/*
   * POSIX message queues filesystem for Linux.
   *
   * Copyright (C) 2003,2004  Krzysztof Benedyczak    (golbi@mat.uni.torun.pl)

   *                          Michal Wronski          (michal.wronski@gmail.com)

   *
   * Spinlocks:               Mohamed Abbas           (abbas.mohamed@intel.com)
   * Lockless receive & send, fd based notify:

   *			    Manfred Spraul	    (manfred@colorfullife.com)

   *

   * Audit:                   George Wilson           (ltcgcw@us.ibm.com)
   *

   * This file is released under the GPL.
   */

  #include <linux/capability.h>

  #include <linux/init.h>
  #include <linux/pagemap.h>
  #include <linux/file.h>
  #include <linux/mount.h>

  #include <linux/fs_context.h>

  #include <linux/namei.h>
  #include <linux/sysctl.h>
  #include <linux/poll.h>
  #include <linux/mqueue.h>
  #include <linux/msg.h>
  #include <linux/skbuff.h>

  #include <linux/vmalloc.h>

  #include <linux/netlink.h>
  #include <linux/syscalls.h>

  #include <linux/audit.h>

  #include <linux/signal.h>

  #include <linux/mutex.h>

  #include <linux/nsproxy.h>
  #include <linux/pid.h>

  #include <linux/ipc_namespace.h>

  #include <linux/user_namespace.h>

  #include <linux/slab.h>

  #include <linux/sched/wake_q.h>

  #include <linux/sched/signal.h>

  #include <linux/sched/user.h>

  #include <net/sock.h>
  #include "util.h"

  struct mqueue_fs_context {
  	struct ipc_namespace	*ipc_ns;
  };

  #define MQUEUE_MAGIC	0x19800202
  #define DIRENT_SIZE	20
  #define FILENT_SIZE	80
  
  #define SEND		0
  #define RECV		1
  
  #define STATE_NONE	0

  #define STATE_READY	1

  struct posix_msg_tree_node {
  	struct rb_node		rb_node;
  	struct list_head	msg_list;
  	int			priority;
  };

  struct ext_wait_queue {		/* queue of sleeping tasks */
  	struct task_struct *task;
  	struct list_head list;
  	struct msg_msg *msg;	/* ptr of loaded message */
  	int state;		/* one of STATE_* values */
  };
  
  struct mqueue_inode_info {
  	spinlock_t lock;
  	struct inode vfs_inode;
  	wait_queue_head_t wait_q;

  	struct rb_root msg_tree;

  	struct rb_node *msg_tree_rightmost;

  	struct posix_msg_tree_node *node_cache;

  	struct mq_attr attr;
  
  	struct sigevent notify;

  	struct pid *notify_owner;

  	u32 notify_self_exec_id;

  	struct user_namespace *notify_user_ns;

  	struct user_struct *user;	/* user who created, for accounting */

  	struct sock *notify_sock;
  	struct sk_buff *notify_cookie;
  
  	/* for tasks waiting for free space and messages, respectively */
  	struct ext_wait_queue e_wait_q[2];
  
  	unsigned long qsize; /* size of queue in memory (sum of all msgs) */
  };

  static struct file_system_type mqueue_fs_type;

  static const struct inode_operations mqueue_dir_inode_operations;

  static const struct file_operations mqueue_file_operations;

  static const struct super_operations mqueue_super_ops;

  static const struct fs_context_operations mqueue_fs_context_ops;

  static void remove_notification(struct mqueue_inode_info *info);

  static struct kmem_cache *mqueue_inode_cachep;

  static struct ctl_table_header *mq_sysctl_table;

  
  static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
  {
  	return container_of(inode, struct mqueue_inode_info, vfs_inode);
  }

  /*
   * This routine should be called with the mq_lock held.
   */
  static inline struct ipc_namespace *__get_ns_from_inode(struct inode *inode)

  {

  	return get_ipc_ns(inode->i_sb->s_fs_info);

  }

  static struct ipc_namespace *get_ns_from_inode(struct inode *inode)

  {

  	struct ipc_namespace *ns;
  
  	spin_lock(&mq_lock);
  	ns = __get_ns_from_inode(inode);
  	spin_unlock(&mq_lock);
  	return ns;

  }

  /* Auxiliary functions to manipulate messages' list */
  static int msg_insert(struct msg_msg *msg, struct mqueue_inode_info *info)
  {
  	struct rb_node **p, *parent = NULL;
  	struct posix_msg_tree_node *leaf;

  	bool rightmost = true;

  
  	p = &info->msg_tree.rb_node;
  	while (*p) {
  		parent = *p;
  		leaf = rb_entry(parent, struct posix_msg_tree_node, rb_node);
  
  		if (likely(leaf->priority == msg->m_type))
  			goto insert_msg;

  		else if (msg->m_type < leaf->priority) {

  			p = &(*p)->rb_left;

  			rightmost = false;
  		} else

  			p = &(*p)->rb_right;
  	}

  	if (info->node_cache) {
  		leaf = info->node_cache;
  		info->node_cache = NULL;
  	} else {
  		leaf = kmalloc(sizeof(*leaf), GFP_ATOMIC);
  		if (!leaf)
  			return -ENOMEM;

  		INIT_LIST_HEAD(&leaf->msg_list);

  	}

  	leaf->priority = msg->m_type;

  
  	if (rightmost)
  		info->msg_tree_rightmost = &leaf->rb_node;

  	rb_link_node(&leaf->rb_node, parent, p);
  	rb_insert_color(&leaf->rb_node, &info->msg_tree);

  insert_msg:
  	info->attr.mq_curmsgs++;
  	info->qsize += msg->m_ts;
  	list_add_tail(&msg->m_list, &leaf->msg_list);
  	return 0;
  }

  static inline void msg_tree_erase(struct posix_msg_tree_node *leaf,
  				  struct mqueue_inode_info *info)
  {
  	struct rb_node *node = &leaf->rb_node;
  
  	if (info->msg_tree_rightmost == node)
  		info->msg_tree_rightmost = rb_prev(node);
  
  	rb_erase(node, &info->msg_tree);
  	if (info->node_cache) {
  		kfree(leaf);
  	} else {
  		info->node_cache = leaf;
  	}
  }

  static inline struct msg_msg *msg_get(struct mqueue_inode_info *info)
  {

  	struct rb_node *parent = NULL;

  	struct posix_msg_tree_node *leaf;
  	struct msg_msg *msg;
  
  try_again:

  	/*
  	 * During insert, low priorities go to the left and high to the
  	 * right.  On receive, we want the highest priorities first, so
  	 * walk all the way to the right.
  	 */
  	parent = info->msg_tree_rightmost;

  	if (!parent) {
  		if (info->attr.mq_curmsgs) {
  			pr_warn_once("Inconsistency in POSIX message queue, "
  				     "no tree element, but supposedly messages "
  				     "should exist!
  ");
  			info->attr.mq_curmsgs = 0;
  		}
  		return NULL;
  	}
  	leaf = rb_entry(parent, struct posix_msg_tree_node, rb_node);

  	if (unlikely(list_empty(&leaf->msg_list))) {

  		pr_warn_once("Inconsistency in POSIX message queue, "
  			     "empty leaf node but we haven't implemented "
  			     "lazy leaf delete!
  ");

  		msg_tree_erase(leaf, info);

  		goto try_again;
  	} else {
  		msg = list_first_entry(&leaf->msg_list,
  				       struct msg_msg, m_list);
  		list_del(&msg->m_list);
  		if (list_empty(&leaf->msg_list)) {

  			msg_tree_erase(leaf, info);

