3 * Copyright (C) 1992 Krishna Balasubramanian
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
11 * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
13 * mostly rewritten, threaded and wake-one semantics added
14 * MSGMAX limit removed, sysctl's added
15 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
22 * Pavel Emelianov <xemul@openvz.org>
25 #include <linux/capability.h>
26 #include <linux/msg.h>
27 #include <linux/spinlock.h>
28 #include <linux/init.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>
41 #include <asm/current.h>
42 #include <asm/uaccess.h>
46 * one msg_receiver structure for each sleeping receiver:
49 struct list_head r_list
;
50 struct task_struct
*r_tsk
;
56 struct msg_msg
*volatile r_msg
;
59 /* one msg_sender for each sleeping sender */
61 struct list_head list
;
62 struct task_struct
*tsk
;
66 #define SEARCH_EQUAL 2
67 #define SEARCH_NOTEQUAL 3
68 #define SEARCH_LESSEQUAL 4
69 #define SEARCH_NUMBER 5
71 #define msg_ids(ns) ((ns)->ids[IPC_MSG_IDS])
73 #define msg_unlock(msq) ipc_unlock(&(msq)->q_perm)
75 static void freeque(struct ipc_namespace
*, struct kern_ipc_perm
*);
76 static int newque(struct ipc_namespace
*, struct ipc_params
*);
78 static int sysvipc_msg_proc_show(struct seq_file
*s
, void *it
);
82 * Scale msgmni with the available lowmem size: the memory dedicated to msg
83 * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
84 * Also take into account the number of nsproxies created so far.
85 * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
87 void recompute_msgmni(struct ipc_namespace
*ns
)
90 unsigned long allowed
;
94 allowed
= (((i
.totalram
- i
.totalhigh
) / MSG_MEM_SCALE
) * i
.mem_unit
)
96 nb_ns
= atomic_read(&nr_ipc_ns
);
99 if (allowed
< MSGMNI
) {
100 ns
->msg_ctlmni
= MSGMNI
;
104 if (allowed
> IPCMNI
/ nb_ns
) {
105 ns
->msg_ctlmni
= IPCMNI
/ nb_ns
;
109 ns
->msg_ctlmni
= allowed
;
112 void msg_init_ns(struct ipc_namespace
*ns
)
114 ns
->msg_ctlmax
= MSGMAX
;
115 ns
->msg_ctlmnb
= MSGMNB
;
117 recompute_msgmni(ns
);
119 atomic_set(&ns
->msg_bytes
, 0);
120 atomic_set(&ns
->msg_hdrs
, 0);
121 ipc_init_ids(&ns
->ids
[IPC_MSG_IDS
]);
125 void msg_exit_ns(struct ipc_namespace
*ns
)
127 free_ipcs(ns
, &msg_ids(ns
), freeque
);
128 idr_destroy(&ns
->ids
[IPC_MSG_IDS
].ipcs_idr
);
132 void __init
msg_init(void)
134 msg_init_ns(&init_ipc_ns
);
136 printk(KERN_INFO
"msgmni has been set to %d\n",
137 init_ipc_ns
.msg_ctlmni
);
139 ipc_init_proc_interface("sysvipc/msg",
140 " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
141 IPC_MSG_IDS
, sysvipc_msg_proc_show
);
145 * msg_lock_(check_) routines are called in the paths where the rw_mutex
148 static inline struct msg_queue
*msg_lock(struct ipc_namespace
*ns
, int id
)
150 struct kern_ipc_perm
*ipcp
= ipc_lock(&msg_ids(ns
), id
);
153 return (struct msg_queue
*)ipcp
;
155 return container_of(ipcp
, struct msg_queue
, q_perm
);
158 static inline struct msg_queue
