Initial import

1 files changed, 1046 insertions, 0 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
new file mode 100644
index 000000000..2b6fdbb9e
--- /dev/null
+++ b/ipc/msg.c
@@ -0,0 +1,1046 @@
+/*
+ * linux/ipc/msg.c
+ * Copyright (C) 1992 Krishna Balasubramanian
+ *
+ * Removed all the remaining kerneld mess
+ * Catch the -EFAULT stuff properly
+ * Use GFP_KERNEL for messages as in 1.2
+ * Fixed up the unchecked user space derefs
+ * Copyright (C) 1998 Alan Cox & Andi Kleen
+ *
+ * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
+ *
+ * mostly rewritten, threaded and wake-one semantics added
+ * MSGMAX limit removed, sysctl's added
+ * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
+ *
+ * support for audit of ipc object properties and permission changes
+ * Dustin Kirkland <dustin.kirkland@us.ibm.com>
+ *
+ * namespaces support
+ * OpenVZ, SWsoft Inc.
+ * Pavel Emelianov <xemul@openvz.org>
+ */
+
+#include <linux/capability.h>
+#include <linux/msg.h>
+#include <linux/spinlock.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/list.h>
+#include <linux/security.h>
+#include <linux/sched.h>
+#include <linux/syscalls.h>
+#include <linux/audit.h>
+#include <linux/seq_file.h>
+#include <linux/rwsem.h>
+#include <linux/nsproxy.h>
+#include <linux/ipc_namespace.h>
+
+#include <asm/current.h>
+#include <linux/uaccess.h>
+#include "util.h"
+
+/* one msg_receiver structure for each sleeping receiver */
+struct msg_receiver {
+	struct list_head	r_list;
+	struct task_struct	*r_tsk;
+
+	int			r_mode;
+	long			r_msgtype;
+	long			r_maxsize;
+
+	/*
+	 * Mark r_msg volatile so that the compiler
+	 * does not try to get smart and optimize
+	 * it. We rely on this for the lockless
+	 * receive algorithm.
+	 */
+	struct msg_msg		*volatile r_msg;
+};
+
+/* one msg_sender for each sleeping sender */
+struct msg_sender {
+	struct list_head	list;
+	struct task_struct	*tsk;
+};
+
+#define SEARCH_ANY		1
+#define SEARCH_EQUAL		2
+#define SEARCH_NOTEQUAL		3
+#define SEARCH_LESSEQUAL	4
+#define SEARCH_NUMBER		5
+
+#define msg_ids(ns)	((ns)->ids[IPC_MSG_IDS])
+
+static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return ERR_CAST(ipcp);
+
+	return container_of(ipcp, struct msg_queue, q_perm);
+}
+
+static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
+							int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return ERR_CAST(ipcp);
+
+	return container_of(ipcp, struct msg_queue, q_perm);
+}
+
+static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
+{
+	ipc_rmid(&msg_ids(ns), &s->q_perm);
+}
+
+static void msg_rcu_free(struct rcu_head *head)
+{
+	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
+	struct msg_queue *msq = ipc_rcu_to_struct(p);
+
+	security_msg_queue_free(msq);
+	ipc_rcu_free(head);
+}
+
+/**
+ * newque - Create a new msg queue
+ * @ns: namespace
+ * @params: ptr to the structure that contains the key and msgflg
+ *
+ * Called with msg_ids.rwsem held (writer)
