Root/ipc/msg.c

1/*
2 * linux/ipc/msg.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 *
5 * Removed all the remaining kerneld mess
6 * Catch the -EFAULT stuff properly
7 * Use GFP_KERNEL for messages as in 1.2
8 * Fixed up the unchecked user space derefs
9 * Copyright (C) 1998 Alan Cox & Andi Kleen
10 *
11 * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
12 *
13 * mostly rewritten, threaded and wake-one semantics added
14 * MSGMAX limit removed, sysctl's added
15 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
16 *
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
19 *
20 * namespaces support
21 * OpenVZ, SWsoft Inc.
22 * Pavel Emelianov <xemul@openvz.org>
23 */
24
25#include <linux/capability.h>
26#include <linux/msg.h>
27#include <linux/spinlock.h>
28#include <linux/init.h>
29#include <linux/mm.h>
30#include <linux/proc_fs.h>
31#include <linux/list.h>
32#include <linux/security.h>
33#include <linux/sched.h>
34#include <linux/syscalls.h>
35#include <linux/audit.h>
36#include <linux/seq_file.h>
37#include <linux/rwsem.h>
38#include <linux/nsproxy.h>
39#include <linux/ipc_namespace.h>
40
41#include <asm/current.h>
42#include <asm/uaccess.h>
43#include "util.h"
44
45/*
46 * one msg_receiver structure for each sleeping receiver:
47 */
48struct msg_receiver {
49    struct list_head r_list;
50    struct task_struct *r_tsk;
51
52    int r_mode;
53    long r_msgtype;
54    long r_maxsize;
55
56    struct msg_msg *volatile r_msg;
57};
58
59/* one msg_sender for each sleeping sender */
60struct msg_sender {
61    struct list_head list;
62    struct task_struct *tsk;
63};
64
65#define SEARCH_ANY 1
66#define SEARCH_EQUAL 2
67#define SEARCH_NOTEQUAL 3
68#define SEARCH_LESSEQUAL 4
69
70#define msg_ids(ns) ((ns)->ids[IPC_MSG_IDS])
71
72#define msg_unlock(msq) ipc_unlock(&(msq)->q_perm)
73
74static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
75static int newque(struct ipc_namespace *, struct ipc_params *);
76#ifdef CONFIG_PROC_FS
77static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
78#endif
79
80/*
81 * Scale msgmni with the available lowmem size: the memory dedicated to msg
82 * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
83 * Also take into account the number of nsproxies created so far.
84 * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
85 */
86void recompute_msgmni(struct ipc_namespace *ns)
87{
88    struct sysinfo i;
89    unsigned long allowed;
90    int nb_ns;
91
92    si_meminfo(&i);
93    allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
94        / MSGMNB;
95    nb_ns = atomic_read(&nr_ipc_ns);
96    allowed /= nb_ns;
97
98    if (allowed < MSGMNI) {
99        ns->msg_ctlmni = MSGMNI;
100        return;
101    }
102
103    if (allowed > IPCMNI / nb_ns) {
104        ns->msg_ctlmni = IPCMNI / nb_ns;
105        return;
106    }
107
108    ns->msg_ctlmni = allowed;
109}
110
111void msg_init_ns(struct ipc_namespace *ns)
112{
113    ns->msg_ctlmax = MSGMAX;
114    ns->msg_ctlmnb = MSGMNB;
115
116    recompute_msgmni(ns);
117
118    atomic_set(&ns->msg_bytes, 0);
119    atomic_set(&ns->msg_hdrs, 0);
120    ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
121}
122
123#ifdef CONFIG_IPC_NS
124void msg_exit_ns(struct ipc_namespace *ns)
125{
126    free_ipcs(ns, &msg_ids(ns), freeque);
127    idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
128}
129#endif
130
131void __init msg_init(void)
132{
133    msg_init_ns(&init_ipc_ns);
134
135    printk(KERN_INFO "msgmni has been set to %d\n",
136        init_ipc_ns.msg_ctlmni);
137
138    ipc_init_proc_interface("sysvipc/msg",
139                " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
140                IPC_MSG_IDS, sysvipc_msg_proc_show);
141}
142
143/*
144 * msg_lock_(check_) routines are called in the paths where the rw_mutex
145 * is not held.