*msg_lock_check(struct ipc_namespace
*ns
,
161 struct kern_ipc_perm
*ipcp
= ipc_lock_check(&msg_ids(ns
), id
);
164 return (struct msg_queue
*)ipcp
;
166 return container_of(ipcp
, struct msg_queue
, q_perm
);
169 static inline void msg_rmid(struct ipc_namespace
*ns
, struct msg_queue
*s
)
171 ipc_rmid(&msg_ids(ns
), &s
->q_perm
);
175 * newque - Create a new msg queue
177 * @params: ptr to the structure that contains the key and msgflg
179 * Called with msg_ids.rw_mutex held (writer)
181 static int newque(struct ipc_namespace
*ns
, struct ipc_params
*params
)
183 struct msg_queue
*msq
;
185 key_t key
= params
->key
;
186 int msgflg
= params
->flg
;
188 msq
= ipc_rcu_alloc(sizeof(*msq
));
192 msq
->q_perm
.mode
= msgflg
& S_IRWXUGO
;
193 msq
->q_perm
.key
= key
;
195 msq
->q_perm
.security
= NULL
;
196 retval
= security_msg_queue_alloc(msq
);
202 /* ipc_addid() locks msq upon success. */
203 id
= ipc_addid(&msg_ids(ns
), &msq
->q_perm
, ns
->msg_ctlmni
);
205 security_msg_queue_free(msq
);
210 msq
->q_stime
= msq
->q_rtime
= 0;
211 msq
->q_ctime
= get_seconds();
212 msq
->q_cbytes
= msq
->q_qnum
= 0;
213 msq
->q_qbytes
= ns
->msg_ctlmnb
;
214 msq
->q_lspid
= msq
->q_lrpid
= 0;
215 INIT_LIST_HEAD(&msq
->q_messages
);
216 INIT_LIST_HEAD(&msq
->q_receivers
);
217 INIT_LIST_HEAD(&msq
->q_senders
);
219 ipc_unlock_object(&msq
->q_perm
);
222 return msq
->q_perm
.id
;
225 static inline void ss_add(struct msg_queue
*msq
, struct msg_sender
*mss
)
228 current
->state
= TASK_INTERRUPTIBLE
;
229 list_add_tail(&mss
->list
, &msq
->q_senders
);
232 static inline void ss_del(struct msg_sender
*mss
)
234 if (mss
->list
.next
!= NULL
)
235 list_del(&mss
->list
);
238 static void ss_wakeup(struct list_head
*h
, int kill
)
240 struct msg_sender
*mss
, *t
;
242 list_for_each_entry_safe(mss
, t
, h
, list
) {
244 mss
->list
.next
= NULL
;
245 wake_up_process(mss
->tsk
);
249 static void expunge_all(struct msg_queue
*msq
, int res
)
251 struct msg_receiver
*msr
, *t
;
253 list_for_each_entry_safe(msr
, t
, &msq
->q_receivers
, r_list
) {
255 wake_up_process(msr
->r_tsk
);
257 msr
->r_msg
= ERR_PTR(res
);
262 * freeque() wakes up waiters on the sender and receiver waiting queue,
263 * removes the message queue from message queue ID IDR, and cleans up all the
264 * messages associated with this queue.
266 * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
267 * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
269 static void freeque(struct ipc_namespace
*ns
, struct kern_ipc_perm
*ipcp
)
271 struct msg_msg
*msg
, *t
;
272 struct msg_queue
*msq
= container_of(ipcp
, struct msg_queue
, q_perm
);
274 expunge_all(msq
, -EIDRM
);
275 ss_wakeup(&msq
->q_senders
, 1);
279 list_for_each_entry_safe(msg
, t
, &msq
->q_messages
, m_list
) {
280 atomic_dec(&ns
->msg_hdrs
);
283 atomic_sub(msq
->q_cbytes
, &ns
->msg_bytes
);
284 security_msg_queue_free(msq
);
289 * Called with msg_ids.rw_mutex and ipcp locked.
