// 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 RWF_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 *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) {
                kernel_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 */
                        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;
                /* fall-through - 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;
        struct pid *pid;
        
        read_lock(&fown->lock);

        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(&fown->lock);
}

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;
        int ret = 0;
        
        read_lock(&fown->lock);

        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(&fown->lock);
        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!\n");
                        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)