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        err = ipc_update_perm(&msqid64.msg_perm, ipcp);
447        if (err)
448            goto out_unlock;
449
450        msq->q_qbytes = msqid64.msg_qbytes;
451
452        msq->q_ctime = get_seconds();
453        /* sleeping receivers might be excluded by
454         * stricter permissions.
455         */
456        expunge_all(msq, -EAGAIN);
457        /* sleeping senders might be able to send
458         * due to a larger queue size.
459         */
460        ss_wakeup(&msq->q_senders, 0);
461        break;
462    default:
463        err = -EINVAL;
464    }
465out_unlock:
466    msg_unlock(msq);
467out_up:
468    up_write(&msg_ids(ns).rw_mutex);
469    return err;
470}
471
472SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
473{
474    struct msg_queue *msq;
475    int err, version;
476    struct ipc_namespace *ns;
477
478    if (msqid < 0 || cmd < 0)
479        return -EINVAL;
480
481    version = ipc_parse_version(&cmd);
482    ns = current->nsproxy->ipc_ns;
483
484    switch (cmd) {
485    case IPC_INFO:
486    case MSG_INFO:
487    {
488        struct msginfo msginfo;
489        int max_id;
490
491        if (!buf)
492            return -EFAULT;
493        /*
494         * We must not return kernel stack data.
495         * due to padding, it's not enough
496         * to set all member fields.
497         */
498        err = security_msg_queue_msgctl(NULL, cmd);
499        if (err)
500            return err;
501
502        memset(&msginfo, 0, sizeof(msginfo));
503        msginfo.msgmni = ns->msg_ctlmni;
504        msginfo.msgmax = ns->msg_ctlmax;
505        msginfo.msgmnb = ns->msg_ctlmnb;
506        msginfo.msgssz = MSGSSZ;
507        msginfo.msgseg = MSGSEG;
508        down_read(&msg_ids(ns).rw_mutex);
509        if (cmd == MSG_INFO) {
510            msginfo.msgpool = msg_ids(ns).in_use;
511            msginfo.msgmap = atomic_read(&ns->msg_hdrs);
512            msginfo.msgtql = atomic_read(&ns->msg_bytes);
513        } else {
514            msginfo.msgmap = MSGMAP;
515            msginfo.msgpool = MSGPOOL;
516            msginfo.msgtql = MSGTQL;
517        }
518        max_id = ipc_get_maxid(&msg_ids(ns));
519        up_read(&msg_ids(ns).rw_mutex);
520        if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
521            return -EFAULT;
522        return (max_id < 0) ? 0 : max_id;
523    }
524    case MSG_STAT: /* msqid is an index rather than a msg queue id */
525    case IPC_STAT:
526    {
527        struct msqid64_ds tbuf;
528        int success_return;
529
530        if (!buf)
531            return -EFAULT;
532
533        if (cmd == MSG_STAT) {
534            msq = msg_lock(ns, msqid);
535            if (IS_ERR(msq))
536                return PTR_ERR(msq);
537            success_return = msq->q_perm.id;
538        } else {
539            msq = msg_lock_check(ns, msqid);
540            if (IS_ERR(msq))
541                return PTR_ERR(msq);
542            success_return = 0;
543        }
544        err = -EACCES;
545        if (ipcperms(ns, &msq->q_perm, S_IRUGO))
546            goto out_unlock;
547
548        err = security_msg_queue_msgctl(msq, cmd);
549        if (err)
550            goto out_unlock;
551
552        memset(&tbuf, 0, sizeof(tbuf));
553
554        kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
555        tbuf.msg_stime = msq->q_stime;
556        tbuf.msg_rtime = msq->q_rtime;
557        tbuf.msg_ctime = msq->q_ctime;
558        tbuf.msg_cbytes = msq->q_cbytes;
559        tbuf.msg_qnum = msq->q_qnum;
560        tbuf.msg_qbytes = msq->q_qbytes;
561        tbuf.msg_lspid = msq->q_lspid;
562        tbuf.msg_lrpid = msq->q_lrpid;
563        msg_unlock(msq);
564        if (copy_msqid_to_user(buf, &tbuf, version))
565            return -EFAULT;
566        return success_return;
567    }
568    case IPC_SET:
569    case IPC_RMID:
570        err = msgctl_down(ns, msqid, cmd, buf, version);
571        return err;
572    default:
573        return -EINVAL;
574    }
575
576out_unlock:
577    msg_unlock(msq);
578    return err;
579}
580
581static int testmsg(struct msg_msg *msg, long type, int mode)
582{
583    switch(mode)
584    {
585        case SEARCH_ANY:
586            return 1;