+ */
+static int newque(struct ipc_namespace *ns, struct ipc_params *params)
+{
+	struct msg_queue *msq;
+	int id, retval;
+	key_t key = params->key;
+	int msgflg = params->flg;
+
+	msq = ipc_rcu_alloc(sizeof(*msq));
+	if (!msq)
+		return -ENOMEM;
+
+	msq->q_perm.mode = msgflg & S_IRWXUGO;
+	msq->q_perm.key = key;
+
+	msq->q_perm.security = NULL;
+	retval = security_msg_queue_alloc(msq);
+	if (retval) {
+		ipc_rcu_putref(msq, ipc_rcu_free);
+		return retval;
+	}
+
+	/* ipc_addid() locks msq upon success. */
+	id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
+	if (id < 0) {
+		ipc_rcu_putref(msq, msg_rcu_free);
+		return id;
+	}
+
+	msq->q_stime = msq->q_rtime = 0;
+	msq->q_ctime = get_seconds();
+	msq->q_cbytes = msq->q_qnum = 0;
+	msq->q_qbytes = ns->msg_ctlmnb;
+	msq->q_lspid = msq->q_lrpid = 0;
+	INIT_LIST_HEAD(&msq->q_messages);
+	INIT_LIST_HEAD(&msq->q_receivers);
+	INIT_LIST_HEAD(&msq->q_senders);
+
+	ipc_unlock_object(&msq->q_perm);
+	rcu_read_unlock();
+
+	return msq->q_perm.id;
+}
+
+static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
+{
+	mss->tsk = current;
+	__set_current_state(TASK_INTERRUPTIBLE);
+	list_add_tail(&mss->list, &msq->q_senders);
+}
+
+static inline void ss_del(struct msg_sender *mss)
+{
+	if (mss->list.next != NULL)
+		list_del(&mss->list);
+}
+
+static void ss_wakeup(struct list_head *h, int kill)
+{
+	struct msg_sender *mss, *t;
+
+	list_for_each_entry_safe(mss, t, h, list) {
+		if (kill)
+			mss->list.next = NULL;
+		wake_up_process(mss->tsk);
+	}
+}
+
+static void expunge_all(struct msg_queue *msq, int res)
+{
+	struct msg_receiver *msr, *t;
+
+	list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
+		msr->r_msg = NULL; /* initialize expunge ordering */
+		wake_up_process(msr->r_tsk);
+		/*
+		 * Ensure that the wakeup is visible before setting r_msg as
+		 * the receiving end depends on it: either spinning on a nil,
+		 * or dealing with -EAGAIN cases. See lockless receive part 1
+		 * and 2 in do_msgrcv().
+		 */
+		smp_mb();
+		msr->r_msg = ERR_PTR(res);
+	}
+}
+
+/*
+ * freeque() wakes up waiters on the sender and receiver waiting queue,
+ * removes the message queue from message queue ID IDR, and cleans up all the
+ * messages associated with this queue.
+ *
+ * msg_ids.rwsem (writer) and the spinlock for this message queue are held
+ * before freeque() is called. msg_ids.rwsem remains locked on exit.
+ */
+static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
+{
+	struct msg_msg *msg, *t;
+	struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
+
+	expunge_all(msq, -EIDRM);
+	ss_wakeup(&msq->q_senders, 1);
+	msg_rmid(ns, msq);
+	ipc_unlock_object(&msq->q_perm);
+	rcu_read_unlock();
+
+	list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
+		atomic_dec(&ns->msg_hdrs);
+		free_msg(msg);
+	}
+	atomic_sub(msq->q_cbytes, &ns->msg_bytes);
+	ipc_rcu_putref(msq, msg_rcu_free);
+}
+
+/*
+ * Called with msg_ids.rwsem and ipcp locked.