146 */
147static inline struct msg_queue *msg_lock(struct ipc_namespace *ns, int id)
148{
149    struct kern_ipc_perm *ipcp = ipc_lock(&msg_ids(ns), id);
150
151    if (IS_ERR(ipcp))
152        return (struct msg_queue *)ipcp;
153
154    return container_of(ipcp, struct msg_queue, q_perm);
155}
156
157static inline struct msg_queue *msg_lock_check(struct ipc_namespace *ns,
158                        int id)
159{
160    struct kern_ipc_perm *ipcp = ipc_lock_check(&msg_ids(ns), id);
161
162    if (IS_ERR(ipcp))
163        return (struct msg_queue *)ipcp;
164
165    return container_of(ipcp, struct msg_queue, q_perm);
166}
167
168static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
169{
170    ipc_rmid(&msg_ids(ns), &s->q_perm);
171}
172
173/**
174 * newque - Create a new msg queue
175 * @ns: namespace
176 * @params: ptr to the structure that contains the key and msgflg
177 *
178 * Called with msg_ids.rw_mutex held (writer)
179 */
180static int newque(struct ipc_namespace *ns, struct ipc_params *params)
181{
182    struct msg_queue *msq;
183    int id, retval;
184    key_t key = params->key;
185    int msgflg = params->flg;
186
187    msq = ipc_rcu_alloc(sizeof(*msq));
188    if (!msq)
189        return -ENOMEM;
190
191    msq->q_perm.mode = msgflg & S_IRWXUGO;
192    msq->q_perm.key = key;
193
194    msq->q_perm.security = NULL;
195    retval = security_msg_queue_alloc(msq);
196    if (retval) {
197        ipc_rcu_putref(msq);
198        return retval;
199    }
200
201    /*
202     * ipc_addid() locks msq
203     */
204    id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
205    if (id < 0) {
206        security_msg_queue_free(msq);
207        ipc_rcu_putref(msq);
208        return id;
209    }
210
211    msq->q_stime = msq->q_rtime = 0;
212    msq->q_ctime = get_seconds();
213    msq->q_cbytes = msq->q_qnum = 0;
214    msq->q_qbytes = ns->msg_ctlmnb;
215    msq->q_lspid = msq->q_lrpid = 0;
216    INIT_LIST_HEAD(&msq->q_messages);
217    INIT_LIST_HEAD(&msq->q_receivers);
218    INIT_LIST_HEAD(&msq->q_senders);
219
220    msg_unlock(msq);
221
222    return msq->q_perm.id;
223}
224
225static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
226{
227    mss->tsk = current;
228    current->state = TASK_INTERRUPTIBLE;
229    list_add_tail(&mss->list, &msq->q_senders);
230}
231
232static inline void ss_del(struct msg_sender *mss)
233{
234    if (mss->list.next != NULL)
235        list_del(&mss->list);
236}
237
238static void ss_wakeup(struct list_head *h, int kill)
239{
240    struct list_head *tmp;
241
242    tmp = h->next;
243    while (tmp != h) {
244        struct msg_sender *mss;
245
246        mss = list_entry(tmp, struct msg_sender, list);
247        tmp = tmp->next;
248        if (kill)
249            mss->list.next = NULL;
250        wake_up_process(mss->tsk);
251    }
252}
253
254static void expunge_all(struct msg_queue *msq, int res)
255{
256    struct list_head *tmp;
257
258    tmp = msq->q_receivers.next;
259    while (tmp != &msq->q_receivers) {
260        struct msg_receiver *msr;
261
262        msr = list_entry(tmp, struct msg_receiver, r_list);
263        tmp = tmp->next;
264        msr->r_msg = NULL;
265        wake_up_process(msr->r_tsk);
266        smp_mb();
267        msr->r_msg = ERR_PTR(res);
268    }
269}
270
271/*
272 * freeque() wakes up waiters on the sender and receiver waiting queue,
273 * removes the message queue from message queue ID IDR, and cleans up all the
274 * messages associated with this queue.
