msg.c 19 KB

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  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. #include <linux/capability.h>
  21. #include <linux/config.h>
  22. #include <linux/slab.h>
  23. #include <linux/msg.h>
  24. #include <linux/spinlock.h>
  25. #include <linux/init.h>
  26. #include <linux/proc_fs.h>
  27. #include <linux/list.h>
  28. #include <linux/security.h>
  29. #include <linux/sched.h>
  30. #include <linux/syscalls.h>
  31. #include <linux/audit.h>
  32. #include <linux/seq_file.h>
  33. #include <linux/mutex.h>
  34. #include <asm/current.h>
  35. #include <asm/uaccess.h>
  36. #include "util.h"
  37. /* sysctl: */
  38. int msg_ctlmax = MSGMAX;
  39. int msg_ctlmnb = MSGMNB;
  40. int msg_ctlmni = MSGMNI;
  41. /* one msg_receiver structure for each sleeping receiver */
  42. struct msg_receiver {
  43. struct list_head r_list;
  44. struct task_struct* r_tsk;
  45. int r_mode;
  46. long r_msgtype;
  47. long r_maxsize;
  48. struct msg_msg* volatile r_msg;
  49. };
  50. /* one msg_sender for each sleeping sender */
  51. struct msg_sender {
  52. struct list_head list;
  53. struct task_struct* tsk;
  54. };
  55. #define SEARCH_ANY 1
  56. #define SEARCH_EQUAL 2
  57. #define SEARCH_NOTEQUAL 3
  58. #define SEARCH_LESSEQUAL 4
  59. static atomic_t msg_bytes = ATOMIC_INIT(0);
  60. static atomic_t msg_hdrs = ATOMIC_INIT(0);
  61. static struct ipc_ids msg_ids;
  62. #define msg_lock(id) ((struct msg_queue*)ipc_lock(&msg_ids,id))
  63. #define msg_unlock(msq) ipc_unlock(&(msq)->q_perm)
  64. #define msg_rmid(id) ((struct msg_queue*)ipc_rmid(&msg_ids,id))
  65. #define msg_checkid(msq, msgid) \
  66. ipc_checkid(&msg_ids,&msq->q_perm,msgid)
  67. #define msg_buildid(id, seq) \
  68. ipc_buildid(&msg_ids, id, seq)
  69. static void freeque (struct msg_queue *msq, int id);
  70. static int newque (key_t key, int msgflg);
  71. #ifdef CONFIG_PROC_FS
  72. static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
  73. #endif
  74. void __init msg_init (void)
  75. {
  76. ipc_init_ids(&msg_ids,msg_ctlmni);
  77. ipc_init_proc_interface("sysvipc/msg",
  78. " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
  79. &msg_ids,
  80. sysvipc_msg_proc_show);
  81. }
  82. static int newque (key_t key, int msgflg)
  83. {
  84. int id;
  85. int retval;
  86. struct msg_queue *msq;
  87. msq = ipc_rcu_alloc(sizeof(*msq));
  88. if (!msq)
  89. return -ENOMEM;
  90. msq->q_perm.mode = (msgflg & S_IRWXUGO);
  91. msq->q_perm.key = key;
  92. msq->q_perm.security = NULL;
  93. retval = security_msg_queue_alloc(msq);
  94. if (retval) {
  95. ipc_rcu_putref(msq);
  96. return retval;
  97. }
  98. id = ipc_addid(&msg_ids, &msq->q_perm, msg_ctlmni);
  99. if(id == -1) {
  100. security_msg_queue_free(msq);
  101. ipc_rcu_putref(msq);
  102. return -ENOSPC;
  103. }
  104. msq->q_id = msg_buildid(id,msq->q_perm.seq);
  105. msq->q_stime = msq->q_rtime = 0;
  106. msq->q_ctime = get_seconds();
  107. msq->q_cbytes = msq->q_qnum = 0;