587        case SEARCH_LESSEQUAL:
588            if (msg->m_type <=type)
589                return 1;
590            break;
591        case SEARCH_EQUAL:
592            if (msg->m_type == type)
593                return 1;
594            break;
595        case SEARCH_NOTEQUAL:
596            if (msg->m_type != type)
597                return 1;
598            break;
599    }
600    return 0;
601}
602
603static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
604{
605    struct list_head *tmp;
606
607    tmp = msq->q_receivers.next;
608    while (tmp != &msq->q_receivers) {
609        struct msg_receiver *msr;
610
611        msr = list_entry(tmp, struct msg_receiver, r_list);
612        tmp = tmp->next;
613        if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
614            !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
615                           msr->r_msgtype, msr->r_mode)) {
616
617            list_del(&msr->r_list);
618            if (msr->r_maxsize < msg->m_ts) {
619                msr->r_msg = NULL;
620                wake_up_process(msr->r_tsk);
621                smp_mb();
622                msr->r_msg = ERR_PTR(-E2BIG);
623            } else {
624                msr->r_msg = NULL;
625                msq->q_lrpid = task_pid_vnr(msr->r_tsk);
626                msq->q_rtime = get_seconds();
627                wake_up_process(msr->r_tsk);
628                smp_mb();
629                msr->r_msg = msg;
630
631                return 1;
632            }
633        }
634    }
635    return 0;
636}
637
638long do_msgsnd(int msqid, long mtype, void __user *mtext,
639        size_t msgsz, int msgflg)
640{
641    struct msg_queue *msq;
642    struct msg_msg *msg;
643    int err;
644    struct ipc_namespace *ns;
645
646    ns = current->nsproxy->ipc_ns;
647
648    if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
649        return -EINVAL;
650    if (mtype < 1)
651        return -EINVAL;
652
653    msg = load_msg(mtext, msgsz);
654    if (IS_ERR(msg))
655        return PTR_ERR(msg);
656
657    msg->m_type = mtype;
658    msg->m_ts = msgsz;
659
660    msq = msg_lock_check(ns, msqid);
661    if (IS_ERR(msq)) {
662        err = PTR_ERR(msq);
663        goto out_free;
664    }
665
666    for (;;) {
667        struct msg_sender s;
668
669        err = -EACCES;
670        if (ipcperms(ns, &msq->q_perm, S_IWUGO))
671            goto out_unlock_free;
672
673        err = security_msg_queue_msgsnd(msq, msg, msgflg);
674        if (err)
675            goto out_unlock_free;
676
677        if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
678                1 + msq->q_qnum <= msq->q_qbytes) {
679            break;
680        }
681
682        /* queue full, wait: */
683        if (msgflg & IPC_NOWAIT) {
684            err = -EAGAIN;
685            goto out_unlock_free;
686        }
687        ss_add(msq, &s);
688        ipc_rcu_getref(msq);
689        msg_unlock(msq);
690        schedule();
691
692        ipc_lock_by_ptr(&msq->q_perm);
693        ipc_rcu_putref(msq);
694        if (msq->q_perm.deleted) {
695            err = -EIDRM;
696            goto out_unlock_free;
697        }
698        ss_del(&s);
699
700        if (signal_pending(current)) {
701            err = -ERESTARTNOHAND;
702            goto out_unlock_free;
703        }
704    }
705
706    msq->q_lspid = task_tgid_vnr(current);
707    msq->q_stime = get_seconds();
708
709    if (!pipelined_send(msq, msg)) {
710        /* no one is waiting for this message, enqueue it */
711        list_add_tail(&msg->m_list, &msq->q_messages);
712        msq->q_cbytes += msgsz;
713        msq->q_qnum++;
714        atomic_add(msgsz, &ns->msg_bytes);
715        atomic_inc(&ns->msg_hdrs);
716    }
717
718    err = 0;
719    msg = NULL;
720
721out_unlock_free:
722    msg_unlock(msq);
723out_free:
724    if (msg != NULL)
725        free_msg(msg);
726    return err;
727}
728
729SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
730        int, msgflg)
731{
732    long mtype;
733
734    if (get_user(mtype, &msgp->mtype))
735        return -EFAULT;
736    return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
737}
738
739static inline int convert_mode(long *msgtyp, int msgflg)
740{
741    /*
742     * find message of correct type.
