file, cmd, arg);

  	if (err)
  		goto out1;

  	
  	switch (cmd) {

  	case F_GETLK64:

  	case F_OFD_GETLK:

  		err = -EFAULT;
  		if (copy_from_user(&flock, argp, sizeof(flock)))
  			break;
  		err = fcntl_getlk64(f.file, cmd, &flock);
  		if (!err && copy_to_user(argp, &flock, sizeof(flock)))
  			err = -EFAULT;

  		break;
  	case F_SETLK64:
  	case F_SETLKW64:

  	case F_OFD_SETLK:
  	case F_OFD_SETLKW:

  		err = -EFAULT;
  		if (copy_from_user(&flock, argp, sizeof(flock)))
  			break;
  		err = fcntl_setlk64(fd, f.file, cmd, &flock);

  		break;
  	default:
  		err = do_fcntl(fd, cmd, arg, f.file);
  		break;

  	}

  out1:

  	fdput(f);

  out:
  	return err;
  }
  #endif

  #ifdef CONFIG_COMPAT

  /* careful - don't use anywhere else */

  #define copy_flock_fields(dst, src)		\
  	(dst)->l_type = (src)->l_type;		\
  	(dst)->l_whence = (src)->l_whence;	\
  	(dst)->l_start = (src)->l_start;	\
  	(dst)->l_len = (src)->l_len;		\
  	(dst)->l_pid = (src)->l_pid;
  
  static int get_compat_flock(struct flock *kfl, const struct compat_flock __user *ufl)

  {

  	struct compat_flock fl;
  
  	if (copy_from_user(&fl, ufl, sizeof(struct compat_flock)))

  		return -EFAULT;

  	copy_flock_fields(kfl, &fl);

  	return 0;
  }

  static int get_compat_flock64(struct flock *kfl, const struct compat_flock64 __user *ufl)

  {

  	struct compat_flock64 fl;
  
  	if (copy_from_user(&fl, ufl, sizeof(struct compat_flock64)))

  		return -EFAULT;

  	copy_flock_fields(kfl, &fl);

  	return 0;
  }

  static int put_compat_flock(const struct flock *kfl, struct compat_flock __user *ufl)

  {

  	struct compat_flock fl;
  
  	memset(&fl, 0, sizeof(struct compat_flock));

  	copy_flock_fields(&fl, kfl);

  	if (copy_to_user(ufl, &fl, sizeof(struct compat_flock)))

  		return -EFAULT;
  	return 0;
  }

  static int put_compat_flock64(const struct flock *kfl, struct compat_flock64 __user *ufl)

  {

  	struct compat_flock64 fl;

  	BUILD_BUG_ON(sizeof(kfl->l_start) > sizeof(ufl->l_start));
  	BUILD_BUG_ON(sizeof(kfl->l_len) > sizeof(ufl->l_len));

  	memset(&fl, 0, sizeof(struct compat_flock64));

  	copy_flock_fields(&fl, kfl);

  	if (copy_to_user(ufl, &fl, sizeof(struct compat_flock64)))

  		return -EFAULT;
  	return 0;
  }

  #undef copy_flock_fields

  
  static unsigned int
  convert_fcntl_cmd(unsigned int cmd)
  {
  	switch (cmd) {
  	case F_GETLK64:
  		return F_GETLK;
  	case F_SETLK64:
  		return F_SETLK;
  	case F_SETLKW64:
  		return F_SETLKW;
  	}
  
  	return cmd;
  }

  /*
   * GETLK was successful and we need to return the data, but it needs to fit in
   * the compat structure.
   * l_start shouldn't be too big, unless the original start + end is greater than
   * COMPAT_OFF_T_MAX, in which case the app was asking for trouble, so we return
   * -EOVERFLOW in that case.  l_len could be too big, in which case we just
   * truncate it, and only allow the app to see that part of the conflicting lock
   * that might make sense to it anyway
   */
  static int fixup_compat_flock(struct flock *flock)
  {
  	if (flock->l_start > COMPAT_OFF_T_MAX)
  		return -EOVERFLOW;
  	if (flock->l_len > COMPAT_OFF_T_MAX)
  		flock->l_len = COMPAT_OFF_T_MAX;
  	return 0;
  }

  static long do_compat_fcntl64(unsigned int fd, unsigned int cmd,
  			     compat_ulong_t arg)

