Quelle fcntl.c Sprache: C

// 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/filelock.h>
#include <linux/file.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/mount.h>
#include <linux/rw_hint.h>

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

#include "internal.h"

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

static int setfl(int fd, struct file * filp, unsigned int 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(file_mnt_idmap(filp), 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) &&
     !(filp->f_mode & FMODE_CAN_ODIRECT))
  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);
filp->f_iocb_flags = iocb_flags(filp);
spin_unlock(&filp->f_lock);

out:
return error;
}

/*
* Allocate an file->f_owner struct if it doesn't exist, handling racing
* allocations correctly.
*/
int file_f_owner_allocate(struct file *file)
{
struct fown_struct *f_owner;

f_owner = file_f_owner(file);
if (f_owner)
  return 0;

f_owner = kzalloc(sizeof(struct fown_struct), GFP_KERNEL);
if (!f_owner)
  return -ENOMEM;

rwlock_init(&f_owner->lock);
f_owner->file = file;
/* If someone else raced us, drop our allocation. */
if (unlikely(cmpxchg(&file->f_owner, NULL, f_owner)))
  kfree(f_owner);
return 0;
}
EXPORT_SYMBOL(file_f_owner_allocate);

void file_f_owner_release(struct file *file)
{
struct fown_struct *f_owner;

f_owner = file_f_owner(file);
if (f_owner) {
  put_pid(f_owner->pid);
  kfree(f_owner);
}
}

void __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
  int force)
{
struct fown_struct *f_owner;

f_owner = file_f_owner(filp);
if (WARN_ON_ONCE(!f_owner))
  return;

write_lock_irq(&f_owner->lock);
if (force || !f_owner->pid) {
  put_pid(f_owner->pid);
  f_owner->pid = get_pid(pid);
  f_owner->pid_type = type;

  if (pid) {
   const struct cred *cred = current_cred();
   security_file_set_fowner(filp);
   f_owner->uid = cred->uid;
   f_owner->euid = cred->euid;
  }
}
write_unlock_irq(&f_owner->lock);
}
EXPORT_SYMBOL(__f_setown);

int f_setown(struct file *filp, int who, int force)
{
enum pid_type type;
struct pid *pid = NULL;
int ret = 0;

might_sleep();

type = PIDTYPE_TGID;
if (who < 0) {
  /* avoid overflow below */
  if (who == INT_MIN)
   return -EINVAL;

  type = PIDTYPE_PGID;
  who = -who;
}

ret = file_f_owner_allocate(filp);
if (ret)
  return ret;

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_setown(filp, NULL, PIDTYPE_TGID, 1);
}

pid_t f_getown(struct file *filp)
{
pid_t pid = 0;
struct fown_struct *f_owner;

f_owner = file_f_owner(filp);
if (!f_owner)
  return pid;

read_lock_irq(&f_owner->lock);
rcu_read_lock();
if (pid_task(f_owner->pid, f_owner->pid_type)) {
  pid = pid_vnr(f_owner->pid);
  if (f_owner->pid_type == PIDTYPE_PGID)
   pid = -pid;
}
rcu_read_unlock();
read_unlock_irq(&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;
}

ret = file_f_owner_allocate(filp);
if (ret)
  return ret;

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;
struct fown_struct *f_owner;
enum pid_type pid_type = PIDTYPE_PID;

f_owner = file_f_owner(filp);
if (f_owner) {
  read_lock_irq(&f_owner->lock);
  rcu_read_lock();
  if (pid_task(f_owner->pid, f_owner->pid_type))
   owner.pid = pid_vnr(f_owner->pid);
  rcu_read_unlock();
  pid_type = f_owner->pid_type;
}

switch (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;
}
if (f_owner)
  read_unlock_irq(&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();
struct fown_struct *f_owner;
uid_t __user *dst = (void __user *)arg;
uid_t src[2] = {0, 0};
int err;

