V4L: cx88: Avoid a NULL pointer dereference during mpeg_open()

[linux/fpc-iii.git] / net / socket.c

/*
 * NET          An implementation of the SOCKET network access protocol.
 *
 * Version:     @(#)socket.c    1.1.93  18/02/95
 *
 * Authors:     Orest Zborowski, <obz@Kodak.COM>
 *              Ross Biro
 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *
 * Fixes:
 *              Anonymous       :       NOTSOCK/BADF cleanup. Error fix in
 *                                      shutdown()
 *              Alan Cox        :       verify_area() fixes
 *              Alan Cox        :       Removed DDI
 *              Jonathan Kamens :       SOCK_DGRAM reconnect bug
 *              Alan Cox        :       Moved a load of checks to the very
 *                                      top level.
 *              Alan Cox        :       Move address structures to/from user
 *                                      mode above the protocol layers.
 *              Rob Janssen     :       Allow 0 length sends.
 *              Alan Cox        :       Asynchronous I/O support (cribbed from the
 *                                      tty drivers).
 *              Niibe Yutaka    :       Asynchronous I/O for writes (4.4BSD style)
 *              Jeff Uphoff     :       Made max number of sockets command-line
 *                                      configurable.
 *              Matti Aarnio    :       Made the number of sockets dynamic,
 *                                      to be allocated when needed, and mr.
 *                                      Uphoff's max is used as max to be
 *                                      allowed to allocate.
 *              Linus           :       Argh. removed all the socket allocation
 *                                      altogether: it's in the inode now.
 *              Alan Cox        :       Made sock_alloc()/sock_release() public
 *                                      for NetROM and future kernel nfsd type
 *                                      stuff.
 *              Alan Cox        :       sendmsg/recvmsg basics.
 *              Tom Dyas        :       Export net symbols.
 *              Marcin Dalecki  :       Fixed problems with CONFIG_NET="n".
 *              Alan Cox        :       Added thread locking to sys_* calls
 *                                      for sockets. May have errors at the
 *                                      moment.
 *              Kevin Buhr      :       Fixed the dumb errors in the above.
 *              Andi Kleen      :       Some small cleanups, optimizations,
 *                                      and fixed a copy_from_user() bug.
 *              Tigran Aivazian :       sys_send(args) calls sys_sendto(args, NULL, 0)
 *              Tigran Aivazian :       Made listen(2) backlog sanity checks
 *                                      protocol-independent
 *
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 *
 *      This module is effectively the top level interface to the BSD socket
 *      paradigm.
 *
 *      Based upon Swansea University Computer Society NET3.039
 */

#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/file.h>
#include <linux/net.h>
#include <linux/interrupt.h>
#include <linux/rcupdate.h>
#include <linux/netdevice.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>
#include <linux/wanrouter.h>
#include <linux/if_bridge.h>
#include <linux/if_frad.h>
#include <linux/if_vlan.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/cache.h>
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <linux/kmod.h>
#include <linux/audit.h>
#include <linux/wireless.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>

#include <net/compat.h>

#include <net/sock.h>
#include <linux/netfilter.h>

static int sock_no_open(struct inode *irrelevant, struct file *dontcare);
static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
                         unsigned long nr_segs, loff_t pos);
static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
                          unsigned long nr_segs, loff_t pos);
static int sock_mmap(struct file *file, struct vm_area_struct *vma);

static int sock_close(struct inode *inode, struct file *file);
static unsigned int sock_poll(struct file *file,
                              struct poll_table_struct *wait);
static long sock_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
#ifdef CONFIG_COMPAT
static long compat_sock_ioctl(struct file *file,
                              unsigned int cmd, unsigned long arg);
#endif
static int sock_fasync(int fd, struct file *filp, int on);
static ssize_t sock_sendpage(struct file *file, struct page *page,
                             int offset, size_t size, loff_t *ppos, int more);

/*
 *      Socket files have a set of 'special' operations as well as the generic file ones. These don't appear
 *      in the operation structures but are done directly via the socketcall() multiplexor.
 */

static const struct file_operations socket_file_ops = {
        .owner =        THIS_MODULE,
        .llseek =       no_llseek,
        .aio_read =     sock_aio_read,
        .aio_write =    sock_aio_write,
        .poll =         sock_poll,
        .unlocked_ioctl = sock_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = compat_sock_ioctl,
#endif
        .mmap =         sock_mmap,
        .open =         sock_no_open,   /* special open code to disallow open via /proc */
        .release =      sock_close,
        .fasync =       sock_fasync,
        .sendpage =     sock_sendpage,
        .splice_write = generic_splice_sendpage,
};

/*
 *      The protocol list. Each protocol is registered in here.
 */

static DEFINE_SPINLOCK(net_family_lock);
static const struct net_proto_family *net_families[NPROTO] __read_mostly;

/*
 *      Statistics counters of the socket lists
 */

static DEFINE_PER_CPU(int, sockets_in_use) = 0;

/*
 * Support routines.
 * Move socket addresses back and forth across the kernel/user
 * divide and look after the messy bits.
 */

#define MAX_SOCK_ADDR   128             /* 108 for Unix domain -
                                           16 for IP, 16 for IPX,
                                           24 for IPv6,
                                           about 80 for AX.25
                                           must be at least one bigger than
                                           the AF_UNIX size (see net/unix/af_unix.c
                                           :unix_mkname()).
                                         */

/**
 *      move_addr_to_kernel     -       copy a socket address into kernel space
 *      @uaddr: Address in user space
 *      @kaddr: Address in kernel space
 *      @ulen: Length in user space
 *
 *      The address is copied into kernel space. If the provided address is
 *      too long an error code of -EINVAL is returned. If the copy gives
 *      invalid addresses -EFAULT is returned. On a success 0 is returned.
 */

int move_addr_to_kernel(void __user *uaddr, int ulen, void *kaddr)
{
        if (ulen < 0 || ulen > MAX_SOCK_ADDR)
                return -EINVAL;
        if (ulen == 0)
                return 0;
        if (copy_from_user(kaddr, uaddr, ulen))
                return -EFAULT;
        return audit_sockaddr(ulen, kaddr);
}

/**
 *      move_addr_to_user       -       copy an address to user space
 *      @kaddr: kernel space address
 *      @klen: length of address in kernel
 *      @uaddr: user space address
 *      @ulen: pointer to user length field
 *
 *      The value pointed to by ulen on entry is the buffer length available.
 *      This is overwritten with the buffer space used. -EINVAL is returned
 *      if an overlong buffer is specified or a negative buffer size. -EFAULT
 *      is returned if either the buffer or the length field are not
 *      accessible.
 *      After copying the data up to the limit the user specifies, the true
 *      length of the data is written over the length limit the user
 *      specified. Zero is returned for a success.
 */

int move_addr_to_user(void *kaddr, int klen, void __user *uaddr,
                      int __user *ulen)
{
        int err;
        int len;

        err = get_user(len, ulen);
        if (err)
                return err;
        if (len > klen)
                len = klen;
        if (len < 0 || len > MAX_SOCK_ADDR)
                return -EINVAL;
        if (len) {
                if (audit_sockaddr(klen, kaddr))
                        return -ENOMEM;
                if (copy_to_user(uaddr, kaddr, len))
                        return -EFAULT;
        }
        /*
         *      "fromlen shall refer to the value before truncation.."
         *                      1003.1g
         */
        return __put_user(klen, ulen);
}