  		}
  	}
  	info->attr.mq_curmsgs--;
  	info->qsize -= msg->m_ts;
  	return msg;
  }

  static struct inode *mqueue_get_inode(struct super_block *sb,

  		struct ipc_namespace *ipc_ns, umode_t mode,

  		struct mq_attr *attr)

  {

  	struct user_struct *u = current_user();

  	struct inode *inode;

  	int ret = -ENOMEM;

  
  	inode = new_inode(sb);

  	if (!inode)
  		goto err;
  
  	inode->i_ino = get_next_ino();
  	inode->i_mode = mode;
  	inode->i_uid = current_fsuid();
  	inode->i_gid = current_fsgid();

  	inode->i_mtime = inode->i_ctime = inode->i_atime = current_time(inode);

  
  	if (S_ISREG(mode)) {
  		struct mqueue_inode_info *info;

  		unsigned long mq_bytes, mq_treesize;

  
  		inode->i_fop = &mqueue_file_operations;
  		inode->i_size = FILENT_SIZE;
  		/* mqueue specific info */
  		info = MQUEUE_I(inode);
  		spin_lock_init(&info->lock);
  		init_waitqueue_head(&info->wait_q);
  		INIT_LIST_HEAD(&info->e_wait_q[0].list);
  		INIT_LIST_HEAD(&info->e_wait_q[1].list);
  		info->notify_owner = NULL;

  		info->notify_user_ns = NULL;

  		info->qsize = 0;
  		info->user = NULL;	/* set when all is ok */

  		info->msg_tree = RB_ROOT;

  		info->msg_tree_rightmost = NULL;

  		info->node_cache = NULL;

  		memset(&info->attr, 0, sizeof(info->attr));

  		info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max,
  					   ipc_ns->mq_msg_default);
  		info->attr.mq_msgsize = min(ipc_ns->mq_msgsize_max,
  					    ipc_ns->mq_msgsize_default);

  		if (attr) {
  			info->attr.mq_maxmsg = attr->mq_maxmsg;
  			info->attr.mq_msgsize = attr->mq_msgsize;
  		}

  		/*
  		 * We used to allocate a static array of pointers and account
  		 * the size of that array as well as one msg_msg struct per
  		 * possible message into the queue size. That's no longer
  		 * accurate as the queue is now an rbtree and will grow and
  		 * shrink depending on usage patterns.  We can, however, still
  		 * account one msg_msg struct per message, but the nodes are
  		 * allocated depending on priority usage, and most programs
  		 * only use one, or a handful, of priorities.  However, since
  		 * this is pinned memory, we need to assume worst case, so
  		 * that means the min(mq_maxmsg, max_priorities) * struct
  		 * posix_msg_tree_node.
  		 */

  
  		ret = -EINVAL;
  		if (info->attr.mq_maxmsg <= 0 || info->attr.mq_msgsize <= 0)
  			goto out_inode;
  		if (capable(CAP_SYS_RESOURCE)) {
  			if (info->attr.mq_maxmsg > HARD_MSGMAX ||
  			    info->attr.mq_msgsize > HARD_MSGSIZEMAX)
  				goto out_inode;
  		} else {
  			if (info->attr.mq_maxmsg > ipc_ns->mq_msg_max ||
  					info->attr.mq_msgsize > ipc_ns->mq_msgsize_max)
  				goto out_inode;
  		}
  		ret = -EOVERFLOW;
  		/* check for overflow */
  		if (info->attr.mq_msgsize > ULONG_MAX/info->attr.mq_maxmsg)
  			goto out_inode;

  		mq_treesize = info->attr.mq_maxmsg * sizeof(struct msg_msg) +
  			min_t(unsigned int, info->attr.mq_maxmsg, MQ_PRIO_MAX) *
  			sizeof(struct posix_msg_tree_node);

  		mq_bytes = info->attr.mq_maxmsg * info->attr.mq_msgsize;
  		if (mq_bytes + mq_treesize < mq_bytes)
  			goto out_inode;
  		mq_bytes += mq_treesize;

  		spin_lock(&mq_lock);
  		if (u->mq_bytes + mq_bytes < u->mq_bytes ||

  		    u->mq_bytes + mq_bytes > rlimit(RLIMIT_MSGQUEUE)) {

  			spin_unlock(&mq_lock);
  			/* mqueue_evict_inode() releases info->messages */

  			ret = -EMFILE;

  			goto out_inode;

  		}

  		u->mq_bytes += mq_bytes;
  		spin_unlock(&mq_lock);
  
  		/* all is ok */
  		info->user = get_uid(u);
  	} else if (S_ISDIR(mode)) {
  		inc_nlink(inode);
  		/* Some things misbehave if size == 0 on a directory */
  		inode->i_size = 2 * DIRENT_SIZE;
  		inode->i_op = &mqueue_dir_inode_operations;
  		inode->i_fop = &simple_dir_operations;

  	}

  	return inode;
  out_inode:

  	iput(inode);

  err:

  	return ERR_PTR(ret);

  }

  static int mqueue_fill_super(struct super_block *sb, struct fs_context *fc)

  {
  	struct inode *inode;

  	struct ipc_namespace *ns = sb->s_fs_info;

  	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;

  	sb->s_blocksize = PAGE_SIZE;
  	sb->s_blocksize_bits = PAGE_SHIFT;

  	sb->s_magic = MQUEUE_MAGIC;
  	sb->s_op = &mqueue_super_ops;

  	inode = mqueue_get_inode(sb, ns, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
  	if (IS_ERR(inode))
  		return PTR_ERR(inode);

  	sb->s_root = d_make_root(inode);
  	if (!sb->s_root)
  		return -ENOMEM;
  	return 0;

  }

  static int mqueue_get_tree(struct fs_context *fc)

  {

  	struct mqueue_fs_context *ctx = fc->fs_private;

  	return get_tree_keyed(fc, mqueue_fill_super, ctx->ipc_ns);

