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#define SEARCH_NUMBER 5
70
71#define msg_ids(ns) ((ns)->ids[IPC_MSG_IDS])
72
73static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
74static int newque(struct ipc_namespace *, struct ipc_params *);
75#ifdef CONFIG_PROC_FS
76static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
77#endif
78
79/*
80 * Scale msgmni with the available lowmem size: the memory dedicated to msg
81 * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
82 * Also take into account the number of nsproxies created so far.
83 * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
84 */
85void recompute_msgmni(struct ipc_namespace *ns)
86{
87    struct sysinfo i;
88    unsigned long allowed;
89    int nb_ns;
90
91    si_meminfo(&i);
92    allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
93        / MSGMNB;
94    nb_ns = atomic_read(&nr_ipc_ns);
95    allowed /= nb_ns;
96
97    if (allowed < MSGMNI) {
98        ns->msg_ctlmni = MSGMNI;
99        return;
100    }
101
102    if (allowed > IPCMNI / nb_ns) {
103        ns->msg_ctlmni = IPCMNI / nb_ns;
104        return;
105    }
106
107    ns->msg_ctlmni = allowed;
108}
109
110void msg_init_ns(struct ipc_namespace *ns)
111{
112    ns->msg_ctlmax = MSGMAX;
113    ns->msg_ctlmnb = MSGMNB;
114
115    recompute_msgmni(ns);
116
117    atomic_set(&ns->msg_bytes, 0);
118    atomic_set(&ns->msg_hdrs, 0);
119    ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
120}
121
122#ifdef CONFIG_IPC_NS
123void msg_exit_ns(struct ipc_namespace *ns)
124{
125    free_ipcs(ns, &msg_ids(ns), freeque);
126    idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
127}
128#endif
129
130void __init msg_init(void)
131{
132    msg_init_ns(&init_ipc_ns);
133
134    printk(KERN_INFO "msgmni has been set to %d\n",
135        init_ipc_ns.msg_ctlmni);
136
137    ipc_init_proc_interface("sysvipc/msg",
138                " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
139                IPC_MSG_IDS, sysvipc_msg_proc_show);
140}
141
142static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
143{
144    struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
145
146    if (IS_ERR(ipcp))
147        return ERR_CAST(ipcp);
148
149    return container_of(ipcp, struct msg_queue, q_perm);
150}
151
152static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
153                            int id)
154{
155    struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
156
157    if (IS_ERR(ipcp))
158        return ERR_CAST(ipcp);
159
160    return container_of(ipcp, struct msg_queue, q_perm);
161}
162
163static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
164{
165    ipc_rmid(&msg_ids(ns), &s->q_perm);
166}
167
168static void msg_rcu_free(struct rcu_head *head)
169{
170    struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
171    struct msg_queue *msq = ipc_rcu_to_struct(p);
172
173    security_msg_queue_free(msq);
174    ipc_rcu_free(head);
175}
176
177/**
178 * newque - Create a new msg queue
179 * @ns: namespace
180 * @params: ptr to the structure that contains the key and msgflg
181 *
182 * Called with msg_ids.rwsem held (writer)
183 */
184static int newque(struct ipc_namespace *ns, struct ipc_params *params)
185{
186    struct msg_queue *msq;
187    int id, retval;
188    key_t key = params->key;
189    int msgflg = params->flg;
190
191    msq = ipc_rcu_alloc(sizeof(*msq));
192    if (!msq)
193        return -ENOMEM;
194
195    msq->q_perm.mode = msgflg & S_IRWXUGO;
196    msq->q_perm.key = key;
197
198    msq->q_perm.security = NULL;
199    retval = security_msg_queue_alloc(msq);
200    if (retval) {
201        ipc_rcu_putref(msq, ipc_rcu_free);
202        return retval;
203    }
204
205    /* ipc_addid() locks msq upon success. */
206    id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
207    if (id < 0) {
208        ipc_rcu_putref(msq, msg_rcu_free);
209        return id;
210    }
211
212    msq->q_stime = msq->q_rtime = 0;
213    msq->q_ctime = get_seconds();
214    msq->q_cbytes = msq->q_qnum = 0;
215    msq->q_qbytes = ns->msg_ctlmnb;
216    msq->q_lspid = msq->q_lrpid = 0;
217    INIT_LIST_HEAD(&msq->q_messages);
218    INIT_LIST_HEAD(&msq->q_receivers);
219    INIT_LIST_HEAD(&msq->q_senders);
220
221    ipc_unlock_object(&msq->q_perm);
222    rcu_read_unlock();
223
224    return msq->q_perm.id;
225}
226
227static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
228{
229    mss->tsk = current;
230    current->state = TASK_INTERRUPTIBLE;
231    list_add_tail(&mss->list, &msq->q_senders);
232}
233
234static inline void ss_del(struct msg_sender *mss)
235{
236    if (mss->list.next != NULL)
237        list_del(&mss->list);
238}
239
240static void ss_wakeup(struct list_head *h, int kill)
