]>
git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - ipc/msg.c
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/wake_q.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 <linux/uaccess.h>
45 /* one msg_receiver structure for each sleeping receiver */
47 struct list_head r_list
;
48 struct task_struct
*r_tsk
;
54 struct msg_msg
*r_msg
;
57 /* one msg_sender for each sleeping sender */
59 struct list_head list
;
60 struct task_struct
*tsk
;
65 #define SEARCH_EQUAL 2
66 #define SEARCH_NOTEQUAL 3
67 #define SEARCH_LESSEQUAL 4
68 #define SEARCH_NUMBER 5
70 #define msg_ids(ns) ((ns)->ids[IPC_MSG_IDS])
72 static inline struct msg_queue
*msq_obtain_object(struct ipc_namespace
*ns
, int id
)
74 struct kern_ipc_perm
*ipcp
= ipc_obtain_object_idr(&msg_ids(ns
), id
);
77 return ERR_CAST(ipcp
);
79 return container_of(ipcp
, struct msg_queue
, q_perm
);
82 static inline struct msg_queue
*msq_obtain_object_check(struct ipc_namespace
*ns
,
85 struct kern_ipc_perm
*ipcp
= ipc_obtain_object_check(&msg_ids(ns
), id
);
88 return ERR_CAST(ipcp
);
90 return container_of(ipcp
, struct msg_queue
, q_perm
);
93 static inline void msg_rmid(struct ipc_namespace
*ns
, struct msg_queue
*s
)
95 ipc_rmid(&msg_ids(ns
), &s
->q_perm
);
98 static void __msg_free(struct msg_queue
*msq
)
103 static void msg_rcu_free(struct rcu_head
*head
)
105 struct kern_ipc_perm
*p
= container_of(head
, struct kern_ipc_perm
, rcu
);
106 struct msg_queue
*msq
= container_of(p
, struct msg_queue
, q_perm
);
108 security_msg_queue_free(msq
);
113 * newque - Create a new msg queue
115 * @params: ptr to the structure that contains the key and msgflg
117 * Called with msg_ids.rwsem held (writer)
119 static int newque(struct ipc_namespace
*ns
, struct ipc_params
*params
)
121 struct msg_queue
*msq
;
123 key_t key
= params
->key
;
124 int msgflg
= params
->flg
;
126 BUILD_BUG_ON(offsetof(struct msg_queue
, q_perm
) != 0);
128 msq
= container_of(ipc_rcu_alloc(sizeof(*msq
)), struct msg_queue
,
133 msq
->q_perm
.mode
= msgflg
& S_IRWXUGO
;
134 msq
->q_perm
.key
= key
;
136 msq
->q_perm
.security
= NULL
;
137 retval
= security_msg_queue_alloc(msq
);
143 msq
->q_stime
= msq
->q_rtime
= 0;
144 msq
->q_ctime
= get_seconds();
145 msq
->q_cbytes
= msq
->q_qnum
= 0;
146 msq
->q_qbytes
= ns
->msg_ctlmnb
;
147 msq
->q_lspid
= msq
->q_lrpid
= 0;
148 INIT_LIST_HEAD(&msq
->q_messages
);
149 INIT_LIST_HEAD(&msq
->q_receivers
);
150 INIT_LIST_HEAD(&msq
->q_senders
);
152 /* ipc_addid() locks msq upon success. */
153 id
= ipc_addid(&msg_ids(ns
), &msq
->q_perm
, ns
->msg_ctlmni
);
155 ipc_rcu_putref(&msq
->q_perm
, msg_rcu_free
);
159 ipc_unlock_object(&msq
->q_perm
);
162 return msq
->q_perm
.id
;
165 static inline bool msg_fits_inqueue(struct msg_queue
*msq
, size_t msgsz
)
167 return msgsz
+ msq
->q_cbytes
<= msq
->q_qbytes
&&
168 1 + msq
->q_qnum
<= msq
->q_qbytes
;
171 static inline void ss_add(struct msg_queue
*msq
,
172 struct msg_sender
*mss
, size_t msgsz
)
176 __set_current_state(TASK_INTERRUPTIBLE
);
177 list_add_tail(&mss
->list
, &msq
->q_senders
);
180 static inline void ss_del(struct msg_sender
*mss
)
183 list_del(&mss
->list
);
186 static void ss_wakeup(struct msg_queue
*msq
,
187 struct wake_q_head
*wake_q
, bool kill
)
189 struct msg_sender
*mss
, *t
;
190 struct task_struct
*stop_tsk
= NULL
;
191 struct list_head
*h
= &msq
->q_senders
;
193 list_for_each_entry_safe(mss
, t
, h
, list
) {
195 mss
->list
.next
= NULL
;
198 * Stop at the first task we don't wakeup,
199 * we've already iterated the original
202 else if (stop_tsk
== mss
->tsk
)
205 * We are not in an EIDRM scenario here, therefore
206 * verify that we really need to wakeup the task.