275 *
276 * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
277 * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
278 */
279static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
280{
281    struct list_head *tmp;
282    struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
283
284    expunge_all(msq, -EIDRM);
285    ss_wakeup(&msq->q_senders, 1);
286    msg_rmid(ns, msq);
287    msg_unlock(msq);
288
289    tmp = msq->q_messages.next;
290    while (tmp != &msq->q_messages) {
291        struct msg_msg *msg = list_entry(tmp, struct msg_msg, m_list);
292
293        tmp = tmp->next;
294        atomic_dec(&ns->msg_hdrs);
295        free_msg(msg);
296    }
297    atomic_sub(msq->q_cbytes, &ns->msg_bytes);
298    security_msg_queue_free(msq);
299    ipc_rcu_putref(msq);
300}
301
302/*
303 * Called with msg_ids.rw_mutex and ipcp locked.
304 */
305static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
306{
307    struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
308
309    return security_msg_queue_associate(msq, msgflg);
310}
311
312SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
313{
314    struct ipc_namespace *ns;
315    struct ipc_ops msg_ops;
316    struct ipc_params msg_params;
317
318    ns = current->nsproxy->ipc_ns;
319
320    msg_ops.getnew = newque;
321    msg_ops.associate = msg_security;
322    msg_ops.more_checks = NULL;
323
324    msg_params.key = key;
325    msg_params.flg = msgflg;
326
327    return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
328}
329
330static inline unsigned long
331copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
332{
333    switch(version) {
334    case IPC_64:
335        return copy_to_user(buf, in, sizeof(*in));
336    case IPC_OLD:
337    {
338        struct msqid_ds out;
339
340        memset(&out, 0, sizeof(out));
341
342        ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
343
344        out.msg_stime = in->msg_stime;
345        out.msg_rtime = in->msg_rtime;
346        out.msg_ctime = in->msg_ctime;
347
348        if (in->msg_cbytes > USHRT_MAX)
349            out.msg_cbytes = USHRT_MAX;
350        else
351            out.msg_cbytes = in->msg_cbytes;
352        out.msg_lcbytes = in->msg_cbytes;
353
354        if (in->msg_qnum > USHRT_MAX)
355            out.msg_qnum = USHRT_MAX;
356        else
357            out.msg_qnum = in->msg_qnum;
358
359        if (in->msg_qbytes > USHRT_MAX)
360            out.msg_qbytes = USHRT_MAX;
361        else
362            out.msg_qbytes = in->msg_qbytes;
363        out.msg_lqbytes = in->msg_qbytes;
364
365        out.msg_lspid = in->msg_lspid;
366        out.msg_lrpid = in->msg_lrpid;
367
368        return copy_to_user(buf, &out, sizeof(out));
369    }
370    default:
371        return -EINVAL;
372    }
373}
374
375static inline unsigned long
376copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
377{
378    switch(version) {
379    case IPC_64:
380        if (copy_from_user(out, buf, sizeof(*out)))
381            return -EFAULT;
382        return 0;
383    case IPC_OLD:
384    {
385        struct msqid_ds tbuf_old;
386
387        if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
388            return -EFAULT;
389
390        out->msg_perm.uid = tbuf_old.msg_perm.uid;
391        out->msg_perm.gid = tbuf_old.msg_perm.gid;
392        out->msg_perm.mode = tbuf_old.msg_perm.mode;
393
394        if (tbuf_old.msg_qbytes == 0)
395            out->msg_qbytes = tbuf_old.msg_lqbytes;
396        else
397            out->msg_qbytes = tbuf_old.msg_qbytes;
398
399        return 0;
400    }
401    default:
402        return -EINVAL;
403    }
404}
405
406/*
407 * This function handles some msgctl commands which require the rw_mutex
408 * to be held in write mode.