#define SOCKFS_MAGIC 0x534F434B

static struct kmem_cache *sock_inode_cachep __read_mostly;

static struct inode *sock_alloc_inode(struct super_block *sb)
{
        struct socket_alloc *ei;

        ei = kmem_cache_alloc(sock_inode_cachep, GFP_KERNEL);
        if (!ei)
                return NULL;
        init_waitqueue_head(&ei->socket.wait);

        ei->socket.fasync_list = NULL;
        ei->socket.state = SS_UNCONNECTED;
        ei->socket.flags = 0;
        ei->socket.ops = NULL;
        ei->socket.sk = NULL;
        ei->socket.file = NULL;

        return &ei->vfs_inode;
}

static void sock_destroy_inode(struct inode *inode)
{
        kmem_cache_free(sock_inode_cachep,
                        container_of(inode, struct socket_alloc, vfs_inode));
}

static void init_once(void *foo, struct kmem_cache *cachep, unsigned long flags)
{
        struct socket_alloc *ei = (struct socket_alloc *)foo;

        inode_init_once(&ei->vfs_inode);
}

static int init_inodecache(void)
{
        sock_inode_cachep = kmem_cache_create("sock_inode_cache",
                                              sizeof(struct socket_alloc),
                                              0,
                                              (SLAB_HWCACHE_ALIGN |
                                               SLAB_RECLAIM_ACCOUNT |
                                               SLAB_MEM_SPREAD),
                                              init_once,
                                              NULL);
        if (sock_inode_cachep == NULL)
                return -ENOMEM;
        return 0;
}

static struct super_operations sockfs_ops = {
        .alloc_inode =  sock_alloc_inode,
        .destroy_inode =sock_destroy_inode,
        .statfs =       simple_statfs,
};

static int sockfs_get_sb(struct file_system_type *fs_type,
                         int flags, const char *dev_name, void *data,
                         struct vfsmount *mnt)
{
        return get_sb_pseudo(fs_type, "socket:", &sockfs_ops, SOCKFS_MAGIC,
                             mnt);
}

static struct vfsmount *sock_mnt __read_mostly;

static struct file_system_type sock_fs_type = {
        .name =         "sockfs",
        .get_sb =       sockfs_get_sb,
        .kill_sb =      kill_anon_super,
};

static int sockfs_delete_dentry(struct dentry *dentry)
{
        /*
         * At creation time, we pretended this dentry was hashed
         * (by clearing DCACHE_UNHASHED bit in d_flags)
         * At delete time, we restore the truth : not hashed.
         * (so that dput() can proceed correctly)
         */
        dentry->d_flags |= DCACHE_UNHASHED;
        return 0;
}

/*
 * sockfs_dname() is called from d_path().
 */
static char *sockfs_dname(struct dentry *dentry, char *buffer, int buflen)
{
        return dynamic_dname(dentry, buffer, buflen, "socket:[%lu]",
                                dentry->d_inode->i_ino);
}

static struct dentry_operations sockfs_dentry_operations = {
        .d_delete = sockfs_delete_dentry,
        .d_dname  = sockfs_dname,
};

/*
 *      Obtains the first available file descriptor and sets it up for use.
 *
 *      These functions create file structures and maps them to fd space
 *      of the current process. On success it returns file descriptor
 *      and file struct implicitly stored in sock->file.
 *      Note that another thread may close file descriptor before we return
 *      from this function. We use the fact that now we do not refer
 *      to socket after mapping. If one day we will need it, this
 *      function will increment ref. count on file by 1.
 *
 *      In any case returned fd MAY BE not valid!
 *      This race condition is unavoidable
 *      with shared fd spaces, we cannot solve it inside kernel,
 *      but we take care of internal coherence yet.
 */

static int sock_alloc_fd(struct file **filep)
{
        int fd;

        fd = get_unused_fd();
        if (likely(fd >= 0)) {
                struct file *file = get_empty_filp();

                *filep = file;
                if (unlikely(!file)) {
                        put_unused_fd(fd);
                        return -ENFILE;
                }
        } else
                *filep = NULL;
        return fd;
}

static int sock_attach_fd(struct socket *sock, struct file *file)
{
        struct qstr name = { .name = "" };

        file->f_path.dentry = d_alloc(sock_mnt->mnt_sb->s_root, &name);
        if (unlikely(!file->f_path.dentry))
                return -ENOMEM;

        file->f_path.dentry->d_op = &sockfs_dentry_operations;
        /*
         * We dont want to push this dentry into global dentry hash table.
         * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
         * This permits a working /proc/$pid/fd/XXX on sockets
         */
        file->f_path.dentry->d_flags &= ~DCACHE_UNHASHED;
        d_instantiate(file->f_path.dentry, SOCK_INODE(sock));
        file->f_path.mnt = mntget(sock_mnt);
        file->f_mapping = file->f_path.dentry->d_inode->i_mapping;

        sock->file = file;
        file->f_op = SOCK_INODE(sock)->i_fop = &socket_file_ops;
        file->f_mode = FMODE_READ | FMODE_WRITE;
        file->f_flags = O_RDWR;
        file->f_pos = 0;
        file->private_data = sock;

        return 0;
}

int sock_map_fd(struct socket *sock)
{
        struct file *newfile;
        int fd = sock_alloc_fd(&newfile);

        if (likely(fd >= 0)) {
                int err = sock_attach_fd(sock, newfile);

                if (unlikely(err < 0)) {
                        put_filp(newfile);
                        put_unused_fd(fd);
                        return err;
                }
                fd_install(fd, newfile);
        }
        return fd;
}

static struct socket *sock_from_file(struct file *file, int *err)
{
        if (file->f_op == &socket_file_ops)
                return file->private_data;      /* set in sock_map_fd */

        *err = -ENOTSOCK;
        return NULL;
}

/**
 *      sockfd_lookup   -       Go from a file number to its socket slot
 *      @fd: file handle
 *      @err: pointer to an error code return
 *
 *      The file handle passed in is locked and the socket it is bound
 *      too is returned. If an error occurs the err pointer is overwritten
 *      with a negative errno code and NULL is returned. The function checks
 *      for both invalid handles and passing a handle which is not a socket.
 *
 *      On a success the socket object pointer is returned.
 */

struct socket *sockfd_lookup(int fd, int *err)
{
        struct file *file;
        struct socket *sock;

        file = fget(fd);
        if (!file) {
                *err = -EBADF;
                return NULL;
        }

        sock = sock_from_file(file, err);
        if (!sock)
                fput(file);
        return sock;
}

static struct socket *sockfd_lookup_light(int fd, int *err, int *fput_needed)
{
        struct file *file;
        struct socket *sock;

        *err = -EBADF;
        file = fget_light(fd, fput_needed);
        if (file) {
                sock = sock_from_file(file, err);
                if (sock)
                        return sock;
                fput_light(file, *fput_needed);
        }
        return NULL;
}

/**
 *      sock_alloc      -       allocate a socket
 *
 *      Allocate a new inode and socket object. The two are bound together
 *      and initialised. The socket is then returned. If we are out of inodes
 *      NULL is returned.
 */

static struct socket *sock_alloc(void)
{
        struct inode *inode;
        struct socket *sock;

        inode = new_inode(sock_mnt->mnt_sb);
        if (!inode)
                return NULL;

        sock = SOCKET_I(inode);

        inode->i_mode = S_IFSOCK | S_IRWXUGO;
        inode->i_uid = current->fsuid;
        inode->i_gid = current->fsgid;

        get_cpu_var(sockets_in_use)++;
        put_cpu_var(sockets_in_use);
        return sock;
}

/*
 *      In theory you can't get an open on this inode, but /proc provides
 *      a back door. Remember to keep it shut otherwise you'll let the
 *      creepy crawlies in.
 */

static int sock_no_open(struct inode *irrelevant, struct file *dontcare)
{
        return -ENXIO;
}

const struct file_operations bad_sock_fops = {
        .owner = THIS_MODULE,
        .open = sock_no_open,
};

/**
 *      sock_release    -       close a socket
 *      @sock: socket to close
 *
 *      The socket is released from the protocol stack if it has a release
 *      callback, and the inode is then released if the socket is bound to
 *      an inode not a file.
 */

void sock_release(struct socket *sock)
{
        if (sock->ops) {
                struct module *owner = sock->ops->owner;

                sock->ops->release(sock);
                sock->ops = NULL;
                module_put(owner);
        }

        if (sock->fasync_list)
                printk(KERN_ERR "sock_release: fasync list not empty!\n");

        get_cpu_var(sockets_in_use)--;
        put_cpu_var(sockets_in_use);
        if (!sock->file) {
                iput(SOCK_INODE(sock));
                return;
        }
        sock->file = NULL;
}

static inline int __sock_sendmsg(struct kiocb *iocb, struct socket *sock,
                                 struct msghdr *msg, size_t size)
{
        struct sock_iocb *si = kiocb_to_siocb(iocb);
        int err;

        si->sock = sock;
        si->scm = NULL;
        si->msg = msg;
        si->size = size;

        err = security_socket_sendmsg(sock, msg, size);
        if (err)
                return err;

        return sock->ops->sendmsg(iocb, sock, msg, size);
}

int sock_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
        struct kiocb iocb;
        struct sock_iocb siocb;
        int ret;

        init_sync_kiocb(&iocb, NULL);
        iocb.private = &siocb;
        ret = __sock_sendmsg(&iocb, sock, msg, size);
        if (-EIOCBQUEUED == ret)
                ret = wait_on_sync_kiocb(&iocb);
        return ret;
}

int kernel_sendmsg(struct socket *sock, struct msghdr *msg,
                   struct kvec *vec, size_t num, size_t size)
{
        mm_segment_t oldfs = get_fs();
        int result;

        set_fs(KERNEL_DS);
        /*
         * the following is safe, since for compiler definitions of kvec and
         * iovec are identical, yielding the same in-core layout and alignment
         */
        msg->msg_iov = (struct iovec *)vec;
        msg->msg_iovlen = num;
        result = sock_sendmsg(sock, msg, size);
        set_fs(oldfs);
        return result;
}