207 * To maintain current semantics and wakeup order,
208 * move the sender to the tail on behalf of the
211 else if (!msg_fits_inqueue(msq
, mss
->msgsz
)) {
215 list_move_tail(&mss
->list
, &msq
->q_senders
);
219 wake_q_add(wake_q
, mss
->tsk
);
223 static void expunge_all(struct msg_queue
*msq
, int res
,
224 struct wake_q_head
*wake_q
)
226 struct msg_receiver
*msr
, *t
;
228 list_for_each_entry_safe(msr
, t
, &msq
->q_receivers
, r_list
) {
229 wake_q_add(wake_q
, msr
->r_tsk
);
230 WRITE_ONCE(msr
->r_msg
, ERR_PTR(res
));
235 * freeque() wakes up waiters on the sender and receiver waiting queue,
236 * removes the message queue from message queue ID IDR, and cleans up all the
237 * messages associated with this queue.
239 * msg_ids.rwsem (writer) and the spinlock for this message queue are held
240 * before freeque() is called. msg_ids.rwsem remains locked on exit.
242 static void freeque(struct ipc_namespace
*ns
, struct kern_ipc_perm
*ipcp
)
244 struct msg_msg
*msg
, *t
;
245 struct msg_queue
*msq
= container_of(ipcp
, struct msg_queue
, q_perm
);
246 DEFINE_WAKE_Q(wake_q
);
248 expunge_all(msq
, -EIDRM
, &wake_q
);
249 ss_wakeup(msq
, &wake_q
, true);
251 ipc_unlock_object(&msq
->q_perm
);
255 list_for_each_entry_safe(msg
, t
, &msq
->q_messages
, m_list
) {
256 atomic_dec(&ns
->msg_hdrs
);
259 atomic_sub(msq
->q_cbytes
, &ns
->msg_bytes
);
260 ipc_rcu_putref(&msq
->q_perm
, msg_rcu_free
);
264 * Called with msg_ids.rwsem and ipcp locked.