291 static inline int msg_security(struct kern_ipc_perm
*ipcp
, int msgflg
)
293 struct msg_queue
*msq
= container_of(ipcp
, struct msg_queue
, q_perm
);
295 return security_msg_queue_associate(msq
, msgflg
);
298 SYSCALL_DEFINE2(msgget
, key_t
, key
, int, msgflg
)
300 struct ipc_namespace
*ns
;
301 struct ipc_ops msg_ops
;
302 struct ipc_params msg_params
;
304 ns
= current
->nsproxy
->ipc_ns
;
306 msg_ops
.getnew
= newque
;
307 msg_ops
.associate
= msg_security
;
308 msg_ops
.more_checks
= NULL
;
310 msg_params
.key
= key
;
311 msg_params
.flg
= msgflg
;
313 return ipcget(ns
, &msg_ids(ns
), &msg_ops
, &msg_params
);
316 static inline unsigned long
317 copy_msqid_to_user(void __user
*buf
, struct msqid64_ds
*in
, int version
)
321 return copy_to_user(buf
, in
, sizeof(*in
));
326 memset(&out
, 0, sizeof(out
));
328 ipc64_perm_to_ipc_perm(&in
->msg_perm
, &out
.msg_perm
);
330 out
.msg_stime
= in
->msg_stime
;
331 out
.msg_rtime
= in
->msg_rtime
;
332 out
.msg_ctime
= in
->msg_ctime
;
334 if (in
->msg_cbytes
> USHRT_MAX
)
335 out
.msg_cbytes
= USHRT_MAX
;
337 out
.msg_cbytes
= in
->msg_cbytes
;
338 out
.msg_lcbytes
= in
->msg_cbytes
;
340 if (in
->msg_qnum
> USHRT_MAX
)
341 out
.msg_qnum
= USHRT_MAX
;
343 out
.msg_qnum
= in
->msg_qnum
;
345 if (in
->msg_qbytes
> USHRT_MAX
)
346 out
.msg_qbytes
= USHRT_MAX
;
348 out
.msg_qbytes
= in
->msg_qbytes
;
349 out
.msg_lqbytes
= in
->msg_qbytes
;
351 out
.msg_lspid
= in
->msg_lspid
;
352 out
.msg_lrpid
= in
->msg_lrpid
;
354 return copy_to_user(buf
, &out
, sizeof(out
));
361 static inline unsigned long
362 copy_msqid_from_user(struct msqid64_ds
*out
, void __user
*buf
, int version
)
366 if (copy_from_user(out
, buf
, sizeof(*out
)))
371 struct msqid_ds tbuf_old
;
373 if (copy_from_user(&tbuf_old
, buf
, sizeof(tbuf_old
)))
376 out
->msg_perm
.uid
= tbuf_old
.msg_perm
.uid
;
377 out
->msg_perm
.gid
= tbuf_old
.msg_perm
.gid
;
378 out
->msg_perm
.mode
= tbuf_old
.msg_perm
.mode
;
380 if (tbuf_old
.msg_qbytes
== 0)
381 out
->msg_qbytes
= tbuf_old
.msg_lqbytes
;
383 out
->msg_qbytes
= tbuf_old
.msg_qbytes
;
393 * This function handles some msgctl commands which require the rw_mutex
394 * to be held in write mode.
395 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
397 static int msgctl_down(struct ipc_namespace
*ns
, int msqid
, int cmd
,
398 struct msqid_ds __user
*buf
, int version
)
400 struct kern_ipc_perm
*ipcp
;
401 struct msqid64_ds
uninitialized_var(msqid64
);
402 struct msg_queue
*msq
;
405 if (cmd
== IPC_SET
) {
406 if (copy_msqid_from_user(&msqid64
, buf
, version
))
410 down_write(&msg_ids(ns
).rw_mutex
);
413 ipcp
= ipcctl_pre_down(ns
, &msg_ids(ns
), msqid
, cmd
,
414 &msqid64
.msg_perm
, msqid64
.msg_qbytes
);
417 /* the ipc lock is not held upon failure */
421 msq
= container_of(ipcp
, struct msg_queue
, q_perm
);
423 err
= security_msg_queue_msgctl(msq
, cmd
);
429 /* freeque unlocks the ipc object and rcu */
433 if (msqid64
.msg_qbytes
> ns
->msg_ctlmnb
&&
434 !capable(CAP_SYS_RESOURCE
)) {
439 err
= ipc_update_perm(&msqid64
.msg_perm
, ipcp
);
443 msq
->q_qbytes
= msqid64
.msg_qbytes
;
445 msq
->q_ctime
= get_seconds();
446 /* sleeping receivers might be excluded by
447 * stricter permissions.
449 expunge_all(msq
, -EAGAIN
);
450 /* sleeping senders might be able to send
451 * due to a larger queue size.
453 ss_wakeup(&msq
->q_senders
, 0);
460 ipc_unlock_object(&msq
->q_perm
);
464 up_write(&msg_ids(ns
).rw_mutex
);
468 SYSCALL_DEFINE3(msgctl
, int, msqid
, int, cmd
, struct msqid_ds __user
*, buf
)
470 struct msg_queue
*msq
;
472 struct ipc_namespace
*ns
;
474 if (msqid
< 0 || cmd
< 0)
477 version
= ipc_parse_version(&cmd
);
478 ns
= current
->nsproxy
->ipc_ns
;
484 struct msginfo msginfo
;
490 * We must not return kernel stack data.
491 * due to padding, it's not enough
492 * to set all member fields.