743     * msgtyp = 0 => get first.
744     * msgtyp > 0 => get first message of matching type.
745     * msgtyp < 0 => get message with least type must be < abs(msgtype).
746     */
747    if (*msgtyp == 0)
748        return SEARCH_ANY;
749    if (*msgtyp < 0) {
750        *msgtyp = -*msgtyp;
751        return SEARCH_LESSEQUAL;
752    }
753    if (msgflg & MSG_EXCEPT)
754        return SEARCH_NOTEQUAL;
755    return SEARCH_EQUAL;
756}
757
758static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
759{
760    struct msgbuf __user *msgp = dest;
761    size_t msgsz;
762
763    if (put_user(msg->m_type, &msgp->mtype))
764        return -EFAULT;
765
766    msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
767    if (store_msg(msgp->mtext, msg, msgsz))
768        return -EFAULT;
769    return msgsz;
770}
771
772#ifdef CONFIG_CHECKPOINT_RESTORE
773/*
774 * This function creates new kernel message structure, large enough to store
775 * bufsz message bytes.
776 */
777static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz,
778                       int msgflg, long *msgtyp,
779                       unsigned long *copy_number)
780{
781    struct msg_msg *copy;
782
783    *copy_number = *msgtyp;
784    *msgtyp = 0;
785    /*
786     * Create dummy message to copy real message to.
787     */
788    copy = load_msg(buf, bufsz);
789    if (!IS_ERR(copy))
790        copy->m_ts = bufsz;
791    return copy;
792}
793
794static inline void free_copy(struct msg_msg *copy)
795{
796    if (copy)
797        free_msg(copy);
798}
799#else
800static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz,
801                       int msgflg, long *msgtyp,
802                       unsigned long *copy_number)
803{
804    return ERR_PTR(-ENOSYS);
805}
806
807static inline void free_copy(struct msg_msg *copy)
808{
809}
810#endif
811
812long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
813           int msgflg,
814           long (*msg_handler)(void __user *, struct msg_msg *, size_t))
815{
816    struct msg_queue *msq;
817    struct msg_msg *msg;
818    int mode;
819    struct ipc_namespace *ns;
820    struct msg_msg *copy = NULL;
821    unsigned long copy_number = 0;
822
823    ns = current->nsproxy->ipc_ns;
824
825    if (msqid < 0 || (long) bufsz < 0)
826        return -EINVAL;
827    if (msgflg & MSG_COPY) {
828        copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax),
829                    msgflg, &msgtyp, &copy_number);
830        if (IS_ERR(copy))
831            return PTR_ERR(copy);
832    }
833    mode = convert_mode(&msgtyp, msgflg);
834
835    msq = msg_lock_check(ns, msqid);
836    if (IS_ERR(msq)) {
837        free_copy(copy);
838        return PTR_ERR(msq);
839    }
840
841    for (;;) {
842        struct msg_receiver msr_d;
843        struct list_head *tmp;
844        long msg_counter = 0;
845
846        msg = ERR_PTR(-EACCES);
847        if (ipcperms(ns, &msq->q_perm, S_IRUGO))
848            goto out_unlock;
849
850        msg = ERR_PTR(-EAGAIN);
851        tmp = msq->q_messages.next;
852        while (tmp != &msq->q_messages) {
853            struct msg_msg *walk_msg;
854
855            walk_msg = list_entry(tmp, struct msg_msg, m_list);
856            if (testmsg(walk_msg, msgtyp, mode) &&
857                !security_msg_queue_msgrcv(msq, walk_msg, current,
858                               msgtyp, mode)) {
859
860                msg = walk_msg;
861                if (mode == SEARCH_LESSEQUAL &&
862                        walk_msg->m_type != 1) {
863                    msgtyp = walk_msg->m_type - 1;
864                } else if (msgflg & MSG_COPY) {
865                    if (copy_number == msg_counter) {
866                        /*
867                         * Found requested message.
868                         * Copy it.
869                         */
870                        msg = copy_msg(msg, copy);
871                        if (IS_ERR(msg))
872                            goto out_unlock;
873                        break;
874                    }
875                    msg = ERR_PTR(-EAGAIN);
876                } else
877                    break;
878                msg_counter++;
879            }
880            tmp = tmp->next;
881        }
882        if (!IS_ERR(msg)) {
883            /*
884             * Found a suitable message.
885             * Unlink it from the queue.