266 static inline int msg_security(struct kern_ipc_perm
*ipcp
, int msgflg
)
268 struct msg_queue
*msq
= container_of(ipcp
, struct msg_queue
, q_perm
);
270 return security_msg_queue_associate(msq
, msgflg
);
273 SYSCALL_DEFINE2(msgget
, key_t
, key
, int, msgflg
)
275 struct ipc_namespace
*ns
;
276 static const struct ipc_ops msg_ops
= {
278 .associate
= msg_security
,
280 struct ipc_params msg_params
;
282 ns
= current
->nsproxy
->ipc_ns
;
284 msg_params
.key
= key
;
285 msg_params
.flg
= msgflg
;
287 return ipcget(ns
, &msg_ids(ns
), &msg_ops
, &msg_params
);
290 static inline unsigned long
291 copy_msqid_to_user(void __user
*buf
, struct msqid64_ds
*in
, int version
)
295 return copy_to_user(buf
, in
, sizeof(*in
));
300 memset(&out
, 0, sizeof(out
));
302 ipc64_perm_to_ipc_perm(&in
->msg_perm
, &out
.msg_perm
);
304 out
.msg_stime
= in
->msg_stime
;
305 out
.msg_rtime
= in
->msg_rtime
;
306 out
.msg_ctime
= in
->msg_ctime
;
308 if (in
->msg_cbytes
> USHRT_MAX
)
309 out
.msg_cbytes
= USHRT_MAX
;
311 out
.msg_cbytes
= in
->msg_cbytes
;
312 out
.msg_lcbytes
= in
->msg_cbytes
;
314 if (in
->msg_qnum
> USHRT_MAX
)
315 out
.msg_qnum
= USHRT_MAX
;
317 out
.msg_qnum
= in
->msg_qnum
;
319 if (in
->msg_qbytes
> USHRT_MAX
)
320 out
.msg_qbytes
= USHRT_MAX
;
322 out
.msg_qbytes
= in
->msg_qbytes
;
323 out
.msg_lqbytes
= in
->msg_qbytes
;
325 out
.msg_lspid
= in
->msg_lspid
;
326 out
.msg_lrpid
= in
->msg_lrpid
;
328 return copy_to_user(buf
, &out
, sizeof(out
));
335 static inline unsigned long
336 copy_msqid_from_user(struct msqid64_ds
*out
, void __user
*buf
, int version
)
340 if (copy_from_user(out
, buf
, sizeof(*out
)))
345 struct msqid_ds tbuf_old
;
347 if (copy_from_user(&tbuf_old
, buf
, sizeof(tbuf_old
)))
350 out
->msg_perm
.uid
= tbuf_old
.msg_perm
.uid
;
351 out
->msg_perm
.gid
= tbuf_old
.msg_perm
.gid
;
352 out
->msg_perm
.mode
= tbuf_old
.msg_perm
.mode
;
354 if (tbuf_old
.msg_qbytes
== 0)
355 out
->msg_qbytes
= tbuf_old
.msg_lqbytes
;
357 out
->msg_qbytes
= tbuf_old
.msg_qbytes
;
367 * This function handles some msgctl commands which require the rwsem
368 * to be held in write mode.
369 * NOTE: no locks must be held, the rwsem is taken inside this function.
371 static int msgctl_down(struct ipc_namespace
*ns
, int msqid
, int cmd
,
372 struct msqid_ds __user
*buf
, int version
)
374 struct kern_ipc_perm
*ipcp
;
375 struct msqid64_ds
uninitialized_var(msqid64
);
376 struct msg_queue
*msq
;
379 if (cmd
== IPC_SET
) {
380 if (copy_msqid_from_user(&msqid64
, buf
, version
))
384 down_write(&msg_ids(ns
).rwsem
);
387 ipcp
= ipcctl_pre_down_nolock(ns
, &msg_ids(ns
), msqid
, cmd
,
388 &msqid64
.msg_perm
, msqid64
.msg_qbytes
);
394 msq
= container_of(ipcp
, struct msg_queue
, q_perm
);
396 err
= security_msg_queue_msgctl(msq
, cmd
);
402 ipc_lock_object(&msq
->q_perm
);
403 /* freeque unlocks the ipc object and rcu */
408 DEFINE_WAKE_Q(wake_q
);
410 if (msqid64
.msg_qbytes
> ns
->msg_ctlmnb
&&
411 !capable(CAP_SYS_RESOURCE
)) {
416 ipc_lock_object(&msq
->q_perm
);
417 err
= ipc_update_perm(&msqid64
.msg_perm
, ipcp
);
421 msq
->q_qbytes
= msqid64
.msg_qbytes
;
423 msq
->q_ctime
= get_seconds();
425 * Sleeping receivers might be excluded by
426 * stricter permissions.
428 expunge_all(msq
, -EAGAIN
, &wake_q
);
430 * Sleeping senders might be able to send
431 * due to a larger queue size.
433 ss_wakeup(msq
, &wake_q
, false);
434 ipc_unlock_object(&msq
->q_perm
);
445 ipc_unlock_object(&msq
->q_perm
);
449 up_write(&msg_ids(ns
).rwsem
);
453 static int msgctl_nolock(struct ipc_namespace
*ns
, int msqid
,
454 int cmd
, int version
, void __user
*buf
)
457 struct msg_queue
*msq
;
463 struct msginfo msginfo
;
470 * We must not return kernel stack data.