241{
242    struct msg_sender *mss, *t;
243
244    list_for_each_entry_safe(mss, t, h, list) {
245        if (kill)
246            mss->list.next = NULL;
247        wake_up_process(mss->tsk);
248    }
249}
250
251static void expunge_all(struct msg_queue *msq, int res)
252{
253    struct msg_receiver *msr, *t;
254
255    list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
256        msr->r_msg = NULL; /* initialize expunge ordering */
257        wake_up_process(msr->r_tsk);
258        /*
259         * Ensure that the wakeup is visible before setting r_msg as
260         * the receiving end depends on it: either spinning on a nil,
261         * or dealing with -EAGAIN cases. See lockless receive part 1
262         * and 2 in do_msgrcv().
263         */
264        smp_mb();
265        msr->r_msg = ERR_PTR(res);
266    }
267}
268
269/*
270 * freeque() wakes up waiters on the sender and receiver waiting queue,
271 * removes the message queue from message queue ID IDR, and cleans up all the
272 * messages associated with this queue.
273 *
274 * msg_ids.rwsem (writer) and the spinlock for this message queue are held
275 * before freeque() is called. msg_ids.rwsem remains locked on exit.
276 */
277static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
278{
279    struct msg_msg *msg, *t;
280    struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
281
282    expunge_all(msq, -EIDRM);
283    ss_wakeup(&msq->q_senders, 1);
284    msg_rmid(ns, msq);
285    ipc_unlock_object(&msq->q_perm);
286    rcu_read_unlock();
287
288    list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
289        atomic_dec(&ns->msg_hdrs);
290        free_msg(msg);
291    }
292    atomic_sub(msq->q_cbytes, &ns->msg_bytes);
293    ipc_rcu_putref(msq, msg_rcu_free);
294}
295
296/*
297 * Called with msg_ids.rwsem and ipcp locked.
298 */
299static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
300{
301    struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
302
303    return security_msg_queue_associate(msq, msgflg);
304}
305
306SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
307{
308    struct ipc_namespace *ns;
309    struct ipc_ops msg_ops;
310    struct ipc_params msg_params;
311
312    ns = current->nsproxy->ipc_ns;
313
314    msg_ops.getnew = newque;
315    msg_ops.associate = msg_security;
316    msg_ops.more_checks = NULL;
317
318    msg_params.key = key;
319    msg_params.flg = msgflg;
320
321    return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
322}
323
324static inline unsigned long
325copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
326{
327    switch (version) {
328    case IPC_64:
329        return copy_to_user(buf, in, sizeof(*in));
330    case IPC_OLD:
331    {
332        struct msqid_ds out;
333
334        memset(&out, 0, sizeof(out));
335
336        ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
337
338        out.msg_stime = in->msg_stime;
339        out.msg_rtime = in->msg_rtime;
340        out.msg_ctime = in->msg_ctime;
341
342        if (in->msg_cbytes > USHRT_MAX)
343            out.msg_cbytes = USHRT_MAX;
344        else
345            out.msg_cbytes = in->msg_cbytes;
346        out.msg_lcbytes = in->msg_cbytes;
347
348        if (in->msg_qnum > USHRT_MAX)
349            out.msg_qnum = USHRT_MAX;
350        else
351            out.msg_qnum = in->msg_qnum;
352
353        if (in->msg_qbytes > USHRT_MAX)
354            out.msg_qbytes = USHRT_MAX;
355        else
356            out.msg_qbytes = in->msg_qbytes;
357        out.msg_lqbytes = in->msg_qbytes;
358
359        out.msg_lspid = in->msg_lspid;
360        out.msg_lrpid = in->msg_lrpid;
361
362        return copy_to_user(buf, &out, sizeof(out));
363    }
364    default:
365        return -EINVAL;
366    }
367}
368
369static inline unsigned long
370copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
371{
372    switch (version) {
373    case IPC_64:
374        if (copy_from_user(out, buf, sizeof(*out)))
375            return -EFAULT;
376        return 0;
377    case IPC_OLD:
378    {
379        struct msqid_ds tbuf_old;
380
381        if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
382            return -EFAULT;
383
384        out->msg_perm.uid = tbuf_old.msg_perm.uid;
385        out->msg_perm.gid = tbuf_old.msg_perm.gid;
386        out->msg_perm.mode = tbuf_old.msg_perm.mode;
387
388        if (tbuf_old.msg_qbytes == 0)
389            out->msg_qbytes = tbuf_old.msg_lqbytes;
390        else
391            out->msg_qbytes = tbuf_old.msg_qbytes;
392
393        return 0;
394    }
395    default:
396        return -EINVAL;
397    }
398}
399
400/*
401 * This function handles some msgctl commands which require the rwsem
402 * to be held in write mode.
