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    /*
     * 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/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 <net/sock.h>
    #include "util.h"
    
    #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 posix_msg_tree_node *node_cache;
    	struct mq_attr attr;
    
    	struct sigevent notify;
    	struct pid *notify_owner;
    	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 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 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;
    
    	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;
    		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;
    	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 struct msg_msg *msg_get(struct mqueue_inode_info *info)
    {
    	struct rb_node **p, *parent = NULL;
    	struct posix_msg_tree_node *leaf;
    	struct msg_msg *msg;
    
    try_again:
    	p = &info->msg_tree.rb_node;
    	while (*p) {
    		parent = *p;
    		/*
    		 * 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.
    		 */
    		p = &(*p)->rb_right;
    	}
    	if (!parent) {
    		if (info->attr.mq_curmsgs) {
    			pr_warn_once("Inconsistency in POSIX message queue, "
    				     "no tree element, but supposedly messages "
    				     "should exist!\n");
    			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!\n");
    		rb_erase(&leaf->rb_node, &info->msg_tree);
    		if (info->node_cache) {
    			kfree(leaf);
    		} else {
    			info->node_cache = leaf;
    		}
    		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)) {
    			rb_erase(&leaf->rb_node, &info->msg_tree);
    			if (info->node_cache) {
    				kfree(leaf);
    			} else {
    				info->node_cache = leaf;
    			}
    		}
    	}
    	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->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.
    		 */
    		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);
    		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, void *data, int silent)
    {
    	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 struct dentry *mqueue_mount(struct file_system_type *fs_type,
    			 int flags, const char *dev_name,
    			 void *data)
    {
    	struct ipc_namespace *ns;
    	if (flags & MS_KERNMOUNT) {
    		ns = data;
    		data = NULL;
    	} else {
    		ns = current->nsproxy->ipc_ns;
    	}
    	return mount_ns(fs_type, flags, data, ns, ns->user_ns, mqueue_fill_super);
    }
    
    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_i_callback(struct rcu_head *head)
    {
    	struct inode *inode = container_of(head, struct inode, i_rcu);
    	kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
    }
    
    static void mqueue_destroy_inode(struct inode *inode)
    {
    	call_rcu(&inode->i_rcu, mqueue_i_callback);
    }
    
    static void mqueue_evict_inode(struct inode *inode)
    {
    	struct mqueue_inode_info *info;
    	struct user_struct *user;
    	unsigned long mq_bytes, mq_treesize;
    	struct ipc_namespace *ipc_ns;
    	struct msg_msg *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)
    		free_msg(msg);
    	kfree(info->node_cache);
    	spin_unlock(&info->lock);
    
    	/* 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);
    
    	user = info->user;
    	if (user) {
    		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(struct inode *dir, struct dentry *dentry,
    				umode_t mode, bool excl)
    {
    	struct inode *inode;
    	struct mq_attr *attr = dentry->d_fsdata;
    	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_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\n",
    			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 unsigned int mqueue_poll_file(struct file *filp, struct poll_table_struct *poll_tab)
    {
    	struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));
    	int retval = 0;
    
    	poll_wait(filp, &info->wait_q, poll_tab);
    
    	spin_lock(&info->lock);
    	if (info->attr.mq_curmsgs)
    		retval = POLLIN | POLLRDNORM;
    
    	if (info->attr.mq_curmsgs < info->attr.mq_maxmsg)
    		retval |= POLLOUT | POLLWRNORM;
    	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;
    
    	ewp->task = current;
    
    	list_for_each_entry(walk, &info->e_wait_q[sr].list, list) {
    		if (walk->task->static_prio <= current->static_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)
    {
    	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) {
    		struct siginfo sig_i;
    		switch (info->notify.sigev_notify) {
    		case SIGEV_NONE:
    			break;
    		case SIGEV_SIGNAL:
    			/* sends signal */
    
    			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;
    			/* map current pid/uid into info->owner's namespaces */
    			rcu_read_lock();
    			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());
    			rcu_read_unlock();
    
    			kill_pid_info(info->notify.sigev_signo,
    				      &sig_i, info->notify_owner);
    			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 timespec __user *u_abs_timeout,
    			   ktime_t *expires, struct timespec *ts)
    {
    	if (copy_from_user(ts, u_abs_timeout, sizeof(struct timespec)))
    		return -EFAULT;
    	if (!timespec_valid(ts))
    		return -EINVAL;
    