  108. msq->q_qbytes = msg_ctlmnb;
  109. msq->q_lspid = msq->q_lrpid = 0;
  110. INIT_LIST_HEAD(&msq->q_messages);
  111. INIT_LIST_HEAD(&msq->q_receivers);
  112. INIT_LIST_HEAD(&msq->q_senders);
  113. msg_unlock(msq);
  114. return msq->q_id;
  115. }
  116. static inline void ss_add(struct msg_queue* msq, struct msg_sender* mss)
  117. {
  118. mss->tsk=current;
  119. current->state=TASK_INTERRUPTIBLE;
  120. list_add_tail(&mss->list,&msq->q_senders);
  121. }
  122. static inline void ss_del(struct msg_sender* mss)
  123. {
  124. if(mss->list.next != NULL)
  125. list_del(&mss->list);
  126. }
  127. static void ss_wakeup(struct list_head* h, int kill)
  128. {
  129. struct list_head *tmp;
  130. tmp = h->next;
  131. while (tmp != h) {
  132. struct msg_sender* mss;
  133. mss = list_entry(tmp,struct msg_sender,list);
  134. tmp = tmp->next;
  135. if(kill)
  136. mss->list.next=NULL;
  137. wake_up_process(mss->tsk);
  138. }
  139. }
  140. static void expunge_all(struct msg_queue* msq, int res)
  141. {
  142. struct list_head *tmp;
  143. tmp = msq->q_receivers.next;
  144. while (tmp != &msq->q_receivers) {
  145. struct msg_receiver* msr;
  146. msr = list_entry(tmp,struct msg_receiver,r_list);
  147. tmp = tmp->next;
  148. msr->r_msg = NULL;
  149. wake_up_process(msr->r_tsk);
  150. smp_mb();
  151. msr->r_msg = ERR_PTR(res);
  152. }
  153. }
  154. /*
  155. * freeque() wakes up waiters on the sender and receiver waiting queue,
  156. * removes the message queue from message queue ID
  157. * array, and cleans up all the messages associated with this queue.
  158. *
  159. * msg_ids.mutex and the spinlock for this message queue is hold
  160. * before freeque() is called. msg_ids.mutex remains locked on exit.
  161. */
  162. static void freeque (struct msg_queue *msq, int id)
  163. {
  164. struct list_head *tmp;
  165. expunge_all(msq,-EIDRM);
  166. ss_wakeup(&msq->q_senders,1);
  167. msq = msg_rmid(id);
  168. msg_unlock(msq);
  169. tmp = msq->q_messages.next;
  170. while(tmp != &msq->q_messages) {
  171. struct msg_msg* msg = list_entry(tmp,struct msg_msg,m_list);
  172. tmp = tmp->next;
  173. atomic_dec(&msg_hdrs);
  174. free_msg(msg);
  175. }
  176. atomic_sub(msq->q_cbytes, &msg_bytes);
  177. security_msg_queue_free(msq);
  178. ipc_rcu_putref(msq);
  179. }
  180. asmlinkage long sys_msgget (key_t key, int msgflg)
  181. {
  182. int id, ret = -EPERM;
  183. struct msg_queue *msq;
  184. mutex_lock(&msg_ids.mutex);
  185. if (key == IPC_PRIVATE)
  186. ret = newque(key, msgflg);
  187. else if ((id = ipc_findkey(&msg_ids, key)) == -1) { /* key not used */
  188. if (!(msgflg & IPC_CREAT))
  189. ret = -ENOENT;
  190. else
  191. ret = newque(key, msgflg);
  192. } else if (msgflg & IPC_CREAT && msgflg & IPC_EXCL) {
  193. ret = -EEXIST;
  194. } else {
  195. msq = msg_lock(id);
  196. BUG_ON(msq==NULL);
  197. if (ipcperms(&msq->q_perm, msgflg))
  198. ret = -EACCES;
  199. else {