+ */
+static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
+{
+	struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
+
+	return security_msg_queue_associate(msq, msgflg);
+}
+
+SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
+{
+	struct ipc_namespace *ns;
+	static const struct ipc_ops msg_ops = {
+		.getnew = newque,
+		.associate = msg_security,
+	};
+	struct ipc_params msg_params;
+
+	ns = current->nsproxy->ipc_ns;
+
+	msg_params.key = key;
+	msg_params.flg = msgflg;
+
+	return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
+}
+
+static inline unsigned long
+copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
+{
+	switch (version) {
+	case IPC_64:
+		return copy_to_user(buf, in, sizeof(*in));
+	case IPC_OLD:
+	{
+		struct msqid_ds out;
+
+		memset(&out, 0, sizeof(out));
+
+		ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
+
+		out.msg_stime		= in->msg_stime;
+		out.msg_rtime		= in->msg_rtime;
+		out.msg_ctime		= in->msg_ctime;
+
+		if (in->msg_cbytes > USHRT_MAX)
+			out.msg_cbytes	= USHRT_MAX;
+		else
+			out.msg_cbytes	= in->msg_cbytes;
+		out.msg_lcbytes		= in->msg_cbytes;
+
+		if (in->msg_qnum > USHRT_MAX)
+			out.msg_qnum	= USHRT_MAX;
+		else
+			out.msg_qnum	= in->msg_qnum;
+
+		if (in->msg_qbytes > USHRT_MAX)
+			out.msg_qbytes	= USHRT_MAX;
+		else
+			out.msg_qbytes	= in->msg_qbytes;
+		out.msg_lqbytes		= in->msg_qbytes;
+
+		out.msg_lspid		= in->msg_lspid;
+		out.msg_lrpid		= in->msg_lrpid;
+
+		return copy_to_user(buf, &out, sizeof(out));
+	}
+	default:
+		return -EINVAL;
+	}
+}
+
+static inline unsigned long
+copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
+{
+	switch (version) {
+	case IPC_64:
+		if (copy_from_user(out, buf, sizeof(*out)))
+			return -EFAULT;
+		return 0;
+	case IPC_OLD:
+	{
+		struct msqid_ds tbuf_old;
+
+		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
+			return -EFAULT;
+
+		out->msg_perm.uid	= tbuf_old.msg_perm.uid;
+		out->msg_perm.gid	= tbuf_old.msg_perm.gid;
+		out->msg_perm.mode	= tbuf_old.msg_perm.mode;
+
+		if (tbuf_old.msg_qbytes == 0)
+			out->msg_qbytes	= tbuf_old.msg_lqbytes;
+		else
+			out->msg_qbytes	= tbuf_old.msg_qbytes;
+
+		return 0;
+	}
+	default:
+		return -EINVAL;
+	}
+}
+
+/*
+ * This function handles some msgctl commands which require the rwsem
+ * to be held in write mode.
+ * NOTE: no locks must be held, the rwsem is taken inside this function.
+ */
+static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
+		       struct msqid_ds __user *buf, int version)
+{
+	struct kern_ipc_perm *ipcp;
+	struct msqid64_ds uninitialized_var(msqid64);
+	struct msg_queue *msq;
+	int err;
+
+	if (cmd == IPC_SET) {
+		if (copy_msqid_from_user(&msqid64, buf, version))
+			return -EFAULT;
+	}
+
+	down_write(&msg_ids(ns).rwsem);
+	rcu_read_lock();
+
+	ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
+				      &msqid64.msg_perm, msqid64.msg_qbytes);
+	if (IS_ERR(ipcp)) {
+		err = PTR_ERR(ipcp);
+		goto out_unlock1;
+	}
+
+	msq = container_of(ipcp, struct msg_queue, q_perm);
+
+	err = security_msg_queue_msgctl(msq, cmd);
+	if (err)
+		goto out_unlock1;
+
+	switch (cmd) {
+	case IPC_RMID:
+		ipc_lock_object(&msq->q_perm);
+		/* freeque unlocks the ipc object and rcu */
+		freeque(ns, ipcp);
+		goto out_up;
+	case IPC_SET:
+		if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
+		    !capable(CAP_SYS_RESOURCE)) {
+			err = -EPERM;
+			goto out_unlock1;
+		}
+
+		ipc_lock_object(&msq->q_perm);
+		err = ipc_update_perm(&msqid64.msg_perm, ipcp);
+		if (err)
+			goto out_unlock0;
+
+		msq->q_qbytes = msqid64.msg_qbytes;
+
+		msq->q_ctime = get_seconds();
+		/* sleeping receivers might be excluded by
+		 * stricter permissions.