/*
 * called from sock_recv_timestamp() if sock_flag(sk, SOCK_RCVTSTAMP)
 */
void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
        struct sk_buff *skb)
{
        ktime_t kt = skb->tstamp;

        if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
                struct timeval tv;
                /* Race occurred between timestamp enabling and packet
                   receiving.  Fill in the current time for now. */
                if (kt.tv64 == 0)
                        kt = ktime_get_real();
                skb->tstamp = kt;
                tv = ktime_to_timeval(kt);
                put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMP, sizeof(tv), &tv);
        } else {
                struct timespec ts;
                /* Race occurred between timestamp enabling and packet
                   receiving.  Fill in the current time for now. */
                if (kt.tv64 == 0)
                        kt = ktime_get_real();
                skb->tstamp = kt;
                ts = ktime_to_timespec(kt);
                put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPNS, sizeof(ts), &ts);
        }
}

EXPORT_SYMBOL_GPL(__sock_recv_timestamp);

static inline int __sock_recvmsg(struct kiocb *iocb, struct socket *sock,
                                 struct msghdr *msg, size_t size, int flags)
{
        int err;
        struct sock_iocb *si = kiocb_to_siocb(iocb);

        si->sock = sock;
        si->scm = NULL;
        si->msg = msg;
        si->size = size;
        si->flags = flags;

        err = security_socket_recvmsg(sock, msg, size, flags);
        if (err)
                return err;

        return sock->ops->recvmsg(iocb, sock, msg, size, flags);
}

int sock_recvmsg(struct socket *sock, struct msghdr *msg,
                 size_t size, int flags)
{
        struct kiocb iocb;
        struct sock_iocb siocb;
        int ret;

        init_sync_kiocb(&iocb, NULL);
        iocb.private = &siocb;
        ret = __sock_recvmsg(&iocb, sock, msg, size, flags);
        if (-EIOCBQUEUED == ret)
                ret = wait_on_sync_kiocb(&iocb);
        return ret;
}

int kernel_recvmsg(struct socket *sock, struct msghdr *msg,
                   struct kvec *vec, size_t num, size_t size, int flags)
{
        mm_segment_t oldfs = get_fs();
        int result;

        set_fs(KERNEL_DS);
        /*
         * the following is safe, since for compiler definitions of kvec and
         * iovec are identical, yielding the same in-core layout and alignment
         */
        msg->msg_iov = (struct iovec *)vec, msg->msg_iovlen = num;
        result = sock_recvmsg(sock, msg, size, flags);
        set_fs(oldfs);
        return result;
}

static void sock_aio_dtor(struct kiocb *iocb)
{
        kfree(iocb->private);
}

static ssize_t sock_sendpage(struct file *file, struct page *page,
                             int offset, size_t size, loff_t *ppos, int more)
{
        struct socket *sock;
        int flags;

        sock = file->private_data;

        flags = !(file->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
        if (more)
                flags |= MSG_MORE;

        return sock->ops->sendpage(sock, page, offset, size, flags);
}

static struct sock_iocb *alloc_sock_iocb(struct kiocb *iocb,
                                         struct sock_iocb *siocb)
{
        if (!is_sync_kiocb(iocb)) {
                siocb = kmalloc(sizeof(*siocb), GFP_KERNEL);
                if (!siocb)
                        return NULL;
                iocb->ki_dtor = sock_aio_dtor;
        }

        siocb->kiocb = iocb;
        iocb->private = siocb;
        return siocb;
}

static ssize_t do_sock_read(struct msghdr *msg, struct kiocb *iocb,
                struct file *file, const struct iovec *iov,
                unsigned long nr_segs)
{
        struct socket *sock = file->private_data;
        size_t size = 0;
        int i;

        for (i = 0; i < nr_segs; i++)
                size += iov[i].iov_len;

        msg->msg_name = NULL;
        msg->msg_namelen = 0;
        msg->msg_control = NULL;
        msg->msg_controllen = 0;
        msg->msg_iov = (struct iovec *)iov;
        msg->msg_iovlen = nr_segs;
        msg->msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;

        return __sock_recvmsg(iocb, sock, msg, size, msg->msg_flags);
}

static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
                                unsigned long nr_segs, loff_t pos)
{
        struct sock_iocb siocb, *x;

        if (pos != 0)
                return -ESPIPE;

        if (iocb->ki_left == 0) /* Match SYS5 behaviour */
                return 0;


        x = alloc_sock_iocb(iocb, &siocb);
        if (!x)
                return -ENOMEM;
        return do_sock_read(&x->async_msg, iocb, iocb->ki_filp, iov, nr_segs);
}

static ssize_t do_sock_write(struct msghdr *msg, struct kiocb *iocb,
                        struct file *file, const struct iovec *iov,
                        unsigned long nr_segs)
{
        struct socket *sock = file->private_data;
        size_t size = 0;
        int i;

        for (i = 0; i < nr_segs; i++)
                size += iov[i].iov_len;

        msg->msg_name = NULL;
        msg->msg_namelen = 0;
        msg->msg_control = NULL;
        msg->msg_controllen = 0;
        msg->msg_iov = (struct iovec *)iov;
        msg->msg_iovlen = nr_segs;
        msg->msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
        if (sock->type == SOCK_SEQPACKET)
                msg->msg_flags |= MSG_EOR;

        return __sock_sendmsg(iocb, sock, msg, size);
}

static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
                          unsigned long nr_segs, loff_t pos)
{
        struct sock_iocb siocb, *x;

        if (pos != 0)
                return -ESPIPE;

        if (iocb->ki_left == 0) /* Match SYS5 behaviour */
                return 0;

        x = alloc_sock_iocb(iocb, &siocb);
        if (!x)
                return -ENOMEM;

        return do_sock_write(&x->async_msg, iocb, iocb->ki_filp, iov, nr_segs);
}

/*
 * Atomic setting of ioctl hooks to avoid race
 * with module unload.
 */

static DEFINE_MUTEX(br_ioctl_mutex);
static int (*br_ioctl_hook) (unsigned int cmd, void __user *arg) = NULL;

void brioctl_set(int (*hook) (unsigned int, void __user *))
{
        mutex_lock(&br_ioctl_mutex);
        br_ioctl_hook = hook;
        mutex_unlock(&br_ioctl_mutex);
}

EXPORT_SYMBOL(brioctl_set);

static DEFINE_MUTEX(vlan_ioctl_mutex);
static int (*vlan_ioctl_hook) (void __user *arg);

void vlan_ioctl_set(int (*hook) (void __user *))
{
        mutex_lock(&vlan_ioctl_mutex);
        vlan_ioctl_hook = hook;
        mutex_unlock(&vlan_ioctl_mutex);
}

EXPORT_SYMBOL(vlan_ioctl_set);

static DEFINE_MUTEX(dlci_ioctl_mutex);
static int (*dlci_ioctl_hook) (unsigned int, void __user *);

void dlci_ioctl_set(int (*hook) (unsigned int, void __user *))
{
        mutex_lock(&dlci_ioctl_mutex);
        dlci_ioctl_hook = hook;
        mutex_unlock(&dlci_ioctl_mutex);
}

EXPORT_SYMBOL(dlci_ioctl_set);