  200. int qid = msg_buildid(id, msq->q_perm.seq);
  201. ret = security_msg_queue_associate(msq, msgflg);
  202. if (!ret)
  203. ret = qid;
  204. }
  205. msg_unlock(msq);
  206. }
  207. mutex_unlock(&msg_ids.mutex);
  208. return ret;
  209. }
  210. static inline unsigned long copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
  211. {
  212. switch(version) {
  213. case IPC_64:
  214. return copy_to_user (buf, in, sizeof(*in));
  215. case IPC_OLD:
  216. {
  217. struct msqid_ds out;
  218. memset(&out,0,sizeof(out));
  219. ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
  220. out.msg_stime = in->msg_stime;
  221. out.msg_rtime = in->msg_rtime;
  222. out.msg_ctime = in->msg_ctime;
  223. if(in->msg_cbytes > USHRT_MAX)
  224. out.msg_cbytes = USHRT_MAX;
  225. else
  226. out.msg_cbytes = in->msg_cbytes;
  227. out.msg_lcbytes = in->msg_cbytes;
  228. if(in->msg_qnum > USHRT_MAX)
  229. out.msg_qnum = USHRT_MAX;
  230. else
  231. out.msg_qnum = in->msg_qnum;
  232. if(in->msg_qbytes > USHRT_MAX)
  233. out.msg_qbytes = USHRT_MAX;
  234. else
  235. out.msg_qbytes = in->msg_qbytes;
  236. out.msg_lqbytes = in->msg_qbytes;
  237. out.msg_lspid = in->msg_lspid;
  238. out.msg_lrpid = in->msg_lrpid;
  239. return copy_to_user (buf, &out, sizeof(out));
  240. }
  241. default:
  242. return -EINVAL;
  243. }
  244. }
  245. struct msq_setbuf {
  246. unsigned long qbytes;
  247. uid_t uid;
  248. gid_t gid;
  249. mode_t mode;
  250. };
  251. static inline unsigned long copy_msqid_from_user(struct msq_setbuf *out, void __user *buf, int version)
  252. {
  253. switch(version) {
  254. case IPC_64:
  255. {
  256. struct msqid64_ds tbuf;
  257. if (copy_from_user (&tbuf, buf, sizeof (tbuf)))
  258. return -EFAULT;
  259. out->qbytes = tbuf.msg_qbytes;
  260. out->uid = tbuf.msg_perm.uid;
  261. out->gid = tbuf.msg_perm.gid;
  262. out->mode = tbuf.msg_perm.mode;
  263. return 0;
  264. }
  265. case IPC_OLD:
  266. {
  267. struct msqid_ds tbuf_old;
  268. if (copy_from_user (&tbuf_old, buf, sizeof (tbuf_old)))
  269. return -EFAULT;
  270. out->uid = tbuf_old.msg_perm.uid;
  271. out->gid = tbuf_old.msg_perm.gid;
  272. out->mode = tbuf_old.msg_perm.mode;
  273. if(tbuf_old.msg_qbytes == 0)
  274. out->qbytes = tbuf_old.msg_lqbytes;
  275. else
  276. out->qbytes = tbuf_old.msg_qbytes;
  277. return 0;
  278. }
  279. default:
  280. return -EINVAL;
  281. }
  282. }
  283. asmlinkage long sys_msgctl (int msqid, int cmd, struct msqid_ds __user *buf)
  284. {
  285. int err, version;
  286. struct msg_queue *msq;
  287. struct msq_setbuf setbuf;
  288. struct kern_ipc_perm *ipcp;
  289. if (msqid < 0 || cmd < 0)
  290. return -EINVAL;
  291. version = ipc_parse_version(&cmd);
  292. switch (cmd) {
  293. case IPC_INFO:
  294. case MSG_INFO:
  295. {
  296. struct msginfo msginfo;
  297. int max_id;
  298. if (!buf)
  299. return -EFAULT;
  300. /* We must not return kernel stack data.
  301. * due to padding, it's not enough
  302. * to set all member fields.