+		 */
+		expunge_all(msq, -EAGAIN);
+		/* sleeping senders might be able to send
+		 * due to a larger queue size.
+		 */
+		ss_wakeup(&msq->q_senders, 0);
+		break;
+	default:
+		err = -EINVAL;
+		goto out_unlock1;
+	}
+
+out_unlock0:
+	ipc_unlock_object(&msq->q_perm);
+out_unlock1:
+	rcu_read_unlock();
+out_up:
+	up_write(&msg_ids(ns).rwsem);
+	return err;
+}
+
+static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
+			 int cmd, int version, void __user *buf)
+{
+	int err;
+	struct msg_queue *msq;
+
+	switch (cmd) {
+	case IPC_INFO:
+	case MSG_INFO:
+	{
+		struct msginfo msginfo;
+		int max_id;
+
+		if (!buf)
+			return -EFAULT;
+
+		/*
+		 * We must not return kernel stack data.
+		 * due to padding, it's not enough
+		 * to set all member fields.
+		 */
+		err = security_msg_queue_msgctl(NULL, cmd);
+		if (err)
+			return err;
+
+		memset(&msginfo, 0, sizeof(msginfo));
+		msginfo.msgmni = ns->msg_ctlmni;
+		msginfo.msgmax = ns->msg_ctlmax;
+		msginfo.msgmnb = ns->msg_ctlmnb;
+		msginfo.msgssz = MSGSSZ;
+		msginfo.msgseg = MSGSEG;
+		down_read(&msg_ids(ns).rwsem);
+		if (cmd == MSG_INFO) {
+			msginfo.msgpool = msg_ids(ns).in_use;
+			msginfo.msgmap = atomic_read(&ns->msg_hdrs);
+			msginfo.msgtql = atomic_read(&ns->msg_bytes);
+		} else {
+			msginfo.msgmap = MSGMAP;
+			msginfo.msgpool = MSGPOOL;
+			msginfo.msgtql = MSGTQL;
+		}
+		max_id = ipc_get_maxid(&msg_ids(ns));
+		up_read(&msg_ids(ns).rwsem);
+		if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
+			return -EFAULT;
+		return (max_id < 0) ? 0 : max_id;
+	}
+
+	case MSG_STAT:
+	case IPC_STAT:
+	{
+		struct msqid64_ds tbuf;
+		int success_return;
+
+		if (!buf)
+			return -EFAULT;
+
+		memset(&tbuf, 0, sizeof(tbuf));
+
+		rcu_read_lock();
+		if (cmd == MSG_STAT) {
+			msq = msq_obtain_object(ns, msqid);
+			if (IS_ERR(msq)) {
+				err = PTR_ERR(msq);
+				goto out_unlock;
+			}
+			success_return = msq->q_perm.id;
+		} else {
+			msq = msq_obtain_object_check(ns, msqid);
+			if (IS_ERR(msq)) {
+				err = PTR_ERR(msq);
+				goto out_unlock;
+			}
+			success_return = 0;
+		}
+
+		err = -EACCES;
+		if (ipcperms(ns, &msq->q_perm, S_IRUGO))
+			goto out_unlock;
+
+		err = security_msg_queue_msgctl(msq, cmd);
+		if (err)
+			goto out_unlock;
+
+		kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
+		tbuf.msg_stime  = msq->q_stime;
+		tbuf.msg_rtime  = msq->q_rtime;
+		tbuf.msg_ctime  = msq->q_ctime;
+		tbuf.msg_cbytes = msq->q_cbytes;
+		tbuf.msg_qnum   = msq->q_qnum;
+		tbuf.msg_qbytes = msq->q_qbytes;
+		tbuf.msg_lspid  = msq->q_lspid;
+		tbuf.msg_lrpid  = msq->q_lrpid;
+		rcu_read_unlock();
+
+		if (copy_msqid_to_user(buf, &tbuf, version))
+			return -EFAULT;
+		return success_return;
+	}
+
+	default:
+		return -EINVAL;
+	}
+
+	return err;
+out_unlock:
+	rcu_read_unlock();
+	return err;
+}
+
+SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
+{
+	int version;
+	struct ipc_namespace *ns;
+
+	if (msqid < 0 || cmd < 0)
+		return -EINVAL;
+
+	version = ipc_parse_version(&cmd);
+	ns = current->nsproxy->ipc_ns;
+
+	switch (cmd) {
+	case IPC_INFO:
+	case MSG_INFO:
+	case MSG_STAT:	/* msqid is an index rather than a msg queue id */
+	case IPC_STAT:
+		return msgctl_nolock(ns, msqid, cmd, version, buf);
+	case IPC_SET:
+	case IPC_RMID:
+		return msgctl_down(ns, msqid, cmd, buf, version);
+	default:
+		return  -EINVAL;
+	}
+}
+
+static int testmsg(struct msg_msg *msg, long type, int mode)
+{
+	switch (mode) {
+	case SEARCH_ANY:
+	case SEARCH_NUMBER:
+		return 1;
+	case SEARCH_LESSEQUAL:
+		if (msg->m_type <= type)
+			return 1;
+		break;
+	case SEARCH_EQUAL:
+		if (msg->m_type == type)
+			return 1;
+		break;
+	case SEARCH_NOTEQUAL:
+		if (msg->m_type != type)
+			return 1;
+		break;
+	}
+	return 0;
+}
+
+static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
+{
+	struct msg_receiver *msr, *t;
+
+	list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
+		if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
+		    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
+					       msr->r_msgtype, msr->r_mode)) {
+
+			list_del(&msr->r_list);
+			if (msr->r_maxsize < msg->m_ts) {
+				/* initialize pipelined send ordering */
+				msr->r_msg = NULL;
+				wake_up_process(msr->r_tsk);
+				smp_mb(); /* see barrier comment below */
+				msr->r_msg = ERR_PTR(-E2BIG);
+			} else {
+				msr->r_msg = NULL;
+				msq->q_lrpid = task_pid_vnr(msr->r_tsk);
+				msq->q_rtime = get_seconds();
+				wake_up_process(msr->r_tsk);
+				/*
+				 * Ensure that the wakeup is visible before
+				 * setting r_msg, as the receiving end depends
+				 * on it. See lockless receive part 1 and 2 in
+				 * do_msgrcv().
+				 */
+				smp_mb();
+				msr->r_msg = msg;
+
+				return 1;
+			}
+		}
+	}
+
+	return 0;
+}
+
+long do_msgsnd(int msqid, long mtype, void __user *mtext,
+		size_t msgsz, int msgflg)
+{
+	struct msg_queue *msq;
+	struct msg_msg *msg;
+	int err;
+	struct ipc_namespace *ns;
+
+	ns = current->nsproxy->ipc_ns;
+
+	if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
+		return -EINVAL;
+	if (mtype < 1)
+		return -EINVAL;
+
+	msg = load_msg(mtext, msgsz);
+	if (IS_ERR(msg))
+		return PTR_ERR(msg);
+
+	msg->m_type = mtype;
+	msg->m_ts = msgsz;
+
+	rcu_read_lock();
+	msq = msq_obtain_object_check(ns, msqid);
+	if (IS_ERR(msq)) {
+		err = PTR_ERR(msq);
+		goto out_unlock1;
+	}
+
+	ipc_lock_object(&msq->q_perm);
+
+	for (;;) {
+		struct msg_sender s;
+
+		err = -EACCES;
+		if (ipcperms(ns, &msq->q_perm, S_IWUGO))
+			goto out_unlock0;
+
+		/* raced with RMID? */
+		if (!ipc_valid_object(&msq->q_perm)) {