886             */
887            if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
888                msg = ERR_PTR(-E2BIG);
889                goto out_unlock;
890            }
891            /*
892             * If we are copying, then do not unlink message and do
893             * not update queue parameters.
894             */
895            if (msgflg & MSG_COPY)
896                goto out_unlock;
897            list_del(&msg->m_list);
898            msq->q_qnum--;
899            msq->q_rtime = get_seconds();
900            msq->q_lrpid = task_tgid_vnr(current);
901            msq->q_cbytes -= msg->m_ts;
902            atomic_sub(msg->m_ts, &ns->msg_bytes);
903            atomic_dec(&ns->msg_hdrs);
904            ss_wakeup(&msq->q_senders, 0);
905            msg_unlock(msq);
906            break;
907        }
908        /* No message waiting. Wait for a message */
909        if (msgflg & IPC_NOWAIT) {
910            msg = ERR_PTR(-ENOMSG);
911            goto out_unlock;
912        }
913        list_add_tail(&msr_d.r_list, &msq->q_receivers);
914        msr_d.r_tsk = current;
915        msr_d.r_msgtype = msgtyp;
916        msr_d.r_mode = mode;
917        if (msgflg & MSG_NOERROR)
918            msr_d.r_maxsize = INT_MAX;
919        else
920            msr_d.r_maxsize = bufsz;
921        msr_d.r_msg = ERR_PTR(-EAGAIN);
922        current->state = TASK_INTERRUPTIBLE;
923        msg_unlock(msq);
924
925        schedule();
926
927        /* Lockless receive, part 1:
928         * Disable preemption. We don't hold a reference to the queue
929         * and getting a reference would defeat the idea of a lockless
930         * operation, thus the code relies on rcu to guarantee the
931         * existence of msq:
932         * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
933         * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
934         * rcu_read_lock() prevents preemption between reading r_msg
935         * and the spin_lock() inside ipc_lock_by_ptr().
936         */
937        rcu_read_lock();
938
939        /* Lockless receive, part 2:
940         * Wait until pipelined_send or expunge_all are outside of
941         * wake_up_process(). There is a race with exit(), see
942         * ipc/mqueue.c for the details.
943         */
944        msg = (struct msg_msg*)msr_d.r_msg;
945        while (msg == NULL) {
946            cpu_relax();
947            msg = (struct msg_msg *)msr_d.r_msg;
948        }
949
950        /* Lockless receive, part 3:
951         * If there is a message or an error then accept it without
952         * locking.
953         */
954        if (msg != ERR_PTR(-EAGAIN)) {
955            rcu_read_unlock();
956            break;
957        }
958
959        /* Lockless receive, part 3:
960         * Acquire the queue spinlock.
961         */
962        ipc_lock_by_ptr(&msq->q_perm);
963        rcu_read_unlock();
964
965        /* Lockless receive, part 4:
966         * Repeat test after acquiring the spinlock.
967         */
968        msg = (struct msg_msg*)msr_d.r_msg;
969        if (msg != ERR_PTR(-EAGAIN))
970            goto out_unlock;
971
972        list_del(&msr_d.r_list);
973        if (signal_pending(current)) {
974            msg = ERR_PTR(-ERESTARTNOHAND);
975out_unlock:
976            msg_unlock(msq);
977            break;
978        }
979    }
980    if (IS_ERR(msg)) {
981        free_copy(copy);
982        return PTR_ERR(msg);
983    }
984
985    bufsz = msg_handler(buf, msg, bufsz);
986    free_msg(msg);
987
988    return bufsz;
989}
990
991SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
992        long, msgtyp, int, msgflg)
993{
994    return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
995}
996
997#ifdef CONFIG_PROC_FS
998static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
999{
1000    struct user_namespace *user_ns = seq_user_ns(s);
1001    struct msg_queue *msq = it;
1002
1003    return seq_printf(s,
1004            "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1005            msq->q_perm.key,
1006            msq->q_perm.id,
1007            msq->q_perm.mode,
1008            msq->q_cbytes,
1009            msq->q_qnum,
1010            msq->q_lspid,
1011            msq->q_lrpid,
1012            from_kuid_munged(user_ns, msq->q_perm.uid),
1013            from_kgid_munged(user_ns, msq->q_perm.gid),
1014            from_kuid_munged(user_ns, msq->q_perm.cuid),
1015            from_kgid_munged(user_ns, msq->q_perm.cgid),
1016            msq->q_stime,
1017            msq->q_rtime,
1018            msq->q_ctime);
1019}
1020#endif
1021

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