  {

  	struct fd f = fdget_raw(fd);
  	struct flock flock;
  	long err = -EBADF;
  
  	if (!f.file)
  		return err;
  
  	if (unlikely(f.file->f_mode & FMODE_PATH)) {
  		if (!check_fcntl_cmd(cmd))
  			goto out_put;
  	}
  
  	err = security_file_fcntl(f.file, cmd, arg);
  	if (err)
  		goto out_put;

  
  	switch (cmd) {
  	case F_GETLK:

  		err = get_compat_flock(&flock, compat_ptr(arg));
  		if (err)
  			break;
  		err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);
  		if (err)
  			break;
  		err = fixup_compat_flock(&flock);

  		if (!err)
  			err = put_compat_flock(&flock, compat_ptr(arg));

  		break;
  	case F_GETLK64:
  	case F_OFD_GETLK:
  		err = get_compat_flock64(&flock, compat_ptr(arg));
  		if (err)
  			break;
  		err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);

  		if (!err)
  			err = put_compat_flock64(&flock, compat_ptr(arg));

  		break;

  	case F_SETLK:
  	case F_SETLKW:

  		err = get_compat_flock(&flock, compat_ptr(arg));
  		if (err)

  			break;

  		err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);

  		break;

  	case F_SETLK64:
  	case F_SETLKW64:

  	case F_OFD_SETLK:
  	case F_OFD_SETLKW:

  		err = get_compat_flock64(&flock, compat_ptr(arg));
  		if (err)

  			break;

  		err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);

  		break;

  	default:

  		err = do_fcntl(fd, cmd, arg, f.file);

  		break;
  	}

  out_put:
  	fdput(f);
  	return err;

  }

  COMPAT_SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
  		       compat_ulong_t, arg)
  {
  	return do_compat_fcntl64(fd, cmd, arg);
  }

  COMPAT_SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd,
  		       compat_ulong_t, arg)
  {
  	switch (cmd) {
  	case F_GETLK64:
  	case F_SETLK64:
  	case F_SETLKW64:
  	case F_OFD_GETLK:
  	case F_OFD_SETLK:
  	case F_OFD_SETLKW:
  		return -EINVAL;
  	}

  	return do_compat_fcntl64(fd, cmd, arg);

  }
  #endif

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

  static const __poll_t band_table[NSIGPOLL] = {

  	EPOLLIN | EPOLLRDNORM,			/* POLL_IN */
  	EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND,	/* POLL_OUT */
  	EPOLLIN | EPOLLRDNORM | EPOLLMSG,		/* POLL_MSG */
  	EPOLLERR,				/* POLL_ERR */
  	EPOLLPRI | EPOLLRDBAND,			/* POLL_PRI */
  	EPOLLHUP | EPOLLERR			/* 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 = ((uid_eq(fown->euid, GLOBAL_ROOT_UID) ||
  		uid_eq(fown->euid, cred->suid) || uid_eq(fown->euid, cred->uid) ||
  		uid_eq(fown->uid,  cred->suid) || uid_eq(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, enum pid_type type)

  {

  	/*
  	 * F_SETSIG can change ->signum lockless in parallel, make
  	 * sure we read it once and use the same value throughout.
  	 */

  	int signum = READ_ONCE(fown->signum);

  
  	if (!sigio_perm(p, fown, signum))

  		return;

  	switch (signum) {

  		default: {
  			kernel_siginfo_t si;

  			/* 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 */

  			clear_siginfo(&si);

  			si.si_signo = signum;

  			si.si_errno = 0;
  		        si.si_code  = reason;