471 * due to padding, it's not enough
472 * to set all member fields.
474 err
= security_msg_queue_msgctl(NULL
, cmd
);
478 memset(&msginfo
, 0, sizeof(msginfo
));
479 msginfo
.msgmni
= ns
->msg_ctlmni
;
480 msginfo
.msgmax
= ns
->msg_ctlmax
;
481 msginfo
.msgmnb
= ns
->msg_ctlmnb
;
482 msginfo
.msgssz
= MSGSSZ
;
483 msginfo
.msgseg
= MSGSEG
;
484 down_read(&msg_ids(ns
).rwsem
);
485 if (cmd
== MSG_INFO
) {
486 msginfo
.msgpool
= msg_ids(ns
).in_use
;
487 msginfo
.msgmap
= atomic_read(&ns
->msg_hdrs
);
488 msginfo
.msgtql
= atomic_read(&ns
->msg_bytes
);
490 msginfo
.msgmap
= MSGMAP
;
491 msginfo
.msgpool
= MSGPOOL
;
492 msginfo
.msgtql
= MSGTQL
;
494 max_id
= ipc_get_maxid(&msg_ids(ns
));
495 up_read(&msg_ids(ns
).rwsem
);
496 if (copy_to_user(buf
, &msginfo
, sizeof(struct msginfo
)))
498 return (max_id
< 0) ? 0 : max_id
;
504 struct msqid64_ds tbuf
;
510 memset(&tbuf
, 0, sizeof(tbuf
));
513 if (cmd
== MSG_STAT
) {
514 msq
= msq_obtain_object(ns
, msqid
);
519 success_return
= msq
->q_perm
.id
;
521 msq
= msq_obtain_object_check(ns
, msqid
);
530 if (ipcperms(ns
, &msq
->q_perm
, S_IRUGO
))
533 err
= security_msg_queue_msgctl(msq
, cmd
);
537 kernel_to_ipc64_perm(&msq
->q_perm
, &tbuf
.msg_perm
);
538 tbuf
.msg_stime
= msq
->q_stime
;
539 tbuf
.msg_rtime
= msq
->q_rtime
;
540 tbuf
.msg_ctime
= msq
->q_ctime
;
541 tbuf
.msg_cbytes
= msq
->q_cbytes
;
542 tbuf
.msg_qnum
= msq
->q_qnum
;
543 tbuf
.msg_qbytes
= msq
->q_qbytes
;
544 tbuf
.msg_lspid
= msq
->q_lspid
;
545 tbuf
.msg_lrpid
= msq
->q_lrpid
;
548 if (copy_msqid_to_user(buf
, &tbuf
, version
))
550 return success_return
;
563 SYSCALL_DEFINE3(msgctl
, int, msqid
, int, cmd
, struct msqid_ds __user
*, buf
)
566 struct ipc_namespace
*ns
;
568 if (msqid
< 0 || cmd
< 0)
571 version
= ipc_parse_version(&cmd
);
572 ns
= current
->nsproxy
->ipc_ns
;
577 case MSG_STAT
: /* msqid is an index rather than a msg queue id */
579 return msgctl_nolock(ns
, msqid
, cmd
, version
, buf
);
582 return msgctl_down(ns
, msqid
, cmd
, buf
, version
);
588 static int testmsg(struct msg_msg
*msg
, long type
, int mode
)
594 case SEARCH_LESSEQUAL
:
595 if (msg
->m_type
<= type
)
599 if (msg
->m_type
== type
)
602 case SEARCH_NOTEQUAL
:
603 if (msg
->m_type
!= type
)
610 static inline int pipelined_send(struct msg_queue
*msq
, struct msg_msg
*msg
,
611 struct wake_q_head
*wake_q
)
613 struct msg_receiver
*msr
, *t
;
615 list_for_each_entry_safe(msr
, t
, &msq
->q_receivers
, r_list