  }
  
  static void mqueue_fs_context_free(struct fs_context *fc)
  {
  	struct mqueue_fs_context *ctx = fc->fs_private;

  	put_ipc_ns(ctx->ipc_ns);

  	kfree(ctx);
  }
  
  static int mqueue_init_fs_context(struct fs_context *fc)
  {
  	struct mqueue_fs_context *ctx;
  
  	ctx = kzalloc(sizeof(struct mqueue_fs_context), GFP_KERNEL);
  	if (!ctx)
  		return -ENOMEM;
  
  	ctx->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);

  	put_user_ns(fc->user_ns);
  	fc->user_ns = get_user_ns(ctx->ipc_ns->user_ns);

  	fc->fs_private = ctx;
  	fc->ops = &mqueue_fs_context_ops;
  	return 0;
  }
  
  static struct vfsmount *mq_create_mount(struct ipc_namespace *ns)
  {
  	struct mqueue_fs_context *ctx;
  	struct fs_context *fc;
  	struct vfsmount *mnt;
  
  	fc = fs_context_for_mount(&mqueue_fs_type, SB_KERNMOUNT);
  	if (IS_ERR(fc))
  		return ERR_CAST(fc);
  
  	ctx = fc->fs_private;
  	put_ipc_ns(ctx->ipc_ns);
  	ctx->ipc_ns = get_ipc_ns(ns);

  	put_user_ns(fc->user_ns);
  	fc->user_ns = get_user_ns(ctx->ipc_ns->user_ns);

  
  	mnt = fc_mount(fc);
  	put_fs_context(fc);
  	return mnt;

  }

  static void init_once(void *foo)

  {
  	struct mqueue_inode_info *p = (struct mqueue_inode_info *) foo;

  	inode_init_once(&p->vfs_inode);

  }
  
  static struct inode *mqueue_alloc_inode(struct super_block *sb)
  {
  	struct mqueue_inode_info *ei;

  	ei = kmem_cache_alloc(mqueue_inode_cachep, GFP_KERNEL);

  	if (!ei)
  		return NULL;
  	return &ei->vfs_inode;
  }

  static void mqueue_free_inode(struct inode *inode)

  {
  	kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
  }

  static void mqueue_evict_inode(struct inode *inode)

  {
  	struct mqueue_inode_info *info;
  	struct user_struct *user;

  	struct ipc_namespace *ipc_ns;

  	struct msg_msg *msg, *nmsg;
  	LIST_HEAD(tmp_msg);

  	clear_inode(inode);

  
  	if (S_ISDIR(inode->i_mode))

  		return;

  	ipc_ns = get_ns_from_inode(inode);

  	info = MQUEUE_I(inode);
  	spin_lock(&info->lock);

  	while ((msg = msg_get(info)) != NULL)

  		list_add_tail(&msg->m_list, &tmp_msg);

  	kfree(info->node_cache);

  	spin_unlock(&info->lock);

  	list_for_each_entry_safe(msg, nmsg, &tmp_msg, m_list) {
  		list_del(&msg->m_list);
  		free_msg(msg);
  	}

  	user = info->user;
  	if (user) {

  		unsigned long mq_bytes, mq_treesize;
  
  		/* Total amount of bytes accounted for the mqueue */
  		mq_treesize = info->attr.mq_maxmsg * sizeof(struct msg_msg) +
  			min_t(unsigned int, info->attr.mq_maxmsg, MQ_PRIO_MAX) *
  			sizeof(struct posix_msg_tree_node);
  
  		mq_bytes = mq_treesize + (info->attr.mq_maxmsg *
  					  info->attr.mq_msgsize);

  		spin_lock(&mq_lock);
  		user->mq_bytes -= mq_bytes;

  		/*
  		 * get_ns_from_inode() ensures that the
  		 * (ipc_ns = sb->s_fs_info) is either a valid ipc_ns
  		 * to which we now hold a reference, or it is NULL.
  		 * We can't put it here under mq_lock, though.
  		 */
  		if (ipc_ns)
  			ipc_ns->mq_queues_count--;

  		spin_unlock(&mq_lock);
  		free_uid(user);
  	}

  	if (ipc_ns)
  		put_ipc_ns(ipc_ns);

  }

  static int mqueue_create_attr(struct dentry *dentry, umode_t mode, void *arg)

  {

  	struct inode *dir = dentry->d_parent->d_inode;

  	struct inode *inode;

  	struct mq_attr *attr = arg;

  	int error;

  	struct ipc_namespace *ipc_ns;

  
  	spin_lock(&mq_lock);

  	ipc_ns = __get_ns_from_inode(dir);
  	if (!ipc_ns) {
  		error = -EACCES;
  		goto out_unlock;
  	}

  
  	if (ipc_ns->mq_queues_count >= ipc_ns->mq_queues_max &&
  	    !capable(CAP_SYS_RESOURCE)) {

  		error = -ENOSPC;

  		goto out_unlock;

  	}

  	ipc_ns->mq_queues_count++;

  	spin_unlock(&mq_lock);

  	inode = mqueue_get_inode(dir->i_sb, ipc_ns, mode, attr);

  	if (IS_ERR(inode)) {
  		error = PTR_ERR(inode);

  		spin_lock(&mq_lock);

  		ipc_ns->mq_queues_count--;
  		goto out_unlock;

  	}

  	put_ipc_ns(ipc_ns);

  	dir->i_size += DIRENT_SIZE;

  	dir->i_ctime = dir->i_mtime = dir->i_atime = current_time(dir);

  
  	d_instantiate(dentry, inode);
  	dget(dentry);
  	return 0;

  out_unlock:

  	spin_unlock(&mq_lock);

  	if (ipc_ns)
  		put_ipc_ns(ipc_ns);

  	return error;
  }

  static int mqueue_create(struct inode *dir, struct dentry *dentry,
  				umode_t mode, bool excl)
  {
  	return mqueue_create_attr(dentry, mode, NULL);
  }

  static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
  {

  	struct inode *inode = d_inode(dentry);

  	dir->i_ctime = dir->i_mtime = dir->i_atime = current_time(dir);

  	dir->i_size -= DIRENT_SIZE;

  	drop_nlink(inode);
  	dput(dentry);
  	return 0;

  }
  
  /*
  *	This is routine for system read from queue file.
  *	To avoid mess with doing here some sort of mq_receive we allow
  *	to read only queue size & notification info (the only values
  *	that are interesting from user point of view and aren't accessible
  *	through std routines)
  */
  static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,

  				size_t count, loff_t *off)

  {

  	struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));

  	char buffer[FILENT_SIZE];

  	ssize_t ret;

  
  	spin_lock(&info->lock);
  	snprintf(buffer, sizeof(buffer),
  			"QSIZE:%-10lu NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d
  ",
  			info->qsize,
  			info->notify_owner ? info->notify.sigev_notify : 0,
  			(info->notify_owner &&
  			 info->notify.sigev_notify == SIGEV_SIGNAL) ?
  				info->notify.sigev_signo : 0,

  			pid_vnr(info->notify_owner));

  	spin_unlock(&info->lock);
  	buffer[sizeof(buffer)-1] = '\0';

  	ret = simple_read_from_buffer(u_data, count, off, buffer,
  				strlen(buffer));
  	if (ret <= 0)
  		return ret;

  	file_inode(filp)->i_atime = file_inode(filp)->i_ctime = current_time(file_inode(filp));

  	return ret;

  }

  static int mqueue_flush_file(struct file *filp, fl_owner_t id)

  {

  	struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));

  
  	spin_lock(&info->lock);

  	if (task_tgid(current) == info->notify_owner)

  		remove_notification(info);
  
  	spin_unlock(&info->lock);
  	return 0;
  }

  static __poll_t mqueue_poll_file(struct file *filp, struct poll_table_struct *poll_tab)