409 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
410 */
411static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
412               struct msqid_ds __user *buf, int version)
413{
414    struct kern_ipc_perm *ipcp;
415    struct msqid64_ds uninitialized_var(msqid64);
416    struct msg_queue *msq;
417    int err;
418
419    if (cmd == IPC_SET) {
420        if (copy_msqid_from_user(&msqid64, buf, version))
421            return -EFAULT;
422    }
423
424    ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
425                   &msqid64.msg_perm, msqid64.msg_qbytes);
426    if (IS_ERR(ipcp))
427        return PTR_ERR(ipcp);
428
429    msq = container_of(ipcp, struct msg_queue, q_perm);
430
431    err = security_msg_queue_msgctl(msq, cmd);
432    if (err)
433        goto out_unlock;
434
435    switch (cmd) {
436    case IPC_RMID:
437        freeque(ns, ipcp);
438        goto out_up;
439    case IPC_SET:
440        if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
441            !capable(CAP_SYS_RESOURCE)) {
442            err = -EPERM;
443            goto out_unlock;
444        }
445
446        msq->q_qbytes = msqid64.msg_qbytes;
447
448        ipc_update_perm(&msqid64.msg_perm, ipcp);
449        msq->q_ctime = get_seconds();
450        /* sleeping receivers might be excluded by
451         * stricter permissions.
452         */
453        expunge_all(msq, -EAGAIN);
454        /* sleeping senders might be able to send
455         * due to a larger queue size.
456         */
457        ss_wakeup(&msq->q_senders, 0);
458        break;
459    default:
460        err = -EINVAL;
461    }
462out_unlock:
463    msg_unlock(msq);
464out_up:
465    up_write(&msg_ids(ns).rw_mutex);
466    return err;
467}
468
469SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
470{
471    struct msg_queue *msq;
472    int err, version;
473    struct ipc_namespace *ns;
474
475    if (msqid < 0 || cmd < 0)
476        return -EINVAL;
477
478    version = ipc_parse_version(&cmd);
479    ns = current->nsproxy->ipc_ns;
480
481    switch (cmd) {
482    case IPC_INFO:
483    case MSG_INFO:
484    {
485        struct msginfo msginfo;
486        int max_id;
487
488        if (!buf)
489            return -EFAULT;
490        /*
491         * We must not return kernel stack data.
492         * due to padding, it's not enough
493         * to set all member fields.
494         */
495        err = security_msg_queue_msgctl(NULL, cmd);
496        if (err)
497            return err;
498
499        memset(&msginfo, 0, sizeof(msginfo));
500        msginfo.msgmni = ns->msg_ctlmni;
501        msginfo.msgmax = ns->msg_ctlmax;
502        msginfo.msgmnb = ns->msg_ctlmnb;
503        msginfo.msgssz = MSGSSZ;
504        msginfo.msgseg = MSGSEG;
505        down_read(&msg_ids(ns).rw_mutex);
506        if (cmd == MSG_INFO) {
507            msginfo.msgpool = msg_ids(ns).in_use;
508            msginfo.msgmap = atomic_read(&ns->msg_hdrs);
509            msginfo.msgtql = atomic_read(&ns->msg_bytes);
510        } else {
511            msginfo.msgmap = MSGMAP;
512            msginfo.msgpool = MSGPOOL;
513            msginfo.msgtql = MSGTQL;
514        }
515        max_id = ipc_get_maxid(&msg_ids(ns));
516        up_read(&msg_ids(ns).rw_mutex);
517        if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
518            return -EFAULT;
519        return (max_id < 0) ? 0 : max_id;
520    }
521    case MSG_STAT: /* msqid is an index rather than a msg queue id */
522    case IPC_STAT:
523    {
524        struct msqid64_ds tbuf;
525        int success_return;
526
527        if (!buf)
528            return -EFAULT;
529
530        if (cmd == MSG_STAT) {
531            msq = msg_lock(ns, msqid);
532            if (IS_ERR(msq))
533                return PTR_ERR(msq);
534            success_return = msq->q_perm.id;
535        } else {