  303. */
  304. err = security_msg_queue_msgctl(NULL, cmd);
  305. if (err)
  306. return err;
  307. memset(&msginfo,0,sizeof(msginfo));
  308. msginfo.msgmni = msg_ctlmni;
  309. msginfo.msgmax = msg_ctlmax;
  310. msginfo.msgmnb = msg_ctlmnb;
  311. msginfo.msgssz = MSGSSZ;
  312. msginfo.msgseg = MSGSEG;
  313. mutex_lock(&msg_ids.mutex);
  314. if (cmd == MSG_INFO) {
  315. msginfo.msgpool = msg_ids.in_use;
  316. msginfo.msgmap = atomic_read(&msg_hdrs);
  317. msginfo.msgtql = atomic_read(&msg_bytes);
  318. } else {
  319. msginfo.msgmap = MSGMAP;
  320. msginfo.msgpool = MSGPOOL;
  321. msginfo.msgtql = MSGTQL;
  322. }
  323. max_id = msg_ids.max_id;
  324. mutex_unlock(&msg_ids.mutex);
  325. if (copy_to_user (buf, &msginfo, sizeof(struct msginfo)))
  326. return -EFAULT;
  327. return (max_id < 0) ? 0: max_id;
  328. }
  329. case MSG_STAT:
  330. case IPC_STAT:
  331. {
  332. struct msqid64_ds tbuf;
  333. int success_return;
  334. if (!buf)
  335. return -EFAULT;
  336. if(cmd == MSG_STAT && msqid >= msg_ids.entries->size)
  337. return -EINVAL;
  338. memset(&tbuf,0,sizeof(tbuf));
  339. msq = msg_lock(msqid);
  340. if (msq == NULL)
  341. return -EINVAL;
  342. if(cmd == MSG_STAT) {
  343. success_return = msg_buildid(msqid, msq->q_perm.seq);
  344. } else {
  345. err = -EIDRM;
  346. if (msg_checkid(msq,msqid))
  347. goto out_unlock;
  348. success_return = 0;
  349. }
  350. err = -EACCES;
  351. if (ipcperms (&msq->q_perm, S_IRUGO))
  352. goto out_unlock;
  353. err = security_msg_queue_msgctl(msq, cmd);
  354. if (err)
  355. goto out_unlock;
  356. kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
  357. tbuf.msg_stime = msq->q_stime;
  358. tbuf.msg_rtime = msq->q_rtime;
  359. tbuf.msg_ctime = msq->q_ctime;
  360. tbuf.msg_cbytes = msq->q_cbytes;
  361. tbuf.msg_qnum = msq->q_qnum;
  362. tbuf.msg_qbytes = msq->q_qbytes;
  363. tbuf.msg_lspid = msq->q_lspid;
  364. tbuf.msg_lrpid = msq->q_lrpid;
  365. msg_unlock(msq);
  366. if (copy_msqid_to_user(buf, &tbuf, version))
  367. return -EFAULT;
  368. return success_return;
  369. }
  370. case IPC_SET:
  371. if (!buf)
  372. return -EFAULT;
  373. if (copy_msqid_from_user (&setbuf, buf, version))
  374. return -EFAULT;
  375. break;
  376. case IPC_RMID:
  377. break;
  378. default:
  379. return -EINVAL;
  380. }
  381. mutex_lock(&msg_ids.mutex);
  382. msq = msg_lock(msqid);
  383. err=-EINVAL;
  384. if (msq == NULL)
  385. goto out_up;
  386. err = -EIDRM;
  387. if (msg_checkid(msq,msqid))
  388. goto out_unlock_up;
  389. ipcp = &msq->q_perm;
  390. err = audit_ipc_obj(ipcp);
  391. if (err)
  392. goto out_unlock_up;
  393. err = -EPERM;
  394. if (current->euid != ipcp->cuid &&
  395. current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))
  396. /* We _could_ check for CAP_CHOWN above, but we don't */
  397. goto out_unlock_up;
  398. err = security_msg_queue_msgctl(msq, cmd);
  399. if (err)
  400. goto out_unlock_up;
  401. switch (cmd) {
  402. case IPC_SET:
  403. {
  404. err = audit_ipc_set_perm(setbuf.qbytes, setbuf.uid, setbuf.gid, setbuf.mode, ipcp);
  405. if (err)
  406. goto out_unlock_up;
  407. err = -EPERM;
  408. if (setbuf.qbytes > msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
  409. goto out_unlock_up;
  410. msq->q_qbytes = setbuf.qbytes;
  411. ipcp->uid = setbuf.uid;
  412. ipcp->gid = setbuf.gid;
  413. ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |
  414. (S_IRWXUGO & setbuf.mode);
  415. msq->q_ctime = get_seconds();
  416. /* sleeping receivers might be excluded by
  417. * stricter permissions.