) {
616 if (testmsg(msg
, msr
->r_msgtype
, msr
->r_mode
) &&
617 !security_msg_queue_msgrcv(msq
, msg
, msr
->r_tsk
,
618 msr
->r_msgtype
, msr
->r_mode
)) {
620 list_del(&msr
->r_list
);
621 if (msr
->r_maxsize
< msg
->m_ts
) {
622 wake_q_add(wake_q
, msr
->r_tsk
);
623 WRITE_ONCE(msr
->r_msg
, ERR_PTR(-E2BIG
));
625 msq
->q_lrpid
= task_pid_vnr(msr
->r_tsk
);
626 msq
->q_rtime
= get_seconds();
628 wake_q_add(wake_q
, msr
->r_tsk
);
629 WRITE_ONCE(msr
->r_msg
, msg
);
638 long do_msgsnd(int msqid
, long mtype
, void __user
*mtext
,
639 size_t msgsz
, int msgflg
)
641 struct msg_queue
*msq
;
644 struct ipc_namespace
*ns
;
645 DEFINE_WAKE_Q(wake_q
);
647 ns
= current
->nsproxy
->ipc_ns
;
649 if (msgsz
> ns
->msg_ctlmax
|| (long) msgsz
< 0 || msqid
< 0)
654 msg
= load_msg(mtext
, msgsz
);
662 msq
= msq_obtain_object_check(ns
, msqid
);
668 ipc_lock_object(&msq
->q_perm
);
674 if (ipcperms(ns
, &msq
->q_perm
, S_IWUGO
))
677 /* raced with RMID? */
678 if (!ipc_valid_object(&msq
->q_perm
)) {
683 err
= security_msg_queue_msgsnd(msq
, msg
, msgflg
);
687 if (msg_fits_inqueue(msq
, msgsz
))
690 /* queue full, wait: */
691 if (msgflg
& IPC_NOWAIT
) {
696 /* enqueue the sender and prepare to block */
697 ss_add(msq
, &s
, msgsz
);
699 if (!ipc_rcu_getref(&msq
->q_perm
)) {
704 ipc_unlock_object(&msq
->q_perm
);
709 ipc_lock_object(&msq
->q_perm
);
711 ipc_rcu_putref(&msq
->q_perm
, msg_rcu_free
);
712 /* raced with RMID? */
713 if (!ipc_valid_object(&msq
->q_perm
)) {
719 if (signal_pending(current
)) {
720 err
= -ERESTARTNOHAND
;
726 msq
->q_lspid
= task_tgid_vnr(current
);
727 msq
->q_stime
= get_seconds();
729 if (!pipelined_send(msq
, msg
, &wake_q
)) {
730 /* no one is waiting for this message, enqueue it */
731 list_add_tail(&msg
->m_list
, &msq
->q_messages
);
732 msq
->q_cbytes
+= msgsz
;
734 atomic_add(msgsz
, &ns
->msg_bytes
);
735 atomic_inc(&ns
->msg_hdrs
);
742 ipc_unlock_object(&msq
->q_perm
);
751 SYSCALL_DEFINE4(msgsnd
, int, msqid
, struct msgbuf __user
*, msgp
, size_t, msgsz
,
756 if (get_user(mtype
, &msgp
->mtype
))
758 return do_msgsnd(msqid
, mtype
, msgp
->mtext
, msgsz
, msgflg
);
761 static inline int convert_mode(long *msgtyp
, int msgflg
)
763 if (msgflg
& MSG_COPY
)
764 return SEARCH_NUMBER
;
766 * find message of correct type.
767 * msgtyp = 0 => get first.
768 * msgtyp > 0 => get first message of matching type.
769 * msgtyp < 0 => get message with least type must be < abs(msgtype).