/*
 *      With an ioctl, arg may well be a user mode pointer, but we don't know
 *      what to do with it - that's up to the protocol still.
 */

static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
{
        struct socket *sock;
        void __user *argp = (void __user *)arg;
        int pid, err;

        sock = file->private_data;
        if (cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + 15)) {
                err = dev_ioctl(cmd, argp);
        } else
#ifdef CONFIG_WIRELESS_EXT
        if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) {
                err = dev_ioctl(cmd, argp);
        } else
#endif                          /* CONFIG_WIRELESS_EXT */
                switch (cmd) {
                case FIOSETOWN:
                case SIOCSPGRP:
                        err = -EFAULT;
                        if (get_user(pid, (int __user *)argp))
                                break;
                        err = f_setown(sock->file, pid, 1);
                        break;
                case FIOGETOWN:
                case SIOCGPGRP:
                        err = put_user(f_getown(sock->file),
                                       (int __user *)argp);
                        break;
                case SIOCGIFBR:
                case SIOCSIFBR:
                case SIOCBRADDBR:
                case SIOCBRDELBR:
                        err = -ENOPKG;
                        if (!br_ioctl_hook)
                                request_module("bridge");

                        mutex_lock(&br_ioctl_mutex);
                        if (br_ioctl_hook)
                                err = br_ioctl_hook(cmd, argp);
                        mutex_unlock(&br_ioctl_mutex);
                        break;
                case SIOCGIFVLAN:
                case SIOCSIFVLAN:
                        err = -ENOPKG;
                        if (!vlan_ioctl_hook)
                                request_module("8021q");

                        mutex_lock(&vlan_ioctl_mutex);
                        if (vlan_ioctl_hook)
                                err = vlan_ioctl_hook(argp);
                        mutex_unlock(&vlan_ioctl_mutex);
                        break;
                case SIOCADDDLCI:
                case SIOCDELDLCI:
                        err = -ENOPKG;
                        if (!dlci_ioctl_hook)
                                request_module("dlci");

                        if (dlci_ioctl_hook) {
                                mutex_lock(&dlci_ioctl_mutex);
                                err = dlci_ioctl_hook(cmd, argp);
                                mutex_unlock(&dlci_ioctl_mutex);
                        }
                        break;
                default:
                        err = sock->ops->ioctl(sock, cmd, arg);

                        /*
                         * If this ioctl is unknown try to hand it down
                         * to the NIC driver.
                         */
                        if (err == -ENOIOCTLCMD)
                                err = dev_ioctl(cmd, argp);
                        break;
                }
        return err;
}

int sock_create_lite(int family, int type, int protocol, struct socket **res)
{
        int err;
        struct socket *sock = NULL;

        err = security_socket_create(family, type, protocol, 1);
        if (err)
                goto out;

        sock = sock_alloc();
        if (!sock) {
                err = -ENOMEM;
                goto out;
        }

        sock->type = type;
        err = security_socket_post_create(sock, family, type, protocol, 1);
        if (err)
                goto out_release;

out:
        *res = sock;
        return err;
out_release:
        sock_release(sock);
        sock = NULL;
        goto out;
}

/* No kernel lock held - perfect */
static unsigned int sock_poll(struct file *file, poll_table *wait)
{
        struct socket *sock;

        /*
         *      We can't return errors to poll, so it's either yes or no.
         */
        sock = file->private_data;
        return sock->ops->poll(file, sock, wait);
}

static int sock_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct socket *sock = file->private_data;

        return sock->ops->mmap(file, sock, vma);
}

static int sock_close(struct inode *inode, struct file *filp)
{
        /*
         *      It was possible the inode is NULL we were
         *      closing an unfinished socket.
         */

        if (!inode) {
                printk(KERN_DEBUG "sock_close: NULL inode\n");
                return 0;
        }
        sock_fasync(-1, filp, 0);
        sock_release(SOCKET_I(inode));
        return 0;
}

/*
 *      Update the socket async list
 *
 *      Fasync_list locking strategy.
 *
 *      1. fasync_list is modified only under process context socket lock
 *         i.e. under semaphore.
 *      2. fasync_list is used under read_lock(&sk->sk_callback_lock)
 *         or under socket lock.
 *      3. fasync_list can be used from softirq context, so that
 *         modification under socket lock have to be enhanced with
 *         write_lock_bh(&sk->sk_callback_lock).
 *                                                      --ANK (990710)
 */

static int sock_fasync(int fd, struct file *filp, int on)
{
        struct fasync_struct *fa, *fna = NULL, **prev;
        struct socket *sock;
        struct sock *sk;

        if (on) {
                fna = kmalloc(sizeof(struct fasync_struct), GFP_KERNEL);
                if (fna == NULL)
                        return -ENOMEM;
        }

        sock = filp->private_data;

        sk = sock->sk;
        if (sk == NULL) {
                kfree(fna);
                return -EINVAL;
        }

        lock_sock(sk);

        prev = &(sock->fasync_list);

        for (fa = *prev; fa != NULL; prev = &fa->fa_next, fa = *prev)
                if (fa->fa_file == filp)
                        break;

        if (on) {
                if (fa != NULL) {
                        write_lock_bh(&sk->sk_callback_lock);
                        fa->fa_fd = fd;
                        write_unlock_bh(&sk->sk_callback_lock);

                        kfree(fna);
                        goto out;
                }
                fna->fa_file = filp;
                fna->fa_fd = fd;
                fna->magic = FASYNC_MAGIC;
                fna->fa_next = sock->fasync_list;
                write_lock_bh(&sk->sk_callback_lock);
                sock->fasync_list = fna;
                write_unlock_bh(&sk->sk_callback_lock);
        } else {
                if (fa != NULL) {
                        write_lock_bh(&sk->sk_callback_lock);
                        *prev = fa->fa_next;
                        write_unlock_bh(&sk->sk_callback_lock);
                        kfree(fa);
                }
        }

out:
        release_sock(sock->sk);
        return 0;
}

/* This function may be called only under socket lock or callback_lock */

int sock_wake_async(struct socket *sock, int how, int band)
{
        if (!sock || !sock->fasync_list)
                return -1;
        switch (how) {
        case 1:

                if (test_bit(SOCK_ASYNC_WAITDATA, &sock->flags))
                        break;
                goto call_kill;
        case 2:
                if (!test_and_clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags))
                        break;
                /* fall through */
        case 0:
call_kill:
                __kill_fasync(sock->fasync_list, SIGIO, band);
                break;
        case 3:
                __kill_fasync(sock->fasync_list, SIGURG, band);
        }
        return 0;
}

static int __sock_create(int family, int type, int protocol,
                         struct socket **res, int kern)
{
        int err;
        struct socket *sock;
        const struct net_proto_family *pf;

        /*
         *      Check protocol is in range
         */
        if (family < 0 || family >= NPROTO)
                return -EAFNOSUPPORT;
        if (type < 0 || type >= SOCK_MAX)
                return -EINVAL;

        /* Compatibility.

           This uglymoron is moved from INET layer to here to avoid
           deadlock in module load.
         */
        if (family == PF_INET && type == SOCK_PACKET) {
                static int warned;
                if (!warned) {
                        warned = 1;
                        printk(KERN_INFO "%s uses obsolete (PF_INET,SOCK_PACKET)\n",
                               current->comm);
                }
                family = PF_PACKET;
        }

        err = security_socket_create(family, type, protocol, kern);
        if (err)
                return err;

        /*
         *      Allocate the socket and allow the family to set things up. if
         *      the protocol is 0, the family is instructed to select an appropriate
         *      default.
         */
        sock = sock_alloc();
        if (!sock) {
                if (net_ratelimit())
                        printk(KERN_WARNING "socket: no more sockets\n");
                return -ENFILE; /* Not exactly a match, but its the
                                   closest posix thing */
        }

        sock->type = type;

#if defined(CONFIG_KMOD)
        /* Attempt to load a protocol module if the find failed.
         *
         * 12/09/1996 Marcin: But! this makes REALLY only sense, if the user
         * requested real, full-featured networking support upon configuration.
         * Otherwise module support will break!
         */
        if (net_families[family] == NULL)
                request_module("net-pf-%d", family);
#endif

        rcu_read_lock();
        pf = rcu_dereference(net_families[family]);
        err = -EAFNOSUPPORT;
        if (!pf)
                goto out_release;

        /*
         * We will call the ->create function, that possibly is in a loadable
         * module, so we have to bump that loadable module refcnt first.
         */
        if (!try_module_get(pf->owner))
                goto out_release;