  418. */
  419. expunge_all(msq,-EAGAIN);
  420. /* sleeping senders might be able to send
  421. * due to a larger queue size.
  422. */
  423. ss_wakeup(&msq->q_senders,0);
  424. msg_unlock(msq);
  425. break;
  426. }
  427. case IPC_RMID:
  428. freeque (msq, msqid);
  429. break;
  430. }
  431. err = 0;
  432. out_up:
  433. mutex_unlock(&msg_ids.mutex);
  434. return err;
  435. out_unlock_up:
  436. msg_unlock(msq);
  437. goto out_up;
  438. out_unlock:
  439. msg_unlock(msq);
  440. return err;
  441. }
  442. static int testmsg(struct msg_msg* msg,long type,int mode)
  443. {
  444. switch(mode)
  445. {
  446. case SEARCH_ANY:
  447. return 1;
  448. case SEARCH_LESSEQUAL:
  449. if(msg->m_type <=type)
  450. return 1;
  451. break;
  452. case SEARCH_EQUAL:
  453. if(msg->m_type == type)
  454. return 1;
  455. break;
  456. case SEARCH_NOTEQUAL:
  457. if(msg->m_type != type)
  458. return 1;
  459. break;
  460. }
  461. return 0;
  462. }
  463. static inline int pipelined_send(struct msg_queue* msq, struct msg_msg* msg)
  464. {
  465. struct list_head* tmp;
  466. tmp = msq->q_receivers.next;
  467. while (tmp != &msq->q_receivers) {
  468. struct msg_receiver* msr;
  469. msr = list_entry(tmp,struct msg_receiver,r_list);
  470. tmp = tmp->next;
  471. if(testmsg(msg,msr->r_msgtype,msr->r_mode) &&
  472. !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) {
  473. list_del(&msr->r_list);
  474. if(msr->r_maxsize < msg->m_ts) {
  475. msr->r_msg = NULL;
  476. wake_up_process(msr->r_tsk);
  477. smp_mb();
  478. msr->r_msg = ERR_PTR(-E2BIG);
  479. } else {
  480. msr->r_msg = NULL;
  481. msq->q_lrpid = msr->r_tsk->pid;
  482. msq->q_rtime = get_seconds();
  483. wake_up_process(msr->r_tsk);
  484. smp_mb();
  485. msr->r_msg = msg;
  486. return 1;
  487. }
  488. }
  489. }
  490. return 0;
  491. }
  492. asmlinkage long sys_msgsnd (int msqid, struct msgbuf __user *msgp, size_t msgsz, int msgflg)
  493. {
  494. struct msg_queue *msq;
  495. struct msg_msg *msg;
  496. long mtype;
  497. int err;
  498. if (msgsz > msg_ctlmax || (long) msgsz < 0 || msqid < 0)
  499. return -EINVAL;
  500. if (get_user(mtype, &msgp->mtype))
  501. return -EFAULT;
  502. if (mtype < 1)
  503. return -EINVAL;
  504. msg = load_msg(msgp->mtext, msgsz);
  505. if(IS_ERR(msg))
  506. return PTR_ERR(msg);
  507. msg->m_type = mtype;
  508. msg->m_ts = msgsz;
  509. msq = msg_lock(msqid);
  510. err=-EINVAL;
  511. if(msq==NULL)
  512. goto out_free;
  513. err= -EIDRM;
  514. if (msg_checkid(msq,msqid))
  515. goto out_unlock_free;
  516. for (;;) {
  517. struct msg_sender s;
  518. err=-EACCES;
  519. if (ipcperms(&msq->q_perm, S_IWUGO))
  520. goto out_unlock_free;
  521. err = security_msg_queue_msgsnd(msq, msg, msgflg);
  522. if (err)
  523. goto out_unlock_free;
  524. if(msgsz + msq->q_cbytes <= msq->q_qbytes &&
  525. 1 + msq->q_qnum <= msq->q_qbytes) {
  526. break;
  527. }
  528. /* queue full, wait: */
  529. if(msgflg&IPC_NOWAIT) {
  530. err=-EAGAIN;
  531. goto out_unlock_free;
  532. }
  533. ss_add(msq, &s);
  534. ipc_rcu_getref(msq);