  {

  	struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));

  	__poll_t retval = 0;

  
  	poll_wait(filp, &info->wait_q, poll_tab);
  
  	spin_lock(&info->lock);
  	if (info->attr.mq_curmsgs)

  		retval = EPOLLIN | EPOLLRDNORM;

  
  	if (info->attr.mq_curmsgs < info->attr.mq_maxmsg)

  		retval |= EPOLLOUT | EPOLLWRNORM;

  	spin_unlock(&info->lock);
  
  	return retval;
  }
  
  /* Adds current to info->e_wait_q[sr] before element with smaller prio */
  static void wq_add(struct mqueue_inode_info *info, int sr,
  			struct ext_wait_queue *ewp)
  {
  	struct ext_wait_queue *walk;

  	list_for_each_entry(walk, &info->e_wait_q[sr].list, list) {

  		if (walk->task->prio <= current->prio) {

  			list_add_tail(&ewp->list, &walk->list);
  			return;
  		}
  	}
  	list_add_tail(&ewp->list, &info->e_wait_q[sr].list);
  }
  
  /*
   * Puts current task to sleep. Caller must hold queue lock. After return
   * lock isn't held.
   * sr: SEND or RECV
   */
  static int wq_sleep(struct mqueue_inode_info *info, int sr,

  		    ktime_t *timeout, struct ext_wait_queue *ewp)

  	__releases(&info->lock)

  {
  	int retval;
  	signed long time;
  
  	wq_add(info, sr, ewp);
  
  	for (;;) {

  		__set_current_state(TASK_INTERRUPTIBLE);

  
  		spin_unlock(&info->lock);

  		time = schedule_hrtimeout_range_clock(timeout, 0,
  			HRTIMER_MODE_ABS, CLOCK_REALTIME);

  		if (ewp->state == STATE_READY) {
  			retval = 0;
  			goto out;
  		}
  		spin_lock(&info->lock);
  		if (ewp->state == STATE_READY) {
  			retval = 0;
  			goto out_unlock;
  		}
  		if (signal_pending(current)) {
  			retval = -ERESTARTSYS;
  			break;
  		}
  		if (time == 0) {
  			retval = -ETIMEDOUT;
  			break;
  		}
  	}
  	list_del(&ewp->list);
  out_unlock:
  	spin_unlock(&info->lock);
  out:
  	return retval;
  }
  
  /*
   * Returns waiting task that should be serviced first or NULL if none exists
   */
  static struct ext_wait_queue *wq_get_first_waiter(
  		struct mqueue_inode_info *info, int sr)
  {
  	struct list_head *ptr;
  
  	ptr = info->e_wait_q[sr].list.prev;
  	if (ptr == &info->e_wait_q[sr].list)
  		return NULL;
  	return list_entry(ptr, struct ext_wait_queue, list);
  }

  
  static inline void set_cookie(struct sk_buff *skb, char code)
  {

  	((char *)skb->data)[NOTIFY_COOKIE_LEN-1] = code;

  }
  
  /*
   * The next function is only to split too long sys_mq_timedsend
   */
  static void __do_notify(struct mqueue_inode_info *info)
  {
  	/* notification
  	 * invoked when there is registered process and there isn't process
  	 * waiting synchronously for message AND state of queue changed from
  	 * empty to not empty. Here we are sure that no one is waiting
  	 * synchronously. */
  	if (info->notify_owner &&
  	    info->attr.mq_curmsgs == 1) {

  		switch (info->notify.sigev_notify) {
  		case SIGEV_NONE:
  			break;

  		case SIGEV_SIGNAL: {
  			struct kernel_siginfo sig_i;
  			struct task_struct *task;
  
  			/* do_mq_notify() accepts sigev_signo == 0, why?? */
  			if (!info->notify.sigev_signo)
  				break;

  			clear_siginfo(&sig_i);

  			sig_i.si_signo = info->notify.sigev_signo;
  			sig_i.si_errno = 0;
  			sig_i.si_code = SI_MESGQ;
  			sig_i.si_value = info->notify.sigev_value;

  			rcu_read_lock();

  			/* map current pid/uid into info->owner's namespaces */

  			sig_i.si_pid = task_tgid_nr_ns(current,
  						ns_of_pid(info->notify_owner));

  			sig_i.si_uid = from_kuid_munged(info->notify_user_ns,
  						current_uid());
  			/*
  			 * We can't use kill_pid_info(), this signal should
  			 * bypass check_kill_permission(). It is from kernel
  			 * but si_fromuser() can't know this.
  			 * We do check the self_exec_id, to avoid sending
  			 * signals to programs that don't expect them.
  			 */
  			task = pid_task(info->notify_owner, PIDTYPE_TGID);
  			if (task && task->self_exec_id ==
  						info->notify_self_exec_id) {
  				do_send_sig_info(info->notify.sigev_signo,
  						&sig_i, task, PIDTYPE_TGID);
  			}

  			rcu_read_unlock();

  			break;

  		}

  		case SIGEV_THREAD:
  			set_cookie(info->notify_cookie, NOTIFY_WOKENUP);

  			netlink_sendskb(info->notify_sock, info->notify_cookie);

  			break;
  		}
  		/* after notification unregisters process */

  		put_pid(info->notify_owner);

  		put_user_ns(info->notify_user_ns);

  		info->notify_owner = NULL;

  		info->notify_user_ns = NULL;

  	}
  	wake_up(&info->wait_q);
  }

  static int prepare_timeout(const struct __kernel_timespec __user *u_abs_timeout,

  			   struct timespec64 *ts)

  {

  	if (get_timespec64(ts, u_abs_timeout))

  		return -EFAULT;

  	if (!timespec64_valid(ts))

  		return -EINVAL;

  	return 0;

  }
  
  static void remove_notification(struct mqueue_inode_info *info)
  {

  	if (info->notify_owner != NULL &&

  	    info->notify.sigev_notify == SIGEV_THREAD) {
  		set_cookie(info->notify_cookie, NOTIFY_REMOVED);

  		netlink_sendskb(info->notify_sock, info->notify_cookie);

  	}

  	put_pid(info->notify_owner);

  	put_user_ns(info->notify_user_ns);

  	info->notify_owner = NULL;

  	info->notify_user_ns = NULL;

  }

  static int prepare_open(struct dentry *dentry, int oflag, int ro,
  			umode_t mode, struct filename *name,

  			struct mq_attr *attr)

  {

  	static const int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
  						  MAY_READ | MAY_WRITE };

  	int acc;

  	if (d_really_is_negative(dentry)) {
  		if (!(oflag & O_CREAT))

  			return -ENOENT;

  		if (ro)
  			return ro;
  		audit_inode_parent_hidden(name, dentry->d_parent);
  		return vfs_mkobj(dentry, mode & ~current_umask(),
  				  mqueue_create_attr, attr);

  	}

  	/* it already existed */
  	audit_inode(name, dentry, 0);
  	if ((oflag & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
  		return -EEXIST;