        /* Now protected by module ref count */
        rcu_read_unlock();

        err = pf->create(sock, protocol);
        if (err < 0)
                goto out_module_put;

        /*
         * Now to bump the refcnt of the [loadable] module that owns this
         * socket at sock_release time we decrement its refcnt.
         */
        if (!try_module_get(sock->ops->owner))
                goto out_module_busy;

        /*
         * Now that we're done with the ->create function, the [loadable]
         * module can have its refcnt decremented
         */
        module_put(pf->owner);
        err = security_socket_post_create(sock, family, type, protocol, kern);
        if (err)
                goto out_sock_release;
        *res = sock;

        return 0;

out_module_busy:
        err = -EAFNOSUPPORT;
out_module_put:
        sock->ops = NULL;
        module_put(pf->owner);
out_sock_release:
        sock_release(sock);
        return err;

out_release:
        rcu_read_unlock();
        goto out_sock_release;
}

int sock_create(int family, int type, int protocol, struct socket **res)
{
        return __sock_create(family, type, protocol, res, 0);
}

int sock_create_kern(int family, int type, int protocol, struct socket **res)
{
        return __sock_create(family, type, protocol, res, 1);
}

asmlinkage long sys_socket(int family, int type, int protocol)
{
        int retval;
        struct socket *sock;

        retval = sock_create(family, type, protocol, &sock);
        if (retval < 0)
                goto out;

        retval = sock_map_fd(sock);
        if (retval < 0)
                goto out_release;

out:
        /* It may be already another descriptor 8) Not kernel problem. */
        return retval;

out_release:
        sock_release(sock);
        return retval;
}

/*
 *      Create a pair of connected sockets.
 */

asmlinkage long sys_socketpair(int family, int type, int protocol,
                               int __user *usockvec)
{
        struct socket *sock1, *sock2;
        int fd1, fd2, err;
        struct file *newfile1, *newfile2;

        /*
         * Obtain the first socket and check if the underlying protocol
         * supports the socketpair call.
         */

        err = sock_create(family, type, protocol, &sock1);
        if (err < 0)
                goto out;

        err = sock_create(family, type, protocol, &sock2);
        if (err < 0)
                goto out_release_1;

        err = sock1->ops->socketpair(sock1, sock2);
        if (err < 0)
                goto out_release_both;

        fd1 = sock_alloc_fd(&newfile1);
        if (unlikely(fd1 < 0))
                goto out_release_both;

        fd2 = sock_alloc_fd(&newfile2);
        if (unlikely(fd2 < 0)) {
                put_filp(newfile1);
                put_unused_fd(fd1);
                goto out_release_both;
        }

        err = sock_attach_fd(sock1, newfile1);
        if (unlikely(err < 0)) {
                goto out_fd2;
        }

        err = sock_attach_fd(sock2, newfile2);
        if (unlikely(err < 0)) {
                fput(newfile1);
                goto out_fd1;
        }

        err = audit_fd_pair(fd1, fd2);
        if (err < 0) {
                fput(newfile1);
                fput(newfile2);
                goto out_fd;
        }

        fd_install(fd1, newfile1);
        fd_install(fd2, newfile2);
        /* fd1 and fd2 may be already another descriptors.
         * Not kernel problem.
         */

        err = put_user(fd1, &usockvec[0]);
        if (!err)
                err = put_user(fd2, &usockvec[1]);
        if (!err)
                return 0;

        sys_close(fd2);
        sys_close(fd1);
        return err;

out_release_both:
        sock_release(sock2);
out_release_1:
        sock_release(sock1);
out:
        return err;

out_fd2:
        put_filp(newfile1);
        sock_release(sock1);
out_fd1:
        put_filp(newfile2);
        sock_release(sock2);
out_fd:
        put_unused_fd(fd1);
        put_unused_fd(fd2);
        goto out;
}

/*
 *      Bind a name to a socket. Nothing much to do here since it's
 *      the protocol's responsibility to handle the local address.
 *
 *      We move the socket address to kernel space before we call
 *      the protocol layer (having also checked the address is ok).
 */

asmlinkage long sys_bind(int fd, struct sockaddr __user *umyaddr, int addrlen)
{
        struct socket *sock;
        char address[MAX_SOCK_ADDR];
        int err, fput_needed;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (sock) {
                err = move_addr_to_kernel(umyaddr, addrlen, address);
                if (err >= 0) {
                        err = security_socket_bind(sock,
                                                   (struct sockaddr *)address,
                                                   addrlen);
                        if (!err)
                                err = sock->ops->bind(sock,
                                                      (struct sockaddr *)
                                                      address, addrlen);
                }
                fput_light(sock->file, fput_needed);
        }
        return err;
}

/*
 *      Perform a listen. Basically, we allow the protocol to do anything
 *      necessary for a listen, and if that works, we mark the socket as
 *      ready for listening.
 */

int sysctl_somaxconn __read_mostly = SOMAXCONN;

asmlinkage long sys_listen(int fd, int backlog)
{
        struct socket *sock;
        int err, fput_needed;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (sock) {
                if ((unsigned)backlog > sysctl_somaxconn)
                        backlog = sysctl_somaxconn;

                err = security_socket_listen(sock, backlog);
                if (!err)
                        err = sock->ops->listen(sock, backlog);

                fput_light(sock->file, fput_needed);
        }
        return err;
}

/*
 *      For accept, we attempt to create a new socket, set up the link
 *      with the client, wake up the client, then return the new
 *      connected fd. We collect the address of the connector in kernel
 *      space and move it to user at the very end. This is unclean because
 *      we open the socket then return an error.
 *
 *      1003.1g adds the ability to recvmsg() to query connection pending
 *      status to recvmsg. We need to add that support in a way thats
 *      clean when we restucture accept also.
 */

asmlinkage long sys_accept(int fd, struct sockaddr __user *upeer_sockaddr,
                           int __user *upeer_addrlen)
{
        struct socket *sock, *newsock;
        struct file *newfile;
        int err, len, newfd, fput_needed;
        char address[MAX_SOCK_ADDR];

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (!sock)
                goto out;

        err = -ENFILE;
        if (!(newsock = sock_alloc()))
                goto out_put;

        newsock->type = sock->type;
        newsock->ops = sock->ops;

        /*
         * We don't need try_module_get here, as the listening socket (sock)
         * has the protocol module (sock->ops->owner) held.
         */
        __module_get(newsock->ops->owner);

        newfd = sock_alloc_fd(&newfile);
        if (unlikely(newfd < 0)) {
                err = newfd;
                sock_release(newsock);
                goto out_put;
        }

        err = sock_attach_fd(newsock, newfile);
        if (err < 0)
                goto out_fd_simple;

        err = security_socket_accept(sock, newsock);
        if (err)
                goto out_fd;

        err = sock->ops->accept(sock, newsock, sock->file->f_flags);
        if (err < 0)
                goto out_fd;

        if (upeer_sockaddr) {
                if (newsock->ops->getname(newsock, (struct sockaddr *)address,
                                          &len, 2) < 0) {
                        err = -ECONNABORTED;
                        goto out_fd;
                }
                err = move_addr_to_user(address, len, upeer_sockaddr,
                                        upeer_addrlen);
                if (err < 0)
                        goto out_fd;
        }

        /* File flags are not inherited via accept() unlike another OSes. */

        fd_install(newfd, newfile);
        err = newfd;

        security_socket_post_accept(sock, newsock);

out_put:
        fput_light(sock->file, fput_needed);
out:
        return err;
out_fd_simple:
        sock_release(newsock);
        put_filp(newfile);
        put_unused_fd(newfd);
        goto out_put;
out_fd:
        fput(newfile);
        put_unused_fd(newfd);
        goto out_put;
}

/*
 *      Attempt to connect to a socket with the server address.  The address
 *      is in user space so we verify it is OK and move it to kernel space.
 *
 *      For 1003.1g we need to add clean support for a bind to AF_UNSPEC to
 *      break bindings
 *
 *      NOTE: 1003.1g draft 6.3 is broken with respect to AX.25/NetROM and
 *      other SEQPACKET protocols that take time to connect() as it doesn't
 *      include the -EINPROGRESS status for such sockets.
 */

asmlinkage long sys_connect(int fd, struct sockaddr __user *uservaddr,
                            int addrlen)
{
        struct socket *sock;
        char address[MAX_SOCK_ADDR];
        int err, fput_needed;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (!sock)
                goto out;
        err = move_addr_to_kernel(uservaddr, addrlen, address);
        if (err < 0)
                goto out_put;

        err =
            security_socket_connect(sock, (struct sockaddr *)address, addrlen);
        if (err)
                goto out_put;

        err = sock->ops->connect(sock, (struct sockaddr *)address, addrlen,
                                 sock->file->f_flags);
out_put:
        fput_light(sock->file, fput_needed);
out:
        return err;
}