774 if (*msgtyp
== LONG_MIN
) /* -LONG_MIN is undefined */
778 return SEARCH_LESSEQUAL
;
780 if (msgflg
& MSG_EXCEPT
)
781 return SEARCH_NOTEQUAL
;
785 static long do_msg_fill(void __user
*dest
, struct msg_msg
*msg
, size_t bufsz
)
787 struct msgbuf __user
*msgp
= dest
;
790 if (put_user(msg
->m_type
, &msgp
->mtype
))
793 msgsz
= (bufsz
> msg
->m_ts
) ? msg
->m_ts
: bufsz
;
794 if (store_msg(msgp
->mtext
, msg
, msgsz
))
799 #ifdef CONFIG_CHECKPOINT_RESTORE
801 * This function creates new kernel message structure, large enough to store
802 * bufsz message bytes.
804 static inline struct msg_msg
*prepare_copy(void __user
*buf
, size_t bufsz
)
806 struct msg_msg
*copy
;
809 * Create dummy message to copy real message to.
811 copy
= load_msg(buf
, bufsz
);
817 static inline void free_copy(struct msg_msg
*copy
)
823 static inline struct msg_msg
*prepare_copy(void __user
*buf
, size_t bufsz
)
825 return ERR_PTR(-ENOSYS
);
828 static inline void free_copy(struct msg_msg
*copy
)
833 static struct msg_msg
*find_msg(struct msg_queue
*msq
, long *msgtyp
, int mode
)
835 struct msg_msg
*msg
, *found
= NULL
;
838 list_for_each_entry(msg
, &msq
->q_messages
, m_list
) {
839 if (testmsg(msg
, *msgtyp
, mode
) &&
840 !security_msg_queue_msgrcv(msq
, msg
, current
,
842 if (mode
== SEARCH_LESSEQUAL
&& msg
->m_type
!= 1) {
843 *msgtyp
= msg
->m_type
- 1;
845 } else if (mode
== SEARCH_NUMBER
) {
846 if (*msgtyp
== count
)
854 return found
?: ERR_PTR(-EAGAIN
);
857 long do_msgrcv(int msqid
, void __user
*buf
, size_t bufsz
, long msgtyp
, int msgflg
,
858 long (*msg_handler
)(void __user
*, struct msg_msg
*, size_t))
861 struct msg_queue
*msq
;
862 struct ipc_namespace
*ns
;
863 struct msg_msg
*msg
, *copy
= NULL
;
864 DEFINE_WAKE_Q(wake_q
);
866 ns
= current
->nsproxy
->ipc_ns
;
868 if (msqid
< 0 || (long) bufsz
< 0)
871 if (msgflg
& MSG_COPY
) {
872 if ((msgflg
& MSG_EXCEPT
) || !(msgflg
& IPC_NOWAIT
))
874 copy
= prepare_copy(buf
, min_t(size_t, bufsz
, ns
->msg_ctlmax
));
876 return PTR_ERR(copy
);
878 mode
= convert_mode(&msgtyp
, msgflg
);
881 msq
= msq_obtain_object_check(ns
, msqid
);
889 struct msg_receiver msr_d
;
891 msg
= ERR_PTR(-EACCES
);
892 if (ipcperms(ns
, &msq
->q_perm
, S_IRUGO
))
895 ipc_lock_object(&msq
->q_perm
);
897 /* raced with RMID? */
898 if (!ipc_valid_object(&msq
->q_perm
)) {
899 msg
= ERR_PTR(-EIDRM
);
903 msg
= find_msg(msq
, &msgtyp
, mode
);
906 * Found a suitable message.
907 * Unlink it from the queue.
909 if ((bufsz
< msg
->m_ts
) && !(msgflg
& MSG_NOERROR
)) {
910 msg
= ERR_PTR(-E2BIG
);
914 * If we are copying, then do not unlink message and do
915 * not update queue parameters.