  	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))

  		return -EINVAL;

  	acc = oflag2acc[oflag & O_ACCMODE];

  	return inode_permission(d_inode(dentry), acc);

  }

  static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
  		      struct mq_attr *attr)

  {

  	struct vfsmount *mnt = current->nsproxy->ipc_ns->mq_mnt;
  	struct dentry *root = mnt->mnt_root;

  	struct filename *name;

  	struct path path;

  	int fd, error;

  	int ro;

  	audit_mq_open(oflag, mode, attr);

  	if (IS_ERR(name = getname(u_name)))
  		return PTR_ERR(name);

  	fd = get_unused_fd_flags(O_CLOEXEC);

  	if (fd < 0)
  		goto out_putname;

  	ro = mnt_want_write(mnt);	/* we'll drop it in any case */

  	inode_lock(d_inode(root));

  	path.dentry = lookup_one_len(name->name, root, strlen(name->name));

  	if (IS_ERR(path.dentry)) {
  		error = PTR_ERR(path.dentry);

  		goto out_putfd;

  	}

  	path.mnt = mntget(mnt);

  	error = prepare_open(path.dentry, oflag, ro, mode, name, attr);
  	if (!error) {
  		struct file *file = dentry_open(&path, oflag, current_cred());
  		if (!IS_ERR(file))
  			fd_install(fd, file);
  		else
  			error = PTR_ERR(file);

  	}

  	path_put(&path);

  out_putfd:

  	if (error) {
  		put_unused_fd(fd);
  		fd = error;
  	}

  	inode_unlock(d_inode(root));

  	if (!ro)
  		mnt_drop_write(mnt);

  out_putname:
  	putname(name);
  	return fd;
  }

  SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
  		struct mq_attr __user *, u_attr)
  {
  	struct mq_attr attr;
  	if (u_attr && copy_from_user(&attr, u_attr, sizeof(struct mq_attr)))
  		return -EFAULT;
  
  	return do_mq_open(u_name, oflag, mode, u_attr ? &attr : NULL);
  }

  SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)

  {
  	int err;

  	struct filename *name;

  	struct dentry *dentry;
  	struct inode *inode = NULL;

  	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;

  	struct vfsmount *mnt = ipc_ns->mq_mnt;

  
  	name = getname(u_name);
  	if (IS_ERR(name))
  		return PTR_ERR(name);

  	audit_inode_parent_hidden(name, mnt->mnt_root);

  	err = mnt_want_write(mnt);
  	if (err)
  		goto out_name;

  	inode_lock_nested(d_inode(mnt->mnt_root), I_MUTEX_PARENT);

  	dentry = lookup_one_len(name->name, mnt->mnt_root,
  				strlen(name->name));

  	if (IS_ERR(dentry)) {
  		err = PTR_ERR(dentry);
  		goto out_unlock;
  	}

  	inode = d_inode(dentry);

  	if (!inode) {
  		err = -ENOENT;
  	} else {

  		ihold(inode);

  		err = vfs_unlink(d_inode(dentry->d_parent), dentry, NULL);

  	}

  	dput(dentry);
  
  out_unlock:

  	inode_unlock(d_inode(mnt->mnt_root));

  	if (inode)
  		iput(inode);

  	mnt_drop_write(mnt);
  out_name:
  	putname(name);

  
  	return err;
  }
  
  /* Pipelined send and receive functions.
   *
   * If a receiver finds no waiting message, then it registers itself in the
   * list of waiting receivers. A sender checks that list before adding the new
   * message into the message array. If there is a waiting receiver, then it
   * bypasses the message array and directly hands the message over to the

   * receiver. The receiver accepts the message and returns without grabbing the
   * queue spinlock:
   *
   * - Set pointer to message.
   * - Queue the receiver task for later wakeup (without the info->lock).
   * - Update its state to STATE_READY. Now the receiver can continue.
   * - Wake up the process after the lock is dropped. Should the process wake up
   *   before this wakeup (due to a timeout or a signal) it will either see
   *   STATE_READY and continue or acquire the lock to check the state again.

   *
   * The same algorithm is used for senders.
   */
  
  /* pipelined_send() - send a message directly to the task waiting in
   * sys_mq_timedreceive() (without inserting message into a queue).
   */

  static inline void pipelined_send(struct wake_q_head *wake_q,
  				  struct mqueue_inode_info *info,

  				  struct msg_msg *message,
  				  struct ext_wait_queue *receiver)
  {
  	receiver->msg = message;
  	list_del(&receiver->list);

  	wake_q_add(wake_q, receiver->task);
  	/*
  	 * Rely on the implicit cmpxchg barrier from wake_q_add such
  	 * that we can ensure that updating receiver->state is the last
  	 * write operation: As once set, the receiver can continue,
  	 * and if we don't have the reference count from the wake_q,
  	 * yet, at that point we can later have a use-after-free
  	 * condition and bogus wakeup.
  	 */

  	receiver->state = STATE_READY;
  }
  
  /* pipelined_receive() - if there is task waiting in sys_mq_timedsend()
   * gets its message and put to the queue (we have one free place for sure). */

  static inline void pipelined_receive(struct wake_q_head *wake_q,
  				     struct mqueue_inode_info *info)

  {
  	struct ext_wait_queue *sender = wq_get_first_waiter(info, SEND);
  
  	if (!sender) {
  		/* for poll */
  		wake_up_interruptible(&info->wait_q);
  		return;
  	}

  	if (msg_insert(sender->msg, info))
  		return;

  	list_del(&sender->list);

  	wake_q_add(wake_q, sender->task);

  	sender->state = STATE_READY;
  }

  static int do_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
  		size_t msg_len, unsigned int msg_prio,

  		struct timespec64 *ts)

  {

  	struct fd f;

  	struct inode *inode;
  	struct ext_wait_queue wait;
  	struct ext_wait_queue *receiver;
  	struct msg_msg *msg_ptr;
  	struct mqueue_inode_info *info;

  	ktime_t expires, *timeout = NULL;

  	struct posix_msg_tree_node *new_leaf = NULL;

  	int ret = 0;

  	DEFINE_WAKE_Q(wake_q);

  
  	if (unlikely(msg_prio >= (unsigned long) MQ_PRIO_MAX))
  		return -EINVAL;

  	if (ts) {

  		expires = timespec64_to_ktime(*ts);

  		timeout = &expires;
  	}
  
  	audit_mq_sendrecv(mqdes, msg_len, msg_prio, ts);

  	f = fdget(mqdes);
  	if (unlikely(!f.file)) {

  		ret = -EBADF;

  		goto out;

  	}

  	inode = file_inode(f.file);

  	if (unlikely(f.file->f_op != &mqueue_file_operations)) {

  		ret = -EBADF;

  		goto out_fput;

  	}

  	info = MQUEUE_I(inode);

  	audit_file(f.file);

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

  		ret = -EBADF;

  		goto out_fput;

  	}

  
  	if (unlikely(msg_len > info->attr.mq_msgsize)) {
  		ret = -EMSGSIZE;
  		goto out_fput;
  	}
  