+			err = -EIDRM;
+			goto out_unlock0;
+		}
+
+		err = security_msg_queue_msgsnd(msq, msg, msgflg);
+		if (err)
+			goto out_unlock0;
+
+		if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
+				1 + msq->q_qnum <= msq->q_qbytes) {
+			break;
+		}
+
+		/* queue full, wait: */
+		if (msgflg & IPC_NOWAIT) {
+			err = -EAGAIN;
+			goto out_unlock0;
+		}
+
+		/* enqueue the sender and prepare to block */
+		ss_add(msq, &s);
+
+		if (!ipc_rcu_getref(msq)) {
+			err = -EIDRM;
+			goto out_unlock0;
+		}
+
+		ipc_unlock_object(&msq->q_perm);
+		rcu_read_unlock();
+		schedule();
+
+		rcu_read_lock();
+		ipc_lock_object(&msq->q_perm);
+
+		ipc_rcu_putref(msq, ipc_rcu_free);
+		/* raced with RMID? */
+		if (!ipc_valid_object(&msq->q_perm)) {
+			err = -EIDRM;
+			goto out_unlock0;
+		}
+
+		ss_del(&s);
+
+		if (signal_pending(current)) {
+			err = -ERESTARTNOHAND;
+			goto out_unlock0;
+		}
+
+	}
+	msq->q_lspid = task_tgid_vnr(current);
+	msq->q_stime = get_seconds();
+
+	if (!pipelined_send(msq, msg)) {
+		/* no one is waiting for this message, enqueue it */
+		list_add_tail(&msg->m_list, &msq->q_messages);
+		msq->q_cbytes += msgsz;
+		msq->q_qnum++;
+		atomic_add(msgsz, &ns->msg_bytes);
+		atomic_inc(&ns->msg_hdrs);
+	}
+
+	err = 0;
+	msg = NULL;
+
+out_unlock0:
+	ipc_unlock_object(&msq->q_perm);
+out_unlock1:
+	rcu_read_unlock();
+	if (msg != NULL)
+		free_msg(msg);
+	return err;
+}
+
+SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
+		int, msgflg)
+{
+	long mtype;
+
+	if (get_user(mtype, &msgp->mtype))
+		return -EFAULT;
+	return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
+}
+
+static inline int convert_mode(long *msgtyp, int msgflg)
+{
+	if (msgflg & MSG_COPY)
+		return SEARCH_NUMBER;
+	/*
+	 *  find message of correct type.
+	 *  msgtyp = 0 => get first.
+	 *  msgtyp > 0 => get first message of matching type.
+	 *  msgtyp < 0 => get message with least type must be < abs(msgtype).
+	 */
+	if (*msgtyp == 0)
+		return SEARCH_ANY;
+	if (*msgtyp < 0) {
+		*msgtyp = -*msgtyp;
+		return SEARCH_LESSEQUAL;
+	}
+	if (msgflg & MSG_EXCEPT)
+		return SEARCH_NOTEQUAL;
+	return SEARCH_EQUAL;
+}
+
+static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
+{
+	struct msgbuf __user *msgp = dest;
+	size_t msgsz;
+
+	if (put_user(msg->m_type, &msgp->mtype))
+		return -EFAULT;
+
+	msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
+	if (store_msg(msgp->mtext, msg, msgsz))
+		return -EFAULT;
+	return msgsz;
+}
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+/*
+ * This function creates new kernel message structure, large enough to store
+ * bufsz message bytes.
+ */
+static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
+{
+	struct msg_msg *copy;
+
+	/*
+	 * Create dummy message to copy real message to.