403 * NOTE: no locks must be held, the rwsem is taken inside this function.
404 */
405static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
406               struct msqid_ds __user *buf, int version)
407{
408    struct kern_ipc_perm *ipcp;
409    struct msqid64_ds uninitialized_var(msqid64);
410    struct msg_queue *msq;
411    int err;
412
413    if (cmd == IPC_SET) {
414        if (copy_msqid_from_user(&msqid64, buf, version))
415            return -EFAULT;
416    }
417
418    down_write(&msg_ids(ns).rwsem);
419    rcu_read_lock();
420
421    ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
422                      &msqid64.msg_perm, msqid64.msg_qbytes);
423    if (IS_ERR(ipcp)) {
424        err = PTR_ERR(ipcp);
425        goto out_unlock1;
426    }
427
428    msq = container_of(ipcp, struct msg_queue, q_perm);
429
430    err = security_msg_queue_msgctl(msq, cmd);
431    if (err)
432        goto out_unlock1;
433
434    switch (cmd) {
435    case IPC_RMID:
436        ipc_lock_object(&msq->q_perm);
437        /* freeque unlocks the ipc object and rcu */
438        freeque(ns, ipcp);
439        goto out_up;
440    case IPC_SET:
441        if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
442            !capable(CAP_SYS_RESOURCE)) {
443            err = -EPERM;
444            goto out_unlock1;
445        }
446
447        ipc_lock_object(&msq->q_perm);
448        err = ipc_update_perm(&msqid64.msg_perm, ipcp);
449        if (err)
450            goto out_unlock0;
451
452        msq->q_qbytes = msqid64.msg_qbytes;
453
454        msq->q_ctime = get_seconds();
455        /* sleeping receivers might be excluded by
456         * stricter permissions.
457         */
458        expunge_all(msq, -EAGAIN);
459        /* sleeping senders might be able to send
460         * due to a larger queue size.
461         */
462        ss_wakeup(&msq->q_senders, 0);
463        break;
464    default:
465        err = -EINVAL;
466        goto out_unlock1;
467    }
468
469out_unlock0:
470    ipc_unlock_object(&msq->q_perm);
471out_unlock1:
472    rcu_read_unlock();
473out_up:
474    up_write(&msg_ids(ns).rwsem);
475    return err;
476}
477
478static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
479             int cmd, int version, void __user *buf)
480{
481    int err;
482    struct msg_queue *msq;
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        /*
495         * We must not return kernel stack data.
496         * due to padding, it's not enough
497         * to set all member fields.