  	/* First try to allocate memory, before doing anything with
  	 * existing queues. */
  	msg_ptr = load_msg(u_msg_ptr, msg_len);
  	if (IS_ERR(msg_ptr)) {
  		ret = PTR_ERR(msg_ptr);
  		goto out_fput;
  	}
  	msg_ptr->m_ts = msg_len;
  	msg_ptr->m_type = msg_prio;

  	/*
  	 * msg_insert really wants us to have a valid, spare node struct so
  	 * it doesn't have to kmalloc a GFP_ATOMIC allocation, but it will
  	 * fall back to that if necessary.
  	 */
  	if (!info->node_cache)
  		new_leaf = kmalloc(sizeof(*new_leaf), GFP_KERNEL);

  	spin_lock(&info->lock);

  	if (!info->node_cache && new_leaf) {
  		/* Save our speculative allocation into the cache */

  		INIT_LIST_HEAD(&new_leaf->msg_list);
  		info->node_cache = new_leaf;

  		new_leaf = NULL;
  	} else {
  		kfree(new_leaf);
  	}

  	if (info->attr.mq_curmsgs == info->attr.mq_maxmsg) {

  		if (f.file->f_flags & O_NONBLOCK) {

  			ret = -EAGAIN;

  		} else {
  			wait.task = current;
  			wait.msg = (void *) msg_ptr;
  			wait.state = STATE_NONE;
  			ret = wq_sleep(info, SEND, timeout, &wait);

  			/*
  			 * wq_sleep must be called with info->lock held, and
  			 * returns with the lock released
  			 */
  			goto out_free;

  		}

  	} else {
  		receiver = wq_get_first_waiter(info, RECV);
  		if (receiver) {

  			pipelined_send(&wake_q, info, msg_ptr, receiver);

  		} else {
  			/* adds message to the queue */

  			ret = msg_insert(msg_ptr, info);
  			if (ret)
  				goto out_unlock;

  			__do_notify(info);
  		}
  		inode->i_atime = inode->i_mtime = inode->i_ctime =

  				current_time(inode);

  	}

  out_unlock:
  	spin_unlock(&info->lock);

  	wake_up_q(&wake_q);

  out_free:
  	if (ret)
  		free_msg(msg_ptr);

  out_fput:

  	fdput(f);

  out:
  	return ret;
  }

  static int do_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
  		size_t msg_len, unsigned int __user *u_msg_prio,

  		struct timespec64 *ts)

  {

  	ssize_t ret;
  	struct msg_msg *msg_ptr;

  	struct fd f;

  	struct inode *inode;
  	struct mqueue_inode_info *info;
  	struct ext_wait_queue wait;

  	ktime_t expires, *timeout = NULL;

  	struct posix_msg_tree_node *new_leaf = NULL;

  	if (ts) {

  		expires = timespec64_to_ktime(*ts);

  		timeout = &expires;

  	}

  	audit_mq_sendrecv(mqdes, msg_len, 0, ts);

  	f = fdget(mqdes);
  	if (unlikely(!f.file)) {

  		ret = -EBADF;

  		goto out;

  	}

  	inode = file_inode(f.file);

  	if (unlikely(f.file->f_op != &mqueue_file_operations)) {

  		ret = -EBADF;

  		goto out_fput;

  	}

  	info = MQUEUE_I(inode);

  	audit_file(f.file);

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

  		ret = -EBADF;

  		goto out_fput;

  	}

  
  	/* checks if buffer is big enough */
  	if (unlikely(msg_len < info->attr.mq_msgsize)) {
  		ret = -EMSGSIZE;
  		goto out_fput;
  	}

  	/*
  	 * msg_insert really wants us to have a valid, spare node struct so
  	 * it doesn't have to kmalloc a GFP_ATOMIC allocation, but it will
  	 * fall back to that if necessary.
  	 */
  	if (!info->node_cache)
  		new_leaf = kmalloc(sizeof(*new_leaf), GFP_KERNEL);

  	spin_lock(&info->lock);

  
  	if (!info->node_cache && new_leaf) {
  		/* Save our speculative allocation into the cache */

  		INIT_LIST_HEAD(&new_leaf->msg_list);
  		info->node_cache = new_leaf;

  	} else {
  		kfree(new_leaf);
  	}

  	if (info->attr.mq_curmsgs == 0) {

  		if (f.file->f_flags & O_NONBLOCK) {

  			spin_unlock(&info->lock);
  			ret = -EAGAIN;

  		} else {
  			wait.task = current;
  			wait.state = STATE_NONE;
  			ret = wq_sleep(info, RECV, timeout, &wait);
  			msg_ptr = wait.msg;
  		}
  	} else {

  		DEFINE_WAKE_Q(wake_q);

  		msg_ptr = msg_get(info);
  
  		inode->i_atime = inode->i_mtime = inode->i_ctime =

  				current_time(inode);

  
  		/* There is now free space in queue. */

  		pipelined_receive(&wake_q, info);

  		spin_unlock(&info->lock);

  		wake_up_q(&wake_q);

  		ret = 0;
  	}
  	if (ret == 0) {
  		ret = msg_ptr->m_ts;
  
  		if ((u_msg_prio && put_user(msg_ptr->m_type, u_msg_prio)) ||
  			store_msg(u_msg_ptr, msg_ptr, msg_ptr->m_ts)) {
  			ret = -EFAULT;
  		}
  		free_msg(msg_ptr);
  	}
  out_fput:

  	fdput(f);

  out:
  	return ret;
  }

  SYSCALL_DEFINE5(mq_timedsend, mqd_t, mqdes, const char __user *, u_msg_ptr,
  		size_t, msg_len, unsigned int, msg_prio,

  		const struct __kernel_timespec __user *, u_abs_timeout)

  {

  	struct timespec64 ts, *p = NULL;

  	if (u_abs_timeout) {
  		int res = prepare_timeout(u_abs_timeout, &ts);
  		if (res)
  			return res;
  		p = &ts;
  	}
  	return do_mq_timedsend(mqdes, u_msg_ptr, msg_len, msg_prio, p);
  }
  
  SYSCALL_DEFINE5(mq_timedreceive, mqd_t, mqdes, char __user *, u_msg_ptr,
  		size_t, msg_len, unsigned int __user *, u_msg_prio,

  		const struct __kernel_timespec __user *, u_abs_timeout)

  {

  	struct timespec64 ts, *p = NULL;

  	if (u_abs_timeout) {
  		int res = prepare_timeout(u_abs_timeout, &ts);
  		if (res)
  			return res;
  		p = &ts;
  	}
  	return do_mq_timedreceive(mqdes, u_msg_ptr, msg_len, u_msg_prio, p);
  }

  /*
   * Notes: the case when user wants us to deregister (with NULL as pointer)
   * and he isn't currently owner of notification, will be silently discarded.
   * It isn't explicitly defined in the POSIX.
   */

  static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)