f_owner = file_f_owner(filp);
if (f_owner) {
  read_lock_irq(&f_owner->lock);
  src[0] = from_kuid(user_ns, f_owner->uid);
  src[1] = from_kuid(user_ns, f_owner->euid);
  read_unlock_irq(&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(u64 hint)
{
BUILD_BUG_ON(WRITE_LIFE_NOT_SET != RWH_WRITE_LIFE_NOT_SET);
BUILD_BUG_ON(WRITE_LIFE_NONE != RWH_WRITE_LIFE_NONE);
BUILD_BUG_ON(WRITE_LIFE_SHORT != RWH_WRITE_LIFE_SHORT);
BUILD_BUG_ON(WRITE_LIFE_MEDIUM != RWH_WRITE_LIFE_MEDIUM);
BUILD_BUG_ON(WRITE_LIFE_LONG != RWH_WRITE_LIFE_LONG);
BUILD_BUG_ON(WRITE_LIFE_EXTREME != RWH_WRITE_LIFE_EXTREME);

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_get_rw_hint(struct file *file, unsigned int cmd,
         unsigned long arg)
{
struct inode *inode = file_inode(file);
u64 __user *argp = (u64 __user *)arg;
u64 hint = READ_ONCE(inode->i_write_hint);

if (copy_to_user(argp, &hint, sizeof(*argp)))
  return -EFAULT;
return 0;
}

static long fcntl_set_rw_hint(struct file *file, unsigned int cmd,
         unsigned long arg)
{
struct inode *inode = file_inode(file);
u64 __user *argp = (u64 __user *)arg;
u64 hint;

if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
  return -EPERM;

if (copy_from_user(&hint, argp, sizeof(hint)))
  return -EFAULT;
if (!rw_hint_valid(hint))
  return -EINVAL;

WRITE_ONCE(inode->i_write_hint, hint);

/*
* file->f_mapping->host may differ from inode. As an example,
* blkdev_open() modifies file->f_mapping.
*/
if (file->f_mapping->host != inode)
  WRITE_ONCE(file->f_mapping->host->i_write_hint, hint);

return 0;
}

/* Is the file descriptor a dup of the file? */
static long f_dupfd_query(int fd, struct file *filp)
{
CLASS(fd_raw, f)(fd);

if (fd_empty(f))
  return -EBADF;

/*
* We can do the 'fdput()' immediately, as the only thing that
* matters is the pointer value which isn't changed by the fdput.
*
* Technically we didn't need a ref at all, and 'fdget()' was
* overkill, but given our lockless file pointer lookup, the
* alternatives are complicated.
*/
return fd_file(f) == filp;
}

/* Let the caller figure out whether a given file was just created. */
static long f_created_query(const struct file *filp)
{
return !!(filp->f_mode & FMODE_CREATED);
}

static int f_owner_sig(struct file *filp, int signum, bool setsig)
{
int ret = 0;
struct fown_struct *f_owner;

might_sleep();

if (setsig) {
  if (!valid_signal(signum))
   return -EINVAL;

  ret = file_f_owner_allocate(filp);
  if (ret)
   return ret;
}

f_owner = file_f_owner(filp);
if (setsig)
  f_owner->signum = signum;
else if (f_owner)
  ret = f_owner->signum;
return ret;
}

static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
  struct file *filp)
{
void __user *argp = (void __user *)arg;
int argi = (int)arg;
struct flock flock;
long err = -EINVAL;

switch (cmd) {
case F_CREATED_QUERY:
  err = f_created_query(filp);
  break;
case F_DUPFD:
  err = f_dupfd(argi, filp, 0);
  break;
case F_DUPFD_CLOEXEC:
  err = f_dupfd(argi, filp, O_CLOEXEC);
  break;
case F_DUPFD_QUERY:
  err = f_dupfd_query(argi, 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, argi & FD_CLOEXEC);
  break;
case F_GETFL:
  err = filp->f_flags;
  break;
case F_SETFL:
  err = setfl(fd, filp, argi);
  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:
  fallthrough;
#endif
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, argi, 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 = f_owner_sig(filp, 0, false);
  break;
case F_SETSIG:
  err = f_owner_sig(filp, argi, true);
  break;
case F_GETLEASE:
  err = fcntl_getlease(filp);
  break;
case F_SETLEASE:
  err = fcntl_setlease(fd, filp, argi);
  break;
case F_NOTIFY:
  err = fcntl_dirnotify(fd, filp, argi);
  break;
case F_SETPIPE_SZ:
case F_GETPIPE_SZ:
  err = pipe_fcntl(filp, cmd, argi);
  break;
case F_ADD_SEALS:
case F_GET_SEALS:
  err = memfd_fcntl(filp, cmd, argi);
  break;
case F_GET_RW_HINT:
  err = fcntl_get_rw_hint(filp, cmd, arg);
  break;
case F_SET_RW_HINT:
  err = fcntl_set_rw_hint(filp, cmd, arg);
  break;
default:
  break;
}
return err;
}