917 if (msgflg
& MSG_COPY
) {
918 msg
= copy_msg(msg
, copy
);
922 list_del(&msg
->m_list
);
924 msq
->q_rtime
= get_seconds();
925 msq
->q_lrpid
= task_tgid_vnr(current
);
926 msq
->q_cbytes
-= msg
->m_ts
;
927 atomic_sub(msg
->m_ts
, &ns
->msg_bytes
);
928 atomic_dec(&ns
->msg_hdrs
);
929 ss_wakeup(msq
, &wake_q
, false);
934 /* No message waiting. Wait for a message */
935 if (msgflg
& IPC_NOWAIT
) {
936 msg
= ERR_PTR(-ENOMSG
);
940 list_add_tail(&msr_d
.r_list
, &msq
->q_receivers
);
941 msr_d
.r_tsk
= current
;
942 msr_d
.r_msgtype
= msgtyp
;
944 if (msgflg
& MSG_NOERROR
)
945 msr_d
.r_maxsize
= INT_MAX
;
947 msr_d
.r_maxsize
= bufsz
;
948 msr_d
.r_msg
= ERR_PTR(-EAGAIN
);
949 __set_current_state(TASK_INTERRUPTIBLE
);
951 ipc_unlock_object(&msq
->q_perm
);
956 * Lockless receive, part 1:
957 * We don't hold a reference to the queue and getting a
958 * reference would defeat the idea of a lockless operation,
959 * thus the code relies on rcu to guarantee the existence of
961 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
962 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
967 * Lockless receive, part 2:
968 * The work in pipelined_send() and expunge_all():
969 * - Set pointer to message
970 * - Queue the receiver task for later wakeup
971 * - Wake up the process after the lock is dropped.
973 * Should the process wake up before this wakeup (due to a
974 * signal) it will either see the message and continue ...
976 msg
= READ_ONCE(msr_d
.r_msg
);
977 if (msg
!= ERR_PTR(-EAGAIN
))
981 * ... or see -EAGAIN, acquire the lock to check the message
984 ipc_lock_object(&msq
->q_perm
);
987 if (msg
!= ERR_PTR(-EAGAIN
))
990 list_del(&msr_d
.r_list
);
991 if (signal_pending(current
)) {
992 msg
= ERR_PTR(-ERESTARTNOHAND
);
996 ipc_unlock_object(&msq
->q_perm
);
1000 ipc_unlock_object(&msq
->q_perm
);
1006 return PTR_ERR(msg
);
1009 bufsz
= msg_handler(buf
, msg
, bufsz
);
1015 SYSCALL_DEFINE5(msgrcv
, int, msqid
, struct msgbuf __user
*, msgp
, size_t, msgsz
,
1016 long, msgtyp
, int, msgflg
)
1018 return do_msgrcv(msqid
, msgp
, msgsz
, msgtyp
, msgflg
, do_msg_fill
);
1022 void msg_init_ns(struct ipc_namespace
*ns
)
1024 ns
->msg_ctlmax
= MSGMAX
;
1025 ns
->msg_ctlmnb
= MSGMNB
;
1026 ns
->msg_ctlmni
= MSGMNI
;
1028 atomic_set(&ns
->msg_bytes
, 0);
1029 atomic_set(&ns
->msg_hdrs
, 0);
1030 ipc_init_ids(&ns
->ids
[IPC_MSG_IDS
]);
1033 #ifdef CONFIG_IPC_NS
1034 void msg_exit_ns(struct ipc_namespace
*ns
)
1036 free_ipcs(ns
, &msg_ids(ns
), freeque
);
1037 idr_destroy(&ns
->ids
[IPC_MSG_IDS
].ipcs_idr
);
1041 #ifdef CONFIG_PROC_FS
1042 static int sysvipc_msg_proc_show(struct seq_file
*s
, void *it
)
1044 struct user_namespace
*user_ns
= seq_user_ns(s
);
1045 struct msg_queue
*msq
= it
;
1048 "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1056 from_kuid_munged(user_ns
, msq
->q_perm
.uid
),
1057 from_kgid_munged(user_ns
, msq
->q_perm
.gid
),
1058 from_kuid_munged(user_ns
, msq
->q_perm
.cuid
),
1059 from_kgid_munged(user_ns
, msq
->q_perm
.cgid
),
1068 void __init
msg_init(void)
1070 msg_init_ns(&init_ipc_ns
);
1072 ipc_init_proc_interface("sysvipc/msg",
1073 " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
1074 IPC_MSG_IDS
, sysvipc_msg_proc_show
);