+	 */
+	copy = load_msg(buf, bufsz);
+	if (!IS_ERR(copy))
+		copy->m_ts = bufsz;
+	return copy;
+}
+
+static inline void free_copy(struct msg_msg *copy)
+{
+	if (copy)
+		free_msg(copy);
+}
+#else
+static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline void free_copy(struct msg_msg *copy)
+{
+}
+#endif
+
+static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
+{
+	struct msg_msg *msg, *found = NULL;
+	long count = 0;
+
+	list_for_each_entry(msg, &msq->q_messages, m_list) {
+		if (testmsg(msg, *msgtyp, mode) &&
+		    !security_msg_queue_msgrcv(msq, msg, current,
+					       *msgtyp, mode)) {
+			if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
+				*msgtyp = msg->m_type - 1;
+				found = msg;
+			} else if (mode == SEARCH_NUMBER) {
+				if (*msgtyp == count)
+					return msg;
+			} else
+				return msg;
+			count++;
+		}
+	}
+
+	return found ?: ERR_PTR(-EAGAIN);
+}
+
+long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
+	       long (*msg_handler)(void __user *, struct msg_msg *, size_t))
+{
+	int mode;
+	struct msg_queue *msq;
+	struct ipc_namespace *ns;
+	struct msg_msg *msg, *copy = NULL;
+
+	ns = current->nsproxy->ipc_ns;
+
+	if (msqid < 0 || (long) bufsz < 0)
+		return -EINVAL;
+
+	if (msgflg & MSG_COPY) {
+		if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
+			return -EINVAL;
+		copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
+		if (IS_ERR(copy))
+			return PTR_ERR(copy);
+	}
+	mode = convert_mode(&msgtyp, msgflg);
+
+	rcu_read_lock();
+	msq = msq_obtain_object_check(ns, msqid);
+	if (IS_ERR(msq)) {
+		rcu_read_unlock();
+		free_copy(copy);
+		return PTR_ERR(msq);
+	}
+
+	for (;;) {
+		struct msg_receiver msr_d;
+
+		msg = ERR_PTR(-EACCES);
+		if (ipcperms(ns, &msq->q_perm, S_IRUGO))
+			goto out_unlock1;
+
+		ipc_lock_object(&msq->q_perm);
+
+		/* raced with RMID? */
+		if (!ipc_valid_object(&msq->q_perm)) {
+			msg = ERR_PTR(-EIDRM);
+			goto out_unlock0;
+		}
+
+		msg = find_msg(msq, &msgtyp, mode);
+		if (!IS_ERR(msg)) {
+			/*
+			 * Found a suitable message.
+			 * Unlink it from the queue.
+			 */
+			if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
+				msg = ERR_PTR(-E2BIG);
+				goto out_unlock0;
+			}
+			/*
+			 * If we are copying, then do not unlink message and do
+			 * not update queue parameters.
+			 */
+			if (msgflg & MSG_COPY) {
+				msg = copy_msg(msg, copy);
+				goto out_unlock0;
+			}
+
+			list_del(&msg->m_list);
+			msq->q_qnum--;
+			msq->q_rtime = get_seconds();
+			msq->q_lrpid = task_tgid_vnr(current);
+			msq->q_cbytes -= msg->m_ts;
+			atomic_sub(msg->m_ts, &ns->msg_bytes);
+			atomic_dec(&ns->msg_hdrs);
+			ss_wakeup(&msq->q_senders, 0);
+
+			goto out_unlock0;
+		}
+
+		/* No message waiting. Wait for a message */
+		if (msgflg & IPC_NOWAIT) {
+			msg = ERR_PTR(-ENOMSG);
+			goto out_unlock0;
+		}
+
+		list_add_tail(&msr_d.r_list, &msq->q_receivers);
+		msr_d.r_tsk = current;
+		msr_d.r_msgtype = msgtyp;
+		msr_d.r_mode = mode;
+		if (msgflg & MSG_NOERROR)
+			msr_d.r_maxsize = INT_MAX;
+		else
+			msr_d.r_maxsize = bufsz;
+		msr_d.r_msg = ERR_PTR(-EAGAIN);
+		__set_current_state(TASK_INTERRUPTIBLE);
+
+		ipc_unlock_object(&msq->q_perm);
+		rcu_read_unlock();
+		schedule();
+
+		/* Lockless receive, part 1:
+		 * Disable preemption.  We don't hold a reference to the queue
+		 * and getting a reference would defeat the idea of a lockless
+		 * operation, thus the code relies on rcu to guarantee the
+		 * existence of msq:
+		 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
+		 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
+		 * rcu_read_lock() prevents preemption between reading r_msg
+		 * and acquiring the q_perm.lock in ipc_lock_object().