498         */
499        err = security_msg_queue_msgctl(NULL, cmd);
500        if (err)
501            return err;
502
503        memset(&msginfo, 0, sizeof(msginfo));
504        msginfo.msgmni = ns->msg_ctlmni;
505        msginfo.msgmax = ns->msg_ctlmax;
506        msginfo.msgmnb = ns->msg_ctlmnb;
507        msginfo.msgssz = MSGSSZ;
508        msginfo.msgseg = MSGSEG;
509        down_read(&msg_ids(ns).rwsem);
510        if (cmd == MSG_INFO) {
511            msginfo.msgpool = msg_ids(ns).in_use;
512            msginfo.msgmap = atomic_read(&ns->msg_hdrs);
513            msginfo.msgtql = atomic_read(&ns->msg_bytes);
514        } else {
515            msginfo.msgmap = MSGMAP;
516            msginfo.msgpool = MSGPOOL;
517            msginfo.msgtql = MSGTQL;
518        }
519        max_id = ipc_get_maxid(&msg_ids(ns));
520        up_read(&msg_ids(ns).rwsem);
521        if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
522            return -EFAULT;
523        return (max_id < 0) ? 0 : max_id;
524    }
525
526    case MSG_STAT:
527    case IPC_STAT:
528    {
529        struct msqid64_ds tbuf;
530        int success_return;
531
532        if (!buf)
533            return -EFAULT;
534
535        memset(&tbuf, 0, sizeof(tbuf));
536
537        rcu_read_lock();
538        if (cmd == MSG_STAT) {
539            msq = msq_obtain_object(ns, msqid);
540            if (IS_ERR(msq)) {
541                err = PTR_ERR(msq);
542                goto out_unlock;
543            }
544            success_return = msq->q_perm.id;
545        } else {
546            msq = msq_obtain_object_check(ns, msqid);
547            if (IS_ERR(msq)) {
548                err = PTR_ERR(msq);
549                goto out_unlock;
550            }
551            success_return = 0;
552        }
553
554        err = -EACCES;
555        if (ipcperms(ns, &msq->q_perm, S_IRUGO))
556            goto out_unlock;
557
558        err = security_msg_queue_msgctl(msq, cmd);
559        if (err)
560            goto out_unlock;
561
562        kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
563        tbuf.msg_stime = msq->q_stime;
564        tbuf.msg_rtime = msq->q_rtime;
565        tbuf.msg_ctime = msq->q_ctime;
566        tbuf.msg_cbytes = msq->q_cbytes;
567        tbuf.msg_qnum = msq->q_qnum;
568        tbuf.msg_qbytes = msq->q_qbytes;
569        tbuf.msg_lspid = msq->q_lspid;
570        tbuf.msg_lrpid = msq->q_lrpid;
571        rcu_read_unlock();
572
573        if (copy_msqid_to_user(buf, &tbuf, version))
574            return -EFAULT;
575        return success_return;
576    }
577
578    default:
579        return -EINVAL;
580    }
581
582    return err;
583out_unlock:
584    rcu_read_unlock();
585    return err;
586}
587
588SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
589{
590    int version;
591    struct ipc_namespace *ns;
592
593    if (msqid < 0 || cmd < 0)
594        return -EINVAL;
595
596    version = ipc_parse_version(&cmd);
597    ns = current->nsproxy->ipc_ns;
598
599    switch (cmd) {
600    case IPC_INFO:
601    case MSG_INFO:
602    case MSG_STAT: /* msqid is an index rather than a msg queue id */
603    case IPC_STAT:
604        return msgctl_nolock(ns, msqid, cmd, version, buf);
605    case IPC_SET:
606    case IPC_RMID:
607        return msgctl_down(ns, msqid, cmd, buf, version);
608    default:
609        return -EINVAL;
610    }
611}
612
613static int testmsg(struct msg_msg *msg, long type, int mode)
614{
615    switch (mode)
616    {
617        case SEARCH_ANY:
618        case SEARCH_NUMBER:
619            return 1;
620        case SEARCH_LESSEQUAL:
621            if (msg->m_type <= type)
622                return 1;
623            break;
624        case SEARCH_EQUAL:
625            if (msg->m_type == type)
626                return 1;
627            break;
628        case SEARCH_NOTEQUAL:
629            if (msg->m_type != type)
630                return 1;
631            break;
632    }
633    return 0;
634}
635
636static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
637{
638    struct msg_receiver *msr, *t;
639
640    list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
641        if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
642            !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
643                           msr->r_msgtype, msr->r_mode)) {
644
645            list_del(&msr->r_list);
646            if (msr->r_maxsize < msg->m_ts) {
647                /* initialize pipelined send ordering */
648                msr->r_msg = NULL;
649                wake_up_process(msr->r_tsk);
650                smp_mb(); /* see barrier comment below */
651                msr->r_msg = ERR_PTR(-E2BIG);
652            } else {
653                msr->r_msg = NULL;
654                msq->q_lrpid = task_pid_vnr(msr->r_tsk);
655                msq->q_rtime = get_seconds();
656                wake_up_process(msr->r_tsk);
657                /*
658                 * Ensure that the wakeup is visible before
659                 * setting r_msg, as the receiving end depends
660                 * on it. See lockless receive part 1 and 2 in
661                 * do_msgrcv().
