// SPDX-License-Identifier: GPL-2.0
/*
 * 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/wake_q.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 <linux/rhashtable.h>

#include <asm/current.h>
#include <linux/uaccess.h>
#include "util.h"

/* one msq_queue structure for each present queue on the system */
struct msg_queue {
    struct kern_ipc_perm q_perm;
    time64_t q_stime;       /* last msgsnd time */
    time64_t q_rtime;       /* last msgrcv time */
    time64_t q_ctime;       /* last change time */
    unsigned long q_cbytes; /* current number of bytes on queue */
    unsigned long q_qnum;   /* number of messages in queue */
    unsigned long q_qbytes; /* max number of bytes on queue */
    struct pid *q_lspid;    /* pid of last msgsnd */
    struct pid *q_lrpid;    /* last receive pid */

    struct list_head q_messages;
    struct list_head q_receivers;
    struct list_head q_senders;
} __randomize_layout;

/*
 * MSG_BARRIER Locking:
 *
 * Similar to the optimization used in ipc/mqueue.c, one syscall return path
 * does not acquire any locks when it sees that a message exists in
 * msg_receiver.r_msg. Therefore r_msg is set using smp_store_release()
 * and accessed using READ_ONCE()+smp_acquire__after_ctrl_dep(). In addition,
 * wake_q_add_safe() is used. See ipc/mqueue.c for more details
 */

/* 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;

    struct msg_msg *r_msg;
};

/* one msg_sender for each sleeping sender */
struct msg_sender {
    struct list_head list;
    struct task_struct *tsk;
    size_t msgsz;
};

#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_idr(&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 kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
    struct msg_queue *msq = container_of(p, struct msg_queue, q_perm);

    security_msg_queue_free(&msq->q_perm);
    kvfree(msq);
}

/**
 * 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 retval;
    key_t key = params->key;
    int msgflg = params->flg;

    msq = kvmalloc(sizeof(*msq), GFP_KERNEL);
    if (unlikely(!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->q_perm);
    if (retval) {
        kvfree(msq);
        return retval;
    }

    msq->q_stime = msq->q_rtime = 0;
    msq->q_ctime = ktime_get_real_seconds();
    msq->q_cbytes = msq->q_qnum = 0;
    msq->q_qbytes = ns->msg_ctlmnb;
    msq->q_lspid = msq->q_lrpid = NULL;
    INIT_LIST_HEAD(&msq->q_messages);
    INIT_LIST_HEAD(&msq->q_receivers);
    INIT_LIST_HEAD(&msq->q_senders);

    /* ipc_addid() locks msq upon success. */
    retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
    if (retval < 0) {
        ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
        return retval;
    }

    ipc_unlock_object(&msq->q_perm);
    rcu_read_unlock();

    return msq->q_perm.id;
}

static inline bool msg_fits_inqueue(struct msg_queue *msq, size_t msgsz)
{
    return msgsz + msq->q_cbytes <= msq->q_qbytes && 1 + msq->q_qnum <= msq->q_qbytes;
}

static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss, size_t msgsz)
{
    mss->tsk = current;
    mss->msgsz = msgsz;
    /*
     * No memory barrier required: we did ipc_lock_object(),
     * and the waker obtains that lock before calling wake_q_add().
     */
    __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) {
        list_del(&mss->list);
    }
}

static void ss_wakeup(struct msg_queue *msq, struct wake_q_head *wake_q, bool kill)
{
    struct msg_sender *mss, *t;
    struct task_struct *stop_tsk = NULL;
    struct list_head *h = &msq->q_senders;

    list_for_each_entry_safe(mss, t, h, list)
    {
        if (kill) {
            mss->list.next = NULL;
        } else if (stop_tsk == mss->tsk) {
            break;
        } else if (!msg_fits_inqueue(msq, mss->msgsz)) {
            if (!stop_tsk) {
                stop_tsk = mss->tsk;
            }

            list_move_tail(&mss->list, &msq->q_senders);
            continue;
        }

        wake_q_add(wake_q, mss->tsk);
    }
}

static void expunge_all(struct msg_queue *msq, int res, struct wake_q_head *wake_q)
{
    struct msg_receiver *msr, *t;

    list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list)
    {
        struct task_struct *r_tsk;

        r_tsk = get_task_struct(msr->r_tsk);

        /* see MSG_BARRIER for purpose/pairing */
        smp_store_release(&msr->r_msg, ERR_PTR(res));
        wake_q_add_safe(wake_q, r_tsk);
    }
}