494 err
= security_msg_queue_msgctl(NULL
, cmd
);
498 memset(&msginfo
, 0, sizeof(msginfo
));
499 msginfo
.msgmni
= ns
->msg_ctlmni
;
500 msginfo
.msgmax
= ns
->msg_ctlmax
;
501 msginfo
.msgmnb
= ns
->msg_ctlmnb
;
502 msginfo
.msgssz
= MSGSSZ
;
503 msginfo
.msgseg
= MSGSEG
;
504 down_read(&msg_ids(ns
).rw_mutex
);
505 if (cmd
== MSG_INFO
) {
506 msginfo
.msgpool
= msg_ids(ns
).in_use
;
507 msginfo
.msgmap
= atomic_read(&ns
->msg_hdrs
);
508 msginfo
.msgtql
= atomic_read(&ns
->msg_bytes
);
510 msginfo
.msgmap
= MSGMAP
;
511 msginfo
.msgpool
= MSGPOOL
;
512 msginfo
.msgtql
= MSGTQL
;
514 max_id
= ipc_get_maxid(&msg_ids(ns
));
515 up_read(&msg_ids(ns
).rw_mutex
);
516 if (copy_to_user(buf
, &msginfo
, sizeof(struct msginfo
)))
518 return (max_id
< 0) ? 0 : max_id
;
520 case MSG_STAT
: /* msqid is an index rather than a msg queue id */
523 struct msqid64_ds tbuf
;
529 if (cmd
== MSG_STAT
) {
530 msq
= msg_lock(ns
, msqid
);
533 success_return
= msq
->q_perm
.id
;
535 msq
= msg_lock_check(ns
, msqid
);
541 if (ipcperms(ns
, &msq
->q_perm
, S_IRUGO
))
544 err
= security_msg_queue_msgctl(msq
, cmd
);
548 memset(&tbuf
, 0, sizeof(tbuf
));
550 kernel_to_ipc64_perm(&msq
->q_perm
, &tbuf
.msg_perm
);
551 tbuf
.msg_stime
= msq
->q_stime
;
552 tbuf
.msg_rtime
= msq
->q_rtime
;
553 tbuf
.msg_ctime
= msq
->q_ctime
;
554 tbuf
.msg_cbytes
= msq
->q_cbytes
;
555 tbuf
.msg_qnum
= msq
->q_qnum
;
556 tbuf
.msg_qbytes
= msq
->q_qbytes
;
557 tbuf
.msg_lspid
= msq
->q_lspid
;
558 tbuf
.msg_lrpid
= msq
->q_lrpid
;
560 if (copy_msqid_to_user(buf
, &tbuf
, version
))
562 return success_return
;
566 err
= msgctl_down(ns
, msqid
, cmd
, buf
, version
);
577 static int testmsg(struct msg_msg
*msg
, long type
, int mode
)
584 case SEARCH_LESSEQUAL
:
585 if (msg
->m_type
<=type
)
589 if (msg
->m_type
== type
)
592 case SEARCH_NOTEQUAL
:
593 if (msg
->m_type
!= type
)
600 static inline int pipelined_send(struct msg_queue
*msq
, struct msg_msg
*msg
)
602 struct msg_receiver
*msr
, *t
;
604 list_for_each_entry_safe(msr
, t
, &msq
->q_receivers
, r_list
) {
605 if (testmsg(msg
, msr
->r_msgtype
, msr
->r_mode
) &&
606 !security_msg_queue_msgrcv(msq
, msg
, msr
->r_tsk
,
607 msr
->r_msgtype
, msr
->r_mode
)) {
609 list_del(&msr
->r_list
);
610 if (msr
->r_maxsize
< msg
->m_ts
) {
612 wake_up_process(msr
->r_tsk
);
614 msr
->r_msg
= ERR_PTR(-E2BIG
);
617 msq
->q_lrpid
= task_pid_vnr(msr
->r_tsk
);
618 msq
->q_rtime
= get_seconds();
619 wake_up_process(msr
->r_tsk
);
630 long do_msgsnd(int msqid
, long mtype
, void __user
*mtext
,
631 size_t msgsz
, int msgflg
)
633 struct msg_queue
*msq
;
636 struct ipc_namespace
*ns
;
638 ns
= current
->nsproxy
->ipc_ns
;
640 if (msgsz
> ns
->msg_ctlmax
|| (long) msgsz
< 0 || msqid
< 0)
645 msg
= load_msg(mtext
, msgsz
);
652 msq
= msg_lock_check(ns
, msqid
);
662 if (ipcperms(ns
, &msq
->q_perm
, S_IWUGO
))
663 goto out_unlock_free
;
665 err
= security_msg_queue_msgsnd(msq
, msg
, msgflg
);
667 goto out_unlock_free
;
669 if (msgsz
+ msq
->q_cbytes
<= msq
->q_qbytes
&&
670 1 + msq
->q_qnum
<= msq
->q_qbytes
) {
674 /* queue full, wait: */