536            msq = msg_lock_check(ns, msqid);
537            if (IS_ERR(msq))
538                return PTR_ERR(msq);
539            success_return = 0;
540        }
541        err = -EACCES;
542        if (ipcperms(ns, &msq->q_perm, S_IRUGO))
543            goto out_unlock;
544
545        err = security_msg_queue_msgctl(msq, cmd);
546        if (err)
547            goto out_unlock;
548
549        memset(&tbuf, 0, sizeof(tbuf));
550
551        kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
552        tbuf.msg_stime = msq->q_stime;
553        tbuf.msg_rtime = msq->q_rtime;
554        tbuf.msg_ctime = msq->q_ctime;
555        tbuf.msg_cbytes = msq->q_cbytes;
556        tbuf.msg_qnum = msq->q_qnum;
557        tbuf.msg_qbytes = msq->q_qbytes;
558        tbuf.msg_lspid = msq->q_lspid;
559        tbuf.msg_lrpid = msq->q_lrpid;
560        msg_unlock(msq);
561        if (copy_msqid_to_user(buf, &tbuf, version))
562            return -EFAULT;
563        return success_return;
564    }
565    case IPC_SET:
566    case IPC_RMID:
567        err = msgctl_down(ns, msqid, cmd, buf, version);
568        return err;
569    default:
570        return -EINVAL;
571    }
572
573out_unlock:
574    msg_unlock(msq);
575    return err;
576}
577
578static int testmsg(struct msg_msg *msg, long type, int mode)
579{
580    switch(mode)
581    {
582        case SEARCH_ANY:
583            return 1;
584        case SEARCH_LESSEQUAL:
585            if (msg->m_type <=type)
586                return 1;
587            break;
588        case SEARCH_EQUAL:
589            if (msg->m_type == type)
590                return 1;
591            break;
592        case SEARCH_NOTEQUAL:
593            if (msg->m_type != type)
594                return 1;
595            break;
596    }
597    return 0;
598}
599
600static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
601{
602    struct list_head *tmp;
603
604    tmp = msq->q_receivers.next;
605    while (tmp != &msq->q_receivers) {
606        struct msg_receiver *msr;
607
608        msr = list_entry(tmp, struct msg_receiver, r_list);
609        tmp = tmp->next;
610        if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
611            !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
612                           msr->r_msgtype, msr->r_mode)) {
613
614            list_del(&msr->r_list);
615            if (msr->r_maxsize < msg->m_ts) {
616                msr->r_msg = NULL;
617                wake_up_process(msr->r_tsk);
618                smp_mb();
619                msr->r_msg = ERR_PTR(-E2BIG);
620            } else {
621                msr->r_msg = NULL;
622                msq->q_lrpid = task_pid_vnr(msr->r_tsk);
623                msq->q_rtime = get_seconds();
624                wake_up_process(msr->r_tsk);
625                smp_mb();
626                msr->r_msg = msg;
627
628                return 1;
629            }
630        }
631    }
632    return 0;
633}
634
635long do_msgsnd(int msqid, long mtype, void __user *mtext,
636        size_t msgsz, int msgflg)
637{
638    struct msg_queue *msq;
639    struct msg_msg *msg;
640    int err;
641    struct ipc_namespace *ns;
642
643    ns = current->nsproxy->ipc_ns;
644
645    if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
646        return -EINVAL;
647    if (mtype < 1)
648        return -EINVAL;
649
650    msg = load_msg(mtext, msgsz);
651    if (IS_ERR(msg))
652        return PTR_ERR(msg);
653
654    msg->m_type = mtype;
655    msg->m_ts = msgsz;
656
657    msq = msg_lock_check(ns, msqid);
658    if (IS_ERR(msq)) {
659        err = PTR_ERR(msq);
660        goto out_free;
661    }
662
663    for (;;) {
664        struct msg_sender s;
665
666        err = -EACCES;
667        if (ipcperms(ns, &msq->q_perm, S_IWUGO))
668            goto out_unlock_free;
669
670        err = security_msg_queue_msgsnd(msq, msg, msgflg);
671        if (err)