static int check_fcntl_cmd(unsigned cmd)
{
switch (cmd) {
case F_CREATED_QUERY:
case F_DUPFD:
case F_DUPFD_CLOEXEC:
case F_DUPFD_QUERY:
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)
{
CLASS(fd_raw, f)(fd);
long err;

if (fd_empty(f))
  return -EBADF;

if (unlikely(fd_file(f)->f_mode & FMODE_PATH)) {
  if (!check_fcntl_cmd(cmd))
   return -EBADF;
}

err = security_file_fcntl(fd_file(f), cmd, arg);
if (!err)
  err = do_fcntl(fd, cmd, arg, fd_file(f));

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;
CLASS(fd_raw, f)(fd);
struct flock64 flock;
long err;

if (fd_empty(f))
  return -EBADF;

if (unlikely(fd_file(f)->f_mode & FMODE_PATH)) {
  if (!check_fcntl_cmd(cmd))
   return -EBADF;
}

err = security_file_fcntl(fd_file(f), cmd, arg);
if (err)
  return err;

switch (cmd) {
case F_GETLK64:
case F_OFD_GETLK:
  err = -EFAULT;
  if (copy_from_user(&flock, argp, sizeof(flock)))
   break;
  err = fcntl_getlk64(fd_file(f), 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, fd_file(f), cmd, &flock);
  break;
default:
  err = do_fcntl(fd, cmd, arg, fd_file(f));
  break;
}
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)
{
CLASS(fd_raw, f)(fd);
struct flock flock;
long err;

if (fd_empty(f))
  return -EBADF;

if (unlikely(fd_file(f)->f_mode & FMODE_PATH)) {
  if (!check_fcntl_cmd(cmd))
   return -EBADF;
}

err = security_file_fcntl(fd_file(f), cmd, arg);
if (err)
  return err;

switch (cmd) {
case F_GETLK:
  err = get_compat_flock(&flock, compat_ptr(arg));
  if (err)
   break;
  err = fcntl_getlk(fd_file(f), 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(fd_file(f), 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, fd_file(f), 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, fd_file(f), convert_fcntl_cmd(cmd), &flock);
  break;
default:
  err = do_fcntl(fd, cmd, arg, fd_file(f));
  break;
}
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 file *file)
{
struct fown_struct *fown;
struct task_struct *p;
enum pid_type type;
struct pid *pid;
unsigned long flags;
int ret = 0;

fown = file_f_owner(file);
if (!fown)
  return 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 __ro_after_init;

/*
* 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;
  kfree_rcu(fa, fa_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;
  unsigned long flags;

  if (fa->magic != FASYNC_MAGIC) {
   printk(KERN_ERR "kill_fasync: bad magic number in "
          "fasync_struct!\n");
   return;
  }
  read_lock_irqsave(&fa->fa_lock, flags);
  if (fa->fa_file) {
   fown = file_f_owner(fa->fa_file);
   if (!fown)
    goto next;
   /* 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);
  }
next:
  read_unlock_irqrestore(&fa->fa_lock, flags);
  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(20 - 1 /* for O_RDONLY being 0 */ !=
  HWEIGHT32(
   (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
   __FMODE_EXEC));

fasync_cache = kmem_cache_create("fasync_cache",
      sizeof(struct fasync_struct), 0,
      SLAB_PANIC | SLAB_ACCOUNT, NULL);
return 0;
}

module_init(fcntl_init)

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