/*
 * 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) __releases(RCU) __releases(&msq->q_perm)
{
    struct msg_msg *msg, *t;
    struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
    DEFINE_WAKE_Q(wake_q);

    expunge_all(msq, -EIDRM, &wake_q);
    ss_wakeup(msq, &wake_q, true);
    msg_rmid(ns, msq);
    ipc_unlock_object(&msq->q_perm);
    wake_up_q(&wake_q);
    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_update_pid(&msq->q_lspid, NULL);
    ipc_update_pid(&msq->q_lrpid, NULL);
    ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
}

long ksys_msgget(key_t key, int msgflg)
{
    struct ipc_namespace *ns;
    static const struct ipc_ops msg_ops = {
        .getnew = newque,
        .associate = security_msg_queue_associate,
    };
    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);
}

SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
{
    return ksys_msgget(key, msgflg);
}

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 ipc64_perm *perm, int msg_qbytes)
{
    struct kern_ipc_perm *ipcp;
    struct msg_queue *msq;
    int err;

    down_write(&msg_ids(ns).rwsem);
    rcu_read_lock();

    ipcp = ipcctl_obtain_check(ns, &msg_ids(ns), msqid, cmd, perm, 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->q_perm, 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: {
            DEFINE_WAKE_Q(wake_q);

            if (msg_qbytes > ns->msg_ctlmnb && !capable(CAP_SYS_RESOURCE)) {
                err = -EPERM;
                goto out_unlock1;
            }

            ipc_lock_object(&msq->q_perm);
            err = ipc_update_perm(perm, ipcp);
            if (err) {
                goto out_unlock0;
            }

            msq->q_qbytes = msg_qbytes;

            msq->q_ctime = ktime_get_real_seconds();
            /*
             * Sleeping receivers might be excluded by
             * stricter permissions.
             */
            expunge_all(msq, -EAGAIN, &wake_q);
            /*
             * Sleeping senders might be able to send
             * due to a larger queue size.
             */
            ss_wakeup(msq, &wake_q, false);
            ipc_unlock_object(&msq->q_perm);
            wake_up_q(&wake_q);

            goto out_unlock1;
        }
        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_info(struct ipc_namespace *ns, int msqid, int cmd, struct msginfo *msginfo)
{
    int err;
    int max_idx;

    /*
     * 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_idx = ipc_get_maxidx(&msg_ids(ns));
    up_read(&msg_ids(ns).rwsem);
    return (max_idx < 0) ? 0 : max_idx;
}

static int msgctl_stat(struct ipc_namespace *ns, int msqid, int cmd, struct msqid64_ds *p)
{
    struct msg_queue *msq;
    int err;

    memset(p, 0, sizeof(*p));

    rcu_read_lock();
    if (cmd == MSG_STAT || cmd == MSG_STAT_ANY) {
        msq = msq_obtain_object(ns, msqid);
        if (IS_ERR(msq)) {
            err = PTR_ERR(msq);
            goto out_unlock;
        }
    } else { /* IPC_STAT */
        msq = msq_obtain_object_check(ns, msqid);
        if (IS_ERR(msq)) {
            err = PTR_ERR(msq);
            goto out_unlock;
        }
    }

    /* see comment for SHM_STAT_ANY */
    if (cmd == MSG_STAT_ANY) {
        audit_ipc_obj(&msq->q_perm);
    } else {
        err = -EACCES;
        if (ipcperms(ns, &msq->q_perm, S_IRUGO)) {
            goto out_unlock;
        }
    }

    err = security_msg_queue_msgctl(&msq->q_perm, cmd);
    if (err) {
        goto out_unlock;
    }

    ipc_lock_object(&msq->q_perm);

    if (!ipc_valid_object(&msq->q_perm)) {
        ipc_unlock_object(&msq->q_perm);
        err = -EIDRM;
        goto out_unlock;
    }

    kernel_to_ipc64_perm(&msq->q_perm, &p->msg_perm);
    p->msg_stime = msq->q_stime;
    p->msg_rtime = msq->q_rtime;
    p->msg_ctime = msq->q_ctime;
#ifndef CONFIG_64BIT
    p->msg_stime_high = msq->q_stime >> 0x20;
    p->msg_rtime_high = msq->q_rtime >> 0x20;
    p->msg_ctime_high = msq->q_ctime >> 0x20;
#endif
    p->msg_cbytes = msq->q_cbytes;
    p->msg_qnum = msq->q_qnum;
    p->msg_qbytes = msq->q_qbytes;
    p->msg_lspid = pid_vnr(msq->q_lspid);
    p->msg_lrpid = pid_vnr(msq->q_lrpid);