672            goto out_unlock_free;
673
674        if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
675                1 + msq->q_qnum <= msq->q_qbytes) {
676            break;
677        }
678
679        /* queue full, wait: */
680        if (msgflg & IPC_NOWAIT) {
681            err = -EAGAIN;
682            goto out_unlock_free;
683        }
684        ss_add(msq, &s);
685        ipc_rcu_getref(msq);
686        msg_unlock(msq);
687        schedule();
688
689        ipc_lock_by_ptr(&msq->q_perm);
690        ipc_rcu_putref(msq);
691        if (msq->q_perm.deleted) {
692            err = -EIDRM;
693            goto out_unlock_free;
694        }
695        ss_del(&s);
696
697        if (signal_pending(current)) {
698            err = -ERESTARTNOHAND;
699            goto out_unlock_free;
700        }
701    }
702
703    msq->q_lspid = task_tgid_vnr(current);
704    msq->q_stime = get_seconds();
705
706    if (!pipelined_send(msq, msg)) {
707        /* no one is waiting for this message, enqueue it */
708        list_add_tail(&msg->m_list, &msq->q_messages);
709        msq->q_cbytes += msgsz;
710        msq->q_qnum++;
711        atomic_add(msgsz, &ns->msg_bytes);
712        atomic_inc(&ns->msg_hdrs);
713    }
714
715    err = 0;
716    msg = NULL;
717
718out_unlock_free:
719    msg_unlock(msq);
720out_free:
721    if (msg != NULL)
722        free_msg(msg);
723    return err;
724}
725
726SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
727        int, msgflg)
728{
729    long mtype;
730
731    if (get_user(mtype, &msgp->mtype))
732        return -EFAULT;
733    return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
734}
735
736static inline int convert_mode(long *msgtyp, int msgflg)
737{
738    /*
739     * find message of correct type.
740     * msgtyp = 0 => get first.
741     * msgtyp > 0 => get first message of matching type.
742     * msgtyp < 0 => get message with least type must be < abs(msgtype).
743     */
744    if (*msgtyp == 0)
745        return SEARCH_ANY;
746    if (*msgtyp < 0) {
747        *msgtyp = -*msgtyp;
748        return SEARCH_LESSEQUAL;
749    }
750    if (msgflg & MSG_EXCEPT)
751        return SEARCH_NOTEQUAL;
752    return SEARCH_EQUAL;
753}
754
755long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
756        size_t msgsz, long msgtyp, int msgflg)
757{
758    struct msg_queue *msq;
759    struct msg_msg *msg;
760    int mode;
761    struct ipc_namespace *ns;
762
763    if (msqid < 0 || (long) msgsz < 0)
764        return -EINVAL;
765    mode = convert_mode(&msgtyp, msgflg);
766    ns = current->nsproxy->ipc_ns;
767
768    msq = msg_lock_check(ns, msqid);
769    if (IS_ERR(msq))
770        return PTR_ERR(msq);
771
772    for (;;) {
773        struct msg_receiver msr_d;
774        struct list_head *tmp;
775
776        msg = ERR_PTR(-EACCES);
777        if (ipcperms(ns, &msq->q_perm, S_IRUGO))
778            goto out_unlock;
779
780        msg = ERR_PTR(-EAGAIN);
781        tmp = msq->q_messages.next;
782        while (tmp != &msq->q_messages) {
783            struct msg_msg *walk_msg;
784
785            walk_msg = list_entry(tmp, struct msg_msg, m_list);
786            if (testmsg(walk_msg, msgtyp, mode) &&
787                !security_msg_queue_msgrcv(msq, walk_msg, current,
788                               msgtyp, mode)) {
789
790                msg = walk_msg;
791                if (mode == SEARCH_LESSEQUAL &&
792                        walk_msg->m_type != 1) {
793                    msg = walk_msg;
794                    msgtyp = walk_msg->m_type - 1;
795                } else {
796                    msg = walk_msg;
797                    break;
798                }
799            }
800            tmp = tmp->next;
801        }
802        if (!IS_ERR(msg)) {
803            /*
804             * Found a suitable message.
805             * Unlink it from the queue.