/*
 *      Get the local address ('name') of a socket object. Move the obtained
 *      name to user space.
 */

asmlinkage long sys_getsockname(int fd, struct sockaddr __user *usockaddr,
                                int __user *usockaddr_len)
{
        struct socket *sock;
        char address[MAX_SOCK_ADDR];
        int len, err, fput_needed;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (!sock)
                goto out;

        err = security_socket_getsockname(sock);
        if (err)
                goto out_put;

        err = sock->ops->getname(sock, (struct sockaddr *)address, &len, 0);
        if (err)
                goto out_put;
        err = move_addr_to_user(address, len, usockaddr, usockaddr_len);

out_put:
        fput_light(sock->file, fput_needed);
out:
        return err;
}

/*
 *      Get the remote address ('name') of a socket object. Move the obtained
 *      name to user space.
 */

asmlinkage long sys_getpeername(int fd, struct sockaddr __user *usockaddr,
                                int __user *usockaddr_len)
{
        struct socket *sock;
        char address[MAX_SOCK_ADDR];
        int len, err, fput_needed;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (sock != NULL) {
                err = security_socket_getpeername(sock);
                if (err) {
                        fput_light(sock->file, fput_needed);
                        return err;
                }

                err =
                    sock->ops->getname(sock, (struct sockaddr *)address, &len,
                                       1);
                if (!err)
                        err = move_addr_to_user(address, len, usockaddr,
                                                usockaddr_len);
                fput_light(sock->file, fput_needed);
        }
        return err;
}

/*
 *      Send a datagram to a given address. We move the address into kernel
 *      space and check the user space data area is readable before invoking
 *      the protocol.
 */

asmlinkage long sys_sendto(int fd, void __user *buff, size_t len,
                           unsigned flags, struct sockaddr __user *addr,
                           int addr_len)
{
        struct socket *sock;
        char address[MAX_SOCK_ADDR];
        int err;
        struct msghdr msg;
        struct iovec iov;
        int fput_needed;
        struct file *sock_file;

        sock_file = fget_light(fd, &fput_needed);
        err = -EBADF;
        if (!sock_file)
                goto out;

        sock = sock_from_file(sock_file, &err);
        if (!sock)
                goto out_put;
        iov.iov_base = buff;
        iov.iov_len = len;
        msg.msg_name = NULL;
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_namelen = 0;
        if (addr) {
                err = move_addr_to_kernel(addr, addr_len, address);
                if (err < 0)
                        goto out_put;
                msg.msg_name = address;
                msg.msg_namelen = addr_len;
        }
        if (sock->file->f_flags & O_NONBLOCK)
                flags |= MSG_DONTWAIT;
        msg.msg_flags = flags;
        err = sock_sendmsg(sock, &msg, len);

out_put:
        fput_light(sock_file, fput_needed);
out:
        return err;
}

/*
 *      Send a datagram down a socket.
 */

asmlinkage long sys_send(int fd, void __user *buff, size_t len, unsigned flags)
{
        return sys_sendto(fd, buff, len, flags, NULL, 0);
}

/*
 *      Receive a frame from the socket and optionally record the address of the
 *      sender. We verify the buffers are writable and if needed move the
 *      sender address from kernel to user space.
 */

asmlinkage long sys_recvfrom(int fd, void __user *ubuf, size_t size,
                             unsigned flags, struct sockaddr __user *addr,
                             int __user *addr_len)
{
        struct socket *sock;
        struct iovec iov;
        struct msghdr msg;
        char address[MAX_SOCK_ADDR];
        int err, err2;
        struct file *sock_file;
        int fput_needed;

        sock_file = fget_light(fd, &fput_needed);
        err = -EBADF;
        if (!sock_file)
                goto out;

        sock = sock_from_file(sock_file, &err);
        if (!sock)
                goto out_put;

        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_iovlen = 1;
        msg.msg_iov = &iov;
        iov.iov_len = size;
        iov.iov_base = ubuf;
        msg.msg_name = address;
        msg.msg_namelen = MAX_SOCK_ADDR;
        if (sock->file->f_flags & O_NONBLOCK)
                flags |= MSG_DONTWAIT;
        err = sock_recvmsg(sock, &msg, size, flags);

        if (err >= 0 && addr != NULL) {
                err2 = move_addr_to_user(address, msg.msg_namelen, addr, addr_len);
                if (err2 < 0)
                        err = err2;
        }
out_put:
        fput_light(sock_file, fput_needed);
out:
        return err;
}

/*
 *      Receive a datagram from a socket.
 */

asmlinkage long sys_recv(int fd, void __user *ubuf, size_t size,
                         unsigned flags)
{
        return sys_recvfrom(fd, ubuf, size, flags, NULL, NULL);
}

/*
 *      Set a socket option. Because we don't know the option lengths we have
 *      to pass the user mode parameter for the protocols to sort out.
 */

asmlinkage long sys_setsockopt(int fd, int level, int optname,
                               char __user *optval, int optlen)
{
        int err, fput_needed;
        struct socket *sock;

        if (optlen < 0)
                return -EINVAL;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (sock != NULL) {
                err = security_socket_setsockopt(sock, level, optname);
                if (err)
                        goto out_put;

                if (level == SOL_SOCKET)
                        err =
                            sock_setsockopt(sock, level, optname, optval,
                                            optlen);
                else
                        err =
                            sock->ops->setsockopt(sock, level, optname, optval,
                                                  optlen);
out_put:
                fput_light(sock->file, fput_needed);
        }
        return err;
}

/*
 *      Get a socket option. Because we don't know the option lengths we have
 *      to pass a user mode parameter for the protocols to sort out.
 */

asmlinkage long sys_getsockopt(int fd, int level, int optname,
                               char __user *optval, int __user *optlen)
{
        int err, fput_needed;
        struct socket *sock;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (sock != NULL) {
                err = security_socket_getsockopt(sock, level, optname);
                if (err)
                        goto out_put;

                if (level == SOL_SOCKET)
                        err =
                            sock_getsockopt(sock, level, optname, optval,
                                            optlen);
                else
                        err =
                            sock->ops->getsockopt(sock, level, optname, optval,
                                                  optlen);
out_put:
                fput_light(sock->file, fput_needed);
        }
        return err;
}

/*
 *      Shutdown a socket.
 */

asmlinkage long sys_shutdown(int fd, int how)
{
        int err, fput_needed;
        struct socket *sock;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (sock != NULL) {
                err = security_socket_shutdown(sock, how);
                if (!err)
                        err = sock->ops->shutdown(sock, how);
                fput_light(sock->file, fput_needed);
        }
        return err;
}

/* A couple of helpful macros for getting the address of the 32/64 bit
 * fields which are the same type (int / unsigned) on our platforms.
 */
#define COMPAT_MSG(msg, member) ((MSG_CMSG_COMPAT & flags) ? &msg##_compat->member : &msg->member)
#define COMPAT_NAMELEN(msg)     COMPAT_MSG(msg, msg_namelen)
#define COMPAT_FLAGS(msg)       COMPAT_MSG(msg, msg_flags)

/*
 *      BSD sendmsg interface
 */

asmlinkage long sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
{
        struct compat_msghdr __user *msg_compat =
            (struct compat_msghdr __user *)msg;
        struct socket *sock;
        char address[MAX_SOCK_ADDR];
        struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
        unsigned char ctl[sizeof(struct cmsghdr) + 20]
            __attribute__ ((aligned(sizeof(__kernel_size_t))));
        /* 20 is size of ipv6_pktinfo */
        unsigned char *ctl_buf = ctl;
        struct msghdr msg_sys;
        int err, ctl_len, iov_size, total_len;
        int fput_needed;

        err = -EFAULT;
        if (MSG_CMSG_COMPAT & flags) {
                if (get_compat_msghdr(&msg_sys, msg_compat))
                        return -EFAULT;
        }
        else if (copy_from_user(&msg_sys, msg, sizeof(struct msghdr)))
                return -EFAULT;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (!sock)
                goto out;