    if (cmd == IPC_STAT) {
        /*
         * As defined in SUS:
         * Return 0 on success
         */
        err = 0;
    } else {
        /*
         * MSG_STAT and MSG_STAT_ANY (both Linux specific)
         * Return the full id, including the sequence number
         */
        err = msq->q_perm.id;
    }

    ipc_unlock_object(&msq->q_perm);
out_unlock:
    rcu_read_unlock();
    return err;
}

static long ksys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf, int version)
{
    struct ipc_namespace *ns;
    struct msqid64_ds msqid64;
    int err;

    if (msqid < 0 || cmd < 0) {
        return -EINVAL;
    }

    ns = current->nsproxy->ipc_ns;

    switch (cmd) {
        case IPC_INFO:
        case MSG_INFO: {
            struct msginfo msginfo;
            err = msgctl_info(ns, msqid, cmd, &msginfo);
            if (err < 0) {
                return err;
            }
            if (copy_to_user(buf, &msginfo, sizeof(struct msginfo))) {
                err = -EFAULT;
            }
            return err;
        }
        case MSG_STAT: /* msqid is an index rather than a msg queue id */
        case MSG_STAT_ANY:
        case IPC_STAT:
            err = msgctl_stat(ns, msqid, cmd, &msqid64);
            if (err < 0) {
                return err;
            }
            if (copy_msqid_to_user(buf, &msqid64, version)) {
                err = -EFAULT;
            }
            return err;
        case IPC_SET:
            if (copy_msqid_from_user(&msqid64, buf, version)) {
                return -EFAULT;
            }
            return msgctl_down(ns, msqid, cmd, &msqid64.msg_perm, msqid64.msg_qbytes);
        case IPC_RMID:
            return msgctl_down(ns, msqid, cmd, NULL, 0);
        default:
            return -EINVAL;
    }
}

SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
{
    return ksys_msgctl(msqid, cmd, buf, IPC_64);
}

#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
long ksys_old_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
{
    int version = ipc_parse_version(&cmd);

    return ksys_msgctl(msqid, cmd, buf, version);
}

SYSCALL_DEFINE3(old_msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
{
    return ksys_old_msgctl(msqid, cmd, buf);
}
#endif

#ifdef CONFIG_COMPAT

struct compat_msqid_ds {
    struct compat_ipc_perm msg_perm;
    compat_uptr_t msg_first;
    compat_uptr_t msg_last;
    old_time32_t msg_stime;
    old_time32_t msg_rtime;
    old_time32_t msg_ctime;
    compat_ulong_t msg_lcbytes;
    compat_ulong_t msg_lqbytes;
    unsigned short msg_cbytes;
    unsigned short msg_qnum;
    unsigned short msg_qbytes;
    compat_ipc_pid_t msg_lspid;
    compat_ipc_pid_t msg_lrpid;
};

static int copy_compat_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
{
    memset(out, 0, sizeof(*out));
    if (version == IPC_64) {
        struct compat_msqid64_ds __user *p = buf;
        if (get_compat_ipc64_perm(&out->msg_perm, &p->msg_perm)) {
            return -EFAULT;
        }
        if (get_user(out->msg_qbytes, &p->msg_qbytes)) {
            return -EFAULT;
        }
    } else {
        struct compat_msqid_ds __user *p = buf;
        if (get_compat_ipc_perm(&out->msg_perm, &p->msg_perm)) {
            return -EFAULT;
        }
        if (get_user(out->msg_qbytes, &p->msg_qbytes)) {
            return -EFAULT;
        }
    }
    return 0;
}