662                 */
663                smp_mb();
664                msr->r_msg = msg;
665
666                return 1;
667            }
668        }
669    }
670
671    return 0;
672}
673
674long do_msgsnd(int msqid, long mtype, void __user *mtext,
675        size_t msgsz, int msgflg)
676{
677    struct msg_queue *msq;
678    struct msg_msg *msg;
679    int err;
680    struct ipc_namespace *ns;
681
682    ns = current->nsproxy->ipc_ns;
683
684    if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
685        return -EINVAL;
686    if (mtype < 1)
687        return -EINVAL;
688
689    msg = load_msg(mtext, msgsz);
690    if (IS_ERR(msg))
691        return PTR_ERR(msg);
692
693    msg->m_type = mtype;
694    msg->m_ts = msgsz;
695
696    rcu_read_lock();
697    msq = msq_obtain_object_check(ns, msqid);
698    if (IS_ERR(msq)) {
699        err = PTR_ERR(msq);
700        goto out_unlock1;
701    }
702
703    ipc_lock_object(&msq->q_perm);
704
705    for (;;) {
706        struct msg_sender s;
707
708        err = -EACCES;
709        if (ipcperms(ns, &msq->q_perm, S_IWUGO))
710            goto out_unlock0;
711
712        /* raced with RMID? */
713        if (!ipc_valid_object(&msq->q_perm)) {
714            err = -EIDRM;
715            goto out_unlock0;
716        }
717
718        err = security_msg_queue_msgsnd(msq, msg, msgflg);
719        if (err)
720            goto out_unlock0;
721
722        if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
723                1 + msq->q_qnum <= msq->q_qbytes) {
724            break;
725        }
726
727        /* queue full, wait: */
728        if (msgflg & IPC_NOWAIT) {
729            err = -EAGAIN;
730            goto out_unlock0;
731        }
732
733        /* enqueue the sender and prepare to block */
734        ss_add(msq, &s);
735
736        if (!ipc_rcu_getref(msq)) {
737            err = -EIDRM;
738            goto out_unlock0;
739        }
740
741        ipc_unlock_object(&msq->q_perm);
742        rcu_read_unlock();
743        schedule();
744
745        rcu_read_lock();
746        ipc_lock_object(&msq->q_perm);
747
748        ipc_rcu_putref(msq, ipc_rcu_free);
749        /* raced with RMID? */
750        if (!ipc_valid_object(&msq->q_perm)) {
751            err = -EIDRM;
752            goto out_unlock0;
753        }
754
755        ss_del(&s);
756
757        if (signal_pending(current)) {
758            err = -ERESTARTNOHAND;
759            goto out_unlock0;
760        }
761
762    }
763    msq->q_lspid = task_tgid_vnr(current);
764    msq->q_stime = get_seconds();
765
766    if (!pipelined_send(msq, msg)) {
767        /* no one is waiting for this message, enqueue it */
768        list_add_tail(&msg->m_list, &msq->q_messages);
769        msq->q_cbytes += msgsz;
770        msq->q_qnum++;
771        atomic_add(msgsz, &ns->msg_bytes);
772        atomic_inc(&ns->msg_hdrs);
773    }
774
775    err = 0;
776    msg = NULL;
777
778out_unlock0:
779    ipc_unlock_object(&msq->q_perm);
780out_unlock1:
781    rcu_read_unlock();
782    if (msg != NULL)
783        free_msg(msg);
784    return err;
785}
786
787SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
788        int, msgflg)
789{
790    long mtype;
791
792    if (get_user(mtype, &msgp->mtype))
793        return -EFAULT;
794    return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
795}
796
797static inline int convert_mode(long *msgtyp, int msgflg)
798{
799    if (msgflg & MSG_COPY)
800        return SEARCH_NUMBER;
801    /*
802     * find message of correct type.
803     * msgtyp = 0 => get first.
804     * msgtyp > 0 => get first message of matching type.
805     * msgtyp < 0 => get message with least type must be < abs(msgtype).