  			/*
  			 * Posix definies POLL_IN and friends to be signal
  			 * specific si_codes for SIG_POLL.  Linux extended
  			 * these si_codes to other signals in a way that is
  			 * ambiguous if other signals also have signal
  			 * specific si_codes.  In that case use SI_SIGIO instead
  			 * to remove the ambiguity.
  			 */

  			if ((signum != SIGPOLL) && sig_specific_sicodes(signum))

  				si.si_code = SI_SIGIO;

  			/* Make sure we are called with one of the POLL_*
  			   reasons, otherwise we could leak kernel stack into
  			   userspace.  */

  			BUG_ON((reason < POLL_IN) || ((reason - POLL_IN) >= NSIGPOLL));

  			if (reason - POLL_IN >= NSIGPOLL)
  				si.si_band  = ~0L;
  			else

  				si.si_band = mangle_poll(band_table[reason - POLL_IN]);

  			si.si_fd    = fd;

  			if (!do_send_sig_info(signum, &si, p, type))

  				break;

  		}

  			fallthrough;	/* fall back on the old plain SIGIO signal */

  		case 0:

  			do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, type);

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

  	enum pid_type type;

  	unsigned long flags;

  	struct pid *pid;

  	read_lock_irqsave(&fown->lock, flags);

  	type = fown->pid_type;

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

  
  	if (type <= PIDTYPE_TGID) {
  		rcu_read_lock();
  		p = pid_task(pid, PIDTYPE_PID);

  		if (p)
  			send_sigio_to_task(p, fown, fd, band, type);

  		rcu_read_unlock();
  	} else {
  		read_lock(&tasklist_lock);
  		do_each_pid_task(pid, type, p) {

  			send_sigio_to_task(p, fown, fd, band, type);

  		} while_each_pid_task(pid, type, p);
  		read_unlock(&tasklist_lock);
  	}

   out_unlock_fown:

  	read_unlock_irqrestore(&fown->lock, flags);

  }
  
  static void send_sigurg_to_task(struct task_struct *p,

  				struct fown_struct *fown, enum pid_type type)

  {
  	if (sigio_perm(p, fown, SIGURG))

  		do_send_sig_info(SIGURG, SEND_SIG_PRIV, p, type);

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

  	enum pid_type type;
  	struct pid *pid;

  	unsigned long flags;

  	int ret = 0;

  	read_lock_irqsave(&fown->lock, flags);

  	type = fown->pid_type;

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

  
  	if (type <= PIDTYPE_TGID) {
  		rcu_read_lock();
  		p = pid_task(pid, PIDTYPE_PID);

  		if (p)
  			send_sigurg_to_task(p, fown, type);

  		rcu_read_unlock();
  	} else {
  		read_lock(&tasklist_lock);
  		do_each_pid_task(pid, type, p) {

  			send_sigurg_to_task(p, fown, type);

  		} while_each_pid_task(pid, type, p);
  		read_unlock(&tasklist_lock);
  	}

   out_unlock_fown:

  	read_unlock_irqrestore(&fown->lock, flags);

  	return ret;
  }

  static DEFINE_SPINLOCK(fasync_lock);

  static struct kmem_cache *fasync_cache __read_mostly;

  static void fasync_free_rcu(struct rcu_head *head)
  {
  	kmem_cache_free(fasync_cache,
  			container_of(head, struct fasync_struct, fa_rcu));
  }

  /*

   * Remove a fasync entry. If successfully removed, return
   * positive and clear the FASYNC flag. If no entry exists,
   * do nothing and return 0.
   *
   * NOTE! It is very important that the FASYNC flag always
   * match the state "is the filp on a fasync list".
   *

   */

  int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)

  {
  	struct fasync_struct *fa, **fp;

  	int result = 0;

  	spin_lock(&filp->f_lock);

  	spin_lock(&fasync_lock);

  	for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
  		if (fa->fa_file != filp)
  			continue;

  		write_lock_irq(&fa->fa_lock);

  		fa->fa_file = NULL;

  		write_unlock_irq(&fa->fa_lock);

  		*fp = fa->fa_next;

  		call_rcu(&fa->fa_rcu, fasync_free_rcu);

  		filp->f_flags &= ~FASYNC;
  		result = 1;
  		break;

  	}

  	spin_unlock(&fasync_lock);

  	spin_unlock(&filp->f_lock);
  	return result;
  }

  struct fasync_struct *fasync_alloc(void)
  {
  	return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
  }

  /*

   * NOTE! This can be used only for unused fasync entries:
   * entries that actually got inserted on the fasync list
   * need to be released by rcu - see fasync_remove_entry.