  535. msg_unlock(msq);
  536. schedule();
  537. ipc_lock_by_ptr(&msq->q_perm);
  538. ipc_rcu_putref(msq);
  539. if (msq->q_perm.deleted) {
  540. err = -EIDRM;
  541. goto out_unlock_free;
  542. }
  543. ss_del(&s);
  544. if (signal_pending(current)) {
  545. err=-ERESTARTNOHAND;
  546. goto out_unlock_free;
  547. }
  548. }
  549. msq->q_lspid = current->tgid;
  550. msq->q_stime = get_seconds();
  551. if(!pipelined_send(msq,msg)) {
  552. /* noone is waiting for this message, enqueue it */
  553. list_add_tail(&msg->m_list,&msq->q_messages);
  554. msq->q_cbytes += msgsz;
  555. msq->q_qnum++;
  556. atomic_add(msgsz,&msg_bytes);
  557. atomic_inc(&msg_hdrs);
  558. }
  559. err = 0;
  560. msg = NULL;
  561. out_unlock_free:
  562. msg_unlock(msq);
  563. out_free:
  564. if(msg!=NULL)
  565. free_msg(msg);
  566. return err;
  567. }
  568. static inline int convert_mode(long* msgtyp, int msgflg)
  569. {
  570. /*
  571. * find message of correct type.
  572. * msgtyp = 0 => get first.
  573. * msgtyp > 0 => get first message of matching type.
  574. * msgtyp < 0 => get message with least type must be < abs(msgtype).
  575. */
  576. if(*msgtyp==0)
  577. return SEARCH_ANY;
  578. if(*msgtyp<0) {
  579. *msgtyp=-(*msgtyp);
  580. return SEARCH_LESSEQUAL;
  581. }
  582. if(msgflg & MSG_EXCEPT)
  583. return SEARCH_NOTEQUAL;
  584. return SEARCH_EQUAL;
  585. }
  586. asmlinkage long sys_msgrcv (int msqid, struct msgbuf __user *msgp, size_t msgsz,
  587. long msgtyp, int msgflg)
  588. {
  589. struct msg_queue *msq;
  590. struct msg_msg *msg;
  591. int mode;
  592. if (msqid < 0 || (long) msgsz < 0)
  593. return -EINVAL;
  594. mode = convert_mode(&msgtyp,msgflg);
  595. msq = msg_lock(msqid);
  596. if(msq==NULL)
  597. return -EINVAL;
  598. msg = ERR_PTR(-EIDRM);
  599. if (msg_checkid(msq,msqid))
  600. goto out_unlock;
  601. for (;;) {
  602. struct msg_receiver msr_d;
  603. struct list_head* tmp;
  604. msg = ERR_PTR(-EACCES);
  605. if (ipcperms (&msq->q_perm, S_IRUGO))
  606. goto out_unlock;
  607. msg = ERR_PTR(-EAGAIN);
  608. tmp = msq->q_messages.next;
  609. while (tmp != &msq->q_messages) {
  610. struct msg_msg *walk_msg;
  611. walk_msg = list_entry(tmp,struct msg_msg,m_list);
  612. if(testmsg(walk_msg,msgtyp,mode) &&
  613. !security_msg_queue_msgrcv(msq, walk_msg, current, msgtyp, mode)) {
  614. msg = walk_msg;
  615. if(mode == SEARCH_LESSEQUAL && walk_msg->m_type != 1) {
  616. msg=walk_msg;
  617. msgtyp=walk_msg->m_type-1;
  618. } else {
  619. msg=walk_msg;
  620. break;
  621. }
  622. }
  623. tmp = tmp->next;
  624. }
  625. if(!IS_ERR(msg)) {
  626. /* Found a suitable message. Unlink it from the queue. */
  627. if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
  628. msg = ERR_PTR(-E2BIG);
  629. goto out_unlock;
  630. }
  631. list_del(&msg->m_list);
  632. msq->q_qnum--;
  633. msq->q_rtime = get_seconds();
  634. msq->q_lrpid = current->tgid;
  635. msq->q_cbytes -= msg->m_ts;
  636. atomic_sub(msg->m_ts,&msg_bytes);
  637. atomic_dec(&msg_hdrs);
  638. ss_wakeup(&msq->q_senders,0);