806     */
807    if (*msgtyp == 0)
808        return SEARCH_ANY;
809    if (*msgtyp < 0) {
810        *msgtyp = -*msgtyp;
811        return SEARCH_LESSEQUAL;
812    }
813    if (msgflg & MSG_EXCEPT)
814        return SEARCH_NOTEQUAL;
815    return SEARCH_EQUAL;
816}
817
818static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
819{
820    struct msgbuf __user *msgp = dest;
821    size_t msgsz;
822
823    if (put_user(msg->m_type, &msgp->mtype))
824        return -EFAULT;
825
826    msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
827    if (store_msg(msgp->mtext, msg, msgsz))
828        return -EFAULT;
829    return msgsz;
830}
831
832#ifdef CONFIG_CHECKPOINT_RESTORE
833/*
834 * This function creates new kernel message structure, large enough to store
835 * bufsz message bytes.
836 */
837static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
838{
839    struct msg_msg *copy;
840
841    /*
842     * Create dummy message to copy real message to.
843     */
844    copy = load_msg(buf, bufsz);
845    if (!IS_ERR(copy))
846        copy->m_ts = bufsz;
847    return copy;
848}
849
850static inline void free_copy(struct msg_msg *copy)
851{
852    if (copy)
853        free_msg(copy);
854}
855#else
856static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
857{
858    return ERR_PTR(-ENOSYS);
859}
860
861static inline void free_copy(struct msg_msg *copy)
862{
863}
864#endif
865
866static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
867{
868    struct msg_msg *msg, *found = NULL;
869    long count = 0;
870
871    list_for_each_entry(msg, &msq->q_messages, m_list) {
872        if (testmsg(msg, *msgtyp, mode) &&
873            !security_msg_queue_msgrcv(msq, msg, current,
874                           *msgtyp, mode)) {
875            if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
876                *msgtyp = msg->m_type - 1;
877                found = msg;
878            } else if (mode == SEARCH_NUMBER) {
879                if (*msgtyp == count)
880                    return msg;
881            } else
882                return msg;
883            count++;
884        }
885    }
886
887    return found ?: ERR_PTR(-EAGAIN);
888}
889
890long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
891           long (*msg_handler)(void __user *, struct msg_msg *, size_t))
892{
893    int mode;
894    struct msg_queue *msq;
895    struct ipc_namespace *ns;
896    struct msg_msg *msg, *copy = NULL;
897
898    ns = current->nsproxy->ipc_ns;
899
900    if (msqid < 0 || (long) bufsz < 0)
901        return -EINVAL;
902
903    if (msgflg & MSG_COPY) {
904        if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
905            return -EINVAL;
906        copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
907        if (IS_ERR(copy))
908            return PTR_ERR(copy);
909    }
910    mode = convert_mode(&msgtyp, msgflg);
911
912    rcu_read_lock();
913    msq = msq_obtain_object_check(ns, msqid);
914    if (IS_ERR(msq)) {
915        rcu_read_unlock();
916        free_copy(copy);
917        return PTR_ERR(msq);
918    }
919
920    for (;;) {
921        struct msg_receiver msr_d;
922
923        msg = ERR_PTR(-EACCES);
924        if (ipcperms(ns, &msq->q_perm, S_IRUGO))
925            goto out_unlock1;
926
927        ipc_lock_object(&msq->q_perm);
928
929        /* raced with RMID? */
930        if (!ipc_valid_object(&msq->q_perm)) {
931            msg = ERR_PTR(-EIDRM);
932            goto out_unlock0;
933        }
934
935        msg = find_msg(msq, &msgtyp, mode);
936        if (!IS_ERR(msg)) {
937            /*
938             * Found a suitable message.
939             * Unlink it from the queue.
940             */
941            if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
942                msg = ERR_PTR(-E2BIG);
943                goto out_unlock0;
944            }
945            /*
946             * If we are copying, then do not unlink message and do
947             * not update queue parameters.