        /* do not move before msg_sys is valid */
        err = -EMSGSIZE;
        if (msg_sys.msg_iovlen > UIO_MAXIOV)
                goto out_put;

        /* Check whether to allocate the iovec area */
        err = -ENOMEM;
        iov_size = msg_sys.msg_iovlen * sizeof(struct iovec);
        if (msg_sys.msg_iovlen > UIO_FASTIOV) {
                iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL);
                if (!iov)
                        goto out_put;
        }

        /* This will also move the address data into kernel space */
        if (MSG_CMSG_COMPAT & flags) {
                err = verify_compat_iovec(&msg_sys, iov, address, VERIFY_READ);
        } else
                err = verify_iovec(&msg_sys, iov, address, VERIFY_READ);
        if (err < 0)
                goto out_freeiov;
        total_len = err;

        err = -ENOBUFS;

        if (msg_sys.msg_controllen > INT_MAX)
                goto out_freeiov;
        ctl_len = msg_sys.msg_controllen;
        if ((MSG_CMSG_COMPAT & flags) && ctl_len) {
                err =
                    cmsghdr_from_user_compat_to_kern(&msg_sys, sock->sk, ctl,
                                                     sizeof(ctl));
                if (err)
                        goto out_freeiov;
                ctl_buf = msg_sys.msg_control;
                ctl_len = msg_sys.msg_controllen;
        } else if (ctl_len) {
                if (ctl_len > sizeof(ctl)) {
                        ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL);
                        if (ctl_buf == NULL)
                                goto out_freeiov;
                }
                err = -EFAULT;
                /*
                 * Careful! Before this, msg_sys.msg_control contains a user pointer.
                 * Afterwards, it will be a kernel pointer. Thus the compiler-assisted
                 * checking falls down on this.
                 */
                if (copy_from_user(ctl_buf, (void __user *)msg_sys.msg_control,
                                   ctl_len))
                        goto out_freectl;
                msg_sys.msg_control = ctl_buf;
        }
        msg_sys.msg_flags = flags;

        if (sock->file->f_flags & O_NONBLOCK)
                msg_sys.msg_flags |= MSG_DONTWAIT;
        err = sock_sendmsg(sock, &msg_sys, total_len);

out_freectl:
        if (ctl_buf != ctl)
                sock_kfree_s(sock->sk, ctl_buf, ctl_len);
out_freeiov:
        if (iov != iovstack)
                sock_kfree_s(sock->sk, iov, iov_size);
out_put:
        fput_light(sock->file, fput_needed);
out:
        return err;
}

/*
 *      BSD recvmsg interface
 */

asmlinkage long sys_recvmsg(int fd, struct msghdr __user *msg,
                            unsigned int flags)
{
        struct compat_msghdr __user *msg_compat =
            (struct compat_msghdr __user *)msg;
        struct socket *sock;
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        struct msghdr msg_sys;
        unsigned long cmsg_ptr;
        int err, iov_size, total_len, len;
        int fput_needed;

        /* kernel mode address */
        char addr[MAX_SOCK_ADDR];

        /* user mode address pointers */
        struct sockaddr __user *uaddr;
        int __user *uaddr_len;

        if (MSG_CMSG_COMPAT & flags) {
                if (get_compat_msghdr(&msg_sys, msg_compat))
                        return -EFAULT;
        }
        else if (copy_from_user(&msg_sys, msg, sizeof(struct msghdr)))
                return -EFAULT;

        sock = sockfd_lookup_light(fd, &err, &fput_needed);
        if (!sock)
                goto out;

        err = -EMSGSIZE;
        if (msg_sys.msg_iovlen > UIO_MAXIOV)
                goto out_put;

        /* Check whether to allocate the iovec area */
        err = -ENOMEM;
        iov_size = msg_sys.msg_iovlen * sizeof(struct iovec);
        if (msg_sys.msg_iovlen > UIO_FASTIOV) {
                iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL);
                if (!iov)
                        goto out_put;
        }

        /*
         *      Save the user-mode address (verify_iovec will change the
         *      kernel msghdr to use the kernel address space)
         */

        uaddr = (void __user *)msg_sys.msg_name;
        uaddr_len = COMPAT_NAMELEN(msg);
        if (MSG_CMSG_COMPAT & flags) {
                err = verify_compat_iovec(&msg_sys, iov, addr, VERIFY_WRITE);
        } else
                err = verify_iovec(&msg_sys, iov, addr, VERIFY_WRITE);
        if (err < 0)
                goto out_freeiov;
        total_len = err;

        cmsg_ptr = (unsigned long)msg_sys.msg_control;
        msg_sys.msg_flags = 0;
        if (MSG_CMSG_COMPAT & flags)
                msg_sys.msg_flags = MSG_CMSG_COMPAT;

        if (sock->file->f_flags & O_NONBLOCK)
                flags |= MSG_DONTWAIT;
        err = sock_recvmsg(sock, &msg_sys, total_len, flags);
        if (err < 0)
                goto out_freeiov;
        len = err;

        if (uaddr != NULL) {
                err = move_addr_to_user(addr, msg_sys.msg_namelen, uaddr,
                                        uaddr_len);
                if (err < 0)
                        goto out_freeiov;
        }
        err = __put_user((msg_sys.msg_flags & ~MSG_CMSG_COMPAT),
                         COMPAT_FLAGS(msg));
        if (err)
                goto out_freeiov;
        if (MSG_CMSG_COMPAT & flags)
                err = __put_user((unsigned long)msg_sys.msg_control - cmsg_ptr,
                                 &msg_compat->msg_controllen);
        else
                err = __put_user((unsigned long)msg_sys.msg_control - cmsg_ptr,
                                 &msg->msg_controllen);
        if (err)
                goto out_freeiov;
        err = len;

out_freeiov:
        if (iov != iovstack)
                sock_kfree_s(sock->sk, iov, iov_size);
out_put:
        fput_light(sock->file, fput_needed);
out:
        return err;
}

#ifdef __ARCH_WANT_SYS_SOCKETCALL

/* Argument list sizes for sys_socketcall */
#define AL(x) ((x) * sizeof(unsigned long))
static const unsigned char nargs[18]={
        AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
        AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
        AL(6),AL(2),AL(5),AL(5),AL(3),AL(3)
};

#undef AL

/*
 *      System call vectors.
 *
 *      Argument checking cleaned up. Saved 20% in size.
 *  This function doesn't need to set the kernel lock because
 *  it is set by the callees.
 */

asmlinkage long sys_socketcall(int call, unsigned long __user *args)
{
        unsigned long a[6];
        unsigned long a0, a1;
        int err;

        if (call < 1 || call > SYS_RECVMSG)
                return -EINVAL;

        /* copy_from_user should be SMP safe. */
        if (copy_from_user(a, args, nargs[call]))
                return -EFAULT;

        err = audit_socketcall(nargs[call] / sizeof(unsigned long), a);
        if (err)
                return err;

        a0 = a[0];
        a1 = a[1];

        switch (call) {
        case SYS_SOCKET:
                err = sys_socket(a0, a1, a[2]);
                break;
        case SYS_BIND:
                err = sys_bind(a0, (struct sockaddr __user *)a1, a[2]);
                break;
        case SYS_CONNECT:
                err = sys_connect(a0, (struct sockaddr __user *)a1, a[2]);
                break;
        case SYS_LISTEN:
                err = sys_listen(a0, a1);
                break;
        case SYS_ACCEPT:
                err =
                    sys_accept(a0, (struct sockaddr __user *)a1,
                               (int __user *)a[2]);
                break;
        case SYS_GETSOCKNAME:
                err =
                    sys_getsockname(a0, (struct sockaddr __user *)a1,
                                    (int __user *)a[2]);
                break;
        case SYS_GETPEERNAME:
                err =
                    sys_getpeername(a0, (struct sockaddr __user *)a1,
                                    (int __user *)a[2]);
                break;
        case SYS_SOCKETPAIR:
                err = sys_socketpair(a0, a1, a[2], (int __user *)a[3]);
                break;
        case SYS_SEND:
                err = sys_send(a0, (void __user *)a1, a[2], a[3]);
                break;
        case SYS_SENDTO:
                err = sys_sendto(a0, (void __user *)a1, a[2], a[3],
                                 (struct sockaddr __user *)a[4], a[5]);
                break;
        case SYS_RECV:
                err = sys_recv(a0, (void __user *)a1, a[2], a[3]);
                break;
        case SYS_RECVFROM:
                err = sys_recvfrom(a0, (void __user *)a1, a[2], a[3],
                                   (struct sockaddr __user *)a[4],
                                   (int __user *)a[5]);
                break;
        case SYS_SHUTDOWN:
                err = sys_shutdown(a0, a1);
                break;
        case SYS_SETSOCKOPT:
                err = sys_setsockopt(a0, a1, a[2], (char __user *)a[3], a[4]);
                break;
        case SYS_GETSOCKOPT:
                err =
                    sys_getsockopt(a0, a1, a[2], (char __user *)a[3],
                                   (int __user *)a[4]);
                break;
        case SYS_SENDMSG:
                err = sys_sendmsg(a0, (struct msghdr __user *)a1, a[2]);
                break;
        case SYS_RECVMSG:
                err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
                break;
        default:
                err = -EINVAL;
                break;
        }
        return err;
}