806             */
807            if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
808                msg = ERR_PTR(-E2BIG);
809                goto out_unlock;
810            }
811            list_del(&msg->m_list);
812            msq->q_qnum--;
813            msq->q_rtime = get_seconds();
814            msq->q_lrpid = task_tgid_vnr(current);
815            msq->q_cbytes -= msg->m_ts;
816            atomic_sub(msg->m_ts, &ns->msg_bytes);
817            atomic_dec(&ns->msg_hdrs);
818            ss_wakeup(&msq->q_senders, 0);
819            msg_unlock(msq);
820            break;
821        }
822        /* No message waiting. Wait for a message */
823        if (msgflg & IPC_NOWAIT) {
824            msg = ERR_PTR(-ENOMSG);
825            goto out_unlock;
826        }
827        list_add_tail(&msr_d.r_list, &msq->q_receivers);
828        msr_d.r_tsk = current;
829        msr_d.r_msgtype = msgtyp;
830        msr_d.r_mode = mode;
831        if (msgflg & MSG_NOERROR)
832            msr_d.r_maxsize = INT_MAX;
833        else
834            msr_d.r_maxsize = msgsz;
835        msr_d.r_msg = ERR_PTR(-EAGAIN);
836        current->state = TASK_INTERRUPTIBLE;
837        msg_unlock(msq);
838
839        schedule();
840
841        /* Lockless receive, part 1:
842         * Disable preemption. We don't hold a reference to the queue
843         * and getting a reference would defeat the idea of a lockless
844         * operation, thus the code relies on rcu to guarantee the
845         * existence of msq:
846         * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
847         * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
848         * rcu_read_lock() prevents preemption between reading r_msg
849         * and the spin_lock() inside ipc_lock_by_ptr().
850         */
851        rcu_read_lock();
852
853        /* Lockless receive, part 2:
854         * Wait until pipelined_send or expunge_all are outside of
855         * wake_up_process(). There is a race with exit(), see
856         * ipc/mqueue.c for the details.
857         */
858        msg = (struct msg_msg*)msr_d.r_msg;
859        while (msg == NULL) {
860            cpu_relax();
861            msg = (struct msg_msg *)msr_d.r_msg;
862        }
863
864        /* Lockless receive, part 3:
865         * If there is a message or an error then accept it without
866         * locking.
867         */
868        if (msg != ERR_PTR(-EAGAIN)) {
869            rcu_read_unlock();
870            break;
871        }
872
873        /* Lockless receive, part 3:
874         * Acquire the queue spinlock.
875         */
876        ipc_lock_by_ptr(&msq->q_perm);
877        rcu_read_unlock();
878
879        /* Lockless receive, part 4:
880         * Repeat test after acquiring the spinlock.
881         */
882        msg = (struct msg_msg*)msr_d.r_msg;
883        if (msg != ERR_PTR(-EAGAIN))
884            goto out_unlock;
885
886        list_del(&msr_d.r_list);
887        if (signal_pending(current)) {
888            msg = ERR_PTR(-ERESTARTNOHAND);
889out_unlock:
890            msg_unlock(msq);
891            break;
892        }
893    }
894    if (IS_ERR(msg))
895        return PTR_ERR(msg);
896
897    msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
898    *pmtype = msg->m_type;
899    if (store_msg(mtext, msg, msgsz))
900        msgsz = -EFAULT;
901
902    free_msg(msg);
903
904    return msgsz;
905}
906
907SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
908        long, msgtyp, int, msgflg)
909{
910    long err, mtype;
911
912    err = do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg);
913    if (err < 0)
914        goto out;
915
916    if (put_user(mtype, &msgp->mtype))
917        err = -EFAULT;
918out:
919    return err;
920}
921
922#ifdef CONFIG_PROC_FS
923static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
924{
925    struct msg_queue *msq = it;
926
927    return seq_printf(s,
928            "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
929            msq->q_perm.key,
930            msq->q_perm.id,
931            msq->q_perm.mode,
932            msq->q_cbytes,
933            msq->q_qnum,
934            msq->q_lspid,
935            msq->q_lrpid,
936            msq->q_perm.uid,
937            msq->q_perm.gid,
938            msq->q_perm.cuid,
939            msq->q_perm.cgid,
940            msq->q_stime,
941            msq->q_rtime,
942            msq->q_ctime);
943}
944#endif
945

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