948             */
949            if (msgflg & MSG_COPY) {
950                msg = copy_msg(msg, copy);
951                goto out_unlock0;
952            }
953
954            list_del(&msg->m_list);
955            msq->q_qnum--;
956            msq->q_rtime = get_seconds();
957            msq->q_lrpid = task_tgid_vnr(current);
958            msq->q_cbytes -= msg->m_ts;
959            atomic_sub(msg->m_ts, &ns->msg_bytes);
960            atomic_dec(&ns->msg_hdrs);
961            ss_wakeup(&msq->q_senders, 0);
962
963            goto out_unlock0;
964        }
965
966        /* No message waiting. Wait for a message */
967        if (msgflg & IPC_NOWAIT) {
968            msg = ERR_PTR(-ENOMSG);
969            goto out_unlock0;
970        }
971
972        list_add_tail(&msr_d.r_list, &msq->q_receivers);
973        msr_d.r_tsk = current;
974        msr_d.r_msgtype = msgtyp;
975        msr_d.r_mode = mode;
976        if (msgflg & MSG_NOERROR)
977            msr_d.r_maxsize = INT_MAX;
978        else
979            msr_d.r_maxsize = bufsz;
980        msr_d.r_msg = ERR_PTR(-EAGAIN);
981        current->state = TASK_INTERRUPTIBLE;
982
983        ipc_unlock_object(&msq->q_perm);
984        rcu_read_unlock();
985        schedule();
986
987        /* Lockless receive, part 1:
988         * Disable preemption. We don't hold a reference to the queue
989         * and getting a reference would defeat the idea of a lockless
990         * operation, thus the code relies on rcu to guarantee the
991         * existence of msq:
992         * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
993         * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
994         * rcu_read_lock() prevents preemption between reading r_msg
995         * and acquiring the q_perm.lock in ipc_lock_object().
996         */
997        rcu_read_lock();
998
999        /* Lockless receive, part 2:
1000         * Wait until pipelined_send or expunge_all are outside of
1001         * wake_up_process(). There is a race with exit(), see
1002         * ipc/mqueue.c for the details.
1003         */
1004        msg = (struct msg_msg *)msr_d.r_msg;
1005        while (msg == NULL) {
1006            cpu_relax();
1007            msg = (struct msg_msg *)msr_d.r_msg;
1008        }
1009
1010        /* Lockless receive, part 3:
1011         * If there is a message or an error then accept it without
1012         * locking.
1013         */
1014        if (msg != ERR_PTR(-EAGAIN))
1015            goto out_unlock1;
1016
1017        /* Lockless receive, part 3:
1018         * Acquire the queue spinlock.
1019         */
1020        ipc_lock_object(&msq->q_perm);
1021
1022        /* Lockless receive, part 4:
1023         * Repeat test after acquiring the spinlock.
1024         */
1025        msg = (struct msg_msg *)msr_d.r_msg;
1026        if (msg != ERR_PTR(-EAGAIN))
1027            goto out_unlock0;
1028
1029        list_del(&msr_d.r_list);
1030        if (signal_pending(current)) {
1031            msg = ERR_PTR(-ERESTARTNOHAND);
1032            goto out_unlock0;
1033        }
1034
1035        ipc_unlock_object(&msq->q_perm);
1036    }
1037
1038out_unlock0:
1039    ipc_unlock_object(&msq->q_perm);
1040out_unlock1:
1041    rcu_read_unlock();
1042    if (IS_ERR(msg)) {
1043        free_copy(copy);
1044        return PTR_ERR(msg);
1045    }
1046
1047    bufsz = msg_handler(buf, msg, bufsz);
1048    free_msg(msg);
1049
1050    return bufsz;
1051}
1052
1053SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
1054        long, msgtyp, int, msgflg)
1055{
1056    return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
1057}
1058
1059#ifdef CONFIG_PROC_FS
1060static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1061{
1062    struct user_namespace *user_ns = seq_user_ns(s);
1063    struct msg_queue *msq = it;
1064
1065    return seq_printf(s,
1066            "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1067            msq->q_perm.key,
1068            msq->q_perm.id,
1069            msq->q_perm.mode,
1070            msq->q_cbytes,
1071            msq->q_qnum,
1072            msq->q_lspid,
1073            msq->q_lrpid,
1074            from_kuid_munged(user_ns, msq->q_perm.uid),
1075            from_kgid_munged(user_ns, msq->q_perm.gid),
1076            from_kuid_munged(user_ns, msq->q_perm.cuid),
1077            from_kgid_munged(user_ns, msq->q_perm.cgid),
1078            msq->q_stime,
1079            msq->q_rtime,
1080            msq->q_ctime);
1081}
1082#endif
1083

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