#endif                          /* __ARCH_WANT_SYS_SOCKETCALL */

/**
 *      sock_register - add a socket protocol handler
 *      @ops: description of protocol
 *
 *      This function is called by a protocol handler that wants to
 *      advertise its address family, and have it linked into the
 *      socket interface. The value ops->family coresponds to the
 *      socket system call protocol family.
 */
int sock_register(const struct net_proto_family *ops)
{
        int err;

        if (ops->family >= NPROTO) {
                printk(KERN_CRIT "protocol %d >= NPROTO(%d)\n", ops->family,
                       NPROTO);
                return -ENOBUFS;
        }

        spin_lock(&net_family_lock);
        if (net_families[ops->family])
                err = -EEXIST;
        else {
                net_families[ops->family] = ops;
                err = 0;
        }
        spin_unlock(&net_family_lock);

        printk(KERN_INFO "NET: Registered protocol family %d\n", ops->family);
        return err;
}

/**
 *      sock_unregister - remove a protocol handler
 *      @family: protocol family to remove
 *
 *      This function is called by a protocol handler that wants to
 *      remove its address family, and have it unlinked from the
 *      new socket creation.
 *
 *      If protocol handler is a module, then it can use module reference
 *      counts to protect against new references. If protocol handler is not
 *      a module then it needs to provide its own protection in
 *      the ops->create routine.
 */
void sock_unregister(int family)
{
        BUG_ON(family < 0 || family >= NPROTO);

        spin_lock(&net_family_lock);
        net_families[family] = NULL;
        spin_unlock(&net_family_lock);

        synchronize_rcu();

        printk(KERN_INFO "NET: Unregistered protocol family %d\n", family);
}

static int __init sock_init(void)
{
        /*
         *      Initialize sock SLAB cache.
         */

        sk_init();

        /*
         *      Initialize skbuff SLAB cache
         */
        skb_init();

        /*
         *      Initialize the protocols module.
         */

        init_inodecache();
        register_filesystem(&sock_fs_type);
        sock_mnt = kern_mount(&sock_fs_type);

        /* The real protocol initialization is performed in later initcalls.
         */

#ifdef CONFIG_NETFILTER
        netfilter_init();
#endif

        return 0;
}

core_initcall(sock_init);       /* early initcall */

#ifdef CONFIG_PROC_FS
void socket_seq_show(struct seq_file *seq)
{
        int cpu;
        int counter = 0;

        for_each_possible_cpu(cpu)
            counter += per_cpu(sockets_in_use, cpu);

        /* It can be negative, by the way. 8) */
        if (counter < 0)
                counter = 0;

        seq_printf(seq, "sockets: used %d\n", counter);
}
#endif                          /* CONFIG_PROC_FS */

#ifdef CONFIG_COMPAT
static long compat_sock_ioctl(struct file *file, unsigned cmd,
                              unsigned long arg)
{
        struct socket *sock = file->private_data;
        int ret = -ENOIOCTLCMD;

        if (sock->ops->compat_ioctl)
                ret = sock->ops->compat_ioctl(sock, cmd, arg);

        return ret;
}
#endif

int kernel_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
{
        return sock->ops->bind(sock, addr, addrlen);
}

int kernel_listen(struct socket *sock, int backlog)
{
        return sock->ops->listen(sock, backlog);
}

int kernel_accept(struct socket *sock, struct socket **newsock, int flags)
{
        struct sock *sk = sock->sk;
        int err;

        err = sock_create_lite(sk->sk_family, sk->sk_type, sk->sk_protocol,
                               newsock);
        if (err < 0)
                goto done;

        err = sock->ops->accept(sock, *newsock, flags);
        if (err < 0) {
                sock_release(*newsock);
                goto done;
        }

        (*newsock)->ops = sock->ops;

done:
        return err;
}

int kernel_connect(struct socket *sock, struct sockaddr *addr, int addrlen,
                   int flags)
{
        return sock->ops->connect(sock, addr, addrlen, flags);
}

int kernel_getsockname(struct socket *sock, struct sockaddr *addr,
                         int *addrlen)
{
        return sock->ops->getname(sock, addr, addrlen, 0);
}

int kernel_getpeername(struct socket *sock, struct sockaddr *addr,
                         int *addrlen)
{
        return sock->ops->getname(sock, addr, addrlen, 1);
}

int kernel_getsockopt(struct socket *sock, int level, int optname,
                        char *optval, int *optlen)
{
        mm_segment_t oldfs = get_fs();
        int err;

        set_fs(KERNEL_DS);
        if (level == SOL_SOCKET)
                err = sock_getsockopt(sock, level, optname, optval, optlen);
        else
                err = sock->ops->getsockopt(sock, level, optname, optval,
                                            optlen);
        set_fs(oldfs);
        return err;
}

int kernel_setsockopt(struct socket *sock, int level, int optname,
                        char *optval, int optlen)
{
        mm_segment_t oldfs = get_fs();
        int err;

        set_fs(KERNEL_DS);
        if (level == SOL_SOCKET)
                err = sock_setsockopt(sock, level, optname, optval, optlen);
        else
                err = sock->ops->setsockopt(sock, level, optname, optval,
                                            optlen);
        set_fs(oldfs);
        return err;
}

int kernel_sendpage(struct socket *sock, struct page *page, int offset,
                    size_t size, int flags)
{
        if (sock->ops->sendpage)
                return sock->ops->sendpage(sock, page, offset, size, flags);

        return sock_no_sendpage(sock, page, offset, size, flags);
}

int kernel_sock_ioctl(struct socket *sock, int cmd, unsigned long arg)
{
        mm_segment_t oldfs = get_fs();
        int err;

        set_fs(KERNEL_DS);
        err = sock->ops->ioctl(sock, cmd, arg);
        set_fs(oldfs);

        return err;
}

/* ABI emulation layers need these two */
EXPORT_SYMBOL(move_addr_to_kernel);
EXPORT_SYMBOL(move_addr_to_user);
EXPORT_SYMBOL(sock_create);
EXPORT_SYMBOL(sock_create_kern);
EXPORT_SYMBOL(sock_create_lite);
EXPORT_SYMBOL(sock_map_fd);
EXPORT_SYMBOL(sock_recvmsg);
EXPORT_SYMBOL(sock_register);
EXPORT_SYMBOL(sock_release);
EXPORT_SYMBOL(sock_sendmsg);
EXPORT_SYMBOL(sock_unregister);
EXPORT_SYMBOL(sock_wake_async);
EXPORT_SYMBOL(sockfd_lookup);
EXPORT_SYMBOL(kernel_sendmsg);
EXPORT_SYMBOL(kernel_recvmsg);
EXPORT_SYMBOL(kernel_bind);
EXPORT_SYMBOL(kernel_listen);
EXPORT_SYMBOL(kernel_accept);
EXPORT_SYMBOL(kernel_connect);
EXPORT_SYMBOL(kernel_getsockname);
EXPORT_SYMBOL(kernel_getpeername);
EXPORT_SYMBOL(kernel_getsockopt);
EXPORT_SYMBOL(kernel_setsockopt);
EXPORT_SYMBOL(kernel_sendpage);
EXPORT_SYMBOL(kernel_sock_ioctl);