  {

  	int ret;
  	struct fd f;

  	struct sock *sock;
  	struct inode *inode;

  	struct mqueue_inode_info *info;
  	struct sk_buff *nc;

  	audit_mq_notify(mqdes, notification);

  	nc = NULL;
  	sock = NULL;

  	if (notification != NULL) {
  		if (unlikely(notification->sigev_notify != SIGEV_NONE &&
  			     notification->sigev_notify != SIGEV_SIGNAL &&
  			     notification->sigev_notify != SIGEV_THREAD))

  			return -EINVAL;

  		if (notification->sigev_notify == SIGEV_SIGNAL &&
  			!valid_signal(notification->sigev_signo)) {

  			return -EINVAL;
  		}

  		if (notification->sigev_notify == SIGEV_THREAD) {

  			long timeo;

  			/* create the notify skb */
  			nc = alloc_skb(NOTIFY_COOKIE_LEN, GFP_KERNEL);

  			if (!nc)
  				return -ENOMEM;

  			if (copy_from_user(nc->data,

  					notification->sigev_value.sival_ptr,

  					NOTIFY_COOKIE_LEN)) {

  				ret = -EFAULT;

  				goto free_skb;

  			}
  
  			/* TODO: add a header? */
  			skb_put(nc, NOTIFY_COOKIE_LEN);
  			/* and attach it to the socket */
  retry:

  			f = fdget(notification->sigev_signo);

  			if (!f.file) {

  				ret = -EBADF;

  				goto out;

  			}

  			sock = netlink_getsockbyfilp(f.file);
  			fdput(f);

  			if (IS_ERR(sock)) {
  				ret = PTR_ERR(sock);

  				goto free_skb;

  			}

  			timeo = MAX_SCHEDULE_TIMEOUT;

  			ret = netlink_attachskb(sock, nc, &timeo, NULL);

  			if (ret == 1) {
  				sock = NULL;

  				goto retry;

  			}

  			if (ret)
  				return ret;

  		}
  	}

  	f = fdget(mqdes);
  	if (!f.file) {

  		ret = -EBADF;

  		goto out;

  	}

  	inode = file_inode(f.file);

  	if (unlikely(f.file->f_op != &mqueue_file_operations)) {

  		ret = -EBADF;

  		goto out_fput;

  	}

  	info = MQUEUE_I(inode);
  
  	ret = 0;
  	spin_lock(&info->lock);

  	if (notification == NULL) {

  		if (info->notify_owner == task_tgid(current)) {

  			remove_notification(info);

  			inode->i_atime = inode->i_ctime = current_time(inode);

  		}

  	} else if (info->notify_owner != NULL) {

  		ret = -EBUSY;
  	} else {

  		switch (notification->sigev_notify) {

  		case SIGEV_NONE:
  			info->notify.sigev_notify = SIGEV_NONE;
  			break;
  		case SIGEV_THREAD:
  			info->notify_sock = sock;
  			info->notify_cookie = nc;
  			sock = NULL;
  			nc = NULL;
  			info->notify.sigev_notify = SIGEV_THREAD;
  			break;
  		case SIGEV_SIGNAL:

  			info->notify.sigev_signo = notification->sigev_signo;
  			info->notify.sigev_value = notification->sigev_value;

  			info->notify.sigev_notify = SIGEV_SIGNAL;

  			info->notify_self_exec_id = current->self_exec_id;

  			break;
  		}

  
  		info->notify_owner = get_pid(task_tgid(current));

  		info->notify_user_ns = get_user_ns(current_user_ns());

  		inode->i_atime = inode->i_ctime = current_time(inode);

  	}
  	spin_unlock(&info->lock);
  out_fput:

  	fdput(f);

  out:

  	if (sock)

  		netlink_detachskb(sock, nc);

  	else

  free_skb:

  		dev_kfree_skb(nc);

  	return ret;
  }

  SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
  		const struct sigevent __user *, u_notification)
  {
  	struct sigevent n, *p = NULL;
  	if (u_notification) {
  		if (copy_from_user(&n, u_notification, sizeof(struct sigevent)))
  			return -EFAULT;
  		p = &n;
  	}
  	return do_mq_notify(mqdes, p);
  }
  
  static int do_mq_getsetattr(int mqdes, struct mq_attr *new, struct mq_attr *old)

  {

  	struct fd f;

  	struct inode *inode;
  	struct mqueue_inode_info *info;

  	if (new && (new->mq_flags & (~O_NONBLOCK)))
  		return -EINVAL;

  	f = fdget(mqdes);

  	if (!f.file)
  		return -EBADF;

  	if (unlikely(f.file->f_op != &mqueue_file_operations)) {

  		fdput(f);
  		return -EBADF;

  	}

  
  	inode = file_inode(f.file);

  	info = MQUEUE_I(inode);
  
  	spin_lock(&info->lock);

  	if (old) {
  		*old = info->attr;
  		old->mq_flags = f.file->f_flags & O_NONBLOCK;
  	}
  	if (new) {
  		audit_mq_getsetattr(mqdes, new);

  		spin_lock(&f.file->f_lock);

  		if (new->mq_flags & O_NONBLOCK)

  			f.file->f_flags |= O_NONBLOCK;

  		else

  			f.file->f_flags &= ~O_NONBLOCK;
  		spin_unlock(&f.file->f_lock);

  		inode->i_atime = inode->i_ctime = current_time(inode);

  	}
  
  	spin_unlock(&info->lock);

  	fdput(f);
  	return 0;
  }

  SYSCALL_DEFINE3(mq_getsetattr, mqd_t, mqdes,
  		const struct mq_attr __user *, u_mqstat,
  		struct mq_attr __user *, u_omqstat)
  {
  	int ret;
  	struct mq_attr mqstat, omqstat;
  	struct mq_attr *new = NULL, *old = NULL;

  	if (u_mqstat) {
  		new = &mqstat;
  		if (copy_from_user(new, u_mqstat, sizeof(struct mq_attr)))
  			return -EFAULT;
  	}
  	if (u_omqstat)
  		old = &omqstat;
  
  	ret = do_mq_getsetattr(mqdes, new, old);
  	if (ret || !old)
  		return ret;
  
  	if (copy_to_user(u_omqstat, old, sizeof(struct mq_attr)))
  		return -EFAULT;
  	return 0;
  }
  
  #ifdef CONFIG_COMPAT
  
  struct compat_mq_attr {
  	compat_long_t mq_flags;      /* message queue flags		     */
  	compat_long_t mq_maxmsg;     /* maximum number of messages	     */
  	compat_long_t mq_msgsize;    /* maximum message size		     */
  	compat_long_t mq_curmsgs;    /* number of messages currently queued  */
  	compat_long_t __reserved[4]; /* ignored for input, zeroed for output */
  };
  
  static inline int get_compat_mq_attr(struct mq_attr *attr,
  			const struct compat_mq_attr __user *uattr)
  {
  	struct compat_mq_attr v;
  
  	if (copy_from_user(&v, uattr, sizeof(*uattr)))
  		return -EFAULT;
  
  	memset(attr, 0, sizeof(*attr));
  	attr->mq_flags = v.mq_flags;
  	attr->mq_maxmsg = v.mq_maxmsg;
  	attr->mq_msgsize = v.mq_msgsize;
  	attr->mq_curmsgs = v.mq_curmsgs;
  	return 0;
  }
  
  static inline int put_compat_mq_attr(const struct mq_attr *attr,
  			struct compat_mq_attr __user *uattr)
  {
  	struct compat_mq_attr v;
  
  	memset(&v, 0, sizeof(v));
  	v.mq_flags = attr->mq_flags;
  	v.mq_maxmsg = attr->mq_maxmsg;
  	v.mq_msgsize = attr->mq_msgsize;
  	v.mq_curmsgs = attr->mq_curmsgs;
  	if (copy_to_user(uattr, &v, sizeof(*uattr)))
  		return -EFAULT;
  	return 0;
  }
  