675 if (msgflg
& IPC_NOWAIT
) {
677 goto out_unlock_free
;
681 if (!ipc_rcu_getref(msq
)) {
683 goto out_unlock_free
;
689 ipc_lock_by_ptr(&msq
->q_perm
);
691 if (msq
->q_perm
.deleted
) {
693 goto out_unlock_free
;
697 if (signal_pending(current
)) {
698 err
= -ERESTARTNOHAND
;
699 goto out_unlock_free
;
703 msq
->q_lspid
= task_tgid_vnr(current
);
704 msq
->q_stime
= get_seconds();
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
;
711 atomic_add(msgsz
, &ns
->msg_bytes
);
712 atomic_inc(&ns
->msg_hdrs
);
726 SYSCALL_DEFINE4(msgsnd
, int, msqid
, struct msgbuf __user
*, msgp
, size_t, msgsz
,
731 if (get_user(mtype
, &msgp
->mtype
))
733 return do_msgsnd(msqid
, mtype
, msgp
->mtext
, msgsz
, msgflg
);
736 static inline int convert_mode(long *msgtyp
, int msgflg
)
738 if (msgflg
& MSG_COPY
)
739 return SEARCH_NUMBER
;
741 * find message of correct type.
742 * msgtyp = 0 => get first.
743 * msgtyp > 0 => get first message of matching type.
744 * msgtyp < 0 => get message with least type must be < abs(msgtype).
750 return SEARCH_LESSEQUAL
;
752 if (msgflg
& MSG_EXCEPT
)
753 return SEARCH_NOTEQUAL
;
757 static long do_msg_fill(void __user
*dest
, struct msg_msg
*msg
, size_t bufsz
)
759 struct msgbuf __user
*msgp
= dest
;
762 if (put_user(msg
->m_type
, &msgp
->mtype
))
765 msgsz
= (bufsz
> msg
->m_ts
) ? msg
->m_ts
: bufsz
;
766 if (store_msg(msgp
->mtext
, msg
, msgsz
))
771 #ifdef CONFIG_CHECKPOINT_RESTORE
773 * This function creates new kernel message structure, large enough to store
774 * bufsz message bytes.
776 static inline struct msg_msg
*prepare_copy(void __user
*buf
, size_t bufsz
)
778 struct msg_msg
*copy
;
781 * Create dummy message to copy real message to.
783 copy
= load_msg(buf
, bufsz
);
789 static inline void free_copy(struct msg_msg
*copy
)
795 static inline struct msg_msg
*prepare_copy(void __user
*buf
, size_t bufsz
)
797 return ERR_PTR(-ENOSYS
);
800 static inline void free_copy(struct msg_msg
*copy
)
805 static struct msg_msg
*find_msg(struct msg_queue
*msq
, long *msgtyp
, int mode
)
810 list_for_each_entry(msg
, &msq
->q_messages
, m_list
) {
811 if (testmsg(msg
, *msgtyp
, mode
) &&
812 !security_msg_queue_msgrcv(msq
, msg
, current
,
814 if (mode
== SEARCH_LESSEQUAL
&& msg
->m_type
!= 1) {
815 *msgtyp
= msg
->m_type
- 1;
816 } else if (mode
== SEARCH_NUMBER
) {
817 if (*msgtyp
== count
)
825 return ERR_PTR(-EAGAIN
);
829 long do_msgrcv(int msqid
, void __user
*buf
, size_t bufsz
, long msgtyp
,
831 long (*msg_handler
)(void __user
*, struct msg_msg
*, size_t))
833 struct msg_queue
*msq
;
836 struct ipc_namespace
*ns
;
837 struct msg_msg
*copy
= NULL
;
839 ns
= current
->nsproxy
->ipc_ns
;
841 if (msqid
< 0 || (long) bufsz
< 0)
843 if (msgflg
& MSG_COPY
) {
844 copy
= prepare_copy(buf
, min_t(size_t, bufsz
, ns
->msg_ctlmax
));
846 return PTR_ERR(copy
);
848 mode
= convert_mode(&msgtyp
, msgflg
);
850 msq
= msg_lock_check(ns
, msqid
);
857 struct msg_receiver msr_d
;
859 msg
= ERR_PTR(-EACCES
);
860 if (ipcperms(ns
, &msq
->q_perm
, S_IRUGO
))
863 msg
= find_msg(msq
, &msgtyp
, mode
);
867 * Found a suitable message.