static int copy_compat_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
{
    if (version == IPC_64) {
        struct compat_msqid64_ds v;
        memset(&v, 0, sizeof(v));
        to_compat_ipc64_perm(&v.msg_perm, &in->msg_perm);
        v.msg_stime = lower_32_bits(in->msg_stime);
        v.msg_stime_high = upper_32_bits(in->msg_stime);
        v.msg_rtime = lower_32_bits(in->msg_rtime);
        v.msg_rtime_high = upper_32_bits(in->msg_rtime);
        v.msg_ctime = lower_32_bits(in->msg_ctime);
        v.msg_ctime_high = upper_32_bits(in->msg_ctime);
        v.msg_cbytes = in->msg_cbytes;
        v.msg_qnum = in->msg_qnum;
        v.msg_qbytes = in->msg_qbytes;
        v.msg_lspid = in->msg_lspid;
        v.msg_lrpid = in->msg_lrpid;
        return copy_to_user(buf, &v, sizeof(v));
    } else {
        struct compat_msqid_ds v;
        memset(&v, 0, sizeof(v));
        to_compat_ipc_perm(&v.msg_perm, &in->msg_perm);
        v.msg_stime = in->msg_stime;
        v.msg_rtime = in->msg_rtime;
        v.msg_ctime = in->msg_ctime;
        v.msg_cbytes = in->msg_cbytes;
        v.msg_qnum = in->msg_qnum;
        v.msg_qbytes = in->msg_qbytes;
        v.msg_lspid = in->msg_lspid;
        v.msg_lrpid = in->msg_lrpid;
        return copy_to_user(buf, &v, sizeof(v));
    }
}

static long compat_ksys_msgctl(int msqid, int cmd, void __user *uptr, int version)
{
    struct ipc_namespace *ns;
    int err;
    struct msqid64_ds msqid64;

    ns = current->nsproxy->ipc_ns;

    if (msqid < 0 || cmd < 0) {
        return -EINVAL;
    }

    switch (cmd & (~IPC_64)) {
        case IPC_INFO:
        case MSG_INFO: {
            struct msginfo msginfo;
            err = msgctl_info(ns, msqid, cmd, &msginfo);
            if (err < 0) {
                return err;
            }
            if (copy_to_user(uptr, &msginfo, sizeof(struct msginfo))) {
                err = -EFAULT;
            }
            return err;
        }
        case IPC_STAT:
        case MSG_STAT:
        case MSG_STAT_ANY:
            err = msgctl_stat(ns, msqid, cmd, &msqid64);
            if (err < 0) {
                return err;
            }
            if (copy_compat_msqid_to_user(uptr, &msqid64, version)) {
                err = -EFAULT;
            }
            return err;
        case IPC_SET:
            if (copy_compat_msqid_from_user(&msqid64, uptr, version)) {
                return -EFAULT;
            }
            return msgctl_down(ns, msqid, cmd, &msqid64.msg_perm, msqid64.msg_qbytes);
        case IPC_RMID:
            return msgctl_down(ns, msqid, cmd, NULL, 0);
        default:
            return -EINVAL;
    }
}

COMPAT_SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, void __user *, uptr)
{
    return compat_ksys_msgctl(msqid, cmd, uptr, IPC_64);
}

#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
long compat_ksys_old_msgctl(int msqid, int cmd, void __user *uptr)
{
    int version = compat_ipc_parse_version(&cmd);

    return compat_ksys_msgctl(msqid, cmd, uptr, version);
}

COMPAT_SYSCALL_DEFINE3(old_msgctl, int, msqid, int, cmd, void __user *, uptr)
{
    return compat_ksys_old_msgctl(msqid, cmd, uptr);
}
#endif
#endif

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 wake_q_head *wake_q)
{
    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->q_perm, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) {
            list_del(&msr->r_list);
            if (msr->r_maxsize < msg->m_ts) {
                wake_q_add(wake_q, msr->r_tsk);

                /* See expunge_all regarding memory barrier */
                smp_store_release(&msr->r_msg, ERR_PTR(-E2BIG));
            } else {
                ipc_update_pid(&msq->q_lrpid, task_pid(msr->r_tsk));
                msq->q_rtime = ktime_get_real_seconds();

                wake_q_add(wake_q, msr->r_tsk);

                /* See expunge_all regarding memory barrier */
                smp_store_release(&msr->r_msg, msg);
                return 1;
            }
        }
    }

    return 0;
}

static 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;
    DEFINE_WAKE_Q(wake_q);

    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->q_perm, msg, msgflg);
        if (err) {
            goto out_unlock0;
        }

        if (msg_fits_inqueue(msq, msgsz)) {
            break;
        }

        /* queue full, wait: */
        if (msgflg & IPC_NOWAIT) {
            err = -EAGAIN;
            goto out_unlock0;
        }

        /* enqueue the sender and prepare to block */
        ss_add(msq, &s, msgsz);

        if (!ipc_rcu_getref(&msq->q_perm)) {
            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->q_perm, msg_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;
        }
    }

    ipc_update_pid(&msq->q_lspid, task_tgid(current));
    msq->q_stime = ktime_get_real_seconds();

    if (!pipelined_send(msq, msg, &wake_q)) {
        /* 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);
    wake_up_q(&wake_q);
out_unlock1:
    rcu_read_unlock();
    if (msg != NULL) {
        free_msg(msg);
    }
    return err;
}

long ksys_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);
}

SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, int, msgflg)
{
    return ksys_msgsnd(msqid, msgp, msgsz, msgflg);
}