  COMPAT_SYSCALL_DEFINE4(mq_open, const char __user *, u_name,
  		       int, oflag, compat_mode_t, mode,
  		       struct compat_mq_attr __user *, u_attr)
  {
  	struct mq_attr attr, *p = NULL;
  	if (u_attr && oflag & O_CREAT) {
  		p = &attr;
  		if (get_compat_mq_attr(&attr, u_attr))
  			return -EFAULT;
  	}
  	return do_mq_open(u_name, oflag, mode, p);
  }

  COMPAT_SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
  		       const struct compat_sigevent __user *, u_notification)
  {
  	struct sigevent n, *p = NULL;
  	if (u_notification) {
  		if (get_compat_sigevent(&n, u_notification))
  			return -EFAULT;
  		if (n.sigev_notify == SIGEV_THREAD)
  			n.sigev_value.sival_ptr = compat_ptr(n.sigev_value.sival_int);
  		p = &n;
  	}
  	return do_mq_notify(mqdes, p);
  }
  
  COMPAT_SYSCALL_DEFINE3(mq_getsetattr, mqd_t, mqdes,
  		       const struct compat_mq_attr __user *, u_mqstat,
  		       struct compat_mq_attr __user *, u_omqstat)
  {
  	int ret;
  	struct mq_attr mqstat, omqstat;
  	struct mq_attr *new = NULL, *old = NULL;
  
  	if (u_mqstat) {
  		new = &mqstat;
  		if (get_compat_mq_attr(new, u_mqstat))
  			return -EFAULT;
  	}
  	if (u_omqstat)
  		old = &omqstat;
  
  	ret = do_mq_getsetattr(mqdes, new, old);
  	if (ret || !old)
  		return ret;
  
  	if (put_compat_mq_attr(old, u_omqstat))
  		return -EFAULT;
  	return 0;
  }
  #endif
  
  #ifdef CONFIG_COMPAT_32BIT_TIME

  static int compat_prepare_timeout(const struct old_timespec32 __user *p,

  				   struct timespec64 *ts)

  {

  	if (get_old_timespec32(ts, p))

  		return -EFAULT;

  	if (!timespec64_valid(ts))

  		return -EINVAL;
  	return 0;
  }

  SYSCALL_DEFINE5(mq_timedsend_time32, mqd_t, mqdes,
  		const char __user *, u_msg_ptr,
  		unsigned int, msg_len, unsigned int, msg_prio,
  		const struct old_timespec32 __user *, u_abs_timeout)

  {

  	struct timespec64 ts, *p = NULL;

  	if (u_abs_timeout) {
  		int res = compat_prepare_timeout(u_abs_timeout, &ts);
  		if (res)
  			return res;
  		p = &ts;
  	}
  	return do_mq_timedsend(mqdes, u_msg_ptr, msg_len, msg_prio, p);
  }

  SYSCALL_DEFINE5(mq_timedreceive_time32, mqd_t, mqdes,
  		char __user *, u_msg_ptr,
  		unsigned int, msg_len, unsigned int __user *, u_msg_prio,
  		const struct old_timespec32 __user *, u_abs_timeout)

  {

  	struct timespec64 ts, *p = NULL;

  	if (u_abs_timeout) {
  		int res = compat_prepare_timeout(u_abs_timeout, &ts);
  		if (res)
  			return res;
  		p = &ts;
  	}
  	return do_mq_timedreceive(mqdes, u_msg_ptr, msg_len, u_msg_prio, p);
  }

  #endif

  static const struct inode_operations mqueue_dir_inode_operations = {

  	.lookup = simple_lookup,
  	.create = mqueue_create,
  	.unlink = mqueue_unlink,
  };

  static const struct file_operations mqueue_file_operations = {

  	.flush = mqueue_flush_file,
  	.poll = mqueue_poll_file,
  	.read = mqueue_read_file,

  	.llseek = default_llseek,

  };

  static const struct super_operations mqueue_super_ops = {

  	.alloc_inode = mqueue_alloc_inode,

  	.free_inode = mqueue_free_inode,

  	.evict_inode = mqueue_evict_inode,

  	.statfs = simple_statfs,

  };

  static const struct fs_context_operations mqueue_fs_context_ops = {
  	.free		= mqueue_fs_context_free,
  	.get_tree	= mqueue_get_tree,
  };

  static struct file_system_type mqueue_fs_type = {

  	.name			= "mqueue",
  	.init_fs_context	= mqueue_init_fs_context,
  	.kill_sb		= kill_litter_super,
  	.fs_flags		= FS_USERNS_MOUNT,

  };

  int mq_init_ns(struct ipc_namespace *ns)
  {

  	struct vfsmount *m;

  	ns->mq_queues_count  = 0;
  	ns->mq_queues_max    = DFLT_QUEUESMAX;
  	ns->mq_msg_max       = DFLT_MSGMAX;
  	ns->mq_msgsize_max   = DFLT_MSGSIZEMAX;

  	ns->mq_msg_default   = DFLT_MSG;
  	ns->mq_msgsize_default  = DFLT_MSGSIZE;

  	m = mq_create_mount(ns);
  	if (IS_ERR(m))
  		return PTR_ERR(m);
  	ns->mq_mnt = m;

  	return 0;
  }
  
  void mq_clear_sbinfo(struct ipc_namespace *ns)
  {

  	ns->mq_mnt->mnt_sb->s_fs_info = NULL;

  }
  
  void mq_put_mnt(struct ipc_namespace *ns)
  {

  	kern_unmount(ns->mq_mnt);

  }

  static int __init init_mqueue_fs(void)
  {
  	int error;
  
  	mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
  				sizeof(struct mqueue_inode_info), 0,

  				SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT, init_once);

  	if (mqueue_inode_cachep == NULL)
  		return -ENOMEM;

  	/* ignore failures - they are not fatal */

  	mq_sysctl_table = mq_register_sysctl_table();

  
  	error = register_filesystem(&mqueue_fs_type);
  	if (error)
  		goto out_sysctl;

  	spin_lock_init(&mq_lock);

  	error = mq_init_ns(&init_ipc_ns);
  	if (error)

  		goto out_filesystem;

  	return 0;
  
  out_filesystem:
  	unregister_filesystem(&mqueue_fs_type);
  out_sysctl:
  	if (mq_sysctl_table)
  		unregister_sysctl_table(mq_sysctl_table);

  	kmem_cache_destroy(mqueue_inode_cachep);

  	return error;
  }

  device_initcall(init_mqueue_fs);