  639. msg_unlock(msq);
  640. break;
  641. }
  642. /* No message waiting. Wait for a message */
  643. if (msgflg & IPC_NOWAIT) {
  644. msg = ERR_PTR(-ENOMSG);
  645. goto out_unlock;
  646. }
  647. list_add_tail(&msr_d.r_list,&msq->q_receivers);
  648. msr_d.r_tsk = current;
  649. msr_d.r_msgtype = msgtyp;
  650. msr_d.r_mode = mode;
  651. if(msgflg & MSG_NOERROR)
  652. msr_d.r_maxsize = INT_MAX;
  653. else
  654. msr_d.r_maxsize = msgsz;
  655. msr_d.r_msg = ERR_PTR(-EAGAIN);
  656. current->state = TASK_INTERRUPTIBLE;
  657. msg_unlock(msq);
  658. schedule();
  659. /* Lockless receive, part 1:
  660. * Disable preemption. We don't hold a reference to the queue
  661. * and getting a reference would defeat the idea of a lockless
  662. * operation, thus the code relies on rcu to guarantee the
  663. * existance of msq:
  664. * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
  665. * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
  666. * rcu_read_lock() prevents preemption between reading r_msg
  667. * and the spin_lock() inside ipc_lock_by_ptr().
  668. */
  669. rcu_read_lock();
  670. /* Lockless receive, part 2:
  671. * Wait until pipelined_send or expunge_all are outside of
  672. * wake_up_process(). There is a race with exit(), see
  673. * ipc/mqueue.c for the details.
  674. */
  675. msg = (struct msg_msg*) msr_d.r_msg;
  676. while (msg == NULL) {
  677. cpu_relax();
  678. msg = (struct msg_msg*) msr_d.r_msg;
  679. }
  680. /* Lockless receive, part 3:
  681. * If there is a message or an error then accept it without
  682. * locking.
  683. */
  684. if(msg != ERR_PTR(-EAGAIN)) {
  685. rcu_read_unlock();
  686. break;
  687. }
  688. /* Lockless receive, part 3:
  689. * Acquire the queue spinlock.
  690. */
  691. ipc_lock_by_ptr(&msq->q_perm);
  692. rcu_read_unlock();
  693. /* Lockless receive, part 4:
  694. * Repeat test after acquiring the spinlock.
  695. */
  696. msg = (struct msg_msg*)msr_d.r_msg;
  697. if(msg != ERR_PTR(-EAGAIN))
  698. goto out_unlock;
  699. list_del(&msr_d.r_list);
  700. if (signal_pending(current)) {
  701. msg = ERR_PTR(-ERESTARTNOHAND);
  702. out_unlock:
  703. msg_unlock(msq);
  704. break;
  705. }
  706. }
  707. if (IS_ERR(msg))
  708. return PTR_ERR(msg);
  709. msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
  710. if (put_user (msg->m_type, &msgp->mtype) ||
  711. store_msg(msgp->mtext, msg, msgsz)) {
  712. msgsz = -EFAULT;
  713. }
  714. free_msg(msg);
  715. return msgsz;
  716. }
  717. #ifdef CONFIG_PROC_FS
  718. static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
  719. {
  720. struct msg_queue *msq = it;
  721. return seq_printf(s,
  722. "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
  723. msq->q_perm.key,
  724. msq->q_id,
  725. msq->q_perm.mode,
  726. msq->q_cbytes,
  727. msq->q_qnum,
  728. msq->q_lspid,
  729. msq->q_lrpid,
  730. msq->q_perm.uid,
  731. msq->q_perm.gid,
  732. msq->q_perm.cuid,
  733. msq->q_perm.cgid,
  734. msq->q_stime,
  735. msq->q_rtime,
  736. msq->q_ctime);
  737. }
  738. #endif