   */

  void fasync_free(struct fasync_struct *new)

  {

  	kmem_cache_free(fasync_cache, new);
  }

  /*
   * Insert a new entry into the fasync list.  Return the pointer to the
   * old one if we didn't use the new one.

   *
   * NOTE! It is very important that the FASYNC flag always
   * match the state "is the filp on a fasync list".

   */
  struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
  {
          struct fasync_struct *fa, **fp;

  	spin_lock(&filp->f_lock);

  	spin_lock(&fasync_lock);

  	for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {

  		if (fa->fa_file != filp)
  			continue;

  		write_lock_irq(&fa->fa_lock);

  		fa->fa_fd = fd;

  		write_unlock_irq(&fa->fa_lock);

  		goto out;

  	}

  	rwlock_init(&new->fa_lock);

  	new->magic = FASYNC_MAGIC;
  	new->fa_file = filp;
  	new->fa_fd = fd;
  	new->fa_next = *fapp;

  	rcu_assign_pointer(*fapp, new);

  	filp->f_flags |= FASYNC;

  out:

  	spin_unlock(&fasync_lock);

  	spin_unlock(&filp->f_lock);

  	return fa;
  }
  
  /*
   * Add a fasync entry. Return negative on error, positive if
   * added, and zero if did nothing but change an existing one.

   */
  static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
  {
  	struct fasync_struct *new;
  
  	new = fasync_alloc();
  	if (!new)
  		return -ENOMEM;
  
  	/*
  	 * fasync_insert_entry() returns the old (update) entry if
  	 * it existed.
  	 *
  	 * So free the (unused) new entry and return 0 to let the
  	 * caller know that we didn't add any new fasync entries.
  	 */
  	if (fasync_insert_entry(fd, filp, fapp, new)) {
  		fasync_free(new);
  		return 0;
  	}
  
  	return 1;

  }

  /*
   * fasync_helper() is used by almost all character device drivers
   * to set up the fasync queue, and for regular files by the file
   * lease code. 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)
  {
  	if (!on)
  		return fasync_remove_entry(filp, fapp);
  	return fasync_add_entry(fd, filp, fapp);
  }

  EXPORT_SYMBOL(fasync_helper);

  /*
   * rcu_read_lock() is held
   */
  static void kill_fasync_rcu(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;
  		}

  		read_lock(&fa->fa_lock);

  		if (fa->fa_file) {
  			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);
  		}

  		read_unlock(&fa->fa_lock);

  		fa = rcu_dereference(fa->fa_next);

  	}
  }

  void kill_fasync(struct fasync_struct **fp, int sig, int band)
  {
  	/* First a quick test without locking: usually
  	 * the list is empty.
  	 */
  	if (*fp) {

  		rcu_read_lock();
  		kill_fasync_rcu(rcu_dereference(*fp), sig, band);
  		rcu_read_unlock();

  	}
  }
  EXPORT_SYMBOL(kill_fasync);

  static int __init fcntl_init(void)

  {

  	/*
  	 * Please add new bits here to ensure allocation uniqueness.
  	 * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
  	 * is defined as O_NONBLOCK on some platforms and not on others.
  	 */

  	BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
  		HWEIGHT32(
  			(VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
  			__FMODE_EXEC | __FMODE_NONOTIFY));

  	fasync_cache = kmem_cache_create("fasync_cache",

  		sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);

  	return 0;
  }

  module_init(fcntl_init)