868 * Unlink it from the queue.
870 if ((bufsz
< msg
->m_ts
) && !(msgflg
& MSG_NOERROR
)) {
871 msg
= ERR_PTR(-E2BIG
);
875 * If we are copying, then do not unlink message and do
876 * not update queue parameters.
878 if (msgflg
& MSG_COPY
) {
879 msg
= copy_msg(msg
, copy
);
882 list_del(&msg
->m_list
);
884 msq
->q_rtime
= get_seconds();
885 msq
->q_lrpid
= task_tgid_vnr(current
);
886 msq
->q_cbytes
-= msg
->m_ts
;
887 atomic_sub(msg
->m_ts
, &ns
->msg_bytes
);
888 atomic_dec(&ns
->msg_hdrs
);
889 ss_wakeup(&msq
->q_senders
, 0);
893 /* No message waiting. Wait for a message */
894 if (msgflg
& IPC_NOWAIT
) {
895 msg
= ERR_PTR(-ENOMSG
);
898 list_add_tail(&msr_d
.r_list
, &msq
->q_receivers
);
899 msr_d
.r_tsk
= current
;
900 msr_d
.r_msgtype
= msgtyp
;
902 if (msgflg
& MSG_NOERROR
)
903 msr_d
.r_maxsize
= INT_MAX
;
905 msr_d
.r_maxsize
= bufsz
;
906 msr_d
.r_msg
= ERR_PTR(-EAGAIN
);
907 current
->state
= TASK_INTERRUPTIBLE
;
912 /* Lockless receive, part 1:
913 * Disable preemption. We don't hold a reference to the queue
914 * and getting a reference would defeat the idea of a lockless
915 * operation, thus the code relies on rcu to guarantee the
917 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
918 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
919 * rcu_read_lock() prevents preemption between reading r_msg
920 * and the spin_lock() inside ipc_lock_by_ptr().
924 /* Lockless receive, part 2:
925 * Wait until pipelined_send or expunge_all are outside of
926 * wake_up_process(). There is a race with exit(), see
927 * ipc/mqueue.c for the details.
929 msg
= (struct msg_msg
*)msr_d
.r_msg
;
930 while (msg
== NULL
) {
932 msg
= (struct msg_msg
*)msr_d
.r_msg
;
935 /* Lockless receive, part 3:
936 * If there is a message or an error then accept it without
939 if (msg
!= ERR_PTR(-EAGAIN
)) {
944 /* Lockless receive, part 3:
945 * Acquire the queue spinlock.
947 ipc_lock_by_ptr(&msq
->q_perm
);
950 /* Lockless receive, part 4:
951 * Repeat test after acquiring the spinlock.
953 msg
= (struct msg_msg
*)msr_d
.r_msg
;
954 if (msg
!= ERR_PTR(-EAGAIN
))
957 list_del(&msr_d
.r_list
);
958 if (signal_pending(current
)) {
959 msg
= ERR_PTR(-ERESTARTNOHAND
);
970 bufsz
= msg_handler(buf
, msg
, bufsz
);
976 SYSCALL_DEFINE5(msgrcv
, int, msqid
, struct msgbuf __user
*, msgp
, size_t, msgsz
,
977 long, msgtyp
, int, msgflg
)
979 return do_msgrcv(msqid
, msgp
, msgsz
, msgtyp
, msgflg
, do_msg_fill
);
982 #ifdef CONFIG_PROC_FS
983 static int sysvipc_msg_proc_show(struct seq_file
*s
, void *it
)
985 struct user_namespace
*user_ns
= seq_user_ns(s
);
986 struct msg_queue
*msq
= it
;
989 "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
997 from_kuid_munged(user_ns
, msq
->q_perm
.uid
),
998 from_kgid_munged(user_ns
, msq
->q_perm
.gid
),
999 from_kuid_munged(user_ns
, msq
->q_perm
.cuid
),
1000 from_kgid_munged(user_ns
, msq
->q_perm
.cgid
),
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