    	*expires = timespec_to_ktime(*ts);
    	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 mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr)
    {
    	int mq_treesize;
    	unsigned long total_size;
    
    	if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0)
    		return -EINVAL;
    	if (capable(CAP_SYS_RESOURCE)) {
    		if (attr->mq_maxmsg > HARD_MSGMAX ||
    		    attr->mq_msgsize > HARD_MSGSIZEMAX)
    			return -EINVAL;
    	} else {
    		if (attr->mq_maxmsg > ipc_ns->mq_msg_max ||
    				attr->mq_msgsize > ipc_ns->mq_msgsize_max)
    			return -EINVAL;
    	}
    	/* check for overflow */
    	if (attr->mq_msgsize > ULONG_MAX/attr->mq_maxmsg)
    		return -EOVERFLOW;
    	mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) +
    		min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) *
    		sizeof(struct posix_msg_tree_node);
    	total_size = attr->mq_maxmsg * attr->mq_msgsize;
    	if (total_size + mq_treesize < total_size)
    		return -EOVERFLOW;
    	return 0;
    }
    
    /*
     * Invoked when creating a new queue via sys_mq_open
     */
    static struct file *do_create(struct ipc_namespace *ipc_ns, struct inode *dir,
    			struct path *path, int oflag, umode_t mode,
    			struct mq_attr *attr)
    {
    	const struct cred *cred = current_cred();
    	int ret;
    
    	if (attr) {
    		ret = mq_attr_ok(ipc_ns, attr);
    		if (ret)
    			return ERR_PTR(ret);
    		/* store for use during create */
    		path->dentry->d_fsdata = attr;
    	} else {
    		struct mq_attr def_attr;
    
    		def_attr.mq_maxmsg = min(ipc_ns->mq_msg_max,
    					 ipc_ns->mq_msg_default);
    		def_attr.mq_msgsize = min(ipc_ns->mq_msgsize_max,
    					  ipc_ns->mq_msgsize_default);
    		ret = mq_attr_ok(ipc_ns, &def_attr);
    		if (ret)
    			return ERR_PTR(ret);
    	}
    
    	mode &= ~current_umask();
    	ret = vfs_create(dir, path->dentry, mode, true);
    	path->dentry->d_fsdata = NULL;
    	if (ret)
    		return ERR_PTR(ret);
    	return dentry_open(path, oflag, cred);
    }
    
    /* Opens existing queue */
    static struct file *do_open(struct path *path, int oflag)
    {
    	static const int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
    						  MAY_READ | MAY_WRITE };
    	int acc;
    	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))
    		return ERR_PTR(-EINVAL);
    	acc = oflag2acc[oflag & O_ACCMODE];
    	if (inode_permission(d_inode(path->dentry), acc))
    		return ERR_PTR(-EACCES);
    	return dentry_open(path, oflag, current_cred());
    }
    
    SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
    		struct mq_attr __user *, u_attr)
    {
    	struct path path;
    	struct file *filp;
    	struct filename *name;
    	struct mq_attr attr;
    	int fd, error;
    	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
    	struct vfsmount *mnt = ipc_ns->mq_mnt;
    	struct dentry *root = mnt->mnt_root;
    	int ro;
    
    	if (u_attr && copy_from_user(&attr, u_attr, sizeof(struct mq_attr)))
    		return -EFAULT;
    
    	audit_mq_open(oflag, mode, u_attr ? &attr : NULL);
    
    	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 */
    	error = 0;
    	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);
    
    	if (oflag & O_CREAT) {
    		if (d_really_is_positive(path.dentry)) {	/* entry already exists */
    			audit_inode(name, path.dentry, 0);
    			if (oflag & O_EXCL) {
    				error = -EEXIST;
    				goto out;
    			}
    			filp = do_open(&path, oflag);
    		} else {
    			if (ro) {
    				error = ro;
    				goto out;
    			}
    			audit_inode_parent_hidden(name, root);
    			filp = do_create(ipc_ns, d_inode(root),
    						&path, oflag, mode,
    						u_attr ? &attr : NULL);
    		}
    	} else {
    		if (d_really_is_negative(path.dentry)) {
    			error = -ENOENT;
    			goto out;
    		}
    		audit_inode(name, path.dentry, 0);
    		filp = do_open(&path, oflag);
    	}
    
    	if (!IS_ERR(filp))
    		fd_install(fd, filp);
    	else
    		error = PTR_ERR(filp);
    out:
    	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_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;
    }
    
    SYSCALL_DEFINE5(mq_timedsend, mqd_t, mqdes, const char __user *, u_msg_ptr,
    		size_t, msg_len, unsigned int, msg_prio,
    		const struct timespec __user *, u_abs_timeout)
    {
    	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 timespec ts;
    	struct posix_msg_tree_node *new_leaf = NULL;
    	int ret = 0;
    	WAKE_Q(wake_q);
    
    	if (u_abs_timeout) {
    		int res = prepare_timeout(u_abs_timeout, &expires, &ts);
    		if (res)
    			return res;
    		timeout = &expires;
    	}
    
    	if (unlikely(msg_prio >= (unsigned long) MQ_PRIO_MAX))
    		return -EINVAL;
    
    	audit_mq_sendrecv(mqdes, msg_len, msg_prio, timeout ? &ts : NULL);
    
    	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;