+		 */
+		rcu_read_lock();
+
+		/* Lockless receive, part 2:
+		 * Wait until pipelined_send or expunge_all are outside of
+		 * wake_up_process(). There is a race with exit(), see
+		 * ipc/mqueue.c for the details.
+		 */
+		msg = (struct msg_msg *)msr_d.r_msg;
+		while (msg == NULL) {
+			cpu_relax();
+			msg = (struct msg_msg *)msr_d.r_msg;
+		}
+
+		/* Lockless receive, part 3:
+		 * If there is a message or an error then accept it without
+		 * locking.
+		 */
+		if (msg != ERR_PTR(-EAGAIN))
+			goto out_unlock1;
+
+		/* Lockless receive, part 3:
+		 * Acquire the queue spinlock.
+		 */
+		ipc_lock_object(&msq->q_perm);
+
+		/* Lockless receive, part 4:
+		 * Repeat test after acquiring the spinlock.
+		 */
+		msg = (struct msg_msg *)msr_d.r_msg;
+		if (msg != ERR_PTR(-EAGAIN))
+			goto out_unlock0;
+
+		list_del(&msr_d.r_list);
+		if (signal_pending(current)) {
+			msg = ERR_PTR(-ERESTARTNOHAND);
+			goto out_unlock0;
+		}
+
+		ipc_unlock_object(&msq->q_perm);
+	}
+
+out_unlock0:
+	ipc_unlock_object(&msq->q_perm);
+out_unlock1:
+	rcu_read_unlock();
+	if (IS_ERR(msg)) {
+		free_copy(copy);
+		return PTR_ERR(msg);
+	}
+
+	bufsz = msg_handler(buf, msg, bufsz);
+	free_msg(msg);
+
+	return bufsz;
+}
+
+SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
+		long, msgtyp, int, msgflg)
+{
+	return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
+}
+
+
+void msg_init_ns(struct ipc_namespace *ns)
+{
+	ns->msg_ctlmax = MSGMAX;
+	ns->msg_ctlmnb = MSGMNB;
+	ns->msg_ctlmni = MSGMNI;
+
+	atomic_set(&ns->msg_bytes, 0);
+	atomic_set(&ns->msg_hdrs, 0);
+	ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
+}
+
+#ifdef CONFIG_IPC_NS
+void msg_exit_ns(struct ipc_namespace *ns)
+{
+	free_ipcs(ns, &msg_ids(ns), freeque);
+	idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
+}
+#endif
+
+#ifdef CONFIG_PROC_FS
+static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
+{
+	struct user_namespace *user_ns = seq_user_ns(s);
+	struct msg_queue *msq = it;
+
+	seq_printf(s,
+		   "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
+		   msq->q_perm.key,
+		   msq->q_perm.id,
+		   msq->q_perm.mode,
+		   msq->q_cbytes,
+		   msq->q_qnum,
+		   msq->q_lspid,
+		   msq->q_lrpid,
+		   from_kuid_munged(user_ns, msq->q_perm.uid),
+		   from_kgid_munged(user_ns, msq->q_perm.gid),
+		   from_kuid_munged(user_ns, msq->q_perm.cuid),
+		   from_kgid_munged(user_ns, msq->q_perm.cgid),
+		   msq->q_stime,
+		   msq->q_rtime,
+		   msq->q_ctime);
+
+	return 0;
+}
+#endif
+
+void __init msg_init(void)
+{
+	msg_init_ns(&init_ipc_ns);
+
+	ipc_init_proc_interface("sysvipc/msg",
+				"       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
+				IPC_MSG_IDS, sysvipc_msg_proc_show);
+}