#ifdef CONFIG_COMPAT

struct compat_msgbuf {
    compat_long_t mtype;
    char mtext[1];
};

long compat_ksys_msgsnd(int msqid, compat_uptr_t msgp, compat_ssize_t msgsz, int msgflg)
{
    struct compat_msgbuf __user *up = compat_ptr(msgp);
    compat_long_t mtype;

    if (get_user(mtype, &up->mtype)) {
        return -EFAULT;
    }
    return do_msgsnd(msqid, mtype, up->mtext, (ssize_t)msgsz, msgflg);
}

COMPAT_SYSCALL_DEFINE4(msgsnd, int, msqid, compat_uptr_t, msgp, compat_ssize_t, msgsz, int, msgflg)
{
    return compat_ksys_msgsnd(msqid, msgp, msgsz, msgflg);
}
#endif

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) {
        if (*msgtyp == LONG_MIN) { /* -LONG_MIN is undefined */
            *msgtyp = LONG_MAX;
        } else {
            *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->q_perm, 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);
}

static 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;
    DEFINE_WAKE_Q(wake_q);

    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 = ktime_get_real_seconds();
            ipc_update_pid(&msq->q_lrpid, task_tgid(current));
            msq->q_cbytes -= msg->m_ts;
            atomic_sub(msg->m_ts, &ns->msg_bytes);
            atomic_dec(&ns->msg_hdrs);
            ss_wakeup(msq, &wake_q, false);

            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;
        }

        /* memory barrier not require due to ipc_lock_object() */
        WRITE_ONCE(msr_d.r_msg, ERR_PTR(-EAGAIN));

        /* memory barrier not required, we own ipc_lock_object() */
        __set_current_state(TASK_INTERRUPTIBLE);

        ipc_unlock_object(&msq->q_perm);
        rcu_read_unlock();
        schedule();

        /*
         * Lockless receive, part 1:
         * 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();

        /*
         * Lockless receive, part 2:
         * The work in pipelined_send() and expunge_all():
         * - Set pointer to message
         * - Queue the receiver task for later wakeup
         * - Wake up the process after the lock is dropped.
         *
         * Should the process wake up before this wakeup (due to a
         * signal) it will either see the message and continue ...
         */
        msg = READ_ONCE(msr_d.r_msg);
        if (msg != ERR_PTR(-EAGAIN)) {
            /* see MSG_BARRIER for purpose/pairing */
            smp_acquire__after_ctrl_dep();

            goto out_unlock1;
        }

        /*
         * ... or see -EAGAIN, acquire the lock to check the message
         * again.
         */
        ipc_lock_object(&msq->q_perm);

        msg = READ_ONCE(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);
    wake_up_q(&wake_q);
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;
}

long ksys_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);
}

SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, long, msgtyp, int, msgflg)
{
    return ksys_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg);
}

#ifdef CONFIG_COMPAT
static long compat_do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
{
    struct compat_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;
}

long compat_ksys_msgrcv(int msqid, compat_uptr_t msgp, compat_ssize_t msgsz, compat_long_t msgtyp, int msgflg)
{
    return do_msgrcv(msqid, compat_ptr(msgp), (ssize_t)msgsz, (long)msgtyp, msgflg, compat_do_msg_fill);
}

COMPAT_SYSCALL_DEFINE5(msgrcv, int, msqid, compat_uptr_t, msgp, compat_ssize_t, msgsz, compat_long_t, msgtyp, int,
                       msgflg)
{
    return compat_ksys_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg);
}
#endif

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);
    rhashtable_destroy(&ns->ids[IPC_MSG_IDS].key_ht);
}
#endif

#ifdef CONFIG_PROC_FS
static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
{
    struct pid_namespace *pid_ns = ipc_seq_pid_ns(s);
    struct user_namespace *user_ns = seq_user_ns(s);
    struct kern_ipc_perm *ipcp = it;
    struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);

    seq_printf(s, "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10llu %10llu %10llu\n", msq->q_perm.key,
               msq->q_perm.id, msq->q_perm.mode, msq->q_cbytes, msq->q_qnum, pid_nr_ns(msq->q_lspid, pid_ns),
               pid_nr_ns(msq->q_lrpid